Class 12th Biology 2014 Set2 Delhi Board Paper Solution
A colour-blind child is born to a normal couple. Work out a cross to show how it is possible. Mention the sex of this child.
OR
Mendel published his work on inheritance of characters in 1865, but it remained unrecognised till 1900. Give three reasons for the delay in accepting his work.
Colour blindness is a sex-linked disease. The gene for this disorder is present on the X chromosome. Hence, it is carried by normal females not expressing the disease. If a colour-blind child is born to a normal couple, then the mother would be the carrier of the disease. The child would be male. The following cross shows the inheritance of the disorder
OR
The following are the three reasons that led to the delay in accepting Mendel's work:
1) Lack of communication and publicity.
2) His concept of factors (genes) as discrete units that did not blend with each other was not accepted in the light of variations occurring continuously in nature.
3) Mendel approach to explain biological phenomenon with the help of mathematics was also not accepted.
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(b) Adaptations of plants to water scarcity
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- Q:-
Fill in the blanks:
(a) Humans reproduce __________. (asexually/sexually)
(b) Humans are__________. (oviparous/viviparous/ovoviviparous)
(c) Fertilization is __________ in humans. (external/internal)
(d) Male and female gametes are __________. (diploid/haploid)
(e) Zygote is __________. (diploid/haploid)
(f) The process of release of the ovum from a mature follicle is called__________.
(g) Ovulation is induced by a hormone called the __________.
(h) The fusion of male and female gametes is called _____________.
(i) Fertilisation takes place in _____________.
(j) Zygote divides to form _____________which is implanted in uterus.
(k) The structure which provides vascular connection between fetus and uterus is called ____________.