CBSE Class 12 Biology — Short Answer Questions

(a) Do all pollen grains remain viable for the same length of time? Support your answer with two suitable examples. [2½] (b) How are pollen grains stored in pollen banks? [½]

(a) What is pedigree analysis? Mention its importance in human genetics. (2 pts.) [1+1] (b) Analyse the following pedigree and write the (i) Pattern of inheritance. [½] (ii) Give one example of disease showing such an inheritance pattern. [½] [Pedigree chart provided below the question.]

(a) Mention the scientific name of the source plant and the part from which opioids are extracted. [1] (b) How are morphine and heroin related? Mention the effect each one of them has on human body. [2]

A farmer grew two varieties of corn crop in field A and B. He grew normal corn crops in field A and GM corn crops in field B. He observed that corn borers attacked only in field A. To control it, spores of Bt were sprayed on field A. (a) Name the gene in the spores responsible for control of pest. [½] (b) What effect will the spores of Bt have on insect pest? [1½] (c) How has corn plants of field B developed resistance against this pest? Explain. [1]

Observe the given picture carefully. A mixture of DNA with fragments ranging from 100 base pairs to 1800 base pairs were separated by electrophoresis on agarose gel with the following arrangement: [Diagram 1 provided.] (a) What result will be obtained in staining with ethidium bromide? Explain with reasons. [1] (b) The above setup was modified as shown below and a band with 100 base pairs was obtained at X. [Diagram 2 provided.] What changes were made to the previous design to get a band at 'X'. Why did the band appear at 'X'? [2]

(a) How is Hardy-Weinberg expression $(p^2 + 2pq + q^2) = 1$ derived? [2] (b) List any two factors that disturb the genetic equilibrium. [1]

Draw a neat diagram of megasporangium of an angiosperm and label any six parts. [$\frac{1}{2} \times 6 = 3$]