3.4 Genetic information, variation and relationships between organisms

Question 1

Prokaryotic vs Eukaryotic DNA

Answer 1

Eukaryotic is linear, prokaryotic is circular
Eukaryotic is longer
Eukaryotic is associated with proteins, prokaryotic is not
Eukaryotic is found within the nucleus, prokaryotic is found in cytoplasm
Eukaryotic contains introns

Question 2

What proteins are DNA associated to

Answer 2

Histones

Question 3

Nucleus DNA vs mitochondria/chloroplast DNA

Answer 3

Mitochondria/chloroplast DNA is shorter, circular, not associated with proteins and no introns

Question 4

Gene definition

Answer 4

A base sequence of DNA that codes for:
- the amino acid sequence of a polypeptide
- a functional RNA (including ribosomal RNA and tRNAs).

Question 5

What is a genes fixed position called

Answer 5

A Locus

Question 6

Triplet definition

Answer 6

A sequence of 3 bases that codes for a specific amino acid

Question 7

Coding DNA

Answer 7

Exons

Question 8

Non-coding DNA

Answer 8

introns

Question 9

Why does most DNA not code for polypeptides

Answer 9

Presence of introns and stop/start base sequences. Also repeats of

Question 10

Properties of DNA

Answer 10

Degenerate - multiple triplets code for the same amino acid
Universal - all organisms DNA contain the same 4 bases (A,T,C,G)
Non-overlapping - each triplet is only read once

Question 11

Genome definition

Answer 11

The complete set of genes in a cell

Question 12

Proteome definition

Answer 12

Full range of proteins the cell is able to produce

Question 13

mRNA vs tRNA structure

Answer 13

Both are single stranded molecules
mRNA is linear, tRNA is clover shaped
tRNA has an anticodon
tRNA has an amino acid binding site
mRNA has a base sequence complimentary to DNA

Question 14

Transcription

Answer 14

1. DNA strands separate by breaking Hydrogen bonds
2. Only one strand acts as a template
3. Free RNA nucleotides line up with complimentary pairs (A to U, C to G), forming hydrogen bonds
4. Uracil instead of thymine
5. Adjacent RNA nucleotides joined by RNA polymerase, forming phosphodiester bonds
6. pre-mRNA spliced to remove introns

Question 15

Difference between eukaryotic and prokaryotic transcription

Answer 15

Eukaryotic transcription forms pre-mRNA which is spliced to remove introns to form mRNA. Prokaryotic transcription forms mRNA

Question 16

Translation

Answer 16

1. mRNA leaves nucleus through nuclear pores
2. Ribosome attaches to mRNA
3. tRNA brings a specific amino acid and its anticodon binds to complimentary codon on mRNA
4. adjacent amino acids are joined by peptide bonds
5. using ATP
6. tRNA is released
7. Ribosome moves along mRNA till polypeptide has been synthesised

Question 17

Mutation definition

Answer 17

A change in the base sequence of chromosomes

Question 18

What can increase the rate of gene mutation

Answer 18

Mutagenic agents

Question 19

How does a non-disjunction mutation arise

Answer 19

Through meiosis

Question 20

Meiosis

Answer 20

1. DNA is replicated
2. Meiosis 1. First cell division. Crossing over of homologous chromosomes and independent segregation of homologous chromosomes causes variation.
3. Meiosis 2. Second cell division. Very similar to mitosis
4. Formation of 4 haploid daughter cells

Question 21

How is variation caused

Answer 21

1. Independent segregation of homologous chromosomes
2. Crossing over of homologous chromosomes
3. Random fertilisation of gametes
4. Random mutation
5. Produces new combinations of alleles

Question 22

Differences between mitosis and meiosis

Answer 22

1. One division in mitosis, two in meiosis
2. Daughter cells genetically identical in mitosis, genetically different in meiosis
3. Two cells produced in mitosis, four in meiosis
4. Diploid to diploid in mitosis, diploid to haploid in meiosis
5. Segregation of homologous chromosomes and crossing over of homologous chromosomes only in meiosis

Question 23

Genetic diversity definition

Answer 23

The number of different alleles of genes in a population

Question 24

Natural selection

Answer 24

1. Variation in population due to mutation
2. Allele for _______
3. Individuals with allele more likely to survive and reproduce
4. Allele frequency increases

Question 25

Directional selection

Answer 25

When natural selection favours the extreme allele Example: Abiotic resistance in bacteria

Question 26

Stabilising selection

Answer 26

When natural selection favours the average allele Allele frequency remains constant Example: Human birth weight

Question 27

Disruptive selection

Answer 27

When both extremes of alleles are favoured over intermediate ones. Example: Cuttlefish mating

Question 28

3 types of adaptations and examples

Answer 28

Anatomical - giraffe long neck Physiological - venom production Behavioural - hunting/migration

Question 29

Species definition

Answer 29

Organisms that are able to breed to produce living fertile offspring

Question 30

Courtship behaviour

Answer 30

Allows members of the same species to recognise each other Allows organisms to synchronise mating Allows organisms to for a pair bond Allows organisms to recognise mates capable of breeding, leading to successful mating Allows organisms to get mate in right psychological state to breed

Question 31

What is a phylogenetic classification

Answer 31

A system that attempts to arrange species into groups based on their evolutionary origins and relationships. It uses a hierarchy in which smaller groups (taxes) are placed within larger groups, with no overlap between groups.

Question 32

Order of classification

Answer 32

Kingdom Phylum Class Order Family Genus Species

Question 33

What is the binomial system

Answer 33

Naming using the genus and species e.g. homo sapien

Question 34

3 domain system

Answer 34

Eukaryota Bacteria Archaea

Question 35

Species richness definition

Answer 35

Measure of the different number of species in an ecosystem

Question 36

Index of diversity

Answer 36

An index of diversity describes the relationship between the number of species in a community and the number of individuals in each species.

Question 37

Why is index of diversity more useful than species richness

Answer 37

Takes into account number of each organism of a species

Question 38

Index of diversity equation

Answer 38

d = N(N – 1) ÷ ∑n(n – 1) N - total number or organisms of ALL species n - total number of organisms of EACH species

Question 39

Farming techniques (5)

Answer 39

Use hedgerows instead of fences Crop cycling Growing multiple crops in one field preserving wetlands Use less herbicides and insecticides

Question 40

Methods of comparing genetic diversity

Answer 40

Frequency of measurable characteristics Base sequence of DNA Base sequence of mRNA Amino acid sequence of the proteins encoded by DNA/mRNA

Question 41

Why is comparing frequency of measurable characteristics not always accurate

Answer 41

1. May be coded for by multiple genes 2. May be environmental characteristics 3. Could have arisen separately