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Cell Reproduction
Chapter 8
ChromosomesSection 8.1
Definitions:
Chromosome: rod shaped structure made up of DNA and proteins
Sister Chromatids: identical halves of a chromosomes
Definitions:
Centromere: protein that holds sister chromatids together
Homologous Chromosomes: chromosomes that code for the same traits that come from your mother and your father
Definitions:
Chromatin: less tightly coiled strands of DNAUncoiled so that the cell can read the DNA to
direct the cell’s activities
Chromosomes only occur during cell divisionChromatin coils up to make chromosomes
All normal members of the same species have the same number of chromosomes in their body cells.
Ameba 50 Goldfish 94
Alligator 32
Garden Pea 14
Brown bat 44
Grasshopper 24
Bullfrog 26
Horse 64 Carrot 18
Human 46
Cat 32
Lettuce 18
Chicken 78
Onion 16
Chimpanzee 48
Redwood 22
Corn 20 Sand dollar 52
Earthworm 36
Fruit fly 8
Sex Chromosomes
Definition: chromosomes that determine the sex of the organismMay carry other genes as well
Humans: X and YMales: XYFemales: XX
Autosomes:
Definition: All other chromosomes in the body besides the sex chromosomes
Humans = 46 total chromosomes2 sex chromosomes44 autosomes
Karyotype – map of an organism’s chromosomes
http://www.chromosome18.org/AboutGenetics/BasicGenetics/WhatisaKaryotype/tabid/120/Default.aspx
Karyotype – map of a organism’s chromosomes
Cells having 2 sets of chromosomes are diploid (2N)
The haploid number of a human egg or sperm cell is 23, and there are no homologous chromosomes in either cell (1N)
Diploid and Haploid Cells
MitosisSection 8.2
Why Cells DivideCell size is limited
Cells cannot keep growing indefinitely
Replacement of damaged cells
Growth - embryoAsexual reproduction
Single celled life formsBinary fission
Sexual reproduction - meiosis
Eukaryotic Cell Division
Mitosis (Growth Division): Division of cell producing two identical daughter cells
2n 2n
Meiosis (Reduction Division): Division of cell producing four haploid daughter cells
2n 1n
The Cell Cycle (Life Cycle of the Cell)
2 Major Parts:1. Interphase
G1SG2
2. Cell DivisionMitosis –
nucleusCytokinesis –
cytoplasm
Part 1: Interphase
Stage your cells are in the most amount of time
When cell does its “normal” jobs
Contains 3 stages: G1, S, and G2
cell growth
DNA replicates
Growth and preparationfor mitosis
Mitosis
Cytokinesis
cell doubles in sizeenzymes and ribosomesand mitochondriadouble in number
rapid growth,synthesizing necessaryenzymes and structuresfor mitosis
G1 Phase
S Phase
G2 Phase
S Phase – DNA Replication
Process by which DNA builds an exact copy of itself
After replication has occurred, each double stranded molecule contains one old strand and one new strand of DNA
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: ProphaseChromosomes (2 chromatids) form from
chromatin Nuclear membrane disassemblesCentrioles move to polesSpindle fibers form
Mitosis – Step 2: Metaphase
Chromosomes line up at the middle of the cell “Metaphase Plate”
- Stage where karyotypes are made from!
Mitosis – Step 3: Anaphase
Sister chromatids (from the same chromosome) separate and move to opposite poles
Mitosis – Step 4: Telophase
Spindle fibers disappearNuclear membrane forms againChromosomes go back into chromatin
form2 nuclei (diploid) per one cell
Cytokinesis
Division of cytoplasmCell membrane pinches in to form two
separate cellsResults: 2 IDENTICAL daughter cells
AnimationMitosis
Mitosis “Flip Book” To receive full credit you must:1. Illustrate what is going on in the life cycle
a) Title Pageb) Interphase: G1, S, G2
b) Mitosis: prophase, metaphase, anaphase, telophasec) Cytokinesis: early & lated) Finished product
2. Diploid # (2N) = 8 Haploid # (1N) = 4(represent homologous chromosomes with different
colors)Need help? Consult your book or your notes!
Cont…
3. Diploid # (2n) = 8
Haploid # (1n) = 4
4. Represent homologous pairs with 4 different colors.
Need Help? Consult you book or your notes!
offspring is an exact copy of parents - occurs in lower plants and animals
(bacteria, molds, algae and protozoa)
all cells form through mitosis
Asexual Reproduction
Asexual Reproduction
Regeneration Budding
Binary FissionSpores
Mitosis Slides
MeiosisSection 8.3
2 Stages: 2n
n n
nn n nResults in 4 haploid cells
Meiosis I
Meiosis II
Interphase
Same as mitosis!
3 Stages: G1, S, G2
Meiosis I
Formation of 2 haploid cells from 1 diploid cell
Production of gametes
“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:Synapsis: When a pair of homologous
chromosomes partner up inside a dividing cell
Tetrads: the name given to a partner of homologous chromosomes during synapsis
Crossing over: chromatids of homologous chromosomes twist around and trade places causing an exchange of DNA
Step 2: Metaphase I
Tetrads line up randomly at the metaphase plate
Step 3: Anaphase I
Tetrads are split and each homologue is moved toward opposite poles
Independent assortment: the random separation of maternal and paternal chromosomesResulting in genetic variety of offspring
Step 4: Telophase I
Nuclear membrane reformsSpindle fibers and centrioles disappear2 nuclei per cellEach nucleus now has HAPLOID number
of chromosomes2n 1n
Cytokinesis I
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
End result = 4 haploid cells
Purpose: Gamete Production
Gamete: sex cells (egg & sperm)
Oogenesis – egg production
Spermatogenesis – sperm production
Sexual Reproduction: genetic diversity of offspring
Page 155
Sexual Reproduction
Each parent contributes genes to the offspring.
each offspring has a different set of inherited traits from the parents
gives offspring a better chance of surviving in a changing environment
Mitosis vs Meiosis
Mitosis 1 division2 daughter cellsExact copies of parent cellsDiploid to diploidPurpose
Growth RepairAsexual reproduction
Meiosis2 divisions4 daughter cellsEach uniqueDiploid to haploidPurpose
Make gametes/ sex cells
Leads to genetic variation
Cancer
Cell cycle control systemEnzymes in cell control when and where cells
divide
Malfunction in system means cells divide at inappropriate times and placesBenign tumor - abnormal mass of essentially
normal cellsStay at original site, don’t move
Cancer uncontrolled cell division
Cancer
Problem not only uncontrolled divisionMetastisis
Cancer cells can move to other sitesNew tumor at that site
Three treatmentsSurgery to remove tumorRadiation Chemotherapy
Last two aimed at controlling division
Cancer treatments
Radiation Disrupts cell divisionMost actively dividing cells are tumorCan damage normal cells- ovaries / testes
ChemotherapySome disrupt cell division TaxolTaxol freezes spindleVinblastineVinblastine prevents spindle formation
Cancer cells immortal in cell cultureNormal cells stop growing after 50 culture