Humans carry two copies of most genes. Individuals that carry two identical variants of a gene are called homozygous whereas those that carry two different variants are called heterozygous. For example, if there are two possible variants labelled A and a, then AA and aa individuals are homozygous, whereas Aa and aA individuals are heterozygous. Suppose two heterozygous parents have a child, and each gives one of its genes to the offspring.
(a) How many types of offspring are possible if all that matters is the identity of the genes?
ANS: 2 types of offspring
(b) In some cases the same variant behaves differently if it is inherited from the mother versus the father. How many types of offspring are possible if we account for such effects?
ANS:4 types of offspring
theres no answer in the book. any suggestion of I got it right?
(a) assuming that the types are phenotypes, and A is dominant over a, you are correct.
(b) Is variant dominant or recessive? If dominant, you are correct.
Check by using Punnett square.
Based on the information provided, your answers seem correct. Let me explain how to arrive at these answers:
(a) When two heterozygous parents have a child, each parent can contribute one of their two gene variants. Since there are two possible gene variants (A and a), there are two possible options for the gene contributed by each parent. Therefore, there are 2 * 2 = 4 possible combinations of gene variants for the offspring. However, since we are only concerned with the identity of the genes and not the order in which they are inherited, we divide this number by 2. This gives us a total of 4 / 2 = 2 types of offspring.
(b) Taking into account the fact that the same gene variant can behave differently depending on whether it is inherited from the mother or the father, we need to consider all possible combinations of maternal and paternal gene variants. Each parent can still contribute one of their two gene variants (A or a), but now we have to consider the order in which these variants are contributed. So, for each gene variant contributed by the mother, there are two possible combinations with the gene variants contributed by the father. This means we have 2 * 2 = 4 possible combinations of gene variants for the offspring. Therefore, there are 4 types of offspring if we account for such effects.