RNA polymerase I and III catalyse the transcription of r-RNA and t-RNA respectively

Leydig's cells occur in small masses among the seminiferous tubules of the testes, they secrete testosterone.

Hardy-Weinberg principle states that allele frequencies in a population are stable and remain constant generation after generation; it is called genetic equilibrium.
Genetic drift
Genetic drift refers to the random changes in the allele frequencies of a population, in the allele frequencies of a population, that occur only by chance.
When the change in the allele frequency is so different in the original drifted population that it becomes a new species, the original population becomes founders and such an effect, is called founder effect.

1. Since geitonogamy involves two different flowers of the same plant, it is genetically similar to autogamy; both autogamy and geitonogamy do not result in genetic variation in the progeny.
2. Geitonogamy and cross-pollination involve different flowers and a pollinating agent.

Parthenocarpy.

(i) The process of formation of megaspores from Megaspore Mother Cell or MMC (diploid) is called megasporogenesis.
It occurs inside the nucellus of developing ovule of angiosperms. The process begins very early when nucellus is not conmpletely surrounded by the integuments. The MMC (a large cell containing dense cytoplasm and a prominent nucleus) enlarges in size and divides by meiosis. It first divides transversely into two cells called megaspore dyad. 
These two cells apgain divide transversely as a result, a linear row of four haploid cells megaspore tetrad is produced.

Out of the four megaspores one situated at the chalazal end remains functional and the rest three gradually degenerate. Such a development of embryo sac is called monosporic development, e.g. Pobygonum.
(ii)

Inheritance pattern of ABO blood groups in human population.
(i) Codominance I^A and I^B both are codominant as both of them express themselves independently in blood group AB (I^A I^B).
(ii) Multiple Allelism A phenomenon in which genes exist in more than two allelic forms or combinations.
For example, the gene for blood group exists in three allelic forms 1, and i.

Significance: Connecting links prove the path of evolution and lie midway between two groups. These confirm evolution of amphibians from fishes; mammals from reptiles; arthropods and molluscs from the annelids. Such animals indicate transitional forms of organic evolution.

1. The viruses/bacteriophages grown on radioactive sulphur \(\left( ^{ 35 }{ S } \right) \)    contained radioactive protein but not radioactive DNA, because DNA does not contain sulphur.
2.When these viruses were allowed to infect bacteria, the bacteria did not contain radioactivity, because proteins did not enter the bacteria; hence protein is not the genetic material.
3. The viruses grown on radioactive phosphorus  \(\left( ^{ 32 }{ P } \right) \)   contained radioactive DNA, becauseDNA contains phosphorus and not proteins. 
4. When these viruses were allowed to infect the bacteria, the bacteria were radioactive, indicating that DNA is the genetic material that has passed from the virus into bacteria.