Question

Ген праворукости доминирует над геном леворукости, а кареглазость над голубоглазостью. Определите возможные генотипы потомства у кареглазого леворукого юноши, отец которого имел голубые глаза, и голубоглазой правши девушки.

Answer 1

Правая рука А
левая          а
карие глаза  B
голубые глаза b

Если девушка гомозиготна:
P AAbb  x  aaBb
F1  AaBb   Aabb
Если гетерозиготна:
P Aabb  x  aaBb
F1  AaBb   Aabb  aaBb  aabb

Answer 2

I will try to answer your question in detail. The gene for right-handedness dominates over the gene for left-handedness, and the gene for brown eyes dominates over the gene for blue eyes. To determine the possible genotypes of the offspring of a brown-eyed left-handed boy, whose father had blue eyes, and a blue-eyed right-handed girl, we need to use the Punnett square method.

Let us denote the gene for right-handedness as R and the gene for left-handedness as r. Similarly, let us denote the gene for brown eyes as B and the gene for blue eyes as b. Since the boy is left-handed, he must be homozygous recessive for the hand trait, so his genotype is rr. Since his father had blue eyes, he must have inherited one b allele from him, so his genotype for the eye trait is Bb. Therefore, the boy's overall genotype is rrBb.

The girl is right-handed, so she must have at least one R allele. She is also blue-eyed, so she must be homozygous recessive for the eye trait, bb. Therefore, her overall genotype is Rrbb or RRbb. We do not know for sure if she is homozygous or heterozygous for the hand trait, so we will consider both cases.

If the girl is heterozygous for the hand trait, Rrbb, then the possible genotypes of the offspring are:

| | Rb | rb | |---|----|----| |r | RrBb | rrBb | |r | Rrbb | rrbb |

The phenotypes of the offspring are:

- 25% right-handed and brown-eyed (RrBb) - 25% left-handed and brown-eyed (rrBb) - 25% right-handed and blue-eyed (Rrbb) - 25% left-handed and blue-eyed (rrbb)

If the girl is homozygous for the hand trait, RRbb, then the possible genotypes of the offspring are:

| | Rb | Rb | |---|----|----| |r | RrBb | RrBb | |r | Rrbb | Rrbb |

The phenotypes of the offspring are:

- 50% right-handed and brown-eyed (RrBb) - 50% right-handed and blue-eyed (Rrbb)

There are no left-handed offspring in this case.

I hope this helps you understand the inheritance of these traits. You can find more information about genetics and Punnett squares on the web .