✓ Board-verified↻ asked 3×
Science · 2023 · 4 marks
CBSE 2023 · Region 6 · Set 1 · Q38
All human chromosomes are not paired. Most human chromosomes have a maternal and a paternal copy, and we have $\displaystyle 22$ 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."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.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 $\displaystyle 22$ 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.
"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.
Why do all the gametes formed in human females have an X chromosome ?
Marking-scheme solution
(a) Zygote - $\displaystyle 23$ pairs / $\displaystyle 46$ chromosomes.
Gamete - $\displaystyle 23$ chromosomes.
(b) The temperature at which fertilised eggs are kept determines whether the animals developing in the eggs are male or female.
(c) Sex determination in Human beings
OR
(c) The \(\displaystyle 23^{\text {rd }}\) pair or the sex chromosome in human females contains 'XX' chromosome. At the time of gamete formation, each gamete gets one X-chromosome.
More from Heredity
- In human beings, there are 23 pairs of chromosomes. Out of these 23 pairs of chromosomes (i.e. 46…2025 · asked 3×
- Two pea plants, one with round green seeds (RRyy) and another with wrinkled yellow (rrYY) seeds were crossed…2026 · asked 3×
- Assertion: Human female has a perfect pair of sex chromosome. Reason (R): Sex chromosome contributed by the…2024 · asked 3×
- Assertion: Human populations show a great deal of variations in traits. Reason (R): All variations in a…2023 · asked 3×
- Assertion: A mango seed will germinate to form a mango tree. Reason (R): Heredity determines the process by…2025 · asked 3×
- Consider the following two statements: (i) The trait that expresses itself in F 1 generation. (ii) The trait…2023 · asked 3×
- Using height (tallness / dwarfness) of a plant as an example, show that genes control the characteristics or…2022 · asked 3×
- The statement that correctly describes the characteristic(s) of a gene is:2023 · asked 3×
CBSE Class 10 Science past-paper question from the 2023board exam, with the answer as CBSE’s own marking scheme gives it. Where our answers come from.