Download You have two types of cells in your body: somatic cells, and germ

section6.1.notebook
November 14, 2013
You have two types of cells in your body: somatic cells, and germ cells.
Somatic cells­ are your body cells. They undergo mitosis when they need to divide.
Germ cells­ are your reproductive cells also referred to as gametes.
­male gametes are called sperm cells
­female gametes are called egg cells.
Sexual reproduction­ involves the fusion of two gametes that results in offspring that are a genetic mixture of both parents.
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section6.1.notebook
November 14, 2013
Gametogenesis ­ the production of gametes.
Sperm cells (male gamete)
­smaller than female gamete
­contribution to the embryo is DNA
­must be able to swim, modifications are made to the cell for this to happen.
Egg cells (female gamete)
­gives DNA, contributes organelles, molecular building blocks, and other materials for a successful embryo to develop
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section6.1.notebook
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Fertilization­ the actual fusion of two gametes. Occurs when the sperm fertilizes the egg.
­A zygote is formed that will have the number of chromosomes in a diploid cell.
­Develops by mitosis into a multicellular organism.
Diploid­ a cell with 2 copies of each chromosome, (2n) number of chromosomes, body cells are diploid.
­one from female parent
­one from male parent
Haploid­ gametes that contain only
one of each kind of chromosome (n) number of chromosomes.
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section6.1.notebook
November 14, 2013
Each organism has a specific amount of chromosomes in their cells. The number of chromosomes is not related to the complexity of an organism.
Examples: Adder's Tongue Fern 1260(2n) 630(n)
Fruit Fly 8(2n) 4(n)
Humans 46(2n) 23(n)
Autosomes­ chromosomes that contain genes for characteristics not directly related to the sex of an organism.
­Chromosome pairs 1­22 are autosomes
Sex Chromosomes­ ones that control the development of sexual characteristics. ­Very different from one another. ­X and Y are standard
­XX indicates female, XY indicates male
­Chromosome pair 23. 4
section6.1.notebook
November 14, 2013
Human cells have 46 chromosomes.
­If cells only reproduced through mitosis then when an egg cell and a sperm cell fuse, the new cell would have 92 chromosomes!
Meiosis is the type of cell division that produces gametes with half the number of chromosomes as a parent's body cells.
­Two separate divisions occur (Meiosis I and II)
­Begins with 1 diploid (2n) cell, and results in 4 haploid (n) cells.
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section6.1.notebook
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Homologous chromosomes ­ two chromosomes (one from mom and one from dad) that have the same length and same general appearance.
­contain the same genes in the same order.
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section6.1.notebook
November 14, 2013
Can you identify Homologous Chromosomes?
The diagram below shows chromosomes 1 with four different genes present. These genes are represented by the letters F, g, h, and J. Possible homologous chromosomes of chromosome 1 are labeled 2­
5. Examine the five chromosomes and the genes they contain to determine which of chromosomes 2­5 are homologous with chromosome 1.
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section6.1.notebook
November 14, 2013
1. Could chromosome 2 be homologous with chromosome 1? Explain.
yes, because the genes are in the
same location and position
2. Could chromosomes 4 be homologous with chromosome 1? Explain.
no, because the last gene is not the
same
3. Could chromsome 4 be homologous with chromosome 1? Explain.
no, because they have completely
different genes
4. Could chromosome 5 be homologous with chromosome 1? Explain
yes, same as #1
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