Question Video: Interpreting Punnett Squares to Show the Inheritance of Sex Chromosomes in Humans | Nagwa Question Video: Interpreting Punnett Squares to Show the Inheritance of Sex Chromosomes in Humans | Nagwa

# Question Video: Interpreting Punnett Squares to Show the Inheritance of Sex Chromosomes in Humans Biology • First Year of Secondary School

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Which of the following Punnett squares correctly shows the inheritance of sex chromosomes in humans? [A] Option A [B] Option B [C] Option C [D] Option D

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### Video Transcript

Which of the following Punnett squares correctly shows the inheritance of sex chromosomes in humans?

A Punnett square is a useful tool to show the inheritance of genetic material in the offspring from their parents. When organisms reproduce, their gametes or sex cells combine during fertilization. Each gamete contains 23 chromosomes to give a total of 46 chromosomes in the embryo. The first 22 pairs of chromosomes are called autosomes, and the 23rd pair are called the sex chromosomes.

In humans, there are two types of sex chromosomes, called X and Y. Biological females have two copies of the X chromosome, and biological males have a single copy of the X chromosome and a single copy of the Y chromosome. So when gametes are produced, the ovum will always contain an X chromosome, while the sperm will contain an X or a Y chromosome.

Now let’s fill in a Punnett square to determine the inheritance of sex chromosomes in humans. On the top will be the female gametes, which will be either X or X. And on the side will be the male’s gametes, which will be either X or Y. Now we simply combine them, so the first combination will be a female with one X chromosome from each parent. And if we complete the rest of the Punnett square, we’ll see that the correct answer is answer choice (D).

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