Which chromosome pattern represents a female?

Which chromosome pattern represents a female?

• A. XY
• B. XX
• C. YY
• D. YX

Answer: (B)

Sex determination hinges on the sex chromosomes. Having two X chromosomes is the pattern associated with female development because the presence of the Y chromosome (and its SRY gene) drives male development; without a Y, female development proceeds with two X chromosomes. The egg contributes an X chromosome, and a sperm can contribute either an X or a Y. When the sperm carries X, the fertilized egg becomes XX and develops as female. If a sperm carries Y, the result is XY and develops as male. A pattern with two Ys isn’t viable in humans, and writing XY and YX describe the same male genetic setup (the order doesn’t change the content). So the chromosome pattern that represents a female is two X chromosomes.

Sex determination hinges on the sex chromosomes. Having two X chromosomes is the pattern associated with female development because the presence of the Y chromosome (and its SRY gene) drives male development; without a Y, female development proceeds with two X chromosomes. The egg contributes an X chromosome, and a sperm can contribute either an X or a Y. When the sperm carries X, the fertilized egg becomes XX and develops as female. If a sperm carries Y, the result is XY and develops as male. A pattern with two Ys isn’t viable in humans, and writing XY and YX describe the same male genetic setup (the order doesn’t change the content). So the chromosome pattern that represents a female is two X chromosomes.