CELL REPRODUCTION • Review of Biomolecules• DNA• Cell Reproduction

Mitosis (Asexual Reproduction)

Meiosis (Sexual Reproduction)

Biomolecules ??

• Proteins• Amino Acids (20)

• Nucleic Acids• Nucleotides• DNA/RNA

• Carbohydrates• Monosaccharides• Sugars

• Lipids• Fatty Acids

Cell Reproduction In This Unit:

1. Introduction to chromosomes (the cells’ library of genetic material)

2. Study Mitosis and cell division of Body (Somatic) cells

3. Examine how sex cells (Gametes) form through a process called meiosis

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)

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

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

*Handout

Chromosomes are counted on karyotypes

Karyotype

Of a Human Somatic Cell:• 46 chromosomes

• 23 pairs

• 44 autosomes• 22 pairs

• 2 sex chromosomes• 1 pair

• XX = female• XY = male

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

•ChromatinPartially “unraveled”

Chromosomes

•Chromosome A ‘single’ structure …

DNA*nucleosome proteins

•Chromatid 2 identical copies of a

chromosome (attached)

All refer to the cells’

DNA content at different stages

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

Homologous Chromosomes

From Dad From Mom

eye color locus(ex-blue)

eye color locus (ex-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

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

Cell Cycle Checkpoints- The Controls

Cyclins and cyclin dependent kinases (CDK’s) control the cell cycle.

They regulate gene expression to allow for cell replication and division.

Depending on the presence and action of these proteins, the cell cycle can be speedy or slow, and it may even halt altogether.

*PDGF- Platelet Derived Growth Factor- Wound healing

• Mitosis “Maturation” Promoting Factor (MPF)• Platelet-derived Growth Factor (PDGF)• Cancer Disruption in cell cycle control

3A3 Cyclins and cyclin-dependent kinases control the cell cycle3.A.2a The cell cycle is a complex set of stages that is highly regulated with checkpoints, which determine the ultimate fate of the cell. Internal controls or checkpoints, internal and external signals provide stop & go signs at the checkpoints

CELL CYCLE CONTROL

Cell Cycle Control and Checkpoint Activity 6.12Cells Alive!

P53 pp, .43 clip

• ONCOGENES:Normally stimulate cell growth

• SUPPRESSOR GENES

Normally inhibit cell growth

• REPAIR GENES Normally limit mutations

• Genes are Transcribed• Mutations• Methylation (Hyper or

Demethylation)• Transcription factors• miRNA

• “Normal Control”

GROW/DIVIDE when needed (Repair, growth)

STOP for internal or external controls.• Growth Factors• Density dependent• Anchorage dependent

p53 protein: Transcription Factor for checkpoint control genes “the guardian of the genome”, regulates the cellular response to stress and cancer

Abnormal

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

Telephase• 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/Meiosis Animation

http://www.pbs.org/wgbh/nova/miracle/divi_flash.html

BRIEF INTRO MEIOSIS/COMPARISON TO MITOSIS

MITOSIS

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

Mitosis (body cell) vs. Meiosis (sex cell)