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3.8 Sexual Reproduction and the Diversity of Life. (Sec 3.2 pg.79). The production of gametes is only the first step in sexual reproduction. They must combine to form a diploid cell.
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3.8 Sexual Reproduction and the Diversity of Life (Sec 3.2 pg.79)
The production of gametes is only the first step in sexual reproduction. They must combine to form a diploid cell. • The joining of two gametes (n, haploids) is called fertilization, the first diploid cell of the offspring is called a zygote. • Sperm (n) + egg (n) = zygote (2n)
The zygote receives half of its chromosomes from each parent. This is how sexual reproduction promotes genetic diversity. • The zygote will undergo cell division and produce diploid cells from then on.
The offspring has one set of instructions (genes) that come from both parents. The genes are similar, but not always identical. • For example the instructions from one parent may say brown hair, while the instructions from the other parent says blonde hair. The different forms of the same genes are called alleles.
If you have two sets of different instructions which one do you follow? One is dominant and the other is recessive. • If you have even just one copy of a dominant allele, it is the instructions that you will follow.
Sometimes the two alleles are equally dominant. In that case we call this incomplete dominance and both sets of instructions get followed. • One purpleflower gene + one white flower gene = pink flowers.