Question Video: Identifying the Pattern of Inheritance of Sex in a Punnett Square | Nagwa Question Video: Identifying the Pattern of Inheritance of Sex in a Punnett Square | Nagwa

Question Video: Identifying the Pattern of Inheritance of Sex in a Punnett Square Biology • First Year of Secondary School

Which of the following Punnett squares shows the correct inheritance of sex 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 shows the correct inheritance of sex in humans? (A), (B), (C), or (D).

The 23rd pair of chromosomes in humans is referred to as the sex chromosomes. Biological females inherit two X chromosomes for this set, while biological males inherit one X from their biological mother and one Y from their biological father.

Let’s look at how this would appear in a Punnett square. Since the biological male genotype for these chromosomes is XY, the biological father’s genotype would be XY. Likewise, since the biological female genotype for these chromosomes is XX, the biological mother’s genotype would be XX. When we fill out a Punnett square, we combine the letter from the row header with the letter from the column header. So if we fill out the rest of the Punnett square by the same method, we should end up with this. Basically, biological females receive an X from both parents, while biological males receive an X from their mothers and a Y from their fathers.

If we look through the answer choices to find the best match to this Punnett square, we can see it is (D). The Punnett square that shows the correct inheritance of sex in humans is the one that shows biological female gametes as XX, biological male gametes as XY, and the offspring accurately corresponding to that.

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