CELL REPRODUCTION • Review of Biomolecules• DNA• Cell Reproduction

Mitosis Nuclear/Cell Division + Cytokinesis

Meiosis Sexual Reproduction; ‘2n’ to ‘n’

Biomolecules ??

• Proteins• Amino Acids (20)

• Nucleic Acids• Nucleotides• DNA/RNA

• Carbohydrates• Monosaccharides• Sugars

• Lipids• Fatty Acids

Structure of DNA• Stores Genetic Information• A Double helix ladder of connected nucleotides forming a

sugar-phosphate “backbone” and nitrogen base “steps”• Each nucleotide of DNA consists of:

A sugar “deoxyribose”A phosphate A nitrogenous base:

Adenine ThymineCytosine Guanine

DNA STRUCTURE

*HandoutGene = allele = traits 1 from each parent 2m/6.5’ of DNA/cell

Clip on DNA…compacts tightly• Visualizing Cell Processes• DNA structure• Chromosome Condensation

Cell Reproduction

Introduction to chromosomes

(the cells’ library of genetic material)

Study Two Processes: Mitosis & Meiosis

1. Mitosis -cell division of Body (Somatic) cells. ‘2n’ diploid = complete set #?

2. Meiosis- division of sex cells (Gametes) egg, sperm ‘n’ Haploid = ? In humans

Mitosis: everywhere ; Meiosis: reproductive organs only

P/S: Reasons for Cell Reproduction

1. Replace/Maintenance (skin, blood, digestive)

2. Growth

3. Repair (scrape knee, break bone)

4. Reproduction of species: pass down genetic material for continuation of the species (mutations/adaptions/natural selection)

•ChromatinPartially “unraveled”

Chromosomes (95%)

•Chromosome A ‘single’ structure …

DNA*nucleosome proteins

•Chromatid 2 identical copies of a

chromosome (attached)

“sister chromatids”

All refer to the cells’

DNA content at different stages

Homologous Chromosomes

From Dad From Mom

eye color locus(ex-’b’ blue)

eye color locus (ex-’B’ brown)

hair color locus

hair color locus

CENTROMERE

ALLELE FOR EYE COLOR

_____ _____Sister Chromatids(identical) *Nonsister

Unreplicated Chromosome, when copied = 2 chromatidsHeld together by a centromere- form a replicated chromosomeHomologous chromosomes: 23 PAIRS (From mother/father…similar in size/shape and centromere position

Chromosomes are counted on karyotypes

Karyotype

-Human Somatic Cell: #?• 46 chromosomes

• 23 pairs ….’body’?

• 44 autosomes• 22 pairs ….’sex’?

• 2 sex chromosomes• 1 pair ….M/F?

• XX = female• XY = male

Allele: Different forms of a gene (Blue, brown eyes)

TWO TYPES OF CELLS:SOMATIC and GAMETES

SOMATIC: (Body Cells)

(Body cells: skin/muscle/liver/bone/brain/blood)

Diploid Cells (2n): The # of chromosomes in a somatic cell 2n = ? in humans…varies/species

GAMETES: (Sex Cells)

(Sex cells = Gametes = Humans?) 23 Sperm + 23 Egg = 46 Zygote (The fertilized egg)

Plants?

Haploid Cells (n): The # of chromosomes in a sex cell n = 23 in humans (half a complete set)

46

The Making of New Prokaryotes: Binary Fission (asexual) (see notepage)

• DNA attached to the inner membrane

• DNA (plasmid) copies• New cell wall forms• Then splits in two, creating two bacteria with IDENTICAL DNA. replicates in ~20minutes

EukaryoticCell Cycle: Repeating

set of events that

make up the life of a

cellInterphase +

PMAT (Mitosis)+ Cytokinesis

Cytokinesis:

Cytoplasm Divides

G o P

hase

Mitosis + Cytokinesis

Cell Cycle: An Interactive AnimationCycle of

growth and division.

Interphase-(G1 + S + G2) time between cell divisions (cell growth)

is most active.TIME TO COMPLETE?

Plant Cell: 10-30 HrsAnimal Cell: 18-24 Hrs

PROPHASE• Chromosomes Condense• The nuclear envelope disappears

(dotted line = breakdown or forming• The centrioles move to opposite poled• The spindle starts to form, growing

out of the centrioles towards the

chromosomes

Metaphase• Chromosomes line

up on the equator of the cell• Spindle fibers are attached

to the centromeres

Human Cell- how many

Will be lined across?

Anaphase• Centromeres divide• Spindle fibers contract

and the chromosomes are

pulled to opposite poles

Telophase• In telophase the cell actually divides• The chromosomes are at the poles of the spindle• The spindle disintegrates• The nuclear envelope reforms around the two sets of

chromosomes• Set for cytokinesis to occur

Cytokinesis• Division of cytoplasm and its contents• Results in 2 daughter cells• Animal cells- Furrow formed

by microfilaments- pinches

plasma in half “cleavage furrow”• Plant cells- a new cell wall

made of cellulose forms

between the 2 new nuclei

Summary of Mitosis

Plant Cell Cytokinesis

MITOSIS

• Mitosis + Cytokinesis = 2 new cells with the same genetic information as the original cell