Question

6.Tay-Sachs disease is an autosomal recessive disorder that causes degeneration of nerve tissue in infants. Infants with Tay-Sachs disease develop blindness, paralysis, and die at an early age. The gene for this disorder is located on chromosome 15. Sickle cell anemia is another autosomal recessive disorder. A person who is homozygous recessive for the sickle cell allele will have an abnormal hemoglobin protein which causes the red blood cells to have a sickle shape. The misshapen blood cells block capillaries which restricts blood flow. This gene is located on chromosome 11. A woman finds out she is heterozygous or a carrier of recessive alleles for both genetic disorders. Using your understanding of the laws of segregation and independent assortment, explain how meiosis leads to only a 25% chance of any of her eggs having both recessive alleles. (If you are trying to answer this question using a Punnett square, you are incorrect. A Punnett square simulates fertilization which assumes that meiosis and egg or sperm have already been produced.)

Answer 1

Answer:

Law of Independent Assortment:

                        It states that factors (genes) for different pairs of contrasting characters are assorted independent of one another during gamete formation. This implies that during gamete formation, the alleles for sickle cell disease do not interfere with alleles for Tay0sacgas disease and the two pairs of alleles behave independent of each other.

Tay-sachs gene has two alleles, T & t. Each allele has equal chance (50%) of getting inherited.

Sickle cell anemia has two alleles, S & s. Each allele has equal chance (50%) of getting inherited.

TtSs genotype produces 4 types of gametes, the probability of each gamete is as follows:

TS = 50% * 50% = 25%

Ts = 50% * 50% = 25%

tS = 50% * 50% = 25%

ts = 50% * 50% = 25%