Ch. 9.1: Cell Reproduction

Objectives:

1. Describe how cell reproduction contributes to repair and to growth.

2. Contrast asexual and sexual reproduction.

Vocab.: asexual reproduction; sexual reproduction

Why do cells need to reproduce?

1. Repair and replacement of dead or damaged cells.

2. Growth = increase in size

Asexual Reproduction

Single cell duplicates its genetic material and then splits into 2 genetically identical cells.

1 parent Parent & offspring are identical Most single celled organisms Many multicellular have option (plants, marine

organisms)

Sexual Reproduction

Genetic material from 2 parent combines.

Offspring genetically different fr. parents

Involve sperm & egg Meiosis involved

Ch. 9.2: The Cell Cycle

Objectives:

1. Describe the structure of a chromosome.

2. Name the stages of the cell cycle and explain what happens during each stage.

Vocab.: chromatin, chromosome, sister chromatid, centromere, cell cycle, interphase, mitotic phase, mitosis, cytokinesis

9.2: Cell Cycle

9.2: Chromosomes & Cell Division

Chromatin = long fibers of DNA + proteins

Chromatin --> Chromosomes before cell divides

Chromosomes: Condensed threads of genetic material formed fr. Chromatin as a cell prepares to divide.

Humans: 46 chromosomes (23 pair)

9.2: Chromosomes & Cell DivisionSister Chromatids: 1 pair of

identitical chromosomes created before a cell divides.

Centromeres: Where 2 sister chromatids are joined.

9.2: Cell Cycle Interphase:

When cell is not dividing.

Carrying out metabolic fxns, grow, etc.

~ 90% of cell life

S: DNA duplicated

9.2: Mitosis MitosisStage of the Cell

cycle where cell is DIVIDING.

(M phase)

Mitosis: Nucleus & duplicated chromosomes divide.

Cytokinesis: Cytoplasm divides into 2.

Ch. 9.3: Mitosis• Division of somatic cells (body)

Somatic Cell

Daughter Cells

Chromosomes

• Strands of DNA

• Each human has 23 pair (diploid or 2n)– One from your mother– One from your father

Chromosome

One from MomOne from Dad

Sister chromatidsDNA molecule with attached proteins

Look at figure 8.2

Mitosis• First you duplicate DNA• Why?

– You have 2 pairs of 23 chromosomes

– If cell splits, you will only have 1 pair

– Duplicate DNA, cell splits, still have 2 pair

Sex chromosomes- X and Y: XX is female in humans, XY is male

Interphase• Prior & After Mitosis

• G1 period– 90% of cell life spent here– Cell goes about it’s business

• S period– DNA is duplicated

• G2 period– Cell prepares to divide

• Cannot see DNA- uncoiled as chromatin

1. Prophase

• DNA becomes visible as chromosomes

• Nuclear membrane dissolves

• Centrioles migrate to opposite poles

• Spindle fibers form

Easy to remember- Prophase- proceeding into mitosis

2. Metaphase

• Spindle fibers attach to centromeres

• Chromosomes line up at midline of the cell

Easy to remember- metaphase, DNA at middle

Spindle Equator

Pole

Pole

3. Anaphase

• Spindle fibers pull apart centromeres

• One chromatid goes to each centriole (they look like V’s)

Easy to remember- anaphase, apart they go

4. Telophase

• Chromatids reach centrioles

• Mitosis ends when new nuclear membranes form

• Some evidence of cell dividing

Easy to remember- telophase, terminal phase

Last part- Cytoplasmic division

• Technically not in mitosis– Animal cell- pinching of cell

membrane- cleavage– Plant cell- formation of new cell

wall- cell plate– DNA becomes non-visible,

back to chromatin

• Daughter cells enter G1 period of interphase

Cancer• Uncontrollable mitosis (no G1)

– Cells cease to do what they are supposed to be doing in favor of dividing.

• Pancreatic cancer- no longer in interphase

• Cease production of insulin

• Incomplete digestion of food

• Diabetes, abdominal pain, weight loss

• Cancer does not “poison” your body…

Henrietta Lacks• 1951, a poor 31 Year old African

American mother of 4 was dying of cervical cancer @ Johns Hopkins Hospital– Dr. George Gey- sampled some of

the cancerous cells, found they could live indefinitely and multiply outside the body

– She died 6 months later, but cells live on

• HeLa cells– Used to study many different diseases– Cure for Polio