In humans, a hypothetical trait is under the control of a single gene, A . Four
ID: 3478577 • Letter: I
Question
In humans, a hypothetical trait is under the control of a single gene, A. Four alleles have been found: A1, which is dominant to all others; A2, which is dominant to A3and A4, which are codominant.
A) If gene A is on an autosome, how many different genotypes are possible?
B) If gene A is on an autosome, how many different phenotypes are possible?
C) If gene A is on the X, how many different genotypes are possible?
D) If gene A is on the X and homozygous and hemizygous genotypes have different phenotypes, how many different phenotypes are possible?
Explanation / Answer
Solution:
xxx.
10 xxxxxyxxx xxx x Phenotypes
xx A1 = xx xxxxxxyxx A1 xx = xx xxxxxxyxx xx A3 = A1 xxxxxxyxx xx xx = xx phenotype
xx xx = A2 xxxxxxyxx A2 xx = xx phenotype
xx A4 = xx xxxxxxyxx A3 xx = xx xxxxxxyxx xx A4 = A4 xxxxxxyxx xx xx = xxxx phenotype
xx xxxxx, = 4 xxxxxyxxx and x xxxxxxyxxx Xxx Y = A1 xxxxxxyxx Xxx Y = xx phenotype
Xxx Y = A3 xxxxxxyxx XA4 Y = xx phenotype
xx Females, = xx xxxxxyxxx and x Phenotypes
Xxx Xxx = A1 xxxxxxyxx XA1 Xxx = xx phenotype
Xxx XA3 = xx xxxxxxyxx XA1 Xxx = xx xxxxxxyxx Xxx XA2 = A2 xxxxxxyxx Xxx Xxx = xx phenotype
Xxx Xxx = A2 xxxxxxyxx XA3 Xxx = xx phenotype
Xxx XA4 = xx xxxxxxyxx XA3 Xxx = xxxx xxxxxxyxx xx Different xxxxxxyxxx Possible xxx xxxxxxzyxxxx xxxxxyxx, then,
xx Genotypes xxx xx xxxxxxyxxx XA1 Xxx = xx xxxxxxyxx Xxx XA2 = A1A2 xxxxxxyxx Xxx Xxx = xxxx phenotype
Xxx Xxx = A1A4 xxxxxxyxx XA2 Xxx = xx phenotype
Xxx XA3 = xxxx xxxxxxyxx XA2 Xxx = xxxx xxxxxxyxx Xxx XA3 = A3 xxxxxxyxx Xxx Xxx = xx phenotype
Xxx Xxx = A3A4 xxxxxxyxx
A) A1 A2, A1 A3, A1 A4
B) only one, as A1 is dominant over all others.
In humans, a hypothetical trait is under the control of a single gene, A. Four alleles have been found: A1, which is dominant to all others; A2, which is dominant to A3 and A4, which are codominant.