7.1 Inheritance

Question 1

what does diploid mean

Answer 1

2 copies of each chromosome with one from each parent

Question 2

what are gametes

Answer 2

haploid so only have one allele for each gene

Question 3

how is the diploid genotype created

Answer 3

from the parental chromosome from each gamete come together in the nucleus

Question 4

what is the first set of offspring of two parents called

Answer 4

F1 generation

Question 5

what is the F2 generation

Answer 5

the offspring from the first generation

Question 6

what is monohybrid inheritance

Answer 6

only controlled by one gene
(standard punnet square)

Question 7

4 reasons why the expected ratios are not always expected

Answer 7

• Fertilisation and fusion of gametes is random
• Co dominance
• Sex linkage
• sample taken from small populations

Question 8

What is Co-dominance

Answer 8

if both alleles are expressed in the phenotype as neither one is recessive (blend)
Flower colour = C
White = C^W
Red = C^R
Pink = C^WC^R

Question 9

what is dihybrid inheritance

Answer 9

when a gene has more than one allele (blood type)

Question 10

define sex linkage

Answer 10

any gene that is carried on either the x or y chromosome

Question 11

define autosomal link

Answer 11

where two or more genes are carried on the same autosome (chromosome which isn’t a sex one)

Question 12

How does sex linkage work (4 steps)

Answer 12

1. As the Y chromosome is smaller than the X chromosome most of the sex-linked genes are found on the X chromosome
2. however as makes only have one X chromosomes this means they only have one allele of each sex-linked gene so they only express this characteristic even if it is recessive
3. All Y chromosomes are inherited from fathers so any-sex linked genes in a male must be passed on from female
4. Females have two copies of the X chromosome meaning they have 2 alleles of every X-linked gene

Question 13

How does autosomal linkage work ( steps)

Answer 13

1. If two genes are found close together on the same chromosome they are more likely to be inherited together as they will stay together during segregation of chromosomes in meiosis
2. This could produce an unexpected ratio as there are only 2 outcomes, so there are more gametes containing the linked genes and fewer where they are separated

Question 14

what is epistasis

Answer 14

when alleys mask or suppress the expression of genes at a different locus

Question 15

define recessive epistasis

Answer 15

when the presence of two recessive alleles at the first locus will prevent the expression of the allele at the second locus

Question 16

ratio of recessive epistasis between homozygous recessive and dominant

Answer 16

9:3:4

Question 17

recessive epistasis in my words

Answer 17

the recessive alleles TOGETHER on gene B (bb) will mask anything on A.
A is only seen if Bb or BB

Question 18

Define dominant epistasis

Answer 18

when having at least one of the gene at the first locus will block the expression of the gene at the second locus

Question 19

ratio of dominant epistasis for homozygous dominant and recessive

Answer 19

12:3:1

Question 20

Dominant epistasis in my words

Answer 20

dominant alleles on B (BB or Bb) will mask anything on A
A is only shown if bb