Inheritance

Question 1

Genotype definition

Answer 1

The genetic constitution of an organism

Question 2

Phenotype definition

Answer 2

The expression of the genetic constitution and its appearance due to the environment

Question 3

Gene definition

Answer 3

DNA base sequence which codes for either the amino acid sequence of a polypeptide of functional RNA

Question 4

Allele definition

Answer 4

Different version of a gene

Question 5

Homologous chromosomes definition

Answer 5

Have the same genes

Question 6

Recessive definition

Answer 6

Only expressed in the phenotype when homozygous

Question 7

Dominant definition

Answer 7

Always expressed in the phenotype

Question 8

Locus definition

Answer 8

Fixed position of a gene on a chromosome

Question 9

Homozygous definition

Answer 9

Allele on each homologous chromosome is the same

Question 10

Heterozygous definition

Answer 10

Allele on each homologous chromosome is different

Question 11

Monohybrid inheritance definition

Answer 11

The inheritance of a single gene which determines a single characteristic

Question 12

Why is the observed phenotypic ratio sometimes different to the expected?

Answer 12

Random fertilisation OF GAMETES, small sample size

Question 13

Codominance definition

Answer 13

Both alleles are expressed in the phenotype (e.g. C^R and C^W)

Question 14

Multiple alleles definition

Answer 14

More than 2 alleles which follow a dominance hierarchy e.g. blood type (I^A, I^B and I^O)

Question 15

Sex-linked gene definition

Answer 15

Sex-linked gene is carried on the X chromosome

Question 16

Why are males more likely to express the recessive phenotype than females for sex-linked genes?

Answer 16

Males only have 1 X chromosome so only need 1 recessive allele for it to appear in their phenotype, whereas females need 2 recessive alleles

Question 17

Dihybrid cross definition

Answer 17

2 different genes on different chromosomes (e.g. RrGg)

Question 18

Autosomal linkage definition

Answer 18

2 genes carried on the SAME chromosome (dominant genes could be the ones which are linked e.g. Gg and Nn gametes = GN and gn)

Question 19

Epistasis definition

Answer 19

Allele of one gene affects or masks the expression of another gene (e.g. Gene A dominant for red pigment –> Gene B dominant for purple pigment so aabb would be white, Aabb would be red, AaBb would be purple)

Question 20

What does p^2 mean in the Hardy Weinberg equation?

Answer 20

Homozygous DOMINANT

Question 21

What does q^2 mean in the Hardy Weinberg equation?

Answer 21

Homozygous RECESSIVE

Question 22

What does 2pq mean in the Hardy Weinberg equation?

Answer 22

Heterozygous

Question 23

What do p and q mean in the Hardy Weinberg equation?

Answer 23

p = dominant ALLELE frequency
q = recessive ALLELE frequency

Question 24

When given p, how would you work out q?

Answer 24

1 - p = q

Question 25

If a question gives you p^2 and asks you to calculate heterozygous frequency, what should you do?

Answer 25

Find q^2 FIRST (1 - p^2)
1 - q = p
Heterozygous = 2pq

Question 26

What are the 4 assumptions made by Hardy-Weinberg?

Answer 26

1. Mating is random
2. No immigration
3. No mutations
4. No selection