Science (English Medium) इयत्ता १२ - CBSE Question Bank Solutions for Biology

Each gamete carry ______.

If 30 percent of an organism’s DNA is thymine, then ______.

H-bonds between Cytosine and Guanine are ______.

By which bonds the purine and pyrimidine pairs of Complementary Strands of DNA held together?

There is no DNA in ______.

DNA is made of two chains that twist about one another in the shape of a ______.

______ occurs in RNA instead of the nitrogenous base thymine found in DNA.

Which ratio is constant for DNA?

Which of the following is a structural subunit of DNA?

Assertion: When the two genes in a dihybrid cross are situated on the same chromosome, the proportion of parental gene combinations is much higher than the nonparental type.

Reason: Higher parental gene combinations can be attributed to crossing over between two genes.

Given below is a dihybrid cross performed on Drosophila.

Which of the following conclusions can be drawn on the basis of this cross? When yellow bodied (y), white-eyed (w) Drosophila females were hybridized with brown bodied (y+), red-eyed males (w+) and F1 progenies were intercrossed, F2 generation would have shown the following ratio:

The main reason for the presence of both a leading and a lagging strand during DNA replication is, ______ 

Which of the following is not an invasive alien species in the Indian context?

Where among the following will you find pitcher plant?

The one - homed rhinoceros is specific to which of the following sanctuary?

Which one of the following is an endangered plant species of India?

Retroviruses do not follow central Dogma. Comment.

During in vitro synthesis of DNA, a researcher used 2’, 3’ – dideoxy cytidine triphosphate as raw nucleotide in place of 2’-deoxy cytidine. What would be the consequence?

The scientists believe that evolution is gradual. But extinction, part of evolutionary story, are 'sudden' and 'abrupt' and also group-specific. Comment whether a natural disaster can be the cause for extinction of species.

When we say "survival of the fittest", does it mean that

1. Those which are fit only survive, or
2. Those that survive are called fit

Comment.