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I am studying for my Bio class and I am stuck with questions that I came up with during this chapter of Meiosis. I understand that human somatic cell is made up of 22 pairs of autosomes and 1 pair of sex chromosome. I am confused about what made up each pair of autosomes? is that 1 chromosome from the father and 1 chromosome from mother made up 1 pair of autosomes in somatic cells? and therefore, since each pair of autosomes consisted of 1 chromosome from dad and 1 from mom, we can say human somatic cells consisted of 22 pairs of homologous chromosomes (not to mention the sex of the human), right?

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  • $\begingroup$ @PolypipeWrangler 22.5?! You can't have half a homologous pair. But I get what you're trying to say and it's true... There are 22 homologous pairs and half the time there is a homologous XX pair. The other half the time there's a heterologous XY pair, though even portions of those chromosomes are homologous... $\endgroup$ – rotaredom Apr 25 '20 at 16:35
  • $\begingroup$ Got it! thank you so much for the clarification! $\endgroup$ – Sang Huynh Apr 25 '20 at 21:11
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Answer: *Yes , human somatic cells have 22 pairs of homologous chromosomes

The human genome consists of 46 (2n*(22+1) ) chromosomes.

Most of our cells are somatic and diploid (2n), they have two homolgous chromosoms (called homologs, one "father" & "mother") these cells multiply by mitosis.

Reproductiv cells or gonosomal cells, (gametes; Sperm and eggcell(ovum)) are the product of meiosis ( a part of gametogenesis ) . These cells are haploid (1n), they only have one set of chromosomes (1n * (22+1)) which is a combination of "fater&mother". When 2 gametes combine a diploid zygote is formed.

In both cases (Mei- and Mitosis) chromosome (pair (2n)oder single(1n)) number 1 -22 are called autosome , while

Chormosome number 23 is an allosome (sex chromosome), either Y (male) or X (female).

Since the gametes are haploid (1n) they have only 1 single allosome, egg cell always X , and sperm cell either X or Y.

If the allosome (the 23 chormosome pair) of an human is hemizygot ( X–Y ), he is genetically male. Is the allosome pair X-X ,homozygot the person is genetically female.

Somatic cells can have therefore 22 pairs of homologous chromosomes the 22 autosomes. The allosome pair of chromosomes is not considert homologous but either "homozygot / homogametic"[XX] or "hemizygot/ hemigametic"[XY].

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