Genetic information, variation & relationships Flashcards
(54 cards)
1
Q
Define the term exon.
A
Base/nucleotide/triplet sequence coding for polypeptide/sequence of amino acids/primary structure;
2
Q
Give two structural differences between a molecule of messenger RNA (mRNA) and a molecule of transfer RNA (tRNA). [2]
A
- 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;
3
Q
What is an allele?
A
- (Different) form/type/version of a gene
OR
- different base sequence of a gene;
4
Q
What is a gene?
A
- A sequence of DNA (nucleotide) bases that codes for a (specific) polypeptide;
- ‘codes for a functional RNA’
- ‘codes for rRNA/tRNAs’
- ‘codes for a sequence of amino acids/primary structure’
5
Q
What is a TRIPLET?
A
A sequence of 3 DNA (nucleotide) bases
6
Q
What is a CODON?
A
A sequence of 3 mRNA (nucleotide) bases
7
Q
What is an ANTICODON?
A
A sequence of 3 tRNA (nucleotide) bases that is complementary to a specific codon.
8
Q
If a DNA sequence is:
TAG.GCG.AAT.CCG
What is the mRNA sequence?
A
AUC.CGC.UUA.GGC
9
Q
Describe the structure of DNA and the structure of a chromosome. [5]
A
- Polymer of nucleotides; Accept ‘polynucleotide’
- (Nucleotide) consists of deoxyribose, phosphate and an organic/nitrogenous base;
- Phosphodiester bonds (between nucleotides);
- DNA double helix held by H bonds OR 2 strands held by H bonds;
- (Hydrogen bonds/pairing) between adenine, thymine and cytosine, guanine;
Reject adenosine and cysteine
- DNA is associated with histones/proteins;
- (During mitosis/when visible) chromosome consists of two chromatids joined at a centromere;
10
Q
Describe Transcription in Eukaryotes [5]
A
- 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 mature mRNA);
11
Q
Describe Translation [5]
A
- (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;
- (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;
12
Q
Describe the role of ATP in the process of translation in protein synthesis. [2]
A
- Releases energy;
- (So) peptide bonds form between amino acids OR (So) amino acid joins to tRNA;
13
Q
A mutation in a gene coding for an enzyme
could lead to the production of a non-functional enzyme. Explain how [3]
A
- 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;
14
Q
Not all mutations in the nucleotide sequence of a gene cause a change in the structure of a polypeptide. Give two reasons why.
A
- Triplets code for same amino acid
- Occurs in introns /non-coding sequence;
15
Q
Define ‘gene mutation’ and explain how a gene mutation can have:
* no effect on an individual
* a positive effect on an individual.
A
- (Definition of gene mutation)
- Change in the base/nucleotide (sequence of chromosomes/DNA);
- Results in the formation of new allele;
- (Has no effect because)
- 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.
- Does change amino acid but no effect on tertiary structure;
- (New allele) is recessive so does not influence phenotype;
- (Has positive effect because)
- 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’.
- May result in increased reproductive success OR May result in increased survival (chances);
16
Q
Name the type of gene mutation that has no effect on the Primary structure of a polypeptide.
A
Substitution (Silent)
17
Q
Explain how natural selection produces changes within a species. [5]
A
- Variation between members of population / species is caused by mutation;
- 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
18
Q
Name 3 types of single point gene mutation.
A
- Addition
- Deletion
- Substitution
19
Q
Name 4 types of chromosomal mutation
A
- Duplication
- Inversion
- Translocation
- Non-disjunction
20
Q
When do most mutations occur?
A
DNA replication;
S phase of Interphase
21
Q
Which process may lead to:
- Inversion and Translocation mutations
- Non-disjunction mutations?
A
- Meiosis 1
- Meiosis 2
22
Q
State 3 factors that affect reproductive success or survival?
A
- Competition (Inter or Intraspecific)
- Predation
- Pathogens
23
Q
Name 4 selection pressures
A
Any 4 Biotic or Abiotic factors
24
Q
Why is a Log scale graph used?
A
There is a large range in ……….(y axis label)
25
If the T value is 15 and the critical value is 3.4. What can you conclude?
Use the words ***probability*** and ***chance*** in your answer.
The ***probability*** that the difference is due to ***chance*** is less than 5%.
The **difference** is **significant**.
**Reject** the Null hypothesis.
26
When would you use the **Student's T test?**
Comparing the **difference between** TWO **means**
27
What is a species? [2]
* Group of similar organisms / organisms with similar features / organisms with same genes / chromosomes;
* Reproduce to produce fertile offspring;
28
Explain what is meant by a heirarchy [2]
* Groups within groups;
* No overlap (between groups);
29
Explain what is meant by a phylogenetic group.
(Grouped according to) evolutionary links/history/relationships / common ancestry;
30
Describe how organisms are grouped in a phylogenetic classification system.
* Hierarchy (of groups) with no overlaps OR (smaller) groups within (larger) groups with no overlaps;
* (Grouped) according to evolutionary origins/relationships/history;
31
Explain what is meant by genetic
diversity.
* Difference in DNA/base sequence/alleles/genes;
32
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;
33
Define species richness.
The number of different species in a community
34
What is meant by a 'community'.
All the individuals of all the species living in the same area at the same time.
35
Explain how selection produces changes within a species. [5]
* Variation [caused by mutation] between members of population / species;
* (Biotic or Abiotic selection pressures) 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 and changes allelic frequencies
36
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;
37
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;
* Compare RNA base sequence;
* Compare sequence of amino acids /primary structure (of named / same protein);
38
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;
39
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);
40
Suggest one economic argument for maintaining biodiversity.
* A suitable example of how some species may be important financially e.g.
* medical / pharmaceutical uses;
* commercial products / example given;
* tourism;
* agriculture;
* saving local forest communities;
41
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;
* Fewer variety of food sources/types of food/feeding sites;
* Few habitats/ niches;
* Fewer (species of) herbivore so few (species of) carnivores;
* Aspect of agriculture (killing insects);
42
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**;
43
It was not possible for the scientists to measure the length of every filament and the surface area of every lamella.
Suggest how they collected data to give a reliable mean for these variables. [2]
1. Random samples;
Allow in context of fish or gills
2. Large sample size;
44
Define genome and proteome. [2]
(Genome)
1. Complete set of genes in a cell OR (All) the DNA in a cell OR (All) the genes/alleles/genetic material in a cell
OR
The total number of DNA bases in a cell;
Reject ‘all the DNA/genes within a species/population’
(Proteome)
2. (Full) range of proteins that a cell can produce
OR
(Full) range of proteins coded for by the cell’s DNA/genome;
45
In taxonomy, an organism is identified by referring to the species name and the genus name.
What term is used to describe this method of naming organisms?
Binomial
46
What is the full scientific binomial name for the Human species?
*Homo sapien*
47
What are the rules for the binomial naming of species?
Genus followed by species
Only the first letter is capitalised
Written in *italics* or underlined
*Homo sapien* can be written as *H.sapien*
48
What are the levels of heirarchy in classification?
Domain
Kingdom
Phylum
Class
Order
Family
Genus
Species
49
Which taxon has the least genetic diversity?
species
50
Which taxon has the least number of groups within it?
Domain
51
Name the 3 domains
Eukarya
Archaea
Eubacteria
52
In the 3 Domain system of taxonomy, what are the 4 Kingdoms?
Plantae
Animalia
Protista
Fungi
53
Genetic variation within a species is increased during meiosis by crossing over and the independent segregation of homologous chromosomes.
Apart from mutation, explain one other way genetic variation within a species is increased.
1. Random fusion of gametes OR Random fertilisation;
2. (Produces) new allele combinations OR (Produces) new maternal and paternal chromosome combinations;
54
Define 'population' [2]
* All the individuals of the same species in the same area at the same time;
* can interbreed to produce fertile offspring.
