Genetics and Inheritance

Question 1

What is a gene? (1)

Answer 1

A section of DNA that codes for a specific polypeptide

Question 2

What is the genotype? (2)

Answer 2

The genetic constitution of an organism. All the alleles that an organism possesses

Question 3

What is the gene pool? (1)

Answer 3

All the alleles within an interbreeding population (at a specific time)

Question 4

What is a population? (1)

Answer 4

All the individuals of the same species that occupy the same habitat at the same time

Question 5

What is the phenotype? (2)

Answer 5

The expression of its genetic constitution and its interaction with the environment

Question 6

What is an allele? (1)

Answer 6

Different version of the same gene

Question 7

What are multiple alleles and what does this produce? (2)

Answer 7

More than 2 alleles for the same gene. This produces a hierarchy of dominance

Question 8

What is the genome? (1)

Answer 8

The full sequence of genetic material within a cell/organism

Question 9

What is a dominant allele? (1)

Answer 9

Always expressed in the phenotype regardless of whether an organism’s genotype is homozygous or heterozygous

Question 10

What is a recessive allele? (1)

Answer 10

Only expressed in the phenotype if the genotype is homozygous

Question 11

What are codominant alleles? (1)

Answer 11

Both alleles equally expressed within the phenotype

Question 12

Diploid meaning

Answer 12

Two copies of a gene

Question 13

Haploid meaning

Answer 13

One copy of a gene

Question 14

What is the expected offspring ratio of monohybrid inheritance from heterozygous parents

Answer 14

3:1

Question 15

What is the expected offspring ratio of codominance inheritance from heterozygous parents

Answer 15

1:2:1

Question 16

What is the expected offspring ratio of dihybrid inheritance from heterozygous parents

Answer 16

9:3:3:1

Question 17

What is the expected offspring ratio of epistasis inheritance from heterozygous parents

Answer 17

9:4:3 or 15:1 or 9:7

Question 18

What is the expected offspring ratio of autosomal linkage inheritance from heterozygous parents

Answer 18

3:1 if no crossing over

Question 19

What is allelic frequency?

Answer 19

The number of times an allele occurs within a gene pool

Question 20

Hardy-Weinberg Principle for the frequency of the dominant and recessive allele?

Answer 20

P + q = 1.0

Question 21

Hardy-Weinberg Principle for the frequency of all individuals?

Answer 21

P2 + 2Pq + q2 = 1.0

Question 22

What does Hardy-Weinberg principle predict?

Answer 22

The allelic frequency (of a particular gene) from one generation to the next will remain constant if there is no migration, gene mutations or selection for or against a particular allele
There should be a large population and mating within the population should be random

Question 23

Exam Question - what does the Hardy-Weinberg principle predict?

Answer 23

The allelic frequency of a particular gene will remain constant from one generation to the next, providing:
- mating is random
- there are no mutations
- there is a large population
- there is no migration
- there is no natural selection

Question 24

What is monohybrid inheritance? (1)

Answer 24

Inheritance of a single gene which determines a single characteristic

Question 25

What are the dominant characteristic rules?

Answer 25

Affected offspring must have at least one affected parent Unaffected parents only have unaffected offspring If both parents are affected and have an unaffected offspring, both parents must be heterozygous

Question 26

What are the recessive characteristic rules?

Answer 26

Unaffected parents can have an affected offspring if they are heterozygous

Question 27

What is meant by sex-linkage? (2)

Answer 27

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

Question 28

Why are males more likely to express a recessive sex-linked allele? (1)

Answer 28

A female would have two copies of a recessive allele for it to be expressed in the phenotype whereas males only need one

Question 29

To prove a characteristic is not sex-linked, what are the sex link rules for dads and daughters?

Answer 29

If a daughter is affected (homozygous recessive) Her father is not And it is a recessive disease It is not sex-linked

Question 30

To prove a characteristic is not sex-linked, what are the sex link rules for mums and sons?

Answer 30

If a son is affected His mum is not And it is a dominant disease It is not sex-linked

Question 31

What are autosomal chromosomes? (1)

Answer 31

Chromosomes that are not directly involved in determining the sex of an organism

Question 32

What is a linkage group? (1)

Answer 32

A set of genes on the same chromosome which tend to be inherited together

Question 33

What is epistasis? (1)

Answer 33

An interaction between two genes where one allele affects/influences the expression of another

Question 34

What is dihybrid inheritance (2)

Answer 34

Involves a phenotype that is inherited as the result of two different genes, thus two characteristics The two genes either can be on different chromosomes or linked on the same chromosome

Question 35

What is the chi squared test? (1)

Answer 35

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

Question 36

What are the criteria for the chi-squared test? (4)

Answer 36

Data placed in discrete categories Large sample size Only raw count data allowed (i.e. not percentages) No data values equal to zero

Question 37

How is a chi-squared test performed? (2)

Answer 37

The formula results in a number which then compared to a critical value If the number is greater than or equal to the critical value, we conclude there is a significant difference between the observed and expected data and that the results did not occur due to chance