Key Area 3.2

Question 1

Describe and explain what polygenic inheritance is?

Answer 1

• Characteristic controlled by alleles of more than 1 gene
• It is continuous
• It’s effects are additive
• Characteristic that show polygenic inheritance are influenced by the environment

Question 2

What is outbreeding and give an example

Answer 2

Fusion of two gametes from unrelated members of the same species

Examples:
Wild animals
Cross pollinating plants

Question 3

Name an advantage and disadvantage of outbreeding

Answer 3

Advantage:
Promotes heterozygosity

Disadvantage:
Not all offspring will show the desired characteristic of the parents

Question 4

What is inbreeding and give an example

Answer 4

Fusion of two gametes from close relatives of the same species

Examples:
Self pollination plants e.g. Peas, rice

Question 5

Advantage and disadvantage of inbreeding

Answer 5

Advantage:
Ensures each generation receives the alleles for desired characteristic

Disadvantage:
Primates homozygosity

Question 6

What is a test cross

Answer 6

Cross between:

Organism with unknown genotype for characteristic

X

Organism who is homozygous recessive for that characteristic

Question 7

What is the desired and undesired effect of inbreeding

Answer 7

Desired:
Plant/animal bred for years until population breeds true

Undesired:
Loss of heterozygosity which causes inbreeding depression

Question 8

What causes inbreeding depression

Answer 8

Deleterious recessive alleles becoming homozygous

Question 9

What effect does inbreeding depression have?

Answer 9

Decline in:

• vigour
• size
• fertility

Question 10

How can inbreeding depression be avoided

Answer 10

Selecting parent plants who are homozygous for desired characteristics while heterozygous for others

This maintains genetic diversity

Question 11

What is cross breeding

And what is the purpose

Answer 11

Cross breeding is breeding an organism with different but desired genotypes

Allows new alleles to be introduced into plant and animals

Question 12

What does cross breeding do?

Answer 12

Helps avoid the problems associated with inbreeding

Question 13

What is a back cross

Answer 13

Crossing of an F1 hybrid with its parents

Question 14

What is the purpose of back crossing

Answer 14

Used to introduce a required gene from a parent while still keeping other desired traits

Question 15

How can you achieve an F1 generation

Answer 15

Crossing two genetically dissimilar parents

Question 16

How can a hybrid with both desired characteristics be achieved

Answer 16

Organism with desired trait1

X

organism with desired trait2

Question 17

What does crossing two homozygous parents create

Answer 17

Uniform F1 generation

Question 18

What can be used to maintain a required breed

Answer 18

Selection

Back crossing

Question 19

What will an F1 self cross produce

Answer 19

Produce a genetically diverse F2 generation

Question 20

What is an advantage and disadvantage of a genetically diverse F2 generation

Answer 20

Advantage:
Production of new varieties

Disadvantage:
Unsuitable as a crop

Question 21

What properties do F1 hybrids have and why

Answer 21

Increased:

• vigour
• yield
• fertility

Why?
Recessive alleles are masked

Question 22

Name and describe 3 main factors in a plant

Answer 22

1) Selection of treatment:
To allow fair comparison

2) Number of replicates:
To take account of variability

3) randomisation of treatment:
To eliminate bias when measuring treatment affects

Question 23

What is the aim of plant field trails

Answer 23

1) COMPARE the performance of different plant cultivars under same set of experimental conditions
2) Find out the effects of different ENVIRONMENTAL CONDITIONS of a cultivar of plants

Question 24

How is genetic material passed to crop plant from a bacterial with a modified plasmid

Answer 24

Gene passed horizontally

Question 25

Give an example of genetically modified crop

Answer 25

Gene for vitamin A into ride to make golden rice

Benefit:

Better nutrition for a human consumers in 3rd world countries