Science (English Medium) Class 12 - CBSE Question Bank Solutions for Biology

Answer the following question.
Two children, A and B aged 4 and 5 years respectively visited a hospital with a similar genetic disorder. The girl A was provided enzyme-replacement therapy and was advised to revisit periodically for further treatment. The girl, B was, however, given a therapy that did not require revisit for further treatment.

How was the girl B cured permanently?

While planning for an artificial hybridization programme involving dioecious plants, which of the following steps would not be relevant?

Haploid plants are preferred over diploids for mutation study because in haploids ______.

Albinism is known to be due to an autosomal recessive mutation. The first child of a couple with normal skin pigmentation was an albino. What is the probability that their second child will also be an albino?

One of the parents of a cross has mutation in its mitochondria. In that cross, that parent is taken as a male. During segregation of F2 progenies that mutation is found in ______.

In split genes, the coding sequence are called ______.

Rate of mutation is affected by ______.

The correct sequence of gene expression is:

1. Formation of the primary transcript
2. Regulation of splicing
3. Transport of mRNA from the nucleus to the cytoplasm
4. Translation

The term gene was coined by ______.

The transcription unit is represented in the diagram given below.

Identify site (i), factor (ii), and Enzyme (iii) responsible for carrying out the process.

Given below are the events that are observed in an artificial hybridization programme. Arrange them in the correct sequential order in which they are followed in the hybridisation programme.

1. Re-bagging
2. Selection of parents
3. Bagging
4. Dusting the pollen on stigma
5. Emasculation
6. Collection of pollen from male parent

How are alleles of particular gene differ from each other? Explain its significance.

How does a mutagen induce mutation? Explain with example.

Define a cistron. Giving examples differentiate between monocistronic and polycistronic transcription unit.

Do you think that the alternate splicing of exons may enable a structural gene to code for several isoproteins from one and the same gene? If yes, how? If not, why so?

One of the major approaches of crop improvement programme is Artificial Hybridisation. Explain the steps involved in making sure that only the desired pollen grain pollinate the stigma of a bisexual flower by a plant breeder. 

Variations caused due to mutations are ______.

Explain the various types of cancer

Cancer is one of the most dreaded diseases. Explain 'Contact inhibition' and 'Metastasis' with respect to the disease

Name any two techniques that are useful in detecting cancers of internal organs.