Title
Demonstrate understanding of gene expression
Date version published
17 November 2011
This achievement standard involves demonstrating understanding of gene expression.
Achievement Criteria:
Achievement
· Demonstrate understanding of gene expression.
Achievement with Merit
· Demonstrate in-depth understanding of gene expression.
Achievement with Excellence
· Demonstrate comprehensive understanding of gene expression.
Explanatory Notes:
1 This achievement standard is derived from The New Zealand Curriculum, Learning Media, Ministry of Education, 2007, Level 7. It is aligned with the following achievement objective in the Living World strand:
Evolution
· Understand that DNA and the environment interact in gene expression
and is related to the material in the Teaching and Learning Guide for Biology, Ministry of Education, 2010 at http://seniorsecondary.tki.org.nz.
2 Demonstrate understanding involves defining, using annotated diagrams or models to explain, and giving characteristics of, or an account of, gene expression.
Demonstrate in-depth understanding involves providing a reason as to how or why biological ideas and processes affect gene expression.
Demonstrate comprehensive understanding involves linking biological ideas and processes about gene expression. The explanation may involve justifying, relating, evaluating, comparing and contrasting, or analysing.
3 Gene expression involves a selection from the following biological ideas and processes:
· nucleic acid structure and nature of the genetic code
· significance of proteins
· protein synthesis
· the determination of phenotype via metabolic pathways
· effect of environment on genotype through mutations
· effect of environment on expression of phenotype.
4 Biological ideas and processes relating to nucleic acid structure and nature of the genetic code are selected from:
· molecular components and their role in carrying the genetic code: nucleotide monomers, deoxyribose and/or ribose sugar, phosphate, nitrogenous bases, complementary base pairing resulting in coding and template strand
· nature of the genetic code including triplets, codons and anticodons
· redundancy due to degeneracy within the code.
5 Biological ideas and processes relating to the significance of proteins are selected from:
· proteins as the products of gene expression: DNA à mRNA à polypeptide or protein
· identification of one gene à one polypeptide relationship
· significance of proteins is limited to their structural and catalytic role in living things.
6 Biological ideas and processes relating to protein synthesis are selected from:
· the role of DNA sequence in determining the structure of a protein and how that protein is produced (transcription and translation)
· the role of enzymes in controlling the process (specific names of enzymes are not required).
7 Biological ideas and processes relating to the determination of phenotype via metabolic pathways are selected from:
· biochemical reactions are catalysed by specific enzymes and every enzyme is coded for by a specific gene(s)
· biochemical reactions do not occur in isolation but form part of a chain reaction so that the product of one becomes the substrate of another step in metabolism
· phenotype is determined by the presence, absence, or amount of specific metabolic products.
8 Biological ideas and processes relating to the effect of the environment on genotype through mutations are selected from:
· mutagens (specific mutagens are recognised but their effect at molecular level is not required)
· the potential effect on genotype and phenotype of gene mutations at the gene level.
9 Biological ideas and processes relating to the effect of environment on expression of phenotype involve ways that environmental factors may change phenotype without changing genotype.
10 Assessment Specifications for this achievement standard can be accessed through the Biology Resources page found at http://www.nzqa.govt.nz/qualifications-standards/qualifications/ncea/subjects/.
Key Words: These are the words that you are expected to understand when used in questions and be able to use in your answers.
Core Vocabulary & Glossary:
· Amino acid - a simple organic compound containing both a carboxyl (—COOH) and an amino (—NH2) group.
· Anaphase - is a stage in mitosis and meiosis where chromosomes begin moving to opposite ends (poles) of the cell.
· Anticodon - a sequence of three nucleotides in a region of transfer RNA that recognizes a complementary coding triplet of nucleotides in messenger RNA during translation by the ribosomes in protein biosynthesis.
· Chromosome mutation - a mutation involving a long segment of DNA. These mutations can involve deletions, insertions, or inversions of sections of DNA.
· Coding Strand - the DNA strand with the same sequence as the transcribed mRNA (given U in RNA and T in DNA) and containing the linear array of codons which interact with anticodons of tRNA during translation to give the primary sequence of a protein.
· Codon - a sequence of three nucleotides which together form a unit of genetic code in a DNA or RNA molecule.
· Complementary Base Pairs - either of the nucleotide bases linked by a hydrogen bond on opposite strands of DNA or double-stranded RNA: guanine is the complementary base of cytosine, and adenine is the complementary base of thymine in DNA and of uracil in RNA.
· Cytokinesis - is the division of cells after either Mitosis or Meiosis I and II. During Cytokinesis, the cytoplasm (the liquid center of the cell that holds the organelles into place.)
· Degenerate Code - a code in which several code words have the same meaning. The genetic code is degenerate because there are many instances in which different codons specify the same amino acid. A genetic code in which some amino acids may each be encoded by more than one codon.
· Deletion - in genetics, a deletion (also called gene deletion, deficiency, or deletion mutation) (sign: Δ) is a mutation (a genetic aberration) in which a part of a chromosome or a sequence of DNA is missing. Deletion is the loss of genetic material.
· Disulphide Bridges - true covalent bonds (between the sulfurs of two cysteine side chains) and are thus considered part of the primary structure of a protein by most definitions.
· DNA Ligase - is a specific type of enzyme, that facilitates the joining of DNA strands together by catalyzing the formation of a phospho-diester bond.
· DNA Polymerase - is a type of enzyme that is responsible for forming new copies of DNA, in the form of nucleic acid molecules.
· Duplication - Part of a chromosome in duplicate, a particular kind of mutation (change) involving the production of one or more copies of any piece of DNA, including a gene or even an entire chromosome.
· Eukaryotic - is any organism whose cells contain a nucleus and other structures enclosed within membranes.
· Exon - a segment of a DNA or RNA molecule containing information coding for a protein or peptide sequence.
· Frame Shift - a mutation caused by the addition or deletion of a base pair or base pairs in the DNA of a gene resulting in the translation of the genetic code in an unnatural reading frame from the position of the mutation to the end of the gene.
· Gametic - relates to gametes i.e. sex reproductive cells egg and sperm cells.
· Gene Expression - is the process by which information from a gene is used in the synthesis of a functional gene product. These products are often proteins, but in non-protein coding genes such as ribosomal RNA (rRNA), transfer RNA (tRNA) or small nuclear RNA (snRNA) genes, the product is a functional RNA.
· Gene mutation - is a permanent change in the DNA sequence that makes up a gene. Mutations range in size from a single DNA building block (DNA base) to a large segment of a chromosome. Gene mutations occur in two ways: they can be inherited from a parent or acquired during a person's lifetime.
· Helicase - any of the enzymes that use the energy derived from the hydrolysis of nucleoside triphosphates to unwind the double-stranded helical structure of nucleic acids: RNA and DNA helicases.
· Induced - Point mutations may arise from spontaneous mutations that occur during DNA replication. The rate of mutation may be increased by mutagens. Mutagens can be physical, such as radiation from UV rays, X-rays or extreme heat, or chemical (molecules that misplace base pairs or disrupt the helical shape of DNA).
· Inducer - is a molecule that starts gene expression. An inducer can bind to repressors or activators. Inducers function by disabling repressors. The gene is expressed because an inducer binds to the repressor.
· Insertion - is the addition of one or more nucleotide base pairs into a DNA sequence. This can often happen in microsatellite regions due to the DNA polymerase slipping.
· Interphase - A stage in the cell cycle when a cell doubles its cytoplasm and synthesizes DNA. Interphase is the "holding" stage or the stage between two successive cell divisions. Introduction to mitosis and the process of cell division.
· Intron - a segment of a DNA or RNA molecule which does not code for proteins and interrupts the sequence of genes.
· Inversion - is a chromosome rearrangement in which a segment of a chromosome is reversed end to end. An inversion occurs when a single chromosome undergoes breakage and rearrangement within itself.
· Karyotype - The characterization of the chromosome complement of a species (such as the shape, type, number, etc. of chromosomes). The karyotype of an organism is usually displayed in photomicrographs wherein chromosomes are arranged in homologous pairs, and in descending order of size and relative position of the centromere. Karyotype is used to study chromosomal aberrations, cellular function, or taxonomic relationships, or to gather information about past evolutionary events.
· Missense - is when the change of a single base pair causes the substitution of a different amino acid in the resulting protein. This amino acid substitution may have no effect, or it may render the protein nonfunctional.
· Metabolic Pathway - A series of chemical reactions catalyzed by enzymes and are connected by their intermediates, i.e. the reactants of one reaction are the products of the previous one.
· Metaphase - the second stage of cell division, between prophase and anaphase, during which the chromosomes become attached to the spindle fibres.
· Monomer - a molecule that can be bonded to other identical molecules to form a polymer.
· mRNA - messenger RNA is a large family of RNA molecules that convey genetic information from DNA to the ribosome, where they specify the amino acid sequence of the protein products of gene expression.
· Nonsense - a mutation in which a sense codon that corresponds to one of the twenty amino acids specified by the genetic code is changed to a chain-terminating codon.
· Operator Site - is a segment of DNA to which a transcription factor protein binds. It is classically defined in the lac operon as a segment between the promoter and the genes of the operon. In the case of a repressor, the repressor protein physically obstructs the RNA polymerase from transcribing the genes.
· Operon - a unit made up of linked genes which is thought to regulate other genes responsible for protein synthesis.
· Phenylalanine - an amino acid widely distributed in plant proteins. It is an essential nutrient in the diet of vertebrates.
· Polymer - a substance which has a molecular structure built up chiefly or completely from a large number of similar units called monomers bonded together, e.g. many synthetic organic materials used as plastics and resins and biological molecules like carbohydrates, lipids, proteins and nucleic acids.
· Polysomy - is a condition in which an organism has at least one more chromosome than normal, i.e., there may be three or more copies of the chromosome rather than the expected two copies.
· Prokaryotic - is a single-celled organism which lacks a membrane-bound nucleus, mitochondria, or any other membrane-bound organelle. The word prokaryote comes from the Greek πρό- "before" and καρυόν "nut or kernel".-
· Promoter Site - DNA sequence that define where transcription of a gene by RNA polymerase begins. Promoter sequences are typically located directly upstream or at the 5' end of the transcription initiation site.
· Prophase - the first stage of cell division, before metaphase, during which the chromosomes become visible as paired chromatids and the nuclear envelope disappears. The first prophase of meiosis includes the reduction division.
· Protein - any of a class of nitrogenous organic compounds which have large molecules composed of one or more long chains of amino acids and are an essential part of all living organisms, especially as structural components of body tissues such as muscle, hair, etc., and as enzymes and antibodies.
· Protein Synthesis - the process by which amino acids are linearly arranged into proteins through the involvement of ribosomal RNA, transfer RNA, messenger RNA, and various enzymes.
· Purines - a substituted derivative of purine, especially the bases adenine and guanine present in DNA.
· Pyrimidines - a substituted derivative of pyrimidine, especially the bases thymine and cytosine present in DNA.
· Reading frame - is a way of dividing the sequence of nucleotides in a nucleic acid (DNA or RNA) molecule into a set of consecutive, non-overlapping triplets.
· Regulator Gene - a regulator, or regulatory gene is a gene involved in controlling the expression of one or more other genes. A regulator gene may encode a protein, or it may work at the level of RNA, as in the case of genes encoding microRNAs. In prokaryotes, regulator genes often code for repressor proteins.
· RNA Polymerase - also known as DNA-dependent RNA polymerase, is an enzyme that produces primary transcript RNA. In cells, RNAP is necessary for constructing RNA chains using DNA genes as templates, a process called transcription.
· RNA - ribonucleic acid, a nucleic acid present in all living cells. Its principal role is to act as a messenger carrying instructions from DNA for controlling the synthesis of proteins (mRNA), although in some viruses RNA itself rather than DNA carries the genetic information. It also transfers free amino acids to ribosomes for protein synthesis (tRNA) and ribosomes themselves are made of it (rRNA).
· Somatic - relating to the soma i.e. bodily non-reproductive cells.
· Spontaneous - a mutation that arises naturally and not as a result of exposure to mutagens. Also called natural mutation.
· Start Codon - is the first codon of a messenger RNA (mRNA) transcript translated by a ribosome. The start codon always codes for methionine in eukaryotes and a modified Met (fMet) in prokaryotes. The most common start codon is AUG.
· Stop Codon - is a trinucleotide sequence within a messenger RNA (mRNA) molecule that signals a halt to protein synthesis. The genetic code describes the relationship between the sequence of DNA bases (A, C, G, and T) in a gene and the corresponding protein sequence that it encodes.
· Structural Gene - is a gene that codes for any RNA or protein product other than a regulatory factor (i.e. regulatory protein). It may code for a structural protein, an enzyme, or an RNA molecule not involved in regulation.
· Substitution - a type of mutation due to replacement of one nucleotide in a DNA sequence by another nucleotide or replacement of one amino acid in a protein by another amino acid. Substitution is a type of mutation where one base pair is replaced by a different base pair.
· Syndrome - a group of symptoms which consistently occur together, or a condition characterized by a set of associated symptoms.
· Tautomerism - is a special case of structural isomerism and can play an important role in non-canonical base pairing in DNA and especially RNA molecules.
· Telophase - the final phase of cell division, between anaphase and interphase, in which the chromatids or chromosomes move to opposite ends of the cell and two nuclei are formed.
· Template Strand - refers to the sequence of DNA that is copied during the synthesis of mRNA.
· Transcription - is the process by which the information in a strand of DNA is copied into a new molecule of messenger RNA (mRNA). DNA safely and stably stores genetic material in the nuclei of cells as a reference, or template.
· Translation - it is part of the process of gene expression. In translation, messenger RNA (mRNA) produced by transcription is decoded by a ribosome complex to produce a specific amino acid chain, or polypeptide, that will later fold into an active protein.
· Translocation - a chromosome translocation is a chromosome abnormality caused by rearrangement of parts between nonhomologous chromosomes.
· Triplet - the genetic code defines how sequences of these nucleotide triplets, called codons, specify which amino acid will be added next during protein synthesis.
· tRNA - a Transfer RNA is an adaptor molecule composed of RNA, typically 73 to 94 nucleotides in length, that serves as the physical link between the nucleotide sequence of nucleic acids and the amino acid sequence of proteins.
At the end of this unit of work you should be able to use the core knowledge listed in the statements below to describe, explain and discuss aspects of cell structure and function. Questions may be presented to you in novel or applied situations that will require you to recognise and link these ideas together.
1. Describe the structure of nucleic acids and the nature of the genetic code
2. Describe the structure and function of DNA and RNA.
3. Describe the nature of the genetic code is and state the function of this code.
4. Describe the process of protein synthesis.
5. Explain the role of the DNA sequence in determining the structure of a protein
6. Describe the structure, function and significance of proteins.
7. Describe the structure, function and role of enzymes in controlling pathways.
8. Explain how the phenotype is determined via metabolic pathways.
9. Describe the control of gene expression in eukaryotes.
10. Describe mutagens and give examples.
11. Describe the effect of gene mutations; identify types of gene mutations and explain the range of potential consequences
of these on the expression of the genotype and phenotype.
12. Describe the effect of block mutations; identify types of block mutations and the range of potential consequences of these
on the expression of the genotype and phenotype.
13. Describe the effect of the environment on expression of the phenotype.
14. Show understanding of gene expression by using the core knowledge to link ideas e.g. in justifying, relating, evaluating,
comparing and contrasting or analysing.
15. Communicate ideas clearly and succinctly using the biological language relevant to this topic.
Demonstrate understanding of gene expression
Date version published
17 November 2011
This achievement standard involves demonstrating understanding of gene expression.
Achievement Criteria:
Achievement
· Demonstrate understanding of gene expression.
Achievement with Merit
· Demonstrate in-depth understanding of gene expression.
Achievement with Excellence
· Demonstrate comprehensive understanding of gene expression.
Explanatory Notes:
1 This achievement standard is derived from The New Zealand Curriculum, Learning Media, Ministry of Education, 2007, Level 7. It is aligned with the following achievement objective in the Living World strand:
Evolution
· Understand that DNA and the environment interact in gene expression
and is related to the material in the Teaching and Learning Guide for Biology, Ministry of Education, 2010 at http://seniorsecondary.tki.org.nz.
2 Demonstrate understanding involves defining, using annotated diagrams or models to explain, and giving characteristics of, or an account of, gene expression.
Demonstrate in-depth understanding involves providing a reason as to how or why biological ideas and processes affect gene expression.
Demonstrate comprehensive understanding involves linking biological ideas and processes about gene expression. The explanation may involve justifying, relating, evaluating, comparing and contrasting, or analysing.
3 Gene expression involves a selection from the following biological ideas and processes:
· nucleic acid structure and nature of the genetic code
· significance of proteins
· protein synthesis
· the determination of phenotype via metabolic pathways
· effect of environment on genotype through mutations
· effect of environment on expression of phenotype.
4 Biological ideas and processes relating to nucleic acid structure and nature of the genetic code are selected from:
· molecular components and their role in carrying the genetic code: nucleotide monomers, deoxyribose and/or ribose sugar, phosphate, nitrogenous bases, complementary base pairing resulting in coding and template strand
· nature of the genetic code including triplets, codons and anticodons
· redundancy due to degeneracy within the code.
5 Biological ideas and processes relating to the significance of proteins are selected from:
· proteins as the products of gene expression: DNA à mRNA à polypeptide or protein
· identification of one gene à one polypeptide relationship
· significance of proteins is limited to their structural and catalytic role in living things.
6 Biological ideas and processes relating to protein synthesis are selected from:
· the role of DNA sequence in determining the structure of a protein and how that protein is produced (transcription and translation)
· the role of enzymes in controlling the process (specific names of enzymes are not required).
7 Biological ideas and processes relating to the determination of phenotype via metabolic pathways are selected from:
· biochemical reactions are catalysed by specific enzymes and every enzyme is coded for by a specific gene(s)
· biochemical reactions do not occur in isolation but form part of a chain reaction so that the product of one becomes the substrate of another step in metabolism
· phenotype is determined by the presence, absence, or amount of specific metabolic products.
8 Biological ideas and processes relating to the effect of the environment on genotype through mutations are selected from:
· mutagens (specific mutagens are recognised but their effect at molecular level is not required)
· the potential effect on genotype and phenotype of gene mutations at the gene level.
9 Biological ideas and processes relating to the effect of environment on expression of phenotype involve ways that environmental factors may change phenotype without changing genotype.
10 Assessment Specifications for this achievement standard can be accessed through the Biology Resources page found at http://www.nzqa.govt.nz/qualifications-standards/qualifications/ncea/subjects/.
Key Words: These are the words that you are expected to understand when used in questions and be able to use in your answers.
Core Vocabulary & Glossary:
· Amino acid - a simple organic compound containing both a carboxyl (—COOH) and an amino (—NH2) group.
· Anaphase - is a stage in mitosis and meiosis where chromosomes begin moving to opposite ends (poles) of the cell.
· Anticodon - a sequence of three nucleotides in a region of transfer RNA that recognizes a complementary coding triplet of nucleotides in messenger RNA during translation by the ribosomes in protein biosynthesis.
· Chromosome mutation - a mutation involving a long segment of DNA. These mutations can involve deletions, insertions, or inversions of sections of DNA.
· Coding Strand - the DNA strand with the same sequence as the transcribed mRNA (given U in RNA and T in DNA) and containing the linear array of codons which interact with anticodons of tRNA during translation to give the primary sequence of a protein.
· Codon - a sequence of three nucleotides which together form a unit of genetic code in a DNA or RNA molecule.
· Complementary Base Pairs - either of the nucleotide bases linked by a hydrogen bond on opposite strands of DNA or double-stranded RNA: guanine is the complementary base of cytosine, and adenine is the complementary base of thymine in DNA and of uracil in RNA.
· Cytokinesis - is the division of cells after either Mitosis or Meiosis I and II. During Cytokinesis, the cytoplasm (the liquid center of the cell that holds the organelles into place.)
· Degenerate Code - a code in which several code words have the same meaning. The genetic code is degenerate because there are many instances in which different codons specify the same amino acid. A genetic code in which some amino acids may each be encoded by more than one codon.
· Deletion - in genetics, a deletion (also called gene deletion, deficiency, or deletion mutation) (sign: Δ) is a mutation (a genetic aberration) in which a part of a chromosome or a sequence of DNA is missing. Deletion is the loss of genetic material.
· Disulphide Bridges - true covalent bonds (between the sulfurs of two cysteine side chains) and are thus considered part of the primary structure of a protein by most definitions.
· DNA Ligase - is a specific type of enzyme, that facilitates the joining of DNA strands together by catalyzing the formation of a phospho-diester bond.
· DNA Polymerase - is a type of enzyme that is responsible for forming new copies of DNA, in the form of nucleic acid molecules.
· Duplication - Part of a chromosome in duplicate, a particular kind of mutation (change) involving the production of one or more copies of any piece of DNA, including a gene or even an entire chromosome.
· Eukaryotic - is any organism whose cells contain a nucleus and other structures enclosed within membranes.
· Exon - a segment of a DNA or RNA molecule containing information coding for a protein or peptide sequence.
· Frame Shift - a mutation caused by the addition or deletion of a base pair or base pairs in the DNA of a gene resulting in the translation of the genetic code in an unnatural reading frame from the position of the mutation to the end of the gene.
· Gametic - relates to gametes i.e. sex reproductive cells egg and sperm cells.
· Gene Expression - is the process by which information from a gene is used in the synthesis of a functional gene product. These products are often proteins, but in non-protein coding genes such as ribosomal RNA (rRNA), transfer RNA (tRNA) or small nuclear RNA (snRNA) genes, the product is a functional RNA.
· Gene mutation - is a permanent change in the DNA sequence that makes up a gene. Mutations range in size from a single DNA building block (DNA base) to a large segment of a chromosome. Gene mutations occur in two ways: they can be inherited from a parent or acquired during a person's lifetime.
· Helicase - any of the enzymes that use the energy derived from the hydrolysis of nucleoside triphosphates to unwind the double-stranded helical structure of nucleic acids: RNA and DNA helicases.
· Induced - Point mutations may arise from spontaneous mutations that occur during DNA replication. The rate of mutation may be increased by mutagens. Mutagens can be physical, such as radiation from UV rays, X-rays or extreme heat, or chemical (molecules that misplace base pairs or disrupt the helical shape of DNA).
· Inducer - is a molecule that starts gene expression. An inducer can bind to repressors or activators. Inducers function by disabling repressors. The gene is expressed because an inducer binds to the repressor.
· Insertion - is the addition of one or more nucleotide base pairs into a DNA sequence. This can often happen in microsatellite regions due to the DNA polymerase slipping.
· Interphase - A stage in the cell cycle when a cell doubles its cytoplasm and synthesizes DNA. Interphase is the "holding" stage or the stage between two successive cell divisions. Introduction to mitosis and the process of cell division.
· Intron - a segment of a DNA or RNA molecule which does not code for proteins and interrupts the sequence of genes.
· Inversion - is a chromosome rearrangement in which a segment of a chromosome is reversed end to end. An inversion occurs when a single chromosome undergoes breakage and rearrangement within itself.
· Karyotype - The characterization of the chromosome complement of a species (such as the shape, type, number, etc. of chromosomes). The karyotype of an organism is usually displayed in photomicrographs wherein chromosomes are arranged in homologous pairs, and in descending order of size and relative position of the centromere. Karyotype is used to study chromosomal aberrations, cellular function, or taxonomic relationships, or to gather information about past evolutionary events.
· Missense - is when the change of a single base pair causes the substitution of a different amino acid in the resulting protein. This amino acid substitution may have no effect, or it may render the protein nonfunctional.
· Metabolic Pathway - A series of chemical reactions catalyzed by enzymes and are connected by their intermediates, i.e. the reactants of one reaction are the products of the previous one.
· Metaphase - the second stage of cell division, between prophase and anaphase, during which the chromosomes become attached to the spindle fibres.
· Monomer - a molecule that can be bonded to other identical molecules to form a polymer.
· mRNA - messenger RNA is a large family of RNA molecules that convey genetic information from DNA to the ribosome, where they specify the amino acid sequence of the protein products of gene expression.
· Nonsense - a mutation in which a sense codon that corresponds to one of the twenty amino acids specified by the genetic code is changed to a chain-terminating codon.
· Operator Site - is a segment of DNA to which a transcription factor protein binds. It is classically defined in the lac operon as a segment between the promoter and the genes of the operon. In the case of a repressor, the repressor protein physically obstructs the RNA polymerase from transcribing the genes.
· Operon - a unit made up of linked genes which is thought to regulate other genes responsible for protein synthesis.
· Phenylalanine - an amino acid widely distributed in plant proteins. It is an essential nutrient in the diet of vertebrates.
· Polymer - a substance which has a molecular structure built up chiefly or completely from a large number of similar units called monomers bonded together, e.g. many synthetic organic materials used as plastics and resins and biological molecules like carbohydrates, lipids, proteins and nucleic acids.
· Polysomy - is a condition in which an organism has at least one more chromosome than normal, i.e., there may be three or more copies of the chromosome rather than the expected two copies.
· Prokaryotic - is a single-celled organism which lacks a membrane-bound nucleus, mitochondria, or any other membrane-bound organelle. The word prokaryote comes from the Greek πρό- "before" and καρυόν "nut or kernel".-
· Promoter Site - DNA sequence that define where transcription of a gene by RNA polymerase begins. Promoter sequences are typically located directly upstream or at the 5' end of the transcription initiation site.
· Prophase - the first stage of cell division, before metaphase, during which the chromosomes become visible as paired chromatids and the nuclear envelope disappears. The first prophase of meiosis includes the reduction division.
· Protein - any of a class of nitrogenous organic compounds which have large molecules composed of one or more long chains of amino acids and are an essential part of all living organisms, especially as structural components of body tissues such as muscle, hair, etc., and as enzymes and antibodies.
· Protein Synthesis - the process by which amino acids are linearly arranged into proteins through the involvement of ribosomal RNA, transfer RNA, messenger RNA, and various enzymes.
· Purines - a substituted derivative of purine, especially the bases adenine and guanine present in DNA.
· Pyrimidines - a substituted derivative of pyrimidine, especially the bases thymine and cytosine present in DNA.
· Reading frame - is a way of dividing the sequence of nucleotides in a nucleic acid (DNA or RNA) molecule into a set of consecutive, non-overlapping triplets.
· Regulator Gene - a regulator, or regulatory gene is a gene involved in controlling the expression of one or more other genes. A regulator gene may encode a protein, or it may work at the level of RNA, as in the case of genes encoding microRNAs. In prokaryotes, regulator genes often code for repressor proteins.
· RNA Polymerase - also known as DNA-dependent RNA polymerase, is an enzyme that produces primary transcript RNA. In cells, RNAP is necessary for constructing RNA chains using DNA genes as templates, a process called transcription.
· RNA - ribonucleic acid, a nucleic acid present in all living cells. Its principal role is to act as a messenger carrying instructions from DNA for controlling the synthesis of proteins (mRNA), although in some viruses RNA itself rather than DNA carries the genetic information. It also transfers free amino acids to ribosomes for protein synthesis (tRNA) and ribosomes themselves are made of it (rRNA).
· Somatic - relating to the soma i.e. bodily non-reproductive cells.
· Spontaneous - a mutation that arises naturally and not as a result of exposure to mutagens. Also called natural mutation.
· Start Codon - is the first codon of a messenger RNA (mRNA) transcript translated by a ribosome. The start codon always codes for methionine in eukaryotes and a modified Met (fMet) in prokaryotes. The most common start codon is AUG.
· Stop Codon - is a trinucleotide sequence within a messenger RNA (mRNA) molecule that signals a halt to protein synthesis. The genetic code describes the relationship between the sequence of DNA bases (A, C, G, and T) in a gene and the corresponding protein sequence that it encodes.
· Structural Gene - is a gene that codes for any RNA or protein product other than a regulatory factor (i.e. regulatory protein). It may code for a structural protein, an enzyme, or an RNA molecule not involved in regulation.
· Substitution - a type of mutation due to replacement of one nucleotide in a DNA sequence by another nucleotide or replacement of one amino acid in a protein by another amino acid. Substitution is a type of mutation where one base pair is replaced by a different base pair.
· Syndrome - a group of symptoms which consistently occur together, or a condition characterized by a set of associated symptoms.
· Tautomerism - is a special case of structural isomerism and can play an important role in non-canonical base pairing in DNA and especially RNA molecules.
· Telophase - the final phase of cell division, between anaphase and interphase, in which the chromatids or chromosomes move to opposite ends of the cell and two nuclei are formed.
· Template Strand - refers to the sequence of DNA that is copied during the synthesis of mRNA.
· Transcription - is the process by which the information in a strand of DNA is copied into a new molecule of messenger RNA (mRNA). DNA safely and stably stores genetic material in the nuclei of cells as a reference, or template.
· Translation - it is part of the process of gene expression. In translation, messenger RNA (mRNA) produced by transcription is decoded by a ribosome complex to produce a specific amino acid chain, or polypeptide, that will later fold into an active protein.
· Translocation - a chromosome translocation is a chromosome abnormality caused by rearrangement of parts between nonhomologous chromosomes.
· Triplet - the genetic code defines how sequences of these nucleotide triplets, called codons, specify which amino acid will be added next during protein synthesis.
· tRNA - a Transfer RNA is an adaptor molecule composed of RNA, typically 73 to 94 nucleotides in length, that serves as the physical link between the nucleotide sequence of nucleic acids and the amino acid sequence of proteins.
At the end of this unit of work you should be able to use the core knowledge listed in the statements below to describe, explain and discuss aspects of cell structure and function. Questions may be presented to you in novel or applied situations that will require you to recognise and link these ideas together.
1. Describe the structure of nucleic acids and the nature of the genetic code
2. Describe the structure and function of DNA and RNA.
3. Describe the nature of the genetic code is and state the function of this code.
4. Describe the process of protein synthesis.
5. Explain the role of the DNA sequence in determining the structure of a protein
6. Describe the structure, function and significance of proteins.
7. Describe the structure, function and role of enzymes in controlling pathways.
8. Explain how the phenotype is determined via metabolic pathways.
9. Describe the control of gene expression in eukaryotes.
10. Describe mutagens and give examples.
11. Describe the effect of gene mutations; identify types of gene mutations and explain the range of potential consequences
of these on the expression of the genotype and phenotype.
12. Describe the effect of block mutations; identify types of block mutations and the range of potential consequences of these
on the expression of the genotype and phenotype.
13. Describe the effect of the environment on expression of the phenotype.
14. Show understanding of gene expression by using the core knowledge to link ideas e.g. in justifying, relating, evaluating,
comparing and contrasting or analysing.
15. Communicate ideas clearly and succinctly using the biological language relevant to this topic.