Genetics problems
A woman is heterozygous for both type A blood and for Rh factor. If she had a baby with a man who has O+ (0 positive) blood and is fully homozygous for these traits, what are the possible blood types of their children?
The Punnett Square
| ♂ The cross: ♀ | ||||||||
| X | ||||||||
Blood types possible in children?
(Put a “0” in empty squares if there are fewer possibilities than blanks.)
Why can you get the correct results with the Punnett square shown (with only one row for the man, but four for the woman)? (Explain.)
Hemophilia is a recessive, sex-linked trait. If a woman who is a carrier for hemophilia marries a normal man, what are the odds their sons will have hemophilia? What are the odds that their daughters will have hemophilia? What are the odds their daughters will be carriers of the hemophilia gene? Use the following genes for this problem: XN = X gene for normal blood clotting ; Xn = X with hemophilia gene; Y = Y chromosome.
The Punnett Square
| ♂ | |||||||||
| ♂ The cross: ♀ | |||||||||
| X | ♀ | ||||||||
Odds of sons with hemophilia?
| out of |
Odds of daughters with hemophilia? Odds of carrier daughters?
| out of | out of |
In shorthorn cattle the gene for red coat (R) is not dominant over that for white coat (R’). Cattle heterozygous for this gene are roan colored (In other words, inheritance of these traits is governed by incomplete dominance). The gene that codes for the polled condition of the horns (P) is clearly dominant over the gene that codes for long horns (p). (In other words, inheritance of these traits is governed by simple dominance.)
Write out the genotype for a cow that is heterozygous for both traits. What would this cow look like with respect to these traits?
| Genotype | Phenotype |
Do a Punnett square which illustrates the potential offspring for a cross between the cow above and a bull with the same genotype.
| ♂ | |||||
| ♀ | |||||
On average what percentage of the calves of numerous similar crossings would have each of the following sets of characteristics?
| 1) A red coat and polled horns.
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| 2) A white coat and long horns.
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| 3) A roan coat and polled horns. |
