Principles of Inheritance and Variation Test - 20

1.  A cross is made between homozygous yellow round seeds (YYRR) to another homozygous green wrinkled seeds (YyRr). In the F₁ generation, all plants are heterozygous yellow round (YyrRr).

2.  When this plant is subjected to self-pollination, in the F₂ generation, 9 plants are Yellow round, 3 plants are yellow wrinkled, 3 plants are green round and 1 plant is green wrinkled are formed.

3.  The dihybrid phenotypic ratio is 9:3:3:1.  So, in the dihybrid cross, 800 individuals are formed, in this 450 are yellow round 150 are yellow wrinkled, 150 are green round, 50 are green wrinkled.

Colchicines inhibit the cell division or mitosis, but duplication of chromosomes is continue, as a result, diploid becomes tetraploid.

Pesticide resistance describes the decreased susceptibility of a pest population to a pesticide that was previously effective at controlling the pest. Pest species evolve pesticide resistance via natural selection:

1.  The most resistant specimens survive and pass on their acquired heritable changes traits to their offspring. Cases of resistance have been reported in all classes of pests (i.e. crop diseases, weeds, rodents, etc.), with 'crises' in insect control occurring early-on after the introduction of pesticide use in the 20th century.

2.  The Insecticide Resistance Action Committee (IRAC) definition of insecticide resistance is 'a heritable change in the sensitivity of a pest population that is reflected in the repeated failure of a product to achieve the expected level of control when used according to the label recommendation for that pest species'.

3.  Although the evolution of pesticide resistance is usually discussed as a result of pesticide use, it is important to keep in mind that pest populations can also adapt to non-chemical methods of control.

1.  Duplication is presence of extra chromosomal segment which is attached to the normal homologous chromosome causing duplication of set of genes in the same chromosome.

2.  Inversion is chromosomal mutation where a segment of a chromosome is reversed end to end. It occurs by introduction of break in single chromosome, its rotation by l80 degree followed by its reinsertion in the same location.

3.  Loss of one or more nucleotide bases to the DNA segment by removal of an intercalary DNA segment is known as deletion. Cri-du-chat Syndrome characterized by mewing like cry of newborn which is caused by loss of half of the long arm of chromosome 5 causes severe developmental delay in newborn.

4.  Rearrangement of chromosomal segment between two non homologous chromosomes is called reciprocal translocation.

1.  The types of oligosaccharides present on the surface of the red blood cells determine a person's blood type if the antigen A or B is found, the blood is type A or B, respectively, and if both A and B antigens are present, the blood type is AB.

2. In blood type O however no antigens are present on the surface. Here i, ii, i gives the genotype for blood group O.

3. Hence, there will be no oligosaccharide antigen present on the surface of the RBC's in case of this genotype

1.  Test cross is performed to determine the genotype of F₁ plant. In a typical test cross an organism showing dominant phenotype and whose genotype is to be determined is crossed with one that is homozygous recessive for the allele being investigated, instead of self-crossing.

2. The progenies of such a cross can easily be analyzed to predict the genotype of the test organism.

Edwards syndrome, also known as trisomy 18, is a genetic disorder caused by the presence of a third copy of all or part of chromosome 18.

Zech discovered Y-spot.

Down's syndrome is caused due to the Trisomy of 21 chromosomes which is an autosome. It is mainly caused due to the non-disjunction of the chromosomes. Non-disjunction is the condition when the sister chromatids fails to separate during the cell division.