Genetic Diagrams show the Possible Alleles in the a Offspring

Question 1

Scenario:

Answer 1

Cross-breeding hamsters, and that do,r have a normal, boring disposition while others have a leaning towards crazy acrobatics. You suppose you know that the behaviour is due to one gene

The allele which causes crazy nature is recessive - ‘b’
The normal behaviour is due to a dominant allele - ‘B’

Question 2

What genotype must a crazy hamster have?

Answer 2

The genotype bb (must be homozygous for this trait)

Question 3

What genotype does the normal hamster have?

Answer 3

Potentially two:

• BB (homozygous)
• Bb (heterozygous)

Question 4

What does the normal hamster have two possible genotypes?

Answer 4

Because the dominant allele (B) overrules the recessive one (b)

Question 5

What’s the chance of having a normal hamster, and what’s the chance of having a crazy one?

Answer 5

Normal - 75%
Crazy - 25%
3 : 1 ratio of normal : crazy hamsters

Question 6

What is this ratio called?

Answer 6

Phenotypic ratio (because it’s a ratio of different phenotypes)

Question 7

What is the outcome of breeding two homozygous hamsters?

Answer 7

Theres only one possible offspring you can end up with

Question 8

What is an example of breeding two homozygous hamsters?

Answer 8

Breeding BB and bb hamsters can only give offspring with a Bb genotype - they’d all have a normal phenotype