EasyBiologyHigh School (11–12)Heredity and Evolution › Principles of Inheritance and VariationConceptualAPA-LevelIB
Answer the questions for a human and for a hen and a cock…
Contributed by StemPy LabTry it on paper first. A hint, the key idea and the worked solution are here when you need them.
Answer the questions for a human and for a hen and a cock.
- What are the sex chromosomes of a woman?
- What are the sex chromosomes of a man?
- Which parent decides the sex of a human child?
- What are the sex chromosomes of a hen?
- What are the sex chromosomes of a cock?
- Which parent decides the sex of a chick?
- In which of these two animals is the female heterogametic?
Need a reminder? The key ideaShow
In humans and the fruit fly, the father decides the sex, because half the sperm carry X and half carry Y. In birds the egg decides, because the female is ZW. In the honey bee, a fertilised egg (2n = 32) becomes a female and an unfertilised egg (n = 16) becomes a drone.
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. Human. (a) The female is XX. (b) The male is XY. (c) The father decides, because half his sperm carry X and half carry Y.
Step 2. Hen and cock. (d) The hen is ZW. (e) The cock is ZZ. (f) The mother, the hen, decides, because half her eggs carry Z and half carry W.
Step 3. (g) The hen is ZW and makes two kinds of gamete, so the female is heterogametic in birds. In humans the male is.
Answer: XX, XY, father; ZW, ZZ, mother; the female is heterogametic in birds.
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