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Question Video: Describing the Difference in Size of the X and Y Chromosomes Biology

Which of the following correctly describes the difference between the sizes of the sex chromosomes? [A] X chromosomes are much shorter in length than Y chromosomes. [B] Y chromosomes are much shorter in length than X chromosomes. [C] Y and X chromosomes are equal in length.

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Video Transcript

Which of the following correctly describes the difference between the sizes of the sex chromosomes? (A) X chromosomes are much shorter in length than Y chromosomes. (B) Y chromosomes are much shorter in length than X chromosomes. (C) Y and X chromosomes are equal in length.

In humans, we have 46 chromosomes in total or 23 pairs of chromosomes. We get one copy of each chromosome from our biological mother and the other copy from our biological father. Chromosomes one to 22 are called autosomes and are numbered based on their size, with chromosome one being the largest and chromosome 22 being the smallest. The 23rd chromosome pair contains the sex chromosomes, and they determine our biological sex. Having two copies of the X chromosome makes a biological female, while having a single copy of the X and Y chromosome makes a biological male.

So how do chromosomes X and Y differ in length? The X chromosome is about 150 million nucleotides long and contains about 900 genes, while the Y chromosome is about 60 million nucleotides long and contains about 55 genes. So the correct answer is answer choice (B). Y chromosomes are much shorter in length than X chromosomes.

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