Chromosome
A long, coiled strand of DNA containing many genes. Human body cells have 23 pairs.
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Analogy
One volume in a set of encyclopaedias.
Example
Body cell: 46 (23 pairs)Egg cell: 23Sperm cell: 23Egg + sperm = 46
In practice
You get one chromosome of each pair from your mother and one from your father.
Practice
Flashcards
- How many chromosomes are in a human body cell?46, in 23 pairs.
- How many chromosomes does a human sperm or egg have?23, which is half the normal number.
Questions people ask
Why do chromosomes come in pairs?
You inherit one set of 23 chromosomes from your mother's egg and one set of 23 from your father's sperm. The two sets match up into pairs that carry the same genes in the same places, though they may have different alleles. Together they make the 46 chromosomes in a body cell.
What is Down syndrome?
Down syndrome happens when a person has three copies of chromosome 21 instead of two. It occurs when chromosomes fail to separate properly during the making of an egg or sperm. People with Down syndrome have extra chromosome material in every cell, which affects learning and health.