How a gene makes a protein that shows as a trait, how genes sit on chromosomes and pass on, and how the sex of a child is decided.
3 lessons, about 1 h 15 min3 simulations10 problems3 practice questionsPython in every lesson
Created by StemPy LabDNA carries the information for making proteins. A section of DNA that holds the information for one protein is a gene. Proteins, such as enzymes, control how the body is built and works, and so they show as traits. A plant is tall when its gene makes an enzyme that produces enough growth hormone. Each trait is influenced by DNA from both parents.
Genes are carried on chromosomes, which come in pairs in body cells. Each parent gives one chromosome of every pair. Gametes carry only one set, so the zygote gets the full number again and it stays constant from one generation to the next. Genes on different chromosomes are passed on independently, which is why traits can mix in new ways.
In some animals the environment decides the sex: in some reptiles the temperature of the eggs decides it, and some snails can change sex. In human beings the sex is decided by genes. Women have two X chromosomes, while men have an X and a smaller Y. Every egg carries an X, so the sperm decides the sex, and each child has an equal chance of being a girl or a boy.
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