More Biology Questions!?

Question

Thanks to ther person that answered my last ones!

1. In Humans, the genotype XO results from

a. Trisomy.
b. Nondisjunction. - i'm pretty sure it's that.
c. Inversion.
d. Insertion.

2. Why is pattern balness more commin in men than in women?

3. A couple has four children, and each child has a different ABO blood type. What are the blood types and genotypes of the children and parents?

Answer 1

1. not sure.....

2. Why is pattern balness more commin in men than in women?---because pattern baldness is a sex-linked trait, meaning that the allele for baldness is carried on the X and Y chromosomes. The Y chromosome, however, is too small to carry an allele, so, if the mother passes down the recessive gene for baldness and the father passes down the Y, making a boy, then there is no way for the Y to have a dominant allele to cancel out the baldness and so the boy has pattern baldness.

3. A couple has four children, and each child has a different ABO blood type. What are the blood types and genotypes of the children and parents?

parent one has heterozygous A blood(I^A i), parent two has heterozygous B blood(I^b i). you can't do superscripts here so the ^ means that the A and B are small and above the I to the right, this is just how they are written.

child 1: I^A I^B (type AB)
child 2: I^B i (type B)
chld 3: I^A i (type A)
child 4: i i (type O)

Answer 2

Question 1: YOU ARE RIGHT!!! Trisomy gives you an extra chromsome, so there is a corresponding choromosome. Inversion and Insertion would still give you the choromosome. Nondijunction would give rise to a wrong number of choromsomes because the segregation was a failure.

Question 2: Pattern Baldness comes from the sex chromosome. In the male genome, the sex choromsome is XY while the female is XX. It happens that the gene giving rise to pattern baldness is a recessive gene. In male, the Y choromsome is shorter. Again, it happens that the gene causing pattern baldness is on the higher end of the X choromsome whereby the Y chorosome is unable to give a corresponding allele to "counteract" its effect. Unlike female, they have both X choromosome, so long as one of them is a domiant gene, it should prevent the women from having pattern baldness.

Another reason is that all males get their X chorosome from the female. This is because the only way for male to get Y chormosome must have been from the male side since women do not have Y chromosome. So as long as the mother is a carrier, there is 50% chance of passing that gene to the male. With this + the above reason, this give rise to male being more common to having pattern baldness.

Question 3) Children can have blood genotype type: AB, AO, BO, OO
Phenotype: AB, A, B, O
Parents should have blood genotype: AO and BO.
Phenotype: A, B

Reason: AO + BO --> AB, AO, BO, OO.