Cell Reproduction Chapter 8 Chromosomes Section 8 1

Cell Reproduction Chapter 8

Chromosomes Section 8. 1

Definitions: l Chromosome: rod shaped structure made up of DNA and proteins l Sister Chromatids: identical halves of a chromosomes

Definitions: l Centromere: protein that holds sister chromatids together l Homologous Chromosomes: chromosomes that code for the same traits that come from your mother and your father

Definitions: l Chromatin: less tightly coiled strands of DNA ¡Uncoiled so that the cell can read the DNA to direct the cell’s activities l Chromosomes only occur during cell division ¡Chromatin coils up to make chromosomes

Ameba 50 Goldfish 94 Alligator 32 Garden Pea 14 Brown bat 44 Grasshopper 24 Bullfrog 26 Horse Human 46 Cat 32 Lettuce 18 Chicken 78 Onion 16 Chimpanzee 48 Redwood 22 Corn Earthworm 36 Fruit fly 64 Carrot 18 20 Sand dollar 52 8 All normal members of the same species have the same number of chromosomes in their body cells.

Sex Chromosomes l Definition: chromosomes that determine the sex of the organism ¡May carry other genes as well l Humans: X and Y ¡Males: XY ¡Females: XX

Autosomes: l Definition: All other chromosomes in the body besides the sex chromosomes l Humans = 46 total chromosomes ¡ 2 sex chromosomes ¡ 44 autosomes

Karyotype – map of an organism’s chromosomes l http: //www. chromosome 18. org/About. Gene tics/Basic. Genetics/Whatisa. Karyotype/tabi d/120/Default. aspx

Karyotype – map of a organism’s chromosomes

Diploid and Haploid Cells l Cells having 2 sets of chromosomes are diploid (2 N) l The haploid number of a human egg or sperm cell is 23, and there are no homologous chromosomes in either cell (1 N)

Mitosis Section 8. 2

Why Cells Divide l Cell size is limited ¡Cells cannot keep growing indefinitely l Replacement of damaged cells l Growth - embryo l Asexual reproduction ¡Single celled life forms ¡Binary fission l Sexual reproduction meiosis

Eukaryotic Cell Division l Mitosis (Growth Division): Division of cell producing two identical daughter cells 2 n l Meiosis (Reduction Division): Division of cell producing four haploid daughter cells 2 n 1 n

The Cell Cycle (Life Cycle of the Cell) 2 Major Parts: 1. Interphase G 1 S G 2 2. Cell Division Mitosis – nucleus Cytokinesis – cytoplasm

Part 1: Interphase l Stage your cells are in the most amount of time l When cell does its “normal” jobs l Contains 3 stages: G 1, S, and G 2

G 1 Phase S Phase G 2 Phase

S Phase – DNA Replication l Process by which DNA builds an exact copy of itself l After replication has occurred, each double stranded molecule contains one old strand one new strand of DNA

l 1879 Walter Flemming used red dye to observe cell structures during mitosis, it killed the cells and so he had to take pictures at each stage in order to come up with a pictorial model of mitosis.

Part 2: The Stages of Mitosis (page 156)

Mitosis – Step 1: Prophase l Chromosomes (2 chromatids) form from chromatin l Nuclear membrane disassembles l Centrioles move to poles l Spindle fibers form

Mitosis – Step 2: Metaphase l Chromosomes line up at the middle of the cell ¡“Metaphase Plate” - Stage where karyotypes are made from!

Mitosis – Step 3: Anaphase l Sister chromatids (from the same chromosome) separate and move to opposite poles

Mitosis – Step 4: Telophase l Spindle fibers disappear l Nuclear membrane forms again l Chromosomes go back into chromatin form l 2 nuclei (diploid) per one cell

Cytokinesis l Division of cytoplasm l Cell membrane pinches in to form two separate cells l Results: 2 IDENTICAL daughter cells

Animation l Mitosis

Mitosis “Flip Book” l To receive full credit you must: 1. Illustrate what is going on in the life cycle a) Title Page b) Interphase: G 1, S, G 2 b) Mitosis: prophase, metaphase, anaphase, telophase c) Cytokinesis: early & late d) Finished product 2. Diploid # (2 N) = 8 Haploid # (1 N) = 4 (represent homologous chromosomes with different colors) Need help? Consult your book or your notes!

Cont… 3. Diploid # (2 n) = 8 Haploid # (1 n) = 4 4. Represent homologous pairs with 4 different colors. Need Help? Consult you book or your notes!

Asexual Reproduction l offspring is an exact copy of parents occurs in lower plants and animals (bacteria, molds, algae and protozoa) l all cells form through mitosis

Asexual Reproduction Regeneration Budding Spores Binary Fission

Mitosis Slides

Meiosis Section 8. 3

2 Stages: 2 n Meiosis I n n Meiosis II Results in 4 haploid cells n n

Interphase l Same as mitosis! l 3 Stages: G 1, S, G 2

Meiosis I l Formation of 2 haploid cells from 1 diploid cell l Production of gametes l “Reduction division”

Step 1: Prophase I • Nuclear membrane breaks down • Centrioles move to the poles, spindle fibers form • Synapsis occurs, forming tetrads, allowing for crossing over (genetic variety)

Definitions: l Synapsis: When a pair of homologous chromosomes partner up inside a dividing cell l Tetrads: the name given to a partner of homologous chromosomes during synapsis l Crossing over: chromatids of homologous chromosomes twist around and trade places causing an exchange of DNA

Step 2: Metaphase I l Tetrads line up randomly at the metaphase plate

Step 3: Anaphase I l Tetrads are split and each homologue is moved toward opposite poles l Independent assortment: the random separation of maternal and paternal chromosomes ¡Resulting in genetic variety of offspring

Step 4: Telophase I l Nuclear membrane reforms l Spindle fibers and centrioles disappear l 2 nuclei per cell l Each nucleus now has HAPLOID number of chromosomes ¡ 2 n 1 n

Cytokinesis I l Splitting of the cytoplasm to produce 2 haploid daughter cells

Meiosis II • NO interphase between meiosis I and II • The production of 4 haploid cells from 2 haploid cells. • EXACT same process as mitosis!

Step 1: Prophase II

Step 2: Metaphase II

Step 3: Anaphase II

Step 4: Telophase II

Cytokinesis II l End result = 4 haploid cells

Purpose: Gamete Production l Gamete: sex cells (egg & sperm) l Oogenesis – egg production l Spermatogenesis – sperm production l Sexual Reproduction: genetic diversity of offspring

Page 155

Sexual Reproduction Each parent contributes genes to the offspring. l each offspring has a different set of inherited traits from the parents l gives offspring a better chance of surviving in a changing environment

Mitosis vs Meiosis l Mitosis ¡ 1 division ¡ 2 daughter cells ¡ Exact copies of parent cells ¡ Diploid to diploid ¡ Purpose l Growth l Repair l Asexual reproduction l Meiosis ¡ 2 divisions ¡ 4 daughter cells ¡ Each unique ¡ Diploid to haploid ¡ Purpose l Make gametes/ sex cells l Leads to genetic variation

Cancer l Cell cycle control system ¡Enzymes in cell control when and where cells divide l Malfunction in system means cells divide at inappropriate times and places ¡Benign tumor - abnormal mass of essentially normal cells l. Stay at original site, don’t move ¡Cancer uncontrolled cell division

Cancer l Problem not only uncontrolled division l Metastisis ¡ Cancer cells can move to other sites ¡ New tumor at that site l Three treatments ¡ Surgery to remove tumor ¡ Radiation ¡ Chemotherapy Last two aimed at controlling division

Cancer treatments l Radiation ¡ Disrupts cell division ¡ Most actively dividing cells are tumor ¡ Can damage normal cells- ovaries / testes l Chemotherapy ¡ Some disrupt cell division ¡ Taxol freezes spindle ¡ Vinblastine prevents spindle formation l Cancer cells immortal in cell culture ¡ Normal cells stop growing after 50 culture