EasyBiologyHigh School (9–10)GeneralHeredity and Evolution › Heredity and InheritanceConceptualBoard Exam
Raghav's grandmother says that a mother decides whether her baby is a boy or a girl…
Contributed by StemPy LabTry it on paper first. A hint, the key idea and the worked solution are here when you need them.
Raghav's grandmother says that a mother decides whether her baby is a boy or a girl. Explain to her, using sex chromosomes, why this is not so.
Need a reminder? The key ideaShow
In some reptiles the temperature of the eggs decides the sex, and some snails change sex. Human women are XX and men are XY. Every egg carries X; half the sperm carry X and half Y. An X sperm gives a girl, a Y sperm a boy, with an equal chance each time.
The worked solution
Have you tried it?
Work it out on paper first. It is fine to get stuck or make a mistake: that is how we learn. When you are ready, go through the solution one step at a time, and check each step against your own.
Step 1. The mother. She is XX, so every egg carries an X.
Step 2. The father. He is XY, so half his sperm carry X and half carry Y.
Step 3. The child. An X sperm gives XX, a girl; a Y sperm gives XY, a boy.
Answer: all eggs are alike, so the sperm from the father decides the sex, not the mother.
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