Section 4 - Genetic information, variation and relationships between organisms: 9. Genetic diversity

Question 1

What is a mutation

Answer 1

A change in the arrangement of the bases in an individual gene, or in the structure of the chromosome (leading to changes in the arrangement of genes)

Question 2

What are gene mutations

Answer 2

Changes in the sequence of bases

Question 3

What are the 3 types of gene mutations

Answer 3

• Substitution
• Deletion
• Insertion

Question 4

What is a substitution

Answer 4

When one nucleotide is replaced by another, changing one base in the sequence

Question 5

What is the potential impact of a base substitution

Answer 5

• May have no impact, due to the degenerate code (could code for the same amino acid)
• If the amino acid does change, minimal impact as only one is different

Question 6

What is a deletion

Answer 6

When one nucleotide is lost, so one base is missing from the sequence

Question 7

What is an insertion

Answer 7

When one nucleotide is added, giving an extra base in the sequence

Question 8

What is the potential impact of a base deletion/insertion

Answer 8

Causes a frameshift, as the following triplet codes are all moved along by one, impacting each of the following amino acids
(can completely change the protein structure)

Question 9

What are chromosome mutations

Answer 9

Changes in the structure or number of whole chromosomes

Question 10

What are the 5 types of chromosome mutations

Answer 10

• Deletion
• Duplication
• Inversion
• Translocation
• Whole chromosome mutations

Question 11

What is Gene deletion

Answer 11

When a section of a chromosome is removed

Question 12

What is Gene duplication

Answer 12

When a section of chromosome is added from its homologous partner, giving one chromosome 2 copies of one gene

Question 13

What is Gene inversion

Answer 13

When a section of a chromosome is reversed

Question 14

What is Translocation

Answer 14

When sections of chromosomes are swapped between two chromosomes

Question 15

What are whole chromosome mutations

Answer 15

When an entire chromosome is lost or replaced

Question 16

What is Polyploidy

Answer 16

The process (Chromosome mutations) leading to becoming Polyploid (having more that two sets of chromosomes)

Mainly in plants

Question 17

What is Non-disjunction

Answer 17

When pairs of chromosomes fail to separate in meiosis, leading to one more/less chromosome

Eg. Downs syndrome: Additional chromosome 21

Question 18

What are the possible effects of mutations

Answer 18

• Production of new/superior proteins (Reproductive advantage)
• Neutral mutation (No change, due to degenerate code)
• Production of no/inferior proteins (potentially causing disease and fatality)

Question 19

What is meiosis

Answer 19

Cell division producing 4 daughter cells, each with half the number of chromosomes as the parent

Question 20

What happens during meiosis 1

Answer 20

Homologous chromosomes separate into different cells

Question 21

What happens during meiosis 2

Answer 21

Chromatids from the homologous chromosomes are separated into 4 cells
(same as mitosis, but splits into 4, rather than 2)

Question 22

What is the importance of meiosis

Answer 22

Allows for gametes to be produced with half the number of chromosomes (Haploid number), so when they fuse during fertilisation, the off-spring has the correct diploid number.

Question 23

What is Independent segregation (random assortment)

Answer 23

During meiosis 1, each of the chromosomes in the homologous pair will randomly pass to each daughter cell

Question 24

What is the effect of Independent segregation (random assortment)

Answer 24

As each chromosome will have a different allele of the same gene, the arrangement of the pair before separation in meiosis 1, and the following division of meiosis 2, will impact the allele of the daughter cell

Question 25

What is genetic recombination by crossing over

Answer 25

• When lined up before separation in meiosis 1, chromatids of the homologous chromosomes can become twisted
• This leads to portions of the chromatids being broken off and exchanged between the chromosomes, producing new combinations of alleles

Question 26

What is the chiasma

Answer 26

The point where two chromatids cross during genetic recombination

Question 27

How many possible chromosome combinations can occur in the daughter cell as a result of meiosis (not regarding genetic recombination, which would increase this)

Answer 27

2^n

(n = number of homologous pairs)

Question 28

How many possible chromosome combinations can occur as a result of sexual reproduction (not regarding genetic recombination, which would increase this)

Answer 28

(2^n)^2

(n = number of homologous pairs)

Question 29

What is genetic diversity

Answer 29

The total number of different alleles in a population

Question 30

What is the benefit of greater genetic diversity

Answer 30

Greater chance of some individuals within a population surviving an environmental change

Question 31

What is natural selection

Answer 31

The process by which organisms that are better adapted to their environment tend to survive and breed, passing on their advantageous characteristics

Question 32

What is the selection pressure

Answer 32

The changed environmental factor that determines which traits (and therefore alleles) are more advantageous

Question 33

What is a polygenetic trait

Answer 33

A characteristic that is influenced by more than one gene, most impacted by natural selection

Question 34

What is the process of natural selection

Answer 34

• Gene pool within a population contains a variety of alleles
• A Selection pressure will favour a certain group of alleles, due to their advantageous characteristics
• Individuals with these alleles are more likely to survive and breed, passing on their desired characteristics to the next generations
• This repeats over many generations, resulting in adaptation and evolution

Question 35

What are the 3 types of selection

Answer 35

• Directional
• Disruptive
• Stabilizing

Question 36

What is Directional selection

Answer 36

When one of the extremes of the characteristic is favoured by the selection bias, causing the mode to move in that direction

Question 37

What is an example of Directional selection

Answer 37

• Giraffe evolution: Longer necks could reach leaves
• Pepper moths: darker trees due to soot in the industrial revolution was advantageous for dark coloured moths

Question 38

What is Disruptive selection

Answer 38

When both extremes of the characteristic are favoured, so the current mode is selected against

Question 39

What is an example of Disruptive selection

Answer 39

• Breeding Fish: Large males mate by brute force, small makes ‘sneak’ in an fertilise the eggs
• Prey animals: Large are too big to attack, small can hide

Question 40

What is Stabilizing selection

Answer 40

When environmental conditions remain stable, favouring phenotypes closest to the mean

Question 41

What is an example of stabilizing selection

Answer 41

• Baby weights: Small will lose heat quickly, Large is heavy and hard to pass through the pelvis
• Oyster colour: Too light/too dark, don’t blend and are eaten

Question 42

What are the 3 types of adaptation that can arise from natural selection

Answer 42

• Anatomical (Physical): eg. Thick fur
• Physiological (Biology): eg. Oxidising fats instead of carbs, to give extra water
• Behavioural: eg. Migration patterns