Flashcards · Biology · Inheritance
Inheriting Sex
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Which sex chromosomes does a woman have?
XX.
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Which sex chromosomes does a man have?
XY.
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Which sex chromosome do all eggs carry?
X.
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Which sex chromosomes do sperm carry?
Half carry X and half carry Y.
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What decides the sex of a baby?
Whether the sperm that fertilises the egg carries an X or a Y.
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What is the genotype of a baby girl?
XX.
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What is the chance that a baby is a boy?
1 in 2, or 50%.
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What is the sex ratio from a cross of XX x XY?
1 girl : 1 boy.
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If a couple have four girls, what is the chance that the fifth child is a boy?
Still 50%.
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Which parent decides the sex of the baby?
The father, because his sperm carries X or Y.
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What is the chance of 3 girls in a row?
1 in 8 (12.5%).
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Which gene on the Y chromosome starts male development?
SRY.
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Is the Y chromosome bigger or smaller than the X?
Smaller.
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Which of the 23 pairs of chromosomes are the sex chromosomes?
The 23rd pair.
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What is the common mistake when writing the sex cross?
Writing the mother as XY. A mother is XX.