genetic problems: HELP!!!!!!!!!!!!!! ASAP

Genetics as it applies to evolution, molecular biology, and medical aspects.

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littlebittygirl
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genetic problems: HELP!!!!!!!!!!!!!! ASAP

Post by littlebittygirl » Mon Aug 03, 2009 1:27 am

I have four questions that i need help in answering and explaining:

1. Freckles are due to dominant alleles (F), and no freckles are due to recessive alleles (f). Ted and Mary both have freckles, but their son Billy has no freckles. Give the genotypes of Ted, Mary and Billy. If Ted and Mary have additional children, what is the chance for freckles?

2. Pigmented eyes (generally brown) are dominant to blue eyes. If Ted has blue eyes and Mary is heterozygous, what is the chance that their offspring will have brown eyes?

3. Widow’s peak is due to a dominant allele. If Ted is homozygous dominant and Mary has straight hairline, what is the chance that their offspring will have widow’s peak?

4. If Fred and Wilma are both heterozygous for Widow’s peak, what is the chance that they will have a child with widow’s peak?

kolean
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Post by kolean » Tue Aug 04, 2009 3:52 am

1.Ted has F_ (F allele or f allele ?)
Mary has the same F_ (F allele or f allele ?)
so if Billy is ff , then he has to get a recessive f allele from each of his parents.
Thus, Ted is Ff, and Mary is Ff also.

Ted X Mary is Ff X Ff. Each child has a 1/4 for FF, 1/4 for Ff, 1/4 for Ff, and 1/4 for ff genotype, resulting in 3/4 freckles and 1/4 no freckles phenotype.
In percentages, 75% freckles and 25% no freckles children.

2. If Ted has bb (recessive blue eyes) and Mary has Bb (heterozygous bown eyes), then the chances are a cross of Bb x bb, resulting in the usual 1/4 Bb, 1/4 bb, 1/4 Bb, and 1/4 bb, totalling to 1/2 Bb and 1/2 bb: thus 50 % heterozygous brown and 50 % recessive blue.

3. Ted is WW and Mary is ww (straight hairline assumes recessive alleles), then it is a cross of WW X ww. This results in all offspring 1/4 Ww, 1/4 Ww, 1/4 Ww, 1/4 Ww, or all Ww. 100% dominant heterozygous widow's peak.

4.Ww (Fred: paternal alleles) X Ww (Wilma: maternal alleles) cross wil produce: 1/4 WW, 1/4 Ww, 1/4 Ww, and 1/4 ww: phenotype resulting in 3/4 widow's peak and 1/4 straight hair line: thus 75% chance their child will have a widow's peak.

littlebittygirl
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Re: genetic problems: HELP!!!!!!!!!!!!!! ASAP

Post by littlebittygirl » Tue Aug 04, 2009 5:09 pm

thank you so much....

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