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Science · 2022 · 4 marks
CBSE 2022 · Region 4 · Set 3 · Q15
Sex of an individual is determined by different factors in various species. Some animals rely entirely on the environmental cues, while in some other animals the individuals can change their sex during their life time indicating that sex of some species is not genetically determined. However, in human beings, the sex of an individual is largely determined genetically.(a)What is the statistical probability of getting either a male child or a female child ?(b)Write the number of pair/pairs of sex chromosomes present in human beings. In which one of the parent (male / female) perfect pair / pairs of sex chromosomes are present ?(c)Citing two examples, justify the statement "Sex of an individual is not always determined genetically".OR Draw a flow chart to show that sex is determined genetically in human beings.
Sex of an individual is determined by different factors in various species. Some animals rely entirely on the environmental cues, while in some other animals the individuals can change their sex during their life time indicating that sex of some species is not genetically determined. However, in human beings, the sex of an individual is largely determined genetically.
(a)
What is the statistical probability of getting either a male child or a female child ?
(b)
Write the number of pair/pairs of sex chromosomes present in human beings. In which one of the parent (male / female) perfect pair / pairs of sex chromosomes are present ?
(c)
Citing two examples, justify the statement "Sex of an individual is not always determined genetically".
OR Draw a flow chart to show that sex is determined genetically in human beings.
Marking-scheme solution
(a) $\displaystyle 50$% male and $\displaystyle 50$% female/ $\displaystyle 1$:$\displaystyle 1$ male and female / equal probability of male and female
One pair of sex chromosomes
mother/female has perfect pair of chromosomes
(c)
In reptiles, the temperature at which fertilized eggs are kept determines whether the animals developing in the eggs would be a male or a female.
In snails, they can change their sex during their lifetime.
OR
(c)
Parents
Gametes
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CBSE Class 10 Science past-paper question from the 2022board exam, with the answer as CBSE’s own marking scheme gives it. Where our answers come from.