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Meiosis
Sexual Reproduction:
usually involves two individuals
in humans and other mammals it always involves a male and a female
Sexual Reproduction in plants or animals is the union of two sex cells (gametes) to produce a new individual.
From the female: eggs or ova
From the male: sperm
The union of the sperm cell with the egg cell is called fertilization.
Genes: segment of DNA on a chromosome (there are hundreds of genes on a chromosome)
Homologous chromosomes: chromosomes that are of the same length, centromere position, and gene type and position (locus). One comes from mother, one from father.
Meiosis
One chromosome is like one of the Harry Potter books. The set of chromosomes is the entire series of books. You need the entire series to understand the whole story. If you're missing one book, you're missing information you need for the rest of the story.
This is true with our chromosomes. One chromosome only contains part of the instructions for making a human. A complete set is what makes the human, 46 chromosomes arranged in 23 pairs.
Meiosis
A gene is an uninterrupted segment of DNA containing coded instructions for a specific characteristic.
In the Hatter Potter books, there are letters in uninterrupted groups that make up words. When the interruption happens (a space or punctuation) you know there's a new word.
In chromosomes, the letters are the chemicals, and C G A T are arranged into genes.
Meiosis
For most sexually producing organisms, the chromosomes are organized into pairs.
Dogs: 87 chromosomes
how many pairs is that?
Cats: 19 pairs
how many chromosomes is that?
Meiosis
Gametes are produced through a cell division process called meiosis.
In meiosis, the result is four daughter cells each with half the number of chromosomes of the parent cell.
diploid
haploid
Meiosis produces gametes. When a male gamete and a female gamete join, a new single cell is formed called a zygote. The zygote is the first cell of the new individual and will eventually form an embryo.
The embryo can develop inside the parent or outside in an egg.
Meiosis
Meosis involves a sequence of phases similar to mitosis.
ProphaseMetaphaseAnaphaseTelophase
However Meiosis involves two sequences of this series.
*See printed handout
Spermatogensis: production of sperm
Oogenesis: production of ovaries
Meiosis