I DONT gET THIS??? pLEASE HELP!!?

Question

The principle of segregation says that in diploid organisms genes come in pairs and that when gametes get produced each gamete gets one gene at random from each gene pair but not both.

especially the part about each gene pair passing on a gene but not both? it doesnt make sense to me.

You dont have to know about the principle of segregation!!

Can you just translate this for me?

Answer 1

when you look at illustrations of genes, they would look like letter X (this is a pair of genes)... if you divide the letter X into two, you will come up to something that looks like letter V and inverted V. When genes are paired into other genes, those pairs (ones that look like letter X) will subdivide and become one gene (something like letter V to join another V-looking gene)... then it will later on become a pair that will look like an X again.

So a pair of genes will divide, and the half will join a half (other than its original half) and that half will be the only one (among a particular charateristic) to have its pair of gene from another gamete.

Answer 2

Genes come in pairs. It is necessary to split the chromosome in half to produce gametes, otherwise you would end up with 4 genes come fertilisation.

Mitosis
XX becomes >> + <<

Meiosis (gamete formation)
XX bemomes X + X becomes > + < +> +<

Where X is a chromosome and > or < are chromatids.

As you can see, by the end of meiosis you have 4 daughter cells, each with only one chromatid and thus one gene from the original pair. When the cell undergoes fertilisation it will add its chromatid to that of the other parent DNA, forming a full chromatid again (and a pair of genes)

Answer 3

There are two copies of each chromosome (if the organism is diploid, i'm leaving out some stuff to make this simple). Each chromosome in the pair should contain the same genes, but possibly different versions of each gene.

During formation of the egg and sperm cells, each cell gets 1 of each chromosome. This is segregation, the pair is split up and each cell gets 1 copy of the chromosome instead of both copies (as you would in mitosis).

The result of this is that if you had brown eyes your eye color gene on 1 chromosome could be brown and the same gene on the homologous chromosome (the other one in the pair) could be for blue eyes.

When your chromosomes segregate to form gametes, they'd get 1 of those chromosomes, so either the brown eye gene or the blue eye gene (two versions of the same gene, really).

Hope that helps.

Answer 4

It's been a while, but the way I remember it is that when the gametes reproduce (divide), they do so differently from regular mitosis. They split is such a way that the gene pairs are divided.