The process that produces gametes (eggs and sperm) with half the number of chromosomes as body cells occurs in the sex cells. http://www.youtube.com/watch?v=D1_- mQS_FZ0&safety_mode=true&persist_safety_mode=1 http://www.youtube.com/watch?v=D1_- mQS_FZ0&safety_mode=true&persist_safety_mode=1
DNA replication occurs only once in the process. Meiosis I: the result is two daughter cells. Meiosis II: the result is four haploid cells, each with half the number of chromosomes.
Prophase I: homologous chromosomes pair up. Metaphase I: homologous chromosomes line up in the middle of the cell.
Anaphase I: homologous chromosomes separate and are pulled to opposite sides. Telophase I: one chromosome from each pair is at each pole of the cell.
Prophase II: one chromosome of the homologous pair in each cell. Metaphase II: the x-shaped chromosomes form a single line across the middle.
Anaphase II: sister chromatids move to opposite poles of the cell. Telophase II: a nuclear membrane forms around the chromosomes. http://www.youtube.com/watch?v=R_LUJSqeSrI&NR= 1&safety_mode=true&persist_safety_mode=1 http://www.youtube.com/watch?v=R_LUJSqeSrI&NR= 1&safety_mode=true&persist_safety_mode=1
Mitosis Meiosis In body cells Two daughter cells Same number of chromosomes as parent cell Asexual reproduction In sex organs to produce sex cells Four daughter cells Half the number of chromosomes as the parent cell. Sexual reproduction
1. Mosses: External fertilization Water allows the egg and sperm cells to meet Reproduces both sexually and asexually
Asexual Sexual 1 parent cells No gametes; cell divides Little variation in offspring Little energy required Less parental care Two parent cells 2 sex cells unite to form a zygote Greater variation in offspring Greater energy required Greater parental care
Gregor Mendel Mid-1800s Experimented with inherited traits in pea plants.
Francis Crick & James Watson (1953) Described the structure of DNA and how it replicates.
The Human Genome Project 1986-2003 Genome: consists of the full set of genetic material that makes up an organism. Made a map to identify genes
This information may be used to check for particular diseases. ◦ Ex. Allderdice syndrome where part of one chromosome is reversed. Identified in Sandy Point NL.
A special “picture” of a person showing all their chromosomes arranged in a particular order called a karyotype is studied.