Question

1. Explain the difference between incomplete dominance and codominance.
2. A man with blood type A marries a woman with blood type B. One of their children has blood type O. Show how this is possible.
3. What are polygenic traits? Give an example of a polygenic trait in humans (besides skin color).
4. A male human is heterozygous for detached earlobes (Ee) and could produce sperm that contain either the dominant gene (E) or recessive gene (e). Does this occur during meiosis or mitosis?
5. Linked genes are on ( the same / different ) chromosome(s) and tend to be inherited ( together / separately).

Answer 1

Ans1. Incomplete dominance - in this type of dominance, there is no mixing of character. The gene is either show its nature completely or does not show. For example if a plant show incomplete dominance and red colour is dominant over white Colour and we make a cross between pure red and white then the we get only red plant no intermixed colour.

Co-dominance - while in case of co dominance, both the gene will show its character. There will be mixing of both character. For example take the case provided above, when we cross these plants then we get neither red nor white, we get pink colour.

Ans2. The boy may gets O type blood group when both the parents are heterogenous. Father genotype AO and mother genotype is BO. When we cross this we get results as follows

1 -AB type blood group

1 -A type blood group

1 -B type blood group and

1-O type blood group

Ans3. A polygenic trait mean one character is controlled by several genes. When a character is influenced by many genes then it means this character is a polygenic character. In human, height is an example of polygenic trait.

Ans4. The separation of chromosomes occurs in meiosis. In meiosis the number of chromosomes gets half.

Ans5. Linked genes are occurs on the same chromosomes and tend to be inherited together. Linked genes are those genes which are found attached on the same chromosomes and can not be separated by meiosis.