All human chromosomes are not paired. Most human chromosomes have a maternal and a paternal copy, and we have 22 such pairs. But one pair called the sex chromosomes, is odd in not always being a perfect pair. Women have a perfect pair of sex chromosomes. But men have a mismatched pair in which one is normal sized while the other is a short one.
(a) In humans, how many chromosomes are present in a Zygote and in each gamete?
(b) A few reptiles rely entirely on environmental cues for sex determination. Comment.
(c) "The sex of a child is a matter of chance and none of the parents are considered to be responsible for it." Justify it through flow chart only.
OR
(c) Why do all the gametes formed in human females have an X chromosome?
All human chromosomes are not paired. Most human chromosomes have a maternal and a paternal copy, and we have 22 such pairs. But one pair called the sex chromosomes, is odd in not always being a perfect pair. Women have a perfect pair of sex chromosomes. But men have a mismatched pair in which one is normal sized while the other is a short one.
(a) In humans, how many chromosomes are present in a Zygote and in each gamete?
(b) A few reptiles rely entirely on environmental cues for sex determination. Comment.
(c) "The sex of a child is a matter of chance and none of the parents are considered to be responsible for it." Justify it through flow chart only.
OR
(c) Why do all the gametes formed in human females have an X chromosome?
(a) In humans, 46 chromosomes are present in a zygote and 23 chromosomes are present in each gamete.
(b) In a few reptiles, sex is determined by environmental cues such as temperature. This means that the sex of the offspring is not determined by the genetic makeup of the parents, but by the environment in which the eggs are incubated.
(c) The sex of a child is determined by the type of sex chromosome inherited from the father. If the father contributes an X chromosome, the child will be a girl, and if he contributes a Y chromosome, the child will be a boy. This is a matter of chance and neither parent is responsible for the sex of the child.
Marking Scheme
- 14 marks
Hint
Sex determination in humans is genetically determined, while in a few reptiles it is determined by environmental cues.
Quick Oral Answer
The sex of a child is determined by the type of sex chromosome inherited from the father.
Analysis & Explanation
The question requires the student to understand the concept of sex determination in humans and other species. The student should be able to explain the difference between the number of chromosomes in a zygote and a gamete, and how sex is determined in humans. Additionally, the student should be able to comment on how sex is determined in a few reptiles and justify why the sex of a child is a matter of chance.
Common Mistakes
- 1Confusing the number of chromosomes in a zygote and a gamete
- 2Not understanding how sex is determined in humans and other species
Interesting Facts
Sex determination in humans is genetically determined, while in some species it is determined by environmental cues.
The sex of a child is a matter of chance and neither parent is responsible for it.
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Frequently Asked Questions
How many marks does this question carry in CBSE Class 10 Science 2023?
This question carries 4 marks in the CBSE Class 10 Science 2023 examination.
Which chapter does this question come from in Science?
This question is from the chapter "Heredity" in the CBSE Class 10 Science syllabus.
What topic does this question cover in Science?
This question covers the topic "Sex Determination" from CBSE Class 10 Science.
What type of question is this in the CBSE Class 10 Science 2023 paper?
This question appears in Section Section E in the CBSE Class 10 Science 2023 paper.