Question

7. What type of trait is found the most often in nature? a. mutant trait b. wild-type trait C. dominant trait d. recessive trait 8. A heterozygous person that has one disease allele and one normal allele is referred to as a 9. Tay-Sachs is an autosomal recessive disease. A couple (Jack and Jill) is worried about having a child who has Tay-Sachs, because Jack had a brother with the deadly disease. Since they wanted to have children, they sought the advice of a genetic counselor. Rusing.tbs.saws of the interview the counselor determined that Jack's parents were not affected with Tay-Sachs, yet his brother had it. What is immediately known about the genotypes of Jack's parents? Is the genotype of Jack immediately known? Under what circumstances could Jack and Jill have a child with lay-Sachs? Assume that neither Jack nor Jill has Tay-Sachs Variations on Mendel's Laws Complete the following questions as you read the chapter content-Variations on Mendel's Laws: 1. Complete the following table regarding rules of inheritance that are not Mendelian. Incomplete dominance Polygenic inheritance Codominance Pleiotropy Epigenetic inheritance Characteristics Example

Answer 1

1.The phenotype most commonly found in nature is referred to as the wild type trait.

2. A heterozygous person ho has one disease causing allele and one normal allele is called a carrier of the disease.If the person has a child ith another carrier or a diseased person the offspring might be diseased.

3. Taysach's is autosomal recessive therefore the diseased person will have a genotype tt. Since Jack's parents ere not affected but hs brother was, Jack's parents would be carriers, that is they will be heterozygous with 1 disease allele and 1 normal allele. Genotype of Jack's parents ill be Tt. Knowing this and the fact that Jack is not affected, Jack's ggenotype could be either Tt (carrier) or TT(normal). Since Jill is also not affected she could also have the genotype TT or Tt.Only if both Jack and Jill are carriers i.e if both have the genotype Tt, there is a chance of them having a child who is affected.

If one of them as normal and one as a carrier no affected children

	T	T
T	TT	TT
t	Tt	Tt

If both were carriers there is a possbility of an affected child

	T	t
T	TT	Tt
t	Tt	tt (affected)

4.Incomplete dominance- Neither alleles are dominant, heterozygous individuals show a different phenotype from that of dominant individuals. Eg. Pink flowers in heterozygous snap dragon flowers is due to incomplete dominance here red is dominant and hite flowers are recessive.

Codominance- In this the expression of one allele cannot be masked by the other allele.Both are equally expressed. Eg. AB blood group in humans where both allele A and allele B are expressed.

Pleieotropy- A single gene codes for more than one phenotype. Eg. In phenyl ketonuria only one gene is affected but it causes various symptoms such mental retardation, lack of pigmentation etc hich are phenotypically different but due to mutation in the same gene.

Polygenic inheritance-A single phenotype is controlled by more than one gene. Eg. Skin, hair and eye colour in humans is determined by interactions of multiple genes

Epigenetic inheritance- There is a change in phenotye without a change in enotyppe from arent to child due to eigentic changes such as DNA methylation etc. Eg. Lack of anthocyanin accumulation in maize due to gene silencing.