Inheritance

Question 1

Define genotype

Answer 1

Genetic constitution of an organism (the alleles it has for a gene)

Question 2

Define phenotype

Answer 2

The expression of the genes and its interaction with the environment

Question 3

Define homozygous

Answer 3

A pair of homologous chromosomes carrying the same alleles for a single gene

Question 4

Define heterozygous

Answer 4

A pair of homologous chromosomes carrying 2 different alleles for a single gene

Question 5

Define recessive allele

Answer 5

An allele only expressed if no dominant allele is present

Question 6

Define dominant allele

Answer 6

An allele that will always be expressed in the phenotype

Question 7

Define codominant

Answer 7

Both alleles are expressed in the heterozygote resulting in a different phenotype

Question 8

Define multiple alleles

Answer 8

More than two alleles for a single gene

Question 9

Define sex linkage

Answer 9

A genes whose locus is on the X chromosome

Question 10

Define autosomal linkage

Answer 10

Genes that are located on the same chromosome

Question 11

Define epistasis

Answer 11

When one gene modifies or masks the expression of a different gene at a different locus

Question 12

Define monohybrid

Answer 12

Genetic inheritance cross of a characteristics determined by one gene

Question 13

Define dihybrid

Answer 13

Genetic inheritance cross for a characteristic determined by two genes

Question 14

What phenotypic ratio will you always get in a dihybrid cross with two heterozygous parents

Answer 14

9:3:3:1

Question 15

What 2 things could affect usual phenotypic ratio from a dihybrid cross

Answer 15

Autosomal linkage
Crossing over in meiosis

Question 16

What does crossing over result in

Answer 16

New combinations of alleles in the gametes - predicted gametes in punnet square may differ

Question 17

What is autosomal linkage

Answer 17

When 2 genes are located on the same chromosome so the alleles for each gene linked on the same chromosome will be inherited together

Question 18

How would data representing continuous variation be presented

Answer 18

As a histogram

Question 19

How would data representing discontinuous variation be presented

Answer 19

As a bar chart

Question 20

Define continuous variation

Answer 20

A characteristic with continuous values

Question 21

What are the causes of continuous variation

Answer 21

Genetics and environment

Question 22

How many genes are involved in continuous variation

Answer 22

Many genes (polygenic)

Question 23

Give examples of continuous variation

Answer 23

Mass and height of organisms

Question 24

Define discontinuous variation

Answer 24

A characteristic with categorical (discrete) values

Question 25

What are the causes of discontinuous variation

Answer 25

Genetics

Question 26

How many genes are involved in discontinuous variation

Answer 26

1 or 2

Question 27

Give an example of discontinuous variation

Answer 27

Blood group

Question 28

What are the types of selection

Answer 28

Directional Stabilising

Question 29

What is directional selection

Answer 29

One of the extremes has the selective advantage

Question 30

When does directional selection occur

Answer 30

When there is a change in the environment

Question 31

What happens to the modal trait in directional selection

Answer 31

The modal trait changes

Question 32

What is stabilising selection

Answer 32

Where the modal trait has the selective advantage

Question 33

When does stabilising selection occur

Answer 33

When there is no change in the environment

Question 34

What happens to the modal trait in stabilising selection

Answer 34

Remains the same

Question 35

What happens to standard deviation in stabilising selection

Answer 35

Standard deviation decreases as individuals with the extreme trait decrease

Question 36

Give an example of directional selection

Answer 36

Antibiotic resistance in bacteria

Question 37

What is speciation

Answer 37

The creation of a new species

Question 38

When does speciation occur

Answer 38

When one original population becomes reproductively isolated - isolation means that there are now 2 populations of the same species, but they cannot breed together

Question 39

What can speciation result in

Answer 39

The accumulation of differences in their gene pools - to the extent where two populations would be unable to interbreed to make fertile offspring

Question 40

What are the 2 different ways that populations can become reproductively isolated

Answer 40

Allopatric (geographically) Sympatric (changes in reproductive mechanisms)

Question 41

What is allopatric speciation

Answer 41

Populations become separated geographically isolated Leading to reproductive isolation This leads to accumulation of different benefitial mutations to their environments Due to this accumulation of DNA differences, they would be unable to interbreed to create fertile offspring so they are classified as two different species

Question 42

What is sympatric speciation

Answer 42

Populations become reproductively isolated due to differences in their behaviour Could be a random mutation Could impact reproductive behaivour May cause individuals to perform a different courtship ritual/ be fertile at different times of year There will be no gene flow as they will not reproduce together

Question 43

What is genetic drift

Answer 43

The change in allele frequency within a population between generations

Question 44

What type of genetic drift results in evolution

Answer 44

Substantial genetic drift

Question 45

What are genetic bottlenecks

Answer 45

Caused by events that kill almost all of the population, leaving only a few individuals left This results in a very small gene pool

Question 46

What is the founder effect

Answer 46

When a few individuals from an existing population relocate to an isolated area This results in a small population breeding together, and therefore small gene pool

Question 47

What are the 2 types of genetic variation

Answer 47

Natural selection Artificial selection