1. Chapter 8 Cell Reproduction Section 8.1

2. Chromosomes DNA- deoxyribonucleic acid Consists of six billion pairs of nucleotides

3. Eukaryotic Cells During cell division, DNA is coiled into compact chromosomes Chromosomes are rod-shaped structures made of DNA and proteins

4. Each chromosome is a single DNA molecule wrapped around proteins called histones Histones maintain the shape of the chromosome

5. Nonhistone proteins are involved in controlling the activity of specific regions of the DNA

6. Chromosome Structure Each half is called a chromatid The constricted area is called a centromere

7. When a cell divides, each of the two new cells receives one chromatid from each chromosome

8. Prokaryotic Cells DNA usually consists of only one chromosome DNA molecule is circular

9. Chromosome Numbers Each species has a characteristic number of chromosomes Examples: fruit fly 8 cat 32 human 46

10. Sex Chromosomes Determine the sex of an organism In humans, sex chromosomes are either X or Y Normal females are XX Normal males are XY

11. Autosomes The other 44 chromosomes are autosomes Every cell of an organism produced by sexual reproduction has two copies of each autosome (one from each parent)

12. Homologous Chromosomes Refers to the two copies of each chromosome Same size and shape Carry genes for the same trait

13. Karyotype A photomicrograph of the chromosomes in a dividing cell found in a normal human 46 human chromosomes exist as 22 homologous pairs of autosomes and two sex chromosomes

14. Diploid Cells that have two sets of chromosomes All normal human cells, except for reproductive cells, are diploid Abbreviated as 2n For humans, the diploid (2n) number is 46

15. Haploid Cells that contain only one set of chromosomes Includes sperm and egg cells Abbreviated as 1n The haploid number (1n) of humans is 23

16. Introduction to Cell Reproduction http://www.youtube.com/watch?v=vjA diUMc96w