Genetics question

[rav4182]

Jack is homozygous for an autosomal, dominant, trait. Meridith is homozygous for the recessive allele of the same gene. What percentage of their children would likely express the dominant phenotype?
A. [Yours]
0%.
B.
25%.
C.
50%.
D.
75%.
E. [Correct]
100%.
Explanation
100% of Jack and Meridith's children will express the dominant phenotype. Since Jack is homozygous dominant (TT), he carries two dominant alleles with respect to this gene. Therefore, Jack's gametes always carry the T allele. Since Meredith is homozygous recessive (tt), she carries two recessive alleles with respect to this gene. Therefore, Meridith's gametes always carry the t allele. Therefore, as shown by the punnett square below, all of Jack and Meridith's children will have the heterozygous Tt genotype. Further, since all of their children will be heterozygotes, it can be assumed that 100% of their children will express the dominant phenotype.


i thought since there talking about autosomal traits it would be 0. Arent only the sex chromosomes transferred to the kids?

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[amh137]

If only the sex chromosomes were given to kids, where would the other 44 chromosomes come from? Each parent gives one chromosome to their child. So, 22 autosomes multiplied by 2 gives 44, plus the 2 sex chromosomes.

 

[dentalWorks]

Jack is homozygous for an autosomal, dominant, trait. Meridith is homozygous for the recessive allele of the same gene. What percentage of their children would likely express the dominant phenotype?
A. [Yours]
0%.
B.
25%.
C.
50%.
D.
75%.
E. [Correct]
100%.
Explanation
100% of Jack and Meridith's children will express the dominant phenotype. Since Jack is homozygous dominant (TT), he carries two dominant alleles with respect to this gene. Therefore, Jack's gametes always carry the T allele. Since Meredith is homozygous recessive (tt), she carries two recessive alleles with respect to this gene. Therefore, Meridith's gametes always carry the t allele. Therefore, as shown by the punnett square below, all of Jack and Meridith's children will have the heterozygous Tt genotype. Further, since all of their children will be heterozygotes, it can be assumed that 100% of their children will express the dominant phenotype.


i thought since there talking about autosomal traits it would be 0. Arent only the sex chromosomes transferred to the kids?

autosomal means genes that are found on NON-sex chromosomes.

All the children are going to be Tt (meaning they are expressing the dominate gene, but are carriers of the recessive gene)

The question would be better if they also asked what genotypes ratios the offspring will produce (I know its sick)

 

[voager]

I will agree with dental works when getting this type of questions try to answer the question it didnot ask like genotypic ratio etc. Also sex chromosomes only determines the sex of offspring (which also inlcude few genes on X chromosomes and almost none on y chromosomes)....remaing chromosomes which are not sex chromosomes are autosomes.