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

Assertion: Functional ADA cDNA genes must be inserted in the lymphocytes at the early embryonic stage.

Reason: Cells in the embryonic stage are mortal, differentiated and easy to manipulate.

Explain the formation of placenta after the implantation in a human female.

Draw a diagram showing human foetus within the uterus and label any four, parts in it.

Explain the phases in embryonic development from the morula stage till the establishment of pregnancy in a human female.

A male honeybee has 16 chromosomes whereas its female has 32 chromosomes. Give one reason.

How many chromosomes do drones of honey bees possess?

State the difference between meiocyte and gamete with respect to chromosome number.

Briefly mention the contribution of T. H. Morgan in genetics.

Who had proposed the chromosomal theory of inheritance?

Name the type of cell division involved in the production of sperms by honey bees.

Answer the following question.
Compare in any three ways the chromosomal theory of inheritance as proposed by Sutton and Bovery with that of experimental results on pea plant presented by Mendel.

A plant having the genotype AABbCC will produce ______ kinds of gametes.

A gene pair hides the effect of another. The phenomenon is ______.

Extranuclear inheritance occurs in ______.

Extra nuclear chromosomes occur in ______.

Extranuclear inheritance is a consequence of presence of genes in ______.

In a certain taxon of insects some have 17 chromosomes and the others have 18 chromosomes. The 17 and 18 chromosome-bearing organisms are ______.

Two or more independent genes present on different chromosomes which determine nearly same phenotype are called ______.

Mendel’s work was rediscovered by three scientists in the year ______.

Which three scientists independently rediscovered Mendel’s work?