Topic 8 - Origins of Genetic Variation

Question 1

Types of genetic variation

Answer 1

• Crossing over
• Independent assortment
• Random fertilisation

Question 2

Mendels 2 inheritance laws

Answer 2

1) Law of segregation (one allele is inherited from each parent)
2) Law of independent assortment (different traits are inherited independently of each other)

Question 3

Why does test crossing occur?

Answer 3

To determine the genome of plants and which alleles are either dominant or recessive

Question 4

Pedigree diagrams

Answer 4

Show what happens in reality in a human family over a period of time

Question 5

Why are fruit flies, pea plants, fungi and bacteria used in genetic experiments instead of humans

Answer 5

• Relatively easy and cheap to raise
• Short life cycle, so the results of any crosses of mutations can be seen quickly
• Produce large numbers of offspring so results are statistically relevant
• Clear, defined characteristics such as tall/short or wing length in insects

Question 6

Homogametic

Answer 6

Female mammals that have 2 X chromosomes (all eggs contain X chromosome)

Question 7

Heterogametic

Answer 7

Male mammals have 1 X chromosome & smaller Y. Half sperm have X, half sperm have Y

Question 8

Dihybrid inheritance

Answer 8

When 2 characteristics are determined by 2 different genes on different chromosomes