3.7.1 Inherited Change

Question 1

Answer 1

Question 2

Answer 2

Question 3

What is a recessive allele?

Answer 3

An allele that is only expressed an individual has two copies of that allele. Will not be expressed in a heterozygous individual.

Question 4

Answer 4

Question 5

Answer 5

Question 6

Answer 6

Question 7

Answer 7

Question 8

Answer 8

Question 9

What is a loci?

Answer 9

Position of a gene on a chromosome

Question 10

What is a linked gene (autosomal)?

Answer 10

Linked genes have their loci on the same chromosome and so stay together during independent assortment and are passed on to offspring together

Question 11

How can autosomal linked genes be separated ?

Answer 11

By crossing over to produce “recombinant” gametes

Question 12

What would be the ratio in the F2 generation for a dihybrid cross with no linkage

Answer 12

9:3:3:1

Question 13

What would be the ratio in the F2 generation for a dihybrid cross where the 2 dominant alleles are perfectly linked

Answer 13

3 to 1

Question 14

What makes two genes more closely linked?

Answer 14

Having their loci closer together on the same chromosome

Question 15

What chromosomes do males and females have

Answer 15

Female = XX, Male = XY

Question 16

In birds the sex chromosomes are called Z and W. Which way around is it? (off spec but commonly given as info for application questions)

Answer 16

Female = ZW, Male = ZZ

Question 17

Define sex-linkage

Answer 17

when the locus of a gene is on a sex chromosome

Question 18

Why are males more likely to show sex-linked recessive phenotypes than females ?

Answer 18

They only have one X chromosome, so they often only have one allele for sex linked genes. As they only have one copy, they express the characteristic of this allele even if it is recessive

Question 19

Answer 19

Question 20

Answer 20

Question 21

Give examples of X linked disorders

Answer 21

Colour blindness and haemophilia

Question 22

Define heterozygote

Answer 22

An individual with different alleles of a gene at a particular locus

Question 23

Define allele

Answer 23

Version of a gene

Question 24

Define genotype

Answer 24

The alleles a person has

Question 25

Define phenotype

Answer 25

The characteristics displayed by an organism

Question 26

Define dominant

Answer 26

An allele that is expressed in the phenotype even when there is only one copy

Question 27

Define carrier

Answer 27

If a recessive allele can cause a disease, a carrier is someone who is heterozygous for the gene. They wont have the disease but they carry a copy of the allele for the disease

Question 28

Define co-dominance

Answer 28

Both alleles influence the phenotype because they are both expressed equally

Question 29

In a cross between Red (RR) and white (rr) cows with codominant inheritance what would be the pheotypic ratio of the offspring

Answer 29

100% Roan (Rr)

Question 30

In a cross between two Roan cows (Rr) what would be the ratio of the offspring?

Answer 30

25% white (rr), 50% roan (Rr) , 25% red (RR)

Question 31

Define homozygote

Answer 31

An organism that has 2 copies of the same alleles for a characteristic

Question 32

What is monohybrid inheritance?

Answer 32

The inheritance of a single characteristic controlled by different alleles

Question 33

What is dihybrid inheritance?

Answer 33

The inheritance of 2 characteristics controlled by different alleles (you use a 4x4 punnet square)

Question 34

Answer 34

Question 35

Define 'epistasis'

Answer 35

When the allele of one gene affects or masks the expression of another in the phenotype

Question 36

Answer 36

Question 37

Answer 37

Question 38

Which statistical test do you use to see if the offspring produced are significantly different to those predicted by a genetic cross?

Answer 38

Chi-squared test

Question 39

What is the chi-squared test used to test for

Answer 39

To see if observed frequences are signficantly difference from expected frequencies (e.g. in genetic crosses)

Question 40

how do you use this formula

Answer 40

Question 41

In a chi-squared test, if the P value is greater than 0.05, what does this mean?

Answer 41

The null hypothesis is rejected, there is a significant difference between the observed and the expected frequencies. This difference is not due to chance.

Question 42

Answer 42