Genetics 101 Part 3: Where do your genes come from?
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Genetics 101 Part 3: Where do your genes come from? : Find out how chromosomes and genes are passed down from parent to child.
- Your genes come from your parents, of course.
- And from their parents. And from their parents' parents.
- And well... you get the idea.
- You have two sets of 23 chromosomes.
- One set from each parent.
- For almost every chromosome you inherit from your mohter,
- You also inherit one from your father.
- That has his versions of the same genes.
- Together they form a pair of homologous chromosomes.
- The X and Y chromosomes however, are special.
- Usually, females have two X chromosomes, while males have and X and a Y.
- You get one of your X chromosomes from your mother.
- Whether you get your father's X chromosome or his Y chromosome,
- determines your sex.
- Most adult cells contain two sets of chromosomes,
- but sperm and egg cells have only one set of 23 chromosomes each.
- When the body forms sperm or egg cells, a cell divides and pairs of chromosomes separate.
- A random member or each pair moves into each new cell.
- This is why when you were concieved,
- you obtained half of you mother's genes
- and half of your father's genes
- but your siblibngs didn't necessarity get the same versions of your parents' genes
- that you did,
- unless you happen to be and identical twin.
- To form sperm or egg cells, your chromosomes double
- like so.
- When the homologuos pairs seperate, sometimes they cross over
- and at seemingly random points, exchange DNA.
- This is called genetic recombination.
- Because your genes get shuffled during recombination,
- the chromosomes you pass along to your children
- are not exactly the same as the ones you inherited from your parents.
- This makes it hard to use most of your chromosomes
- to trace your geneology back very far.
- However, most of the Y chromosome is handed down
- from father to son entirely intact.
- Likewise, in humans, DNA in the mitochondria
- is passed on only from mother to child.
- For this reason ancestry along your father's line,
- or your mother's line is easier to trace using the Y chromosome
- or mitochondrial DNA.
- When sperm and egg cells join together at fertilization,
- they create a single cell with two complete sets
- of 23 chromosomes, one set from your mother
- and one from your father.
- This single cell will divide to create new cells
- over and over until it creates a child.
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