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Question
In humans, males are heterogametic and females are homogametic. Explain. Are there any examples where males are homogametic and females heterogametic?
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Solution
The term homogametic and heterogametic refer to the organism depending upon whether all the gametes contain one type of sex chromosome (Homo = same) or two different types of sex chromosomes (Hetero = different) Humans show XX/XY type of sex determination i.e. Females contain 2 copies of X chromosome and males contain 1 X and 1 Y chromosome. Therefore, ova produced by females contain the same sex chromosome i.e. X. On the other hand, the sperms contain 2 different types of chromosomes i.e. 50% sperms have X and 50% have Y chromosome open from half the autosomes (Meiosis) Therefore, the sperms are different with respect to the composition of sex chromosome. In case of humans, females are considered to be homogametic while males are heterogametic. Yes, there are examples where males are homogametic and females are heterogametic. In some birds, the mode of sex determination is denoted by ZZ (males) and ZW (females).
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RELATED QUESTIONS
Answer the following questions related to sex determination in human beings:
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ii. How many pairs of chromosomes are present in human beings?
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(b) 23
(c) 21
(d) 42
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(b) baby girl
(c) adult
(d) either boy or girl
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Autosomes
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In the XX–XO sex determination system, what does the 'O' represent?
How does the haplodiploidy system differ from the XX–XY, XX–XO, and ZW–ZZ systems in determining sex?
In a bird population using the ZW–ZZ sex determination system, if a ZZ male mates with a ZW female, what proportion of offspring would be expected to be female?
