Genetic diversity

Question 1

What is a mutation?

Answer 1

Any change to the quantity or the base sequence of the DNA of an organism

Question 2

What is the gene mutation?

Answer 2

Any change to one or more nucleotide bases, or a change in the sequence of the bases in DNA

Question 3

What can gene mutations involve?

Answer 3

Base substitution and base deletion

Question 4

What’s the danger of base substitution?

Answer 4

A different amino acid may be coded for, meaning that the primary structure of the protein formed is altered, this means the protein may no longer be able to function as the tertiary structure is changed

Question 5

What’s the danger of base deletion?

Answer 5

The polypeptide is entirely different and so is unlikely to function

Question 6

What are chromosome mutations?

Answer 6

Changes in the structure or number of whole chromosomes

Question 7

What are the two forms of chromosome mutations?

Answer 7

Changes in the whole sets of chromosomes and changes in the number of individual chromosomes

Question 8

When do changes in the whole set of chromosomes occur?

Answer 8

When organisms have three or more sets of chromosomes rather than the usual two (polyploidy)

Question 9

Where does polyploidy mostly occur?

Answer 9

In plants

Question 10

When do changes in the number of individual chromosomes occur?

Answer 10

During non-disjunction, this is when individual homologous chromosomes fail to separate during meiosis

Question 11

How does Down’s syndrome affect the chromosomes of humans?

Answer 11

Individuals have an additional chromosome 21

Question 12

What happens during the first division of meiosis?

Answer 12

Homologous chromosomes pair up and their chromatids wrap around each other, by the end of this division the homologous pairs have separated, with one chromosome from each pair going into one of the two daughter cells

Question 13

What is crossing over?

Answer 13

Equivalent portions of these chromatids being exchanged, when the chromatids of the homologous pairs wrap around each other

Question 14

What happens during the second meiotic division?

Answer 14

The chromatids move apart and four daughter cells are produced

Question 15

How does meiosis bring about genetic variation?

Answer 15

Independent segregation of homologous chromosomes and new combinations of maternal and paternal alleles by crossing over

Question 16

What is a gene?

Answer 16

A length of DNA that codes for a polypeptide

Question 17

What is the locus?

Answer 17

The position of a gene on a chromosome or DNA molecule

Question 18

What is an allele?

Answer 18

One of the different forms of a particular gene

Question 19

What are homologous chromosomes?

Answer 19

A pair of chromosomes, one maternal and one paternal, that have the same gene loci

Question 20

What is independent segregation?

Answer 20

Random arrangement and separation of chromosomes during meiosis

Question 21

What causes organisms of the same species to differ?

Answer 21

The combination of alleles, not genes

Question 22

What is genetic diversity?

Answer 22

The total number of different alleles in a population

Question 23

Why aren’t all alleles equally likely to be passed onto the next generation?

Answer 23

Only certain individuals are reproductively successful, affecting allele frequency

Question 24

How are new alleles added to gene pools of a population?

Answer 24

Random mutation

Question 25

How do new alleles affect a population?

Answer 25

In most cases it will be harmful, however in certain environments it might give its possessor and advantage

Question 26

What is selection?

Answer 26

The process by which organisms that are better adapted to their environment tend to survive and breed

Question 27

What is directional selection?

Answer 27

Selection that favours individuals that vary in one direction from the mean of the population

Question 28

What is stabilising selection?

Answer 28

Selection that favours average individuals

Question 29

What are phenotypes?

Answer 29

Observable physical and biochemical characteristic of an organism

Question 30

How does directional selection affect normal distribution graphs?

Answer 30

Causes eventual mean shift to the left or right

Question 31

How does stabilising selection affect some phenotypes?

Answer 31

Eliminates those at the extreme

Question 32

What’s an example of directional selection?

Answer 32

Bacterium resistant to penicillium due to mutation

Question 33

What’s an example of stabilising selection?

Answer 33

Human babies birth weight

Question 34

What adaptations can natural selection cause?

Answer 34

Anatomical, physiological and behavioural

Question 35

What’s an example of anatomical adaptations?

Answer 35

Shorter ears and thicker fur in arctic foxes, compared to foxes in warmer climates

Question 36

What’s an example of a physiological adaptation?

Answer 36

Oxidising of fat rather than carbohydrates in kangaroo rats to produce additional water in a dry desert environment

Question 37

What’s an example of behavioural adaptation?

Answer 37

Autumn migration of swallows from the UK to Africa to avoid food shortages in the UK winter

Question 38

What is the chiasmata?

Answer 38

The physical point of contact or crossing over between duplicated homologous pairs at the beginning of meiosis

Question 39

What is a bivalent?

Answer 39

The pairs of homologous chromosomes bound together by the chiasmata

Question 40

What is non-disjunction?

Answer 40

When the chromosomes fail to separate properly, leading to an unequal amount of chromosomes in the daughter cells

Question 41

How do you calculate the number of genetically different gametes produced by independent segragation?

Answer 41

2^n where n= the number of homologous chromosome pairs