Q13 of 27 Page 1

Draw a well labelled diagram of L.S of a pistil showing the passage of growing of pollen tube up to its destination.


During pollination, the pollen grain which is present on the stigma germinates to produce a pollen tube. The contents of the pollen grain are transferred into the pollen tube. As the length of the pollen tube increases, it reaches the ovary and enters into the ovule through the micropyle. It then enters one of the synergids through filiform apparatus. It is this filiform apparatus which guides the entry of the growing pollen tube.


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11

Explain the events that occur in the host cell on introduction of nematode resistant gene into the tobacco plant by using Agrobacterium vectors.

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Construct a pyramid of biomass starting with phytoplankton. Label three trophic levels. Is the pyramid upright or inverted? Justify your answer.

 14

How does gain or loss of chromosome(s) takes place in humans? Describe one example each of chromosomal disorder along with the symptoms involving an autosome and a sex chromosome.

OR


A small stretch of DNA that codes for a polypeptide is given below


3'--- --- --- --- CAT CAT AGA TGA AAC --- --- --- --- 5'


a) Which type of mutation could have occurred in each type resulting in the following mistakes during replication of the above original sequence?


i. 3`… … … …CAT CAT AGA TGA ATC… … … 5`


ii. 3`… … … …CAT ATA GAT GAA AC… … … 5`


b) How many amino acids will be translated in each of the above two cases?


 15

“Apomixes is a form of asexual reproduction that mimics sexual reproduction in plants”. Explain with the help of a suitable example.