7.1 INHERITANCE

Question 1

define

Genotype

Answer 1

The genetic constitution of an organism

Question 2

define

Phenotype

Answer 2

The expression of an organism’s genetic constitution, combined with its interaction with the environment

Question 3

define

Allele

Answer 3

different forms of a particular gene, found at the same ocus on a chromosome

Question 4

state

number of alleles per gene in diploid organisms

Answer 4

2

Question 5

Define

dominant allele

Answer 5

an allele whose characteristics will always appear in the phenotype, whether one or two are present

Question 6

define

recessive allele

Answer 6

an allele whose characteristic only appears in the phenotype if no dominant allele is present

Question 7

define

codominant alleles

Answer 7

2 dominant alleles that both contribute to the phenotype, either by showing a blend of both characeristic or the characteristics appearing together

Question 8

contrast

homozygous and heterozygous

Answer 8

homozygous = both alleles are dominant or both are recessive

heterozygous = one allele is dominant and the other is recessive

Question 9

define

monohybrid inheritance

Answer 9

when one phenotypic characteristic is controlled by a single gene

Question 10

define

dihybrid inheritance

Answer 10

when two phenotypic characteristics are determined by two different genes present on two different chromosomes at the same time

Question 11

define

sex-linkage

Answer 11

when an allele is located on one of the sex chromosomes, meaning its expression depends on the sex of the individual

Question 12

explain

why males are more likely to express a recessive sex-linked allele

Answer 12

most sex-linked alleles are located on the X chromosome so males only get one copy of the allele and will express this characteristic even if it’s recessive. Females have two alleles so this is less likely

Question 13

state and explain

which parent males inherit sex-linked characteristics from

Answer 13

mother, as the Y chromosome can only come from their father so if the mother is heterozygous for sex-linked alleles, she is a carrier and may pass on the trait

Question 14

define

autosomal linkage

Answer 14

when 2 or more genes are located on the same (non-sex) chromosome. Only 1 homologous pair is needed for all 4 alleles to be present. For genes that aren’t linked, 2 homologous pairs are needed

Question 15

define

epistasis

Answer 15

when 2 non-linked genes interact with 1 gene either masking or suppressing the other gene

Question 16

define

2 types of epistasis

Answer 16

recessive epistasis = where 2 homozygous recessive alleles mask expression of another allele

dominant epistasis = where 1 dominant allele masks expression of multiple other alleles

Question 17

define

chi-squared test

Answer 17

a statistical test to find our whether the difference between observed and expected data is due to chance or a real effect

Question 18

state

criteria for chi-squared test

Answer 18

• data placed in discrete categories
• large sample size
• only raw count data
• no data values equal 0

Question 19

explain

how chi-squared test is performed

Answer 19

formula results in a number which is compared to a critical value, if number is greater or equal to critical value, there is a significant difference.

Question 20

explain

use of chi-squared test in relation to inheritance

Answer 20

comparison of expected phenotypic ratios with observed ratios to test understanding of how different genes and alleles are inherited