Principles of Inheritance and Variation Test - 62

A.Probability of homozygous dwarf progeny in a cross TT x Tt is zero – True because in this cross all progeny formed are tall,either homozygous  or heterozygous.

B.Probability of homozygous tall progeny in a cross TT x TT is one – True, because all progeny formed in the cross are tall.

C.Probability of heterozygous tall progeny in a cross TT x tt is 0.5 – False, because, all the progeny are formed are heterozygous and the probability is 1.

D.Probability of homozygous dwarf progeny in a cross TT x TT is zero – True, because in this cross not dwarf progeny is involved.

Albino and Negro are controlled two pairs of non- allelic genes. So When a cross is made between the parents with negro and albino 4 types of gametes are formed, because, this cross is based on two pairs of contrasting non allelic traits.

A pea plant with heterozygous round shaped seeds(Rr) is selfed, in the next generation, 1600 seeds are formed. When these seeds germinated, 1200 plants with round seeds and 400 plants with wrinkled seeds are formed.

A.Sickel cell anaemia – Pleiotropic alleles

B.Cystic fibrosis – Pleiotropic alleles

C.Phenylketonuria – it is autosomal recessive disorder.

D.Erythroblastosis foetalis – It is also called hemolytic disease of the newborn, type of anemia in which the red blood cells (erythrocytes) of a foetus are destroyed in a maternal immune reaction resulting from a blood group incompatibility between the foetus and its mother.

Sickle cell anaemia is an autosomal disorder.  It is the most common genetical disorder appear in Africans. It is due to pleotrophy. It is due to the homozygous condition of the gene Hb^S Hb^S. The disease is due to the substitution of sixth codon in gene coding for the b-chain of Haemoglobin. Due to this, sixth amino acid in b-chain of Haemoglobin Glutamic acid is replaced by valine. The main symptom of this disorder is decrease of oxygen uptake.

A cross is made between two tall Garden pea plants, produces all tall plants. The genotypes of the parent plants are TT x TT or TT x Tt.

Phenylketonuria is a recessive autosomal disorder related to phenylalanine metabolism. It is controlled by a single gene having  multiple phenotypes. So it is a pleiotrophy. This disorder is due to the absence of a liver enzyme phenylalanine hydroxylase. Due to the lack of this enzyme, phenylalanine follows another pathway and gets converted into phenyl pyruvic acid. This phenyl pyruvic acid upon accumulation in joints causes arthritis. If it hits the brain, it causes mental  retardation known as phenyl pyruvic idiocy.

i)F₁ progeny is first hybrid generation and progeny resembles either of parent – True.

ii)F₂ progeny is a resultant hybrid generation of cross pollination among F₁ progeny and the progeny shows both dwarf and tall plants – False, because F₂ progeny is a resultant hybrid generation of cross pollination among F₁ progeny and the progeny shows either  dwarf or tall plants.

iii)F₂ progeny is second hybrid generation produced by selfing F₁ hybrids and progeny contains both dwarf and tall plants – True.