A child has blood group O. If the father has blood group A and mother blood group B, work out the genotypes of the parents and the possible genotypes of the other offsprings.
Solution and Explanation
The blood group characteristic in humans is controlled by three set of alleles, namely, IA , IB , and i. The alleles, IA and IB , are equally dominant whereas allele, i, is recessive to the other alleles. The individuals with genotype, IA IA and IA i, have blood group A whereas the individuals with genotype, I B IB and IB i, have blood group B. The persons with genotype IA IB have blood group AB while those with blood group O have genotype ii. Hence, if the father has blood group A and mother has blood group B, then the possible genotype of the parents will be Father Mother I A IA or IA i IB IB or IB i
A cross between homozygous parents will produce progeny with AB blood group.
A cross between heterozygous parents will produce progenies with AB blood group (IA I B ) and O blood group (ii).
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In a certain population, the frequency of three genotypes is as follows:
Genotypes: PP Pp pp
Frequency: 22% 62% 16%
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Concepts Used:
Principles of Inheritance and Variation - Mutation
A Mutation is a change in the sequence of our DNA base pairs caused by numerous environmental stimuli such as UV light or mistakes during DNA replication. Germline mutations take place in the eggs and sperm and can be passed onto offspring, whereas somatic mutations take place in body cells and are not passed on.
Types of Mutations
There are three types of mutations, which are as follows:
Silent mutation
It refers to any change in DNA sequence that has no effect on the amino acid sequence in a protein or the functions that a protein performs. There is no phenotypic indication that a mutation has occurred.
Nonsense mutation
When there is a change in the sequence of base pairs due to a point mutation, that results in a stop codon. This leads to a protein that is either shortened or non-functional.
Missense mutation
A missense mutation occurs when a point mutation causes a change in the codon, which then codes for another amino acid.
The mutation is caused by the following factors:
Internal Causes
When DNA copies incorrectly, the majority of mutations occur. Evolution occurs as a result of all of these mutations. DNA makes a copy of itself during cell division. When a copy of DNA isn't flawless, it's called a mutation since it differs somewhat from the original DNA.
External Causes
When certain chemicals or radiations are used to break down DNA, it causes the DNA to break down. The thymine dimers are broken by UV radiation, resulting in altered DNA.