DNA Terminology…. DNA Terminology…. The Cell Cycle….The Cell Cycle….Mitosis and Meiosis…..Mitosis and Meiosis…..

I. ChromosomesI. ChromosomesA. DNA wrapped A. DNA wrapped

around proteins around proteins (histones) is a (histones) is a nucleosomenucleosome

B. Uncoiled, B. Uncoiled, threadlike DNA is threadlike DNA is ChromatinChromatin

(non-dividing cell)(non-dividing cell)

C. DNA called a C. DNA called a chromosome chromosome in dividing in dividing

cells; cells; short, fat rodsshort, fat rods

D.D.Half of a doubled Chromosome Half of a doubled Chromosome = a Chromatid= a Chromatid

1.Contains two identical parts

2. Attach at a point called the Centromere

E. Homologous ChromosomesE. Homologous Chromosomes

1.1. Occurs in pairs; same size and Occurs in pairs; same size and shapeshape

2.2. Structurally different from Structurally different from

all other pairsall other pairs

3. Have the 3. Have the

same gene locationssame gene locations

centromerecentromere

chromatidchromatid

F. GeneF. Gene

1. Distinct unit on a 1. Distinct unit on a chromosomeschromosomes

2. Sequence of 2. Sequence of nucleotidesnucleotides

Eye Color

II. “N” Number = II. “N” Number = The number of The number of chromosomes a cell haschromosomes a cell has

A.A. Diploid (2N)Diploid (2N)1.1. Each species has a Each species has a

characteristic number of characteristic number of chromosomeschromosomes

2.2. Cells with both Cells with both chromosomes of every pair chromosomes of every pair called somatic or body cellscalled somatic or body cells

a)a) 2N for humans = 46 2N for humans = 46 b)b) Ex: Crayfish (200)Ex: Crayfish (200) fruit flies (4)fruit flies (4)

Common Common NameName

Genus and Genus and SpeciesSpecies Diploid NumberDiploid Number

BuffaloBuffalo Bison bisonBison bison 6060

CatCat Felis catusFelis catus 3838

CattleCattle Bos taurus, B. Bos taurus, B. indicusindicus 6060

DogDog Canis familiarisCanis familiaris 7878

DonkeyDonkey E. asinusE. asinus 6262

GoatGoat Capra hircusCapra hircus 6060

HorseHorse Equus caballusEquus caballus 6464

HumanHuman Homo sapiensHomo sapiens 4646

PigPig Sus scrofaSus scrofa 3838

SheepSheep Ovis ariesOvis aries 5454

B.B. Haploid (1N)Haploid (1N)

1.1. Cell with 1 Cell with 1 chromosome of each chromosome of each pairpair

2.2. Sex cell (sperm or Sex cell (sperm or egg)-Gametesegg)-Gametes

III. Asexual and Sexual ReproductionIII. Asexual and Sexual ReproductionA. Mitosis is AsexualA. Mitosis is Asexual

1.1. Functions includeFunctions include

a)a) Unicellular Organism = Unicellular Organism = ReproductionReproduction

b) Multi-cellular Organismsb) Multi-cellular Organisms

1)1) Growth and development from Growth and development from eggegg

2)2) Replacement of dead or Replacement of dead or damaged cellsdamaged cells

c) Passes along the genome (total c) Passes along the genome (total DNA per species)DNA per species)

2.2. Each daughter cell is clone of Each daughter cell is clone of parent.parent.

B.B. Meiosis is SexualMeiosis is Sexual

1.1. Mixes DNAMixes DNA

2.2. Produces Produces ½½ the the number of the number of the chromosomes of chromosomes of the parentsthe parents

3.3. Cells involved in Cells involved in sexual sexual reproduction reproduction

are sperm and are sperm and

eggs (gametes)eggs (gametes)

IV. Cell DivisionIV. Cell DivisionA.A.Prokaryotes: Called Binary FissionProkaryotes: Called Binary FissionB.B.Eukaryotes: Use the Cell CycleEukaryotes: Use the Cell Cycle

1.1.InterphaseInterphase2.2.MitosisMitosis3.3.CytokinesisCytokinesis

V. Cell CycleV. Cell Cycle

= = sequence of growth sequence of growth and division in the life of and division in the life of a cella cell

G1

(growth;Gap 1)

S=Synthesis

G2=Gap 2

1 hr.Cytokinesis

Mitosis

•Rapid cell growth

•Cell doubles in size

•Enzymes + organelles double in number

•Growth

•DNA makes a copy of itself

11 hrs.

7 hrs.•Rapid Growth

•Final preparation for cell division

3 hrs.

Interphase

Cell Cycle =Cell Cycle =Interphase = period of cell growth and

duplication of the DNA

GG11 + S + G + S + G22

Mitosis = division of the cell’s nucleus in which the chromosomes in the parent cell divides into 2 identical sets

Cytokinesis Cytokinesis = cytoplasm divides in 2 = cytoplasm divides in 2 daughter cellsdaughter cells

VI. Stages of MitosisVI. Stages of MitosisProphaseProphase

a) Early Prophasea) Early Prophase

1)1)Chromatin coils to chromosomesChromatin coils to chromosomes

2)2)Nucleolus & nuclear membrane Nucleolus & nuclear membrane break down & disappearbreak down & disappear

3)3)Centrioles move to poles (animal Centrioles move to poles (animal cells only).cells only).

b)b) Middle ProphaseMiddle Prophase

1)1) Spindle fibers Spindle fibers (microtubules) appear(microtubules) appear

2)2) Polar – centriole to Polar – centriole to

centriolecentriole

3)3) Kinetochore – Kinetochore – centromere to centriolecentromere to centriole

c)c) Late ProphaseLate Prophase

1)1)Aster appear Aster appear

(centriole and fibers)(centriole and fibers)

2) Chromosomes 2) Chromosomes

position is randomposition is random

MetaphaseMetaphase

a)a) Kinetochore fibers Kinetochore fibers move chromosomesmove chromosomes

b)b) Chromosomes line up Chromosomes line up along equatoralong equator

Anaphase Anaphase

a)a) Centromere splitsCentromere splits

b)b) Sister chromatids Sister chromatids pulled to opposite pulled to opposite endsends

TelophaseTelophase

a)a) Identical chromatids at Identical chromatids at opposite endopposite end

b)b) Chromatids unwind & Chromatids unwind & elongate to chromatinelongate to chromatin

c)c) Centrioles & spindle Centrioles & spindle disappeardisappear

d)d) Nucleolus & nuclear Nucleolus & nuclear membrane reappearmembrane reappear

1.Prophase

2.Metaphase3.Anaphase

4.Telophase

C.C. CytokinesisCytokinesis1.1. Animal cells form cleavage Animal cells form cleavage

furrowsfurrows2.2. Plant cells form a cell platePlant cells form a cell plate

VII. Reproduction and MeiosisVII. Reproduction and Meiosis

A.A. MeiosisMeiosis in males in males ♂♂

1. Part of 1. Part of spermatogenesisspermatogenesis

2. Occurs in the 2. Occurs in the testestestes

3. Always results in 3. Always results in four sperm cellsfour sperm cells

B.B. Meiosis in females Meiosis in females ♀♀

1.1. Part of oogenesisPart of oogenesis

2.2. Occurs in the ovariesOccurs in the ovaries

3.3. One cell receives One cell receives most of the cytoplasm; most of the cytoplasm; the other 3 cells are the other 3 cells are polar bodiespolar bodies

4.4. Results in mature egg Results in mature egg

( with 23 chromosomes)( with 23 chromosomes)

VIII. Significance of MeiosisVIII. Significance of Meiosis

A.A. Produces genetic variationProduces genetic variation

B.B. Without meiosis, Without meiosis, chromosome numbers would chromosome numbers would continually increasecontinually increase

((teenage mutant Ninja turtles)teenage mutant Ninja turtles)

Common Common NameName

Genus and Genus and SpeciesSpecies

Diploid Diploid NumberNumber

BuffaloBuffalo Bison bisonBison bison 6060

CatCat Felis catusFelis catus 3838

CattleCattle Bos taurus, B. Bos taurus, B. indicusindicus 6060

DogDog Canis familiarisCanis familiaris 7878

DonkeyDonkey E. asinusE. asinus 6262

GoatGoat Capra hircusCapra hircus 6060

HorseHorse Equus caballusEquus caballus 6464

HumanHuman Homo sapiensHomo sapiens 4646

PigPig Sus scrofaSus scrofa 3838

SheepSheep Ovis ariesOvis aries 5454

IX. Review “N” NumberIX. Review “N” NumberMitosis => results in 2N Meiosis => results in 1NMitosis => results in 2N Meiosis => results in 1N

animals animals (1N)(1N) plants (1N)plants (1N)

egg and sperm egg and sperm spores and seeds spores and seeds

(gametes)(gametes)

fusefuse

(2N zygote)(2N zygote)

**♂♂ - sperm all viable after spermatogenesis - sperm all viable after spermatogenesis

**♀♀ - after oogenesis, 1 egg(ootid) and 3 polar - after oogenesis, 1 egg(ootid) and 3 polar bodies (no cytoplasm, just DNA)bodies (no cytoplasm, just DNA)

X. Steps of Meiosis X. Steps of Meiosis (2 Separate Divisions)(2 Separate Divisions)

Meiosis vs MitosisMeiosis vs Mitosis

Meiosis I (starts with 2N)Meiosis I (starts with 2N)Prophase IProphase I Chromatin shortens and coils to chromosomesChromatin shortens and coils to chromosomes Spindle appearsSpindle appears Nucleolus and nuclear membrane disappearNucleolus and nuclear membrane disappear Unique step:Unique step:

– Chromosomes line up next to their homologs Chromosomes line up next to their homologs (called (called synapsissynapsis))

– Homolog pairs twist tightly to form a Homolog pairs twist tightly to form a tetrad tetrad – (4 chromatids that make up two doubled (4 chromatids that make up two doubled

chromosomes)chromosomes)– Crossing over can occur; exchange of DNA Crossing over can occur; exchange of DNA

between homologs and/or 2 sister between homologs and/or 2 sister chromatidschromatids

Tetrad FormationTetrad Formation

Tetrad FormationTetrad Formation

Meiosis IMeiosis IMetaphase IMetaphase I Tetrads move to the equator; homolog Tetrads move to the equator; homolog

pairs stay togetherpairs stay together

Anaphase IAnaphase I Homologous pairs separate and move Homologous pairs separate and move

to each pole ( one chromosome of to each pole ( one chromosome of each pair pulled to pole)each pair pulled to pole)

2 chromatids still joined at centromere2 chromatids still joined at centromere

Meiosis IMeiosis I

Telophase ITelophase I Cytoplasm divides forming 2 Cytoplasm divides forming 2

daughter cellsdaughter cells

Meiosis IIMeiosis II (chromosomes do not (chromosomes do not double; ends with 4 (1n) cellsdouble; ends with 4 (1n) cells

Prophase IIProphase II New spindle formsNew spindle forms Nuclear membrane and nucleolus Nuclear membrane and nucleolus

break apartbreak apart Chromatin shortens and becomes Chromatin shortens and becomes

visible as sister chromatids visible as sister chromatids

Metaphase IIMetaphase II Sister chromatids move to the equatorSister chromatids move to the equator

Meiosis IIMeiosis II

Anapahse IIAnapahse II Centromere divides; sister Centromere divides; sister

chromatids move to opposite poleschromatids move to opposite poles

Telophase IITelophase II Nuclear membrane reforms; Spindle Nuclear membrane reforms; Spindle

disappearsdisappears Cytokinesis occursCytokinesis occurs 4 daughter cells from one parent4 daughter cells from one parent