1. ___1___ : ____1____ is the ratio of homozygous to heterozygous offspring.
The answer is 1:1. It could also be expressed in percentage which is 50% : 50%. This is derived by dividing the number of a particular genotype against the whole offspring population. In this case, each genotype is 2/4 * 100 in percentage.
2. ___50____ % are the homozygous recessive.
The answer is 50%. Homozygous recessive means that, in the genotype of the offspring, both alleles of the gene are recessive. In this case, it is rr. As indicated above, this is derived by 2/4 * 100 since there 2 out of 4 of the offspring are recessive homozygous.
X-linked recessive disorders require two affected (recessive) alleles Xb to express in the female, but requires (the) only one in the male.
Therefore there are no male carriers. A normal male has the XB allele, and the affected male has the Xb allele.
A female either has 2 XB alleles, in which case she is normal and not a carrier.
If she has XBXb alleles, then she is a carrier, but phenotype is normal.
If she has XbXb alleles, she will exhibit colour-blindness.
Since woman's father has colour-blindness and she has normal vision, she is a carrier, because she has XBXb alleles.
Her husband has normal vision, so he has (one) XB allele.
Here's the Punnett square
Mother XB (father)
XB XBXB (normal vision)
Xb XBXb (carrier)
We see that the XbXb (colour-blindness) case is missing, so the phenotype colour-blind is not expected (unless other medical conditions are present)
They have kingdom, class, and phylum, I’m kind of confused about the answer because of that.