Chapter 10 10:1 Cell Reproduction and Cell Division

I Chromosomes A. Structure: Rod shaped structures that are made up of DNA and are found in the nucleus of every cell. 1. DNA – A nucleic acid that contains genetic material and is found on the chromosomes, in the nucleus of every cell. 2. Double Helix - The shape of a DNA molecule. 3. Histones – structures on a DNA molecule that DNA wraps around, these structures help aid in the tightly packing of DNA. 4. NON – histones – Do not participate in the packing of DNA.

Chromatids – Sister chromatids Each chromosomes is made up of 2 identical halves called Chromatids. Centromeres – each chromatid pair is connected together by a centromere. Each chromatid pair will split during cell division. Chromatin – The chromosome state between cell divisions.

2. Chromosomes Numbers A. Sex chromosomes – determine the gender of an organism. 1. XX – female, 2. XY –Male, B. Autosomes – all other chromosomes in the nucleus except the 2 sex chromosomes. 1. 2 of the 46 in human sex cells, egg and sperm, are sex chromosomes, the other 44 chromosomes are Autosomes.

3. Homologous Pairs A. Twin chromosomes that share the same size, shape and traits and come from each parent reproductive cell. When the egg is fertilized by the sperm the 2 sets of 23 chromosomes immediately begin looking for their identical twin to pair up together. 1. These pairs are called homologous pairs. B. Karyotype 1. A visual of all the chromosomes in the nucleus of a dividing cell.

Cell types Female egg – Contains 23 total chromosomes, 22 autosomes and ONE X, only. Male sperm – Contains either an X sperm or a Y sperm along with 22 autosomes. The male contains 2 different types of sperm, the sperm determines the sex of the organism. Body Cells – Each body cell contains 23 pairs, 46 total chromosomes, 44 autosomes and 2 sex chromosomes. Sex Cells – each sex cell contains only 23 total chromosomes, 22 autosomes and 1 sex chromosome also called Gametes. Zygote – Fertilized Egg

Haploid – Cells that contain only 1 pair of each chromosome Haploid – Cells that contain only 1 pair of each chromosome. Reproductive cells are haploid since they only have one set of chromosomes in the sperm and in the egg. Diploid – Cell that contain 2 sets of each chromosome, pairs. Body cell are all diploid because they have been fertilized and have both the chromosomes from the sperm and from the egg combine.

4. Diploid and Haploid Cells A. Diploid – cells that have 2 sets of chromosome. (2n) B. Haploid – Cells that have only one set of chromosomes. (n) such as sperm and egg. 1. 2 haploids together form a diploid cell.