Cell Reproduction Regular Biology Waggy

Chapter Objectives 1. Describe the structure of a chromosome. 2. Explain the differences between sex chromosomes & autosomes. 3. Distinguish between diploid & haploid cells. 4. Summarize the events of mitosis

5. Explain binary fission in prokaryotic cells 6. Discuss the pros and cons of Stem Cells. 7. Summarize the steps of meiosis 8. Compare the end products of mitosis to meiosis

Deoxyribonucleic Acid (DNA) Long thin molecule that holds genetic information If stretched out, one strand of DNA would measure 3 meters in length DNA is made up of nucleotides The human genome has approximately 3 billion nucleotides So how does it fit into a single cell?

Supercoiling The DNA coils into a thick rope The DNA continues to coil until completely coiled into small structure called a chromatid

The two identical chromatids find each other and form the final structure that DNA takes: the chromosome The sister chromatids are connected at the centromere (sticky protein disk)

Types of chromosomes Chromosomes are put into two different categories: 1. Sex chromosomes Determine the sex of an organism In humans: XX = female XY = male

2. Autosomes All other chromosomes Most body cells contain two copies of each autosome

Diploid vs. Haploid Diploid cells contain TWO copies of each chromosome All body cells are diploid EXCEPT for the sex cells (sperm & egg) Shorthand for diploid cells is written: 2n

Haploid cells contain ONLY ONE copy of each chromosome Haploid cells are the sex cells Shorthand for haploid cells is written: n

Karyotypes Used to examine a persons chromosomes Can sometimes help identify some genetic disorders like monosomy (missing chromosome) or trisomy (extra chromosome) Down’s Syndrome = Trisomy 21