Cell Division: sexual and asexual reproduction

Sexual vs. Asexual Sexual reproduction Asexual reproduction Occurs in eukaryotes (multicellular organisms) Asexual reproduction MOSTLY occurs in prokaryotes (unicellular) FEW multicellular organisms use asexual reproduction

Asexual Reproduction

Asexual Reproduction One organism produces one or more new organisms that are identical to itself and that live independently of it Three types Binary fission Budding Regeneration

1. Binary fission Form of asexual reproduction Occurs in prokaryotes (bacteria) Parent organism splits into two genetically identical cells

2. Budding Occurs in eukaryotes and prokaryotes A bud forms from the parent’s cell. The bud grows until it forms a complete new organism with the same genetic material

3. Regeneration Some animals, when cut in pieces will grow into many animals.

Sexual Reproduction Production of offspring from two parents. Sperm + Egg = Zygote 23 + 23 = 46 Haploid + haploid = diploid

Sexual reproduction Plants growing from seeds and animals growing from eggs are examples of organisms that reproduce through sexual reproduction

Categorize Type Cell reproduction

Compare and Contrast Comparing and contrasting sexual and asexual reproduction Venn diagram Double bubble Comparison chart USE PAGES 88-92 in Cells and Heredity

2. Spores Molds & fungi form a copy of the DNA and a protective wall around it. Billions are released; not all survive.

4. Vegetative Propogation When plants send out “runners” to look for light.

Meiosis The production of gametes. Each new cell has ½ the chromosomes of the parent cell. Parent cell = diploid (2n) ex. 46 chromosomes Gamete = haploid (n) ex. 23 chromosomes

Prophase I Chromatin coils to chromosomes. Homologous chromosomes (a pair of chromosomes, each having genes for the same trait) – pair up. Crossing over – homologous chromosomes exchange genes, increasing genetic variety.

Metaphase I Homologous chromosomes line up on the equator of the cell.

Anaphase I Homologous chromosomes are separated.

Telophase I & Prophase II Cell divides into 2 cells Each cell has ½ the chromosomes. Identical sister chromatids are still together

Metaphase II Sister chromatids line up on the equator of each cell.

Anaphase II Sister chromatids are separated in each cell.

Telophase II Each cell divides into 2 new cells. 4 sperm or eggs have been created, each having ½ the original amount of DNA.

Differences Sperm – 4 sperms are made from each parent cell. Egg – 1 egg is formed, the 3 other cells die. www.classzone.com

Sex Determination Autosomes – 22 pairs in humans; code for body parts. Sex chromosomes – 1pair; code for sex XX = female XY = male Karyotype – a picture of the chromosomes

Sex Determination Which sperm gets to the egg first determines the sex. Some sperms have X sex chromosome; some sperms have Y sex chromosome. Female always gives an X.

Nondisjunction When the chromosomes do not separate properly during meiosis. Trisomy - the offspring receive too many chromosomes. Monosomy – the offspring receive too few chromosomes.

Trisomy Down’s Syndrome – trisomy 21 – large tongue, short neck, mental retardation Klinefelter’s Syndrome – XXY – long arms & legs, breasts, hip fat, bad decision maker

Trisomy & Monosomy XYY Syndrome – higher than usual testosterone Turner’s Syndrome – X – webbed neck, no puberty, elbow deformity