Genetic Crosses

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2

Red 50% yellow 50%

Slide 11

Punnett Square

Another method of showing crosses

Slide 12

Gamete genotypes are inserted

Parent genotypes are inserted B=black b=white

Bb male black

bb white female

B

b

b

b

What are the crosses

Bb

bb

Bb

bb

2 white and 2 black offspring

50:50 chance with these parents

Slide 13

Question

2 black rats are mated, they have 13 offspring. All of which are black, what are the genotypes of the parents

The male is re-mated with a white female, the offspring are

6 black and 7 white

What were the genotypes of the original parents

Rats have 2 coat colours – black B, white b.

Both BB BB

BUT

one could be Bb

Female BB Male Bb

Slide 14

Remember think how lucky you are!