MODEL PAPER 7 — BIOLOGY STD 12 Science — Question

Highlight the differences and a similarity between the following population interactions: competition, predation and commensalism.

In peas, tallness is dominant over dwarfness, and red colour of flowers is dominant over the white colour. When a tall plant bearing red flowers was pollinated with a dwarf plant bearing white flowers, the different phenotypic groups were obtained in the progeny in numbers mentioned against them:
Tall, Red = 138
Tall, White = 132
Dwarf, Red = 136
Dwarf, White = 128
Mention the genotypes of the two parents and of the four offspring types.

Identify a, b, c, d, e and f in the table given below:

S. No.	Organism	Bioactive molecule	Use
A.	Monascus purpureus (yeast)	a	b
B.	c	d	antibiotic
C.	e	Cyclosporin A	f

Explain the following.

1. What is the most common example of pleiotropy in humans?
2. How are the pleiotropic genes useful?

Answer the following questions:
Explain sex determination in humans.

A species-area curve is drawn by plotting the number of species against the area. How is it that when a very large area is considered the slope is steeper than that for smaller areas?

How are the structural genes activated in the lac operon in E. coli?

Describe a palindrome with the help of an example.

Monocistronic structural genes in eukaryotes have interrupted coding sequences. Explain. How are they different in prokaryotes?

Define co-extinction and give a example.