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DNA and Proteins
DNA and Proteins definitions 2021 revision
| Term | Definition |
|---|---|
| What does DNA replication allow for? | Genetic information to be inherited |
| What is a gene? | Consists of a unique sequence of nucleotides that codes for a functional protein or RNA molecule |
| What does a gene code for? | A functional protein or RNA molecule |
| The rate of an enzyme-controlled reaction is affected by? | Concentrations of reactants |
| In eukaryotes DNA is... | bound to proteins in linear chromosomes, which are found in the nucleus |
| In prokaryotes (and mitochondria and chloroplasts) DNA is... | Unbound and circular in the cytosol |
| What is an exon? | Coding DNA - transcribed into a molecule of mRNA and translated into a polypeptide or protein molecule |
| What is an intron? | Non-coding DNA - only transcribed into an RNA molecule. Does not code for proteins |
| What does protein synthesis involve? | Transcription of a gene into messenger RNA, and translation of mRNA into an amino acid sequence at the ribosomes. |
| Where does transcription occur in eukaryotes? | In the nucleus |
| The folding of a polypeptide to form a protein with a unique three-dimensional shape is determined by... | Its sequence of amino acids |
| Enzymes have specific functions and are affected by factors including... | temperature, pH, presence of inhibitors |
| Adenine binds with... | Thymine |
| Guanine binds with... | Cytosine |
| The base-pairing rules and method of DNA replication are... | Universal |
| What is a mutation? | A change in the DNA sequence |
| The base sequence of DNA can be determined by | Electrophoresis |
| The results of electrophoresis may be displayed in an... | Electropherogram |
| The results of electrophoresis can be used to construct... | DNA profiles |
| DNA profiling identifies... | The unique genetic makeup of individuals |
| DNA sequencing enables... | Mapping of species' genomes |
| Mutations in genes and chromosomes can result from... | Errors in DNA replication or cell division, or from damage by physical or chemical factors in the environment. |
| Mutation rate can be increased by... | Ionising radiation, mutagenic chemicals, viruses |
| Segments of DNA can be multiplied using | The polymerase chain reaction (PCR) |
| What are the three parts that make up a nucleotide? | A sugar, phosphate group, and nitrogenous base |
| The weak bonds between strands of DNA allow for | Replication to occur |
| Why is complementary base pairing important? | It allows for the base pairs to be arranged in the most favourable way. It is essential in forming the helical DNA structure. |
| Describe semi-conservative replication? | Each DNA molecule made consists of one old or original strand and one newly synthesised strand |
| Describe RNA splicing | During RNA splicing, introns are removed and exons joined to form a contigous coding sequence |
| Describe the relationship between DNA codons, RNA codons, anticodons and amino acids | It is the complementary binding of the codon (mRNA) with the anticodon (tRNA) that ensures the correct amino acid is placed in its correct position on the growing polypeptide chain. |
| What is the primary structure of a protein? | Determined by the sequence of based on the mRNA that codes for its amino acid sequence |
| Proteins are essential to... | Cell structure and function |
| What is the secondary structure of a protein? | Hydrogen bonding of peptide backbone causes amino acids to form beta sheets or alphas helices |
| What is the tertiary structure of a protein? | 3D folding pattern of a protein due to side chain interactions |
| What is the quaternary structure of a protein? | Protein consisting of more than one polypeptide chain |
| Explain why the three dimensional shape of a protein is critical to its function | It determines whether the protein can interact with other molecules |
| What are enzymes | Globular proteins that are specific for their substrate and increase reaction rates by lowering activation energy |
| How to enzymes increase reaction rates | By lowering activation energy |
| Describe induced fit model | Enzyme binds with substrate to form an enzyme substrate complex. Active site changes shape slightly to fit the substrate exactly which puts strain on the chemical bonds. |
| What is competitive inhibition | Competing with the substrates for the active site |
| What is non-competitive inhibition | Doesn't bind to the active site, binds to another part of the cell, however pressure on the cell still changes the shape of the active site and therefore substrate can no longer bind |
| List examples of functional proteins | Enzymes, Receptors, Hormones, Antibodies, Regulatory proteins |
| What is a repressor protein? | Prevent transcription by binding to the DNA to repress it |
| What is an activator protein? | Promote transcription by binding to DNA to activate it |
| Functions of proteins? | Catalyzing reactions, cellular communication, providing structure, regulation of genes, contraction of muscles |
| What is DNA methylation? | Addition of a methyl group to DNA - altering gene expression |
| What is the most methylated base? | Cytosine |
| Can methylated genes be passed on to the next generation? | Yes |
| What causes cancer? | Uncontrolled cell division |
| Epigenetic changes that causes DNA methylation to either tumour suppressor genes or DNA repair genes can ... | Lead to excessive production of cells and thus tumours |
| Epigenetic changes can lead to | Phenotypic differences between identical siblings, phenotypic differences between clones, and may cause human diseases. |
| Mutations in somatic body cells will be | Confined to the individual organism in which they occur |
| When mutations occur in germline cells there is potential that they will be | Passed onto the next generation |
| Explain how inheritable mutations can lead to changes in the characteristics of descendants | If these changes are inherited from gametes, they may lead to absent or altered proteins in the offspring |
| Three stages of PCR? | Denaturing (heating to break hydrogen bonds between strands of target DNA), Annealing (temp cooled, allowing primers to anneal to the separated strands), Extension (temperature increased to optimum temperature of DNA polymerase, extending primers) |
| Describe gel electrophoresis | Separates DNA strands according to their size and charge resulting in a banding pattern |
| What happens to the negatively charged fragments when the current is turned on in an electrophoresis | They move towards the positive electrode |
| Smaller fragments move ... than shorter fragments (electrophroesis) | Faster |
| Ethical issues with the collection of genetic information | Ethical (ownership, discrimination), economic (costs money), cultural (unnatural, invasive, stigmatism) |
| Describe the role of a DNA/ RNA probe | They're antibodies used to isolate a specific gene |
| Provide a method of isolating a specific gene | DNA/RNA probe |
| How does a DNA/RNA probe work | Single stranded DNA or RNA sequence that is complementary to part of a gene. Used to identify and locate a gene. Gene can then be isolated and inserted into the cell of another organism |
| What is a plasmid? | Circular piece of DNA (bacterial cells) - separate from the main chromosome - use as a vector in genetic engineering |
| What is bacterial transformation | A process in which DNA is incorporated into bacteria |
| Transfer of genes between species can be done via... | Viral vectors, Microinjection |
| Benefits of CRISPR | Made genetic engineering faster, more affordable and more accurate |
| What does Cas9 protein do? | Cut DNA by the base sequence of the RNA that is loaded into it - can be used to switch genes on and off |
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biology2021
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