TOPIC 7 - inheritance

Question 1

define genotype

Answer 1

The combination of alleles that an organism has.

Question 2

define phenotype

Answer 2

Physical expression of the genotype and its interaction with the environment.

Question 3

What is an allele?

Answer 3

Variation of a gene

Question 4

How many alleles per gene do diploid organisms carry?

Answer 4

2

Question 5

what is meant by dominant allele?

Answer 5

Allele that is always expressed in the phenotype

Question 6

what is meant by recessive allele?

Answer 6

Allele that is only expressed when homozygous.

Question 7

What is meant by codominant alleles?

Answer 7

Both alleles are expressed in the phenotype

Question 8

What is meant by homozygous or heterozygous?

Answer 8

homozygous = both alleles are dominant/ recessive
heterozygous = one allele is dominant, the other is recessive

Question 9

Define monohybrid inheritance?

Answer 9

where 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

what is meant by sex linkage?

Answer 11

where an allele is located on one of the sex chromosomes, meanings its expression depends on the sex of the individual.

Question 12

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

Answer 12

• most sex linked alleles are located on X chromosome
• therefore males only get one copy of this allele, so will express this characteristic even if it is recessive
• since females get 2 alleles this is less likely

Question 13

which parents do males inherit sex-linked characteristics from?

Answer 13

• mother since Y chromosome comes from their father
• therefore the mother is heterozygous for sex-linked alleles = she is a carrier and may pass the trait on

Question 14

what is meant by autosomal linkage?

Answer 14

where two or more genes are located on the same non sex chromosomes
only one homologous pair is needed for all 4 alleles to be present

Question 15

what is meant by epistasis?

Answer 15

when two non-linked genes interact, with one gene either masking or suppressing the other gene

Question 16

describe two types of epistasis?

Answer 16

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

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

Question 17

what is the chi-squared test?

Answer 17

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

Question 18

what are the criteria for the chi-squared test?

Answer 18

• data placed in discrete categories
  -large sample size
• only raw count data allowed
• no data values equal zero

Question 19

how is a chi squared test performed?

Answer 19

number is compared to a critical value
we conclude that there is a significant difference between the observed and expected data and that the results did not occur due to chance.

Question 20

how can we use a chi- squared test in relation to the content of this topic?

Answer 20

we can compare expected phenotypic ratios with observed ratios to test our understanding of how different genes and alleles are inherited.