Principles of Inheritance & Variation Test 8

The substitution of amino acid in the globin protein results due to the single base substitution at the sixth codon of the betaglobin gene from GAG (Glutamic acid) to GUG (Valine).

Hemophilia A, also called factor VIII (FVIII) deficiency or classic hemophilia, is a genetic disorder caused by missing or defective factor VIII, a clotting protein. Although it is passed down from parents to children, about 1/3 of cases are caused by a spontaneous mutation, a change in a gene.

The aneuploid condition 2n-1 is called monosomy (meaning 'one chromosome') because only one copy of some particular chromosome is present instead of the usual two found in the diploid condition. The ancuploid 2n+1 is called trisomy, where three copies of a particular chromosome can be seen. 2n-2 is null isomy with both the homologous chromosomes missing and n+1 is disomy. 
 

The two genes that produce red and green light-sensitive proteins are located on the X chromosome. Mutations in these genes can cause color blindness. Color blindness is a common inherited sex-linked disorder that affects a person's ability to see or recognize certain colors. Eight to ten percent of all males and one half of a percent of all females are color-blind.

Spontaneous mutations : Mutation have been occurring in nature without a known cause is called spontaneous mutation.

Sickle cell anemia is an autosomal recessive disease, it only occurs if both the maternal and paternal copies of the HBB gene are defective.

It is a condition in boys caused by the presence of an extra X chromosome. Boys normally have one X and one Y chromosome, but most boys with Klinefelter syndrome have two X and one Y chromosome. It is relatively common, occurring in about 1 of every 500 baby boys. There is a wide range findings in this condition, and many cases are not diagnosed until adulthood.

Turner syndrome also known as 45,X or 45,X0, is a condition in which a female is partly or completely missing an X chromosome. Signs and symptoms vary among those affected.

Down syndrome is usually caused by an error in cell division called “nondisjunction.” Nondisjunction results in an embryo with three copies of chromosome 21 instead of the usual two. Prior to or at conception, a pair of 21st chromosomes in either the sperm or the egg fails to separate.

Mutation in single nucleotide base of a DNA segment is called as a point mutation. It occurs by substitution or frameshift mutation. Exchange of one nitrogenous base for another base is called as substitution; option A is correct.