4: Genetic information, variation and relationships between organisms Flashcards
Define the term exon.
Base/nucleotide/triplet sequence coding for polypeptide/sequence of amino acids/primary structure;
Describe Transcription in Eukaryotes [5]
- Hydrogen bonds (between DNA bases) break;
- (Only) one DNA strand acts as a template;
- (Free) RNA nucleotides align by complementary base pairing;
- (In RNA) Uracil base pairs with adenine (on DNA) OR (In RNA) Uracil is used in place of thymine;
- RNA polymerase joins (adjacent RNA) nucleotides;
- (By) phosphodiester bonds (between adjacent nucleotides);
- Pre-mRNA is spliced (to form mRNA) OR Introns are removed (to form mRNA);
Describe Translation [5]
- (mRNA attaches) to ribosomes OR (mRNA attaches) to rough endoplasmic reticulum;
- (tRNA) anticodons (bind to) complementary (mRNA) codons;
- tRNA brings a specific amino acid;
- Amino acids join by peptide bonds via condensation reaction;
- (Amino acids join together) with the use of ATP;
- tRNA released (after amino acid joined to polypeptide);
- The ribosome moves along the mRNA to form the polypeptide;
Describe the role of ATP in the process of translation in protein synthesis.
- Releases energy;
- (So) peptide bonds form between amino acids OR (So) amino acid joins to tRNA;
Give two structural differences between a molecule of messenger RNA (mRNA) and a molecule of transfer RNA (tRNA).
- mRNA does not have hydrogen bonds / base pairing, tRNA does; OR mRNA is linear / straight chain, tRNA is cloverleaf;
- mRNA does not have an amino acid binding site, tRNA does;
- mRNA has more nucleotides;
- (Different) mRNAs have different lengths, all tRNAs are similar / same length;
- mRNA has codons, tRNA has an anticodon;
What is an allele?
(Different) form/type/version of a gene / different base sequence of a gene;
Formed via mutation.
What is a gene?
- A sequence of DNA (nucleotide) bases that codes for a polypeptide;
- ‘codes for a functional RNA’
- ‘codes for rRNA/tRNAs’
- ‘codes for a sequence of amino acids/primary structure’
Define degenerate code
More than one codon for one amino acid
Explain what the term non-overlapping DNA means.
A base from one triplet cannot be used in an adjacent triplet
Explain how selection occurs in living organisms [5]
- Variation due to mutation;
-
Different
selection pressures environmental/abiotic/biotic conditions / Different
selection pressures; - Selection for different/advantageous, features/characteristics/mutation/allele;
- Differential reproductive success / (selected) organisms survive and reproduce;
- Leads to change in allele frequency;
- Occurs over a long period of time;
A mutation in a gene coding for an enzyme
could lead to the production of a non-functional enzyme. Explain how [5]
- Change in base sequence (of DNA/gene);
- Change in amino acid sequence / primary structure (of enzyme);
- Change in hydrogen/ionic/ disulphide bonds;
- Change in the tertiary structure/active site (of enzyme);
- Substrate not complementary/cannot bind (to enzyme / active site) / no enzyme-substrate complexes form;
Not all mutations in the nucleotide sequence of a gene cause a change in the structure of a polypeptide. Give two reasons why
- Triplets code for same amino acid
- Occurs in introns /non-coding sequence;
Define genome
(All) the DNA in a cell/organism;
(all) the ‘genes’/alleles’ ‘genetic material/code’ in a cell/organism/ person’
Define proteome
(The proteome is the full) range of / number of different proteins that a cell is able to produce (at a given time);
OR
(The proteome is the full) range of / number of different proteins the genome / DNA is able to code for;
Define ‘gene mutation’ and explain how a gene mutation can have:
* no effect on an individual
* a positive effect on an individual.
[6]
(Definition of gene mutation)
1. Change in the base/nucleotide (sequence of chromosomes/DNA);
2. Results in the formation of new allele;
(Has no effect because)
3. Genetic code is degenerate (so amino acid sequence may not change); OR
Mutation is in an intron (so amino acid sequence may not change);
Accept description of ‘degenerate’, eg some amino acids have more than one triplet/codon.
4. Does change amino acid but no effect on tertiary structure;
5. (New allele) is recessive so does not influence phenotype;
(Has positive effect because)
6. Results in change in polypeptide that positively changes the properties (of the protein) OR Results in change in polypeptide that positively changes a named protein; For ‘polypeptide’ accept ‘amino acid sequence’ or ‘protein’.
7. May result in increased reproductive success OR May result in increased survival (chances);
Describe two aseptic techniques she would have used when transferring a sample of broth culture on to an agar plate.
Explain why each was important.
- Keep lid on Petri dish OR Open lid of Petri dish as little as possible.
- To prevent unwanted bacteria contaminating the dish.
OR - Wear gloves / Wear mask / Wash hands;
- To prevent contamination from bacteria on hands / mouth / Prevent spread of bacteria outside the lab;
OR - Use sterile pipette / Flame the loop / Flame the neck of the container of the culture;
- To maintain a pure culture of bacteria
Bacteria are able to synthesis human proteins. Suggest why.
Mechanisms of Transcription and Translation are UNIVERSAL.
The genome is…….
(The) complete set of genes in a cell/organism
OR
(All) the DNA in a cell/organism;
The proteome is…….
Range of proteins that a cell/organism can produce
OR
Range of proteins the genome/DNA can code for;
Suggest and explain one reason why bacteria might not be able to produce every human protein.
Cannot splice (pre-mRNA), so cannot remove introns
OR
Do not have Golgi (apparatus), so cannot process/modify (proteins);
OR
Do not have transcriptional factors (required), so cannot carry out transcription/produce mRNA;
What is a substitution mutation?
- Replacement of a base by a different base (in DNA);
Name 3 types of single point gene mutations.
Addition
Deletion
Substitution
Which mutation can be refered to as a silent mutation and explain why. [4]
- Substitution;
- The genetic/DNA code is degenerate;
- More than one triplet can code for the same amino acid;
- Mutation may not lead to a change in the primary structure / number and seguence of amino acids;
What type of mutation leads to a change in chromosome number?
Non-disjunction of chromatids, during meiosis (II).
How would you calculate the number of cells present after a number of divisions?
1 cell divides 5 times
2^n
= 2^5
= 32
2 to the power n (N=number of divisions)
Define genetic diversity.
The number of different alleles of genes in a
population.
State one example of directional selection.
Antibiotic resistance in bacteria
State one example of stabilising selection.
Human birth weight
State two major factors in evolution and diversity within living organisms.
Adaptation & Selection
State two examples of Natural selection
Stabilising & Directional
Disruptive (leads to speciation, covered in year 13)
How can evolution be measured?
Through changes in allelic frequencies (within a population over time)
What is a species?
- Group of similar organisms / organisms with similar features / organisms with same genes / chromosomes;
- (that can)Reproduce to produce fertile offspring;
Explain what is meant by a heirarchy? [2]
- Groups within groups;
- No overlap (between groups);
Explain what is meant by a phylogenetic group?
(Grouped according to) evolutionary links/history/relationships / common ancestry;
Describe how organisms are grouped in a phylogenetic classification system. [2]
- Hierarchy (of groups) with no overlaps
OR (smaller) groups within (larger) groups with no overlaps; - (Grouped) according to evolutionary origins/relationships/history;
Explain what is meant by genetic
diversity.
Difference in DNA/base sequence/alleles/genes;
The number of species present is one way to measure biodiversity.
Explain why an index of diversity may be a more useful measure of biodiversity. [2]
Also measures number of individuals in a species / different proportions of species;
Some species may be present in low/high numbers;
What is meant by species richness?
The number of different species in a community.
Define community.
All the individuals of all the species living in the same area at the same time.
Explain how natural selection produces changes within a species. [6]
- Variation [caused by mutation] between members of population / species;
- Predation / disease / competition results in differential survival;
- Some have adaptations that favour survival;
- Differential reproductive success / survive to reproduce/ have more offspring/
- Pass on their advantageous alleles /
- Changes allelic frequencies
Describe how comparisons of biological molecules in two species could be used to find out if they are closely related. [3]
Compare:
- DNA base sequence;
- RNA base sequence;
- sequence of amino acids /primary structure (of named / same protein)
In classification, comparing the base sequence of a gene provides more information than comparing the amino acid sequence for which the gene codes. Explain why [3]
- Reference to base triplet/triplet code / more bases than amino acids / longer base sequence than amino acid sequence;
- Introns/non-coding DNA;
- Same amino acid may be coded for / DNA code is degenerate;
Scientists can use protein structure to investigate the evolutionary relationships
between different species.
Explain why. [3]
- Amino acid sequences / primary structure;
- Closer the (amino acid) sequence the closer the relationship;
- (Protein structure) related to (DNA) base/triplet sequence;
A forest was cleared to make more land available for agriculture.
After the forest was cleared the species diversity of insects in the area decreased.
Explain why. (4)
- Decrease in variety of plants / fewer plant species;
- Fewer habitats/niches;
- Decrease in variety of food / fewer food sources;
- Aspect of clearing forest (killing insects) eg machinery, pesticides;
Suggest one ethical argument for maintaining biodiversity.
- Prevent extinction
- loss of populations
- reduction in populations
- loss of habitats
- save organisms for future generations (idea of);
Suggest one economic argument for maintaining biodiversity.
A suitable example of how some species may be important financially e.g.
1. medical / pharmaceutical uses;
2. commercial products / example given;
3. tourism;
4. agriculture;
5. saving local forest communities;
Farmers clear tropical forest and grow crops instead. Explain how this causes the diversity of insects in the area to decrease. [4]
- Lower diversity of plants/ few species of plants/less variety of plants/few plant layers;
- Few sources/types of food/feeding sites;
- Few habitats/ niches;
- Fewer (species of) herbivore so few (species of) carnivores;
- Aspect of agriculture (killing insects);
Describe how courtship behaviour increases the probability of successful mating. [5]
- Attracts/recognises same species;
- Attracts/recognises mate/opposite sex;
- Indication of sexual maturity/ fertility / synchronises mating;
- Stimulates release of gametes;
- Form pair bond;
What system is used to scientifically name organisms?
Binomial system consisting of the name of its genus and species
E.g., Homo sapien
In italics; Genus first - species second; only the first letter of the genus is a capital.
What are the different taxa in classification?
Domain
Kingdom
Phylum
Class
Order
Family
Genus
Species
Delicious-King-Prawn-Curry-Or-Fat-Greasy-Sausages
What are the three domains?
Eukarya
Archaea (Bacteria)
(Eu)bacteria
Name the 4 Eukarya Kingdoms
Animals (Animalia)
Plants (Plantae)
Fungi
Protists (Protoctista)
Quantitative investigations of variation within a species must include……
- Collecting Random samples (removes bias)
- Calculating a mean (of recorded values) and standard deviation (reduces the effect of anomolous data)
- Interpretation of mean values using Student T test (STATS TEST) to detemine if differences are significant.
There are different types of gene mutation.
Which describes incorrectly the effect of the mutation in an exon of a gene.
A) A substitution may not result in a change to the encoded amino acid.
B) An inversion will result in a change in the number of DNA bases.
C) A deletion will result in a frame shift.
D) An addition will result in a frame shift.
B) An inversion will result in a change in the number of DNA bases.
Give one reason why antibiotics are not effective against viruses.
Do not have bacterial structures/enzymes
OR
Do not have metabolic processes/synthesise proteins
OR
Do not have a cell wall/murein/peptidoglycan/glycoprotein;
OR
Do not have ribosomes
