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

The cells of endosperm have 24 chromosomes. What will be the number of chromosomes in the gametes?

Amino acids which are specified by single codons are ______.

Which out of the following statements is incorrect?

Some amino acids are coded by more than one codon, hence the genetic code is ______.

The mutations that involve addition, deletion or substitution of a single pair in a gene are referred to as ______.

Sickle cell anemia results from a single base substitution in a gene, thus it is an example of ______.

Select the incorrectly matched pair.

If the sequence of bases in coding strand of DNA is ATTCGATG, then the sequence of bases in mRNA will be ______.

Mark the odd one.

Mark the odd one.

The coconut water from tender coconut is ______

Which of the following statements are true related to Seed X and Y?

SEED X	SEED Y

1. Seed X is dicot and endospermic or albuminous.
2. Seed X is dicot and non-endospermic or non-albuminous.
3. Seed Y is a monocot and endospermic or albuminous.
4. Seed Y is a monocot and non-endospermic or non-albuminous.

Choose the correct option with the respect to the nature of the seed.

AUG on the mRNA will result in the activation of which of the following RNA having the correct combination of amino acids: 

Why does the zygote begin to divide only after the division of Primary endosperm cell (PEC)?

What is Down’s syndrome? Give its symptoms and cause. Why is it that the chances of having a child with Down’s syndrome increases if the age of the mother exceeds forty years?

How was it concluded that genes are located on chromosomes?

Define aneuploidy. How is it different from polyploidy? Describe the individuals having following chromosomal abnormalities.

1. Trisomy of 21^st Chromosome
2. XXY
3. XO

Which of the following statements is the most appropriate for sickle cell anaemia?

Based on your understanding of genetic code, explain the formation of any abnormal hemoglobin molecule. What are the known consequences of such a change?

A single base mutation in a gene may not ‘always’ result in loss or gain of function. Do you think the statement is correct? Defend your answer.