biology punnett

Question

6a) Human blood types show both codominance and multiple alleles. The blood types are A, B, AB, and O. The allele for A, B, and O are IA , IB , and i respectively. A and B are codominant, and O is recessive. Is it possible for a female with type AB blood and a male of type O to have a baby with AB blood? Be sure to show the Punnett square. 6b) What are the possible genotypes of the parents who produce a baby with the genotype IB I B?

Answer 1

The first thing you need to know is how to complete a Punnett Square. Each parent has two possible alleles to donate to the offspring, but the offspring only gets one allele from each parent.

So If one of your parents is type A, he/she will have either two A alleles - homozygous A (i^A/i^A), or one A allele and one O allele - heterozygous A ( i^A/i). If your parent is type O, he/she is - homozygous O (i/i). If your parent is type B, he/she is (homozygous B [i^B/i^B] or heterozygous B [i^B/i]).

If your mom is i^A/i^B, the alleles she would contribute are i^A and i^B

If your dad is i^B/i, the alleles he would contribute are i^B and i.

You would complete the Punnett Square this way: (dad's alleles are in the first column; mom's alleles are in the first row; the possible offspring are placed in the remaining squares)

Mom's alleles are in the first row.

___| A_|_B_

| |

| |

Dad's alleles are in the first column.

___| A_|_B_

B | |

O | |

Start filling in the offspring (you always place A before B). Fill in the first allele for mom down the column.

___| A_|_B_

B | A |

O | A |

Fill in the second column with the second allele from mom.

___| A_|_B_

B | A | B

O | A | B

Fill in the first row with the first allele from dad.

___| A_|_B_

B | AB| BB

O | A | B

Fill in the second row with the second allele from dad.

___| A_|_B_

B | AB| BB

O | AO| BO

You would have the probability of getting

1. 1/4 of the offspring being AB (i^A/i^B)
2. 1/4 of the offspring being heterozygous A ( i^A/i)
3. 1/4 of the offspring being homozygous B ((i^B/i^B)
4. 1/4 of the offspring being heterozygous B ((i^B/i)

Since A and B are codominant, and type O is recessive, you would only get a type O offspring if the child gets an O allele (i) from each parent.

Now, take what you have learned here, and make your Punnett square to see what offspring are possible from the parents in the question you submitted.