- Slides: 27
Cell Division: sexual and asexual reproduction
Sexual vs. Asexual • Sexual reproduction – Occurs in eukaryotes (multicellular organisms) • Asexual reproduction – MOSTLY occurs in prokaryotes (unicellular) – FEW multicellular organisms use 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 Type
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 (2 n) 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 – 1 pair; 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