Advertisements
Advertisements
Question
A cross between a normal couple resulted in a son who was haemophilic and a normal daughter. In course of time, when the daughter was married to a normal man, to their surprise, the grandson was also haemophilic.
(a) Represent this cross in the form of a pedigree chart. Give the genotypes of the daughter and her husband.
(b) Write the conclusion you draw of the inheritance pattern of this disease.
Solution
(a)
Genotype of daughter- XXh
Genotype of husband- XY
(b) Haemophilia is a sex-linked recessive disease. Here, it is transmitted from the carrier female to the sons. From the above pedigree chart, it can be observed that the disease is being transmitted from the carrier female to her daughter (carrier) and son (affected). The carrier daughter transmits this disease to the grandson. This pattern of inheritance is called crisscross inheritance.
APPEARS IN
RELATED QUESTIONS
Define the following:
test cross.
Answer the following question.
British geneticist R.C. Punnett developed a graphical representation of a genetic cross called “Punnett Square”. Mention the possible result this representation predicts of the genetic cross carried.
Differentiate between complete and incomplete linkage.
Analyse the following statements with respect to complete sex linkage and select the correct option.
- It is exhibited by genes located on non-homologous regions of X and Y chromosomes
- Y-linked trait is hypertrichosis.
- X-linked traits are haemophilia, red-green colour blindness, myopia (near sightedness).
Which of the following statement/s are INCORRECT with respect to crossing over?
i. Crossing over produces recombinations of genes by interchanging and exchanging corresponding segments between nonsister chromatids of homologous chromosomes.
ii. Crossing over occurs during zygotene of prophase I of meiosis.
All the linked genes in a particular chromosome, constitute a ____________.
The phenomenon of ____________ is universal and it is necessary for the natural selection, because it increases the chances of variation.
Linkage reduces the frequency of ______.
The contrasting pairs of factors in Mendelian crosses are called ______.
Mendal formulated the law of purity of gametes on the basis of ______.
