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Inheritance, Part 1, MMP, If an X sperm fertilises the ovum, the zygote…
Inheritance, Part 1, MMP
Basic information:
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A chromosome is a thread of DNA, made up of a string of genes.
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Each chromosome has certain characteristics when ready to divide: there are two chromatids, joined at one point called a centromere.
Each chromatid is a string of genes, coding for the person’s characteristics. The other chromatid carries the same genes in the same order.
Inheritance of sex:
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In females, the two sex chromosomes, called the X chromosomes, are the same size as each other.
In males, the two sex chromosomes are of different sizes. One corresponds to the female chromosomes and is called the X chromosome. The other is smaller and is called the Y chromosome.
So the female cells contain XX and male cells contain So the female cells contain XX and male cells contain XY.
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If an X sperm fertilises the ovum, the zygote will be XX and will grow into a girl. If a Y sperm fertilises the ovum, the zygote will be XY and will develop into a boy. There is an equal chance of an X or Y chromosome fertilising an ovum, so the numbers of girl and boy babies are more or less the same.