Q2 of 40 Page 15

Describe in brief Mendel’s monohybrid cross.

Mendel select garden pea plant(Pisum sativum) for his experiment.


Mendel took garden pea plant because of the following reason—


i. It is easy to pollinate pea flowers.


ii. Flowers are bisexual and self pollinating.


iii. It produces a large number of seeds in one generation.


iv. Pea plant has a short life cycle.


Mendel took homozygous tall pea plant and cross it with homozygous drawf pea plant. In F1 generation all the pea plants are tall.


He then self-pollinated F1 generation plants to generate F2 generation plants.


In F2 generation he found 75% of the plants are tall and 25% are drawn.


Observations


i. F1 progenies show one of the parent's trait and trait of other parents was not seen.


ii. F2 stage show both of the parent trait in proportion 3:1.


iii. The contrasting traits did not show any blending at F1 and F2 stage.


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20

Mention the dominant and recessive traits observed by Mendel in the garden pea plant with respect to the seed and flower.

 1

Human evolution has undergone a record of changes during the past 15 million years.

i) Name the different species of mankind in chronological order from primitive to modern man.


ii) When were the primitive caves developed?


iii) Narrate the life led by an early man-like hominids.

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i) I am an acid used as a preservative and I have a sour taste.


ii) I am organic and present in citrus fruits and I give immunity.


iii) I am a cholesterol containing steroid obtained from bread mould. I am the steroid.


iv) I am an enzyme and I cut DNA at specific sites.


v) I am the paste enzyme that joins segments of DNA.

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State whether true or false. Correct the statements that are false.

i) Variations give the organisms an individuality of their own.


ii) Charles Darwin postulated the use and disuse theory.


iii) To understand evolution, a branching diagram or a tree diagram is used to show the inferred evolution and the relationship among various biological species.


iv) Genetic engineering is the modification of the genetic information of living organisms by manipulation of DNA by adding, removing or repairing part of the DNA and changing the phenotype