NEET Sample Paper 2025 PDF by NTA - Model Question Paper With Solution

Codominance MCQ - Practice Questions with Answers

Edited By admin | Updated on Sep 18, 2023 18:34 AM | #NEET

Quick Facts

  • Codominance is considered one of the most asked concept.

  • 24 Questions around this concept.

Solve by difficulty

A person which unknown blood group under ABO system, has suffered much blood loss in an accident and needs immediate blood transfusion. His one friend who has a valid certificate of his own blood type offers blood donation without delay. What would have been the type of blood group of the donor friend?

ABO blood groups in humans are controlled by the gene I.It has three alleles Ia,Ib and i . Since there are three different alleles, six different genotypes are possible. How many phenotypes can occur?
 

ABO blood grouping is controlled by gene I which has three alleles and show co-dominance. There are six genotypes. How many phenotypes in all are possible?

A gene showing codominance has :

If two persons with the 'AB' blood group marry and have a sufficiently large number of children, these children could be classified as 'A' blood group: an 'AB' blood group: a 'B' blood group in a 1:2:1 ratio. Modern technique of protein electrophoresis reveals the presence of both 'A' and 'B' type proteins in 'AB' blood group individuals. This is an example of:

Which ONE of the following is the most likely ratio of blood groups \left ( A:B:AB \right ) among the progeny from heterozygous parents with B and AB blood groups?

Concepts Covered - 1

Codominance
  • A variation on incomplete dominance is codominance, in which both alleles for the same characteristic are simultaneously expressed in the heterozygotes.
  • Hence, in the case of co-dominance, the F1 generation resembles both parents.
  • A good example is the different types of red blood cells that determine ABO blood grouping in human beings. 
  • ABO blood groups are controlled by the gene I, located on chromosome number 9.
  • The gene (I) has three alleles I^{A}, I^{B}and i
  • The alleles IA and IB produce a slightly different form of the sugar while allele i doesn’t produce any sugar. 
  • Because humans are diploid organisms, each person possesses any two of the three I gene alleles. 
  • IA and IB are completely dominant over i, in other words when I^{A} and i are present only I^{A} expresses (because i does not produce any sugar), and when I^{B} and i are present I^{B} expresses.
  • But when IA and IB are present together they both express their own types of sugars: this is because of codominance. 
  • Hence red blood cells have both A and B types of sugars. 
  • Since there are three different alleles, there are six different combinations of these three alleles that are possible a total of six different genotypes of the human ABO blood types.
  • In a self-cross between heterozygotes expressing a codominant trait, the three possible offspring genotypes are phenotypically distinct. 
  • However, the 1:2:1 genotypic ratio characteristic of a Mendelian monohybrid cross still applies.

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Codominance

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