unit 4 Flashcards
DNA – Structure related to function (7)
- stable due to numerous hydrogen bonds so can be passed on from generation to generation;
- weak hydrogen bonds between strands are easily broken for DNA replication or protein synthesis;
- large so can carry a lot of genetic information;
- base pairs are contained within the helix and held in place by the strong sugar-phosphate backbone;
- complementary base pairs allow the synthesis of an identical daughter molecule;
- 2 strands so both can act as templates;
- helical shape means that it can be coiled so compact for storage
DNA – Degenerate and Non-overlapping (2)
- Degenerate: more than one (base) triplet for each amino acid;
- Non-overlapping: each base is part of only one triplet;
DNA – Comparing DNA and mRNA (6)
- DNA double stranded/double helix and mRNA single-stranded;
- DNA (very) long and RNA short;
- Thymine/T in DNA and uracil/U in RNA;
- Deoxyribose in DNA and ribose in RNA;
- DNA has base pairing and mRNA doesn’t/ DNA has hydrogen bonding and mRNA doesn’t;
- DNA has introns/non-coding sequences and mRNA doesn’t;
Comparing mRNA and tRNA (3)
- mRNA longer;
- mRNA is a straight molecule but tRNA is a folded molecule/clover-leaf shaped molecule;
- mRNA contains hydrogen bonds but tRNA has hydrogen bonds;
Define the term exon.
Base sequence coding for polypeptide/sequence of amino acids
Which two molecules are ribosomes made from? (2)
- One of RNA/ribonucleic acid(s)/nucleotide(s)/nucleic acid(s)/rRNA/ribosomal RNA/ribosomal ribonucleic acid;
- One of protein(s)/polypeptide(s)/amino acid(s)/ peptide(s)/ribosomal protein
Name the proteins associated with DNA
Histone
Differences between prokaryotic DNA and
Eukaryotic DNA (5)
(eukaryote v prokaryote
1. (Associated with) histones/proteins v no histones/proteins;
2. Linear v circular;
3. No plasmids v plasmids; Do not credit if suggestion that prokaryotic DNA only exists as plasmids.
4. Introns v no introns;
5. Long(er) v short(er);
Translation – Describe translation (7)
- mRNA binds to ribosome; 2. ribosome moves to start codon/AUG
- Idea of two codons/binding sites;
- (Allows) tRNA with anticodons to bind/associate with codon on mRNA;
- tRNA brings specific amino acid;
- mRNA moves along to the next codon;
- (Catalyses) formation of peptide bond between amino acids (held by tRNA molecules);
Transcription – Describe transcription (7)
- DNA strands separate by breaking hydrogen bonds;
- (Only) one of the strands is used as a template (to make mRNA);
- Complementary base pairing so A to U, T to A, C to G, G to C;
- (RNA) nucleotides joined by RNA polymerase;
- Forms phosphodiester bonds
- Pre-mRNA formed;
- Splicing/ introns removed to form mRNA
Translation – Role of ribosome (5)
- mRNA binds to ribosome; 2. Idea of two codons/binding sites;
- (Allows) tRNA with anticodons to bind/associate;
- (Catalyses) formation of peptide bond between amino acids (held by tRNA molecules);
- Moves along (mRNA to the next codon)/translation described
Translation – Role of tRNA (4)
- anticodon complementary to codon/reads message on mRNA;
- specific amino acid;
- carried/transferred (to ribosome);
- correct sequence of amino acids along polypeptide;
Describe how a phosphodiester bond is formed between two nucleotides within a DNA molecule.
- Condensation (reaction)/loss of water;
2 between phosphate and deoxyribose;
3 (catalysed by) DNA Polymerase
What is a gene
A sequence of DNA nucleotides that codes for a polypeptide;
The genome is…..
(The) complete set of genes in a cell. OR (All) the DNA in a cell/organism;
Meiosis – Causes of Variation (6)
- Homologous chromosomes pair up;
- Chiasmata formed
- Independent segregation; 4. Maternal and paternal chromosomes are re-shuffled in any combination; 5. Crossing over leads to exchange of parts of (non-sister) chromatids/alleles between homologous chromosomes;
- (Both) create new combinations of alleles
Define mutation
A change in the base sequence of DNA, results in a new allele
The proteome is…..
(The full) range/number of different proteins that a cell is able to produce (at a given time);
OR
(The full) range/number of different proteins the genome/DNA is able to code for;
Describe how the process of meiosis results in haploid cells.
- DNA replication (in interphase) creates two identical chromatids;
- (meiosis has) two nuclear divisions;
- (first division) Homologous pairs separated
- (second division) sister chromatids separated
Meiosis – Process of Crossing Over (4)
- Homologous pairs of chromosomes associate / form a bivalent;
- Chiasmata(ta) form;
- (Equal) lengths of (non-sister) chromatids / alleles are exchanged;
- Producing new combinations of alleles;
What is meant by the degenerate code?
More than one codon codes for a single amino acid;
Mutation - How does mutation cause change in enzyme function? (3)
- Change in amino acid / (sequence of) amino acids / primary structure;
- Change in hydrogen / ionic / disulphide bonds alters tertiary structure / active site (of enzyme);
- Substrate not complementary / cannot bind (to enzyme / active site) / no enzyme- substrate complexes form;
Mutation - How does mutation cause change in protein (receptor) structure? (4)
- Change in DNA base (sequence);
- Change in amino acid (sequence)/primary structure;
- Alters (position of) hydrogen/ionic/disulfide bonds;
- Change in tertiary structure (of receptor);
Define the term mutagenic agent.
(A factor that) increases (the rate of) mutations;
Mutation – Mutation leading to evolutionary changes/phylogenetic relationships
- Mutations change base / nucleotide (sequence);
- (Causing) change in amino acid sequence;
- Mutations build up over time;
- Few(er) mutations / differences (in amino acid / base / nucleotide sequence / primary structure) in closely related species;
- Closely related species have recent common ancestor
Name ways which increase genetic variation in a population
- Mutation;
- Meiosis – crossing over and independent segregation
- Random fertilisation/random fusion of gametes
Define how a mutation can have a positive effect on an individual and no effect on a individual
No effect because:
1. Genetic code is degenerate/codon codes for the same amino acid
2. Mutation is in an intron
3. Creates a recessive allele which does not affect phenotype
Positive effect because:
4. (new allele) increases chance of survival
Define genetic diversity
the number of different alleles of genes in a population.
Describe how a student made a 1 in 10 dilution and then used this to make a 1 in 1000 dilution of the original liquid culture of bacteria.
- 1 part bacterial culture to 9 parts water
- Mix
- Repeat using 9 parts fresh (sterile) liquid and 1 part of 10–1 and 10–2 dilutions to make 10–3 dilution;
Why would a 1 in 10 dilution not be appropriate to use to determine cell numbers?
- Count unlikely to be accurate / repeatable / reproducible / reliable
- Because too many cells; Or cells will be overlapping
Describe the aseptic techniques used to transfer
bacterial culture onto an agar plate.
- Use sterile pipette/syringe 2. Flame top of the bottle
- Lift lid of agar plate at an angle
- Use sterile spreader
- Place pipette/spreader onto disinfectant
Define Species
Can interbreed to produce fertile offspring
Explain how the use of antibiotics has led to antibiotic-resistant strains of bacteria.
- Some bacteria have alleles for resistance
- Exposure to antibiotics creates a selection pressure 3. Antibiotics kill bacteria that are not resistant
- Resistance strains survive and reproduce
Describe the principles of natural selection in the
evolution of a population.
Random mutation can result in new alleles of a genes.
Many mutations are harmful but, in certain environments, the new allele of a gene might benefit its possessor, leading to increased reproductive success.
The advantageous allele is inherited by members of the next generation.
over many generations, the new allele increases in frequency in the population.
Give the taxonomic levels of classification
Domain, Kingdom, Phylum, Class, Order, Family, Genus, Species
Which two taxa make up an organisms binomial name?
Genus species
Describe how genetic diversity between species can be measured
- Comparing observable characteristics/features
- Comparing base sequences of DNA
- Comparing Base sequences of mRNA
- Comparing amino acid sequences (of the same protein)
Explain what is meant by a phylogenetic group?
(Grouped according to) evolutionary links/history/relationships /common ancestry;
Classification is hierarchical – what does this mean?
smaller groups are placed within larger groups, with no overlap between groups.
Courtship Behaviour – The importance (3)
- enables male I female to recognise opposite sex;
- enables recognition of own species;
- synchronises mating behaviour
Courtship Behaviour – How it increases probability of mating (4)
- Attracts mate of the same species;
- Indication of sexual maturity / fertility / synchronises mating;
- Stimulates release of gametes;
- Formation of a pair bond / bond between two organisms (to have / raise young)
What is species richness
(A measure of) the number of (different) species in a community;
Why is calculation of index of diversity more reliable than species richness?
(Index of diversity also) measures abundance / number / population (size) of each species; (So useful because) may be many of some species
Suggest one reason the scientists used biomass
instead of the number of individuals of each plant
species when collecting data to measure diversity.
Individual organisms could not be identified/separated OR
Too small/numerous to count individuals
Farming Techniques – Pros and Cons to farmer for Planting Hedges
(Pros)
1. Greater (bio)diversity so increase in predators of pests
2. Increase in predators of pests so more yield/income 3. Increase in pollinators so more yield/income
(Cons)
1. Reduced land area for crop growth/income
2. Greater (bio)diversity so increase pest population
3. Increase pest population so less yield/income
4. Increased competition so less yield/income
Outline a method the ecologists could have used to determine the plant species richness at one
site.
- A method of selecting sampling sites at random e.g. random number generator
- Use of quadrat;
- Identify (plant) species (at site / in each quadrat)
Suggest one ethical argument for maintaining
biodiversity.
Prevent extinction / loss of populations / reduction in populations / loss of habitats
Suggest one economic argument for maintaining
biodiversity.
Medical or pharmaceutical uses of plants Tourism Agriculture Saving forest communities
