In which of the following modes of inheritance, an affected child, who is not th
ID: 259189 • Letter: I
Question
In which of the following modes of inheritance, an affected child, who is not the proband, certainly has at least one affected parent?
XLR in an affected male child
AD with incomplete penetrance
XLR in a homozygous recessive female child
AR traits
XLD with complete penetrance
Two of the above
Which of the following experiments of Mendel is the basis for counseling parents who are both heterozygous for a certain Mendelian trait, on the risk that their child will be born with the recessive phenotype?
His monohybrid P1 cross
His monohybrid F1 self-cross
His monohybrid F2 self-cross
His dihybrid P1 cross
His dihybrid F1 self-cross
A.XLR in an affected male child
B.AD with incomplete penetrance
C.XLR in a homozygous recessive female child
D.AR traits
E.XLD with complete penetrance
F.Two of the above
Explanation / Answer
Q1)In which of the following modes of inheritance, an affected child, who is not the proband, certainly has at least one affected parent?
Answer- F- two of the above.
Explanation - It will be c that is XLR in a homozygous recessive female child.
In this case as it is linked with X chromosome, male have one X and one Y chromosome , and female have two X chromosomes , In a male child X chromosome comes from Mother , so in XLR if father is affected than it will not pass the gene to male child , but it will pass the gene to female child, but if mother is affected or carrier , it will pass the gene to both male and female child. usually this trait affects the male child , so if here father is affetced and mother is a carrier than they will pass the trait to their sons and daughters , so it satisfies the case that an affected child , who is not a proband certainly has one affected parent.
The second answer is F - that is XLD with complete penetrance
Each child with an X-linked dominant trait must have an affected parent , X-linked dominant traits do not skip generations, affected men pass the trait on to all their daughters and not to their sons, affected women (if heterozygous) pass the trait to their sons and of their daughters. complete penetrance means all people will have the disorder.
Q2)
Which of the following experiments of Mendel is the basis for counseling parents who are both heterozygous for a certain Mendelian trait, on the risk that their child will be born with the recessive phenotype?
Answer- A- His monohybrid P1 cross.
Explanation- Here both the parents are heterozygous so parents will be having two types of gametes in parental generation when they are crossed it will show a recessive phenotype
example- suppose the genotype of father is Aa and genotype of mother is Aa both heterozygous , they will be having two types of gamete in parental generation A and a ,(Aa ------> A & a gamete) so when they are crossed,
From the below punnette square it is found that -
so from monohybrid cross of P1 generation itself it is found that the child will be having recessive phenotype
A a A AA Aa a Aa aa (homozygous recessive)