Inherited Change (Chapter 17)

Question 1

Define Gene

Answer 1

Section of DNA that codes for a polypeptide

Question 2

Define Allele

Answer 2

A version of a gene

Question 3

Define Genotype

Answer 3

The genetic makeup of an organism

Question 4

Define Phenotype

Answer 4

Person’s appearance due to their environment and genotype

Question 5

Define Homozygous

Answer 5

When the alleles of a particular gene are identical

Question 6

Define Heterozygous

Answer 6

When the alleles of a particular gene are different

Question 7

Define Haploid

Answer 7

When cells have one copy of each chromosome

Question 8

Define Diploid

Answer 8

When cells have two copies of each chromosome

Question 9

What is the difference between dominant and recessive alleles?

Answer 9

Dominant are always shown in the phenotype but recessive are only shown in the phenotype if there are no dominant alleles.

Question 10

Define Co-Dominance

Answer 10

When both alleles are expressed in the phenotype

Question 11

How are co-dominant alleles shown?

Answer 11

Using superscript letters

Question 12

Define Multiple Alleles

Answer 12

A gene with more than two possible alleles

Question 13

Define Sex-Linked Genes

Answer 13

Any gene found on X or Y chromosome

Question 14

What causes sex-linked conditions?

Answer 14

Mutation of a gene on X chromosomes. The mutation usually leads to a non-functional protein being made. Males will only have one X chromosome so only needs one allele that codes for non-functional [roetins so more likely to have the condition.

Question 15

Why are drosophila used in experiments?

Answer 15

• Short lifecycle
• Small space needed
• Lays lots of eggs
• Not endangered

Question 16

What are some of the assumptions of the Hardy Weinberg technique?

Answer 16

• Random mating
• No mutations
• Large population
• Population genetically isolated
• No migration

Question 17

What is some evidence that proves a gene is recessive?

Answer 17

2 parents don’t have the condition but their child does - parents must be carriers/both parents have the condition, so all their children must too

Question 18

What is some evidence that proves a gene is dominant?

Answer 18

2 parents have the condition but their child does not

Question 19

What is some evidence that proves a gene is sex-linked?

Answer 19

• Dad always passes X chromosome to daughter, so if dad has a dominant condition, daughter will have it too (
• Mum gives son X chromosome so if mum has a recessive allele, she always gives to son.

Question 20

What is Weinburg’s prediction?

Answer 20

Frequency of alleles will stay constant from one generation to next.

Question 21

What is the Hardy-Weinberg equation?

Answer 21

p2 + 2pq + q2 = 1

Question 22

Describe monohybrid inheritance

Answer 22

• One gene

* Dominant and recessive in 3:1 ratio with heterozygous parents

Question 23

Describe dihybrid inheritance

Answer 23

• Two genes on different chromosomes
• Independent characteristics - one does not control the other

• Heterozygous parents produce gametes in 9:3:3:1
9 = two dominant alleles e.g. BbNn
3 = 1 dominant and 1 recessive e.g. Bbnn or bbNN
1 =2 recessive e.g. bbnn

Question 24

Describe multiple alleles

Answer 24

Three or more phenotypes present

Question 25

Which types of inheritance can be used in Hardy-Weinberg?

Answer 25

Monohybrid and Multiple alleles

Question 26

Describe co-dominance

Answer 26

Phenotype is a combination of two alleles

Question 27

Describe epistasis

Answer 27

• Two genes on different chromosomes

* One CONTROLS the other

Question 28

Describe autosomal linkage

Answer 28

• Two genes on SAME chromosome
• Genes are either dominant or recessive so only three genotypes e.g. AABB, aabb or AaBb (unless crossing over has taken place)

Question 29

Why is the ratio of offspring not always as expected?

Answer 29

• Fusion of gametes is random

* Small sample size