Chapter 10Chapter 10The Cellular Basis of InheritanceThe Cellular Basis of Inheritance

Cells have distinct phases of growth, reproduction, and normal functions.

Objectives

• Describe the purpose of cell reproduction

• Contrast two ways that organisms reproduce

All Cells Come From Cells

• Where have you heard that before? – It is part of the Cell Theory!!

• Why do organisms need cellular reproduction to occur?– Allows living things to repair damage– Allows organisms to grow– Allows organisms to produce offspring

Repair and Growth• Did you know that the outer layer of your skin is

all dead cells?

• New cells are continually reproducing underneath and the new cells gradually move upwards to replace dead ones.

Close-Up of your skin!!

2 Types of Reproduction

• Sexual Reproduction:Sexual Reproduction: – 2 parents – Involve gametes (egg & sperm)– Genetic material combines – Offspring are genetically different from

parents

• Asexual Reproduction:Asexual Reproduction:– 1 parent– The process by which a single cell

duplicates its genetic material– Offspring identical to parents– Examples- Budding & regeneration

Types of Asexual Reproduction1. Budding

2. Binary Fission

3. Regeneration

4. Spores

5. Vegetative propagation

Asexual Reproduction - YouTube

Warm UpMatch the type of asexual reproduction with its description.

TYPE DESCRIPTION

1. _____ budding A. Small reproductive cells

2. _____ binary fission B. Splitting of cells to make more (bacteria)

3. _____ vegetative propagation

C. Re-growing lost parts to form a new organism such as in lizards, starfish, and worms.

4. _____ regeneration D. “runners”/stems of plants that form identical plants.

5. Spores E. A identical organism growing off the side of another until it is able to live on its own.

Cell Cycle Objectives

• Describe the structure of a chromosome (9.2)

• Name and Describe the stages of the cell cycle (9.2)

The Cell Cycle• The cell cycle is a regular pattern of

growth, DNA replication, and cell division.

Interphase (preparation)

1. Gap 1 (G1) – cell growth and normal functions

2. Synthesis (S) – DNA Replication = a 2nd copy of the genetic material is made

3. Gap 2 (G2) – additional last minute growth & doubling of organelles Note: Mitosis can ONLY occur if

the cell is large enough and the DNA is not damaged by the end of interphase!

Mitotic Phase (Mitosis or Meiosis)

Mitosis is the actual nuclear division of the cell. It is composed of 4 major stages:

1.Prophase

2.Metaphase

3.Anaphase

4.Telophase

**Cytokinesis = the final splitting of the cytoplasm and “pinching” of the cell membranes.

Cells divide at different rates.• The rate of cell division varies with the need for

those types of cells.

Cell size is limited…Eventually they MUST divide!

• S.A / Volume Ratio needs to be high…or diffusion (essential for cell life) suffers!

WARM-UP

1. What part of the cell cycle is the “preparation” part?

2. What part of the cell cycle is the actual splitting of the nucleus?

Surface area must allow for adequate exchange of materials.!

Therefore…..Cells that must be large have uniqueunique shapes.

With a crazy shape, their surface area/volume ratio remains HIGH and diffusion of materials into/out of them is fast enough to survive!

Surface Area vs. Volume of Cells (Relay) GAME

How the game works: •There will be 4 teams. Each team will get a chance to work with each shaped cell.•Your team must get the provided molecules (beads) into the nucleus in the shortest amount of time! •Only 1 team member can go into the cell at a time and all team members must participate…..so its a relay!!!•Be strategic!!!!•Remember your times for the data table!

Cell A

Cell B

DATA TABLE(write time & a team member’s name)

Cell A (long cell in hallway) Cell B (round one in room)

AVERAGE TIME AVERAGE TIME

WRAP UP

1. What process was represented by the transferring of beads (molecules) into the center (nucleus) of the cells?

2. Which cell went faster? (round or long?)

3. WHY did the above cell go faster?

4. This activity represented that a cells Surface Area/Volume Ratio must be ___________ (high or low) in order for it to be efficient and survive.

Cells divide during mitosis and cytokinesis.

The Cell Cycle in body cells: Mitosis and cytokinesis produce two genetically identical daughter

cells.

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Parent cell

centrioles

spindle fibers

centrosome

nucleus withchromatin

(G1) - The cell grows and performs normal functions

(S) The DNA is duplicated (via DNA Replication)

(G2) The cell undergoes last minute growth & organelle duplication

Events that occur During Interphase

Nuclear Envelope

InterphaseInterphase

Chromatin condenses at the start of mitosis into chromosomes!.

…By having the DNA wrap around proteins.

…The end product is chromosomes!!

Remember: DNA + proteins is called chromatin.

• One half of a duplicated chromosome is a chromatid.

• Sister chromatids are held together at the centromere.

Condensed, duplicated chromosome

chromatid

telomere

centromere

telomere

Events that occur during Prophase

– Chromatin (DNA) condenses

and chromosomes

are visible

– spindle fibers form

– Nuclear envelope

disappears

Nuclear envelope

Breaking apartSister Chromatids

Spindles Forming

Events that occur during Metaphase– chromosomes line up in the middle of the cell

– Spindle fibers attach to centromeres (between sister chromatids)

Sister Chromatids

Centromere

Events that occur during Anaphase

– Sister chromatids separate (at the centromere)

– Spindle fibers pull identical

chromosomes to opposite

sides of the cell.Chromosome

Centromere

Spindle Fiber

Events that occur during Telophase & Cytokinesis

– The new nuclei form

– Chromosomes begin to

uncoil

– Nuclear envelope reappears

Cytokinesis:– Cell splits into two– Two identical daughter

cells form

Nuclear Envelope

Identical Chromosomes

Two Identical Daughter Cells Form (Cytokinesis)

Two Identical Daughter Cells form After Cytokinesis

– In animal cells, the membrane pinches closed (cleavage furrow)

– In plant cells, a cell plate forms.

nucleus withchromatin

• Animal Cells = Cleavage Furrow (pinches the 2 daughter cells apart)

• Plant Cells = cell plate forms (to divide the 2 daughter cells)

Crash Course – Mitosis

• Mitosis: Splitting Up is Complicated - Crash Course Biology #12 - YouTube

Mitosis wrap-up

• Mitosis Rap

cell cycle | Search | Discovery Education

• Standard deviants videos

Find a cell in the following stages: Interphase, Prophase, Metaphase,

Anaphase, and Telophase of mitosis.

Cancer

• Do you know anyone (or of anyone) who has been diagnosed with cancer?

• If so, what cancer did they have? And what types of things did they go through?

• What type of cancers do you think are most prevalent?

Cancer … Mitosis Out of Cancer … Mitosis Out of Control!!!!Control!!!!

• Cancer results from out-of-control cell out-of-control cell productionproduction.

• Abnormal masses of cells are called tumorstumors.

Two Types of Tumors

Tumors can either be:Tumors can either be:

Benign – abnormal mass of normal cells

Malignant – mass of cells resulting from the reproduction of cancer cells. Brain Tumor (MRI)

Metastasis Metastasis

• When cancer cells break off tumors and travel/spread to other places in the body, the cancer is said to have metastasized.

Video: How cancer spreads - MayoClinic.com

Cancer TreatmentCancer Treatment

• Surgery

• Radiation Therapy

• Chemotherapy

Unwanted Side Effects – nausea, damage to organs, sterility, hair loss, etc.

Common Cancers

• Melanoma (type of skin cancer)

• Leukemia (cancer of the circulatory system – blood)

• Lung Cancer

• Colon Cancer

• Breast Cancer

• Bladder Cancer

Warm - up

• Name the 3 reasons cell reproduction is necessary for organisms?

Meiosis Objectives

Contrast haploid and diploid cells

Summarize the process of meiosis

Compare mitosis & meiosis

Explain how genetic variation occurs in offspring of populations

KEY CONCEPTKEY CONCEPT Gametes (sex cells) have half the number of chromosomes that body cells have and

they reproduce via meiosis (not mitosis)

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Mitosis vs. MeiosisMitosis and meiosis are types of nuclear division

that make different types of cells.

Mitosis makes 2 diploid (2n) cells

Occurs in testes & ovariesMitosis occurs in body cells

Meiosis makes4 haploid (n) gametes/sex cells

Sexual Reproduction relies on MeiosisSexual Reproduction relies on Meiosis

• Meiosis – a type of cell division that produces gametes/sex cells (egg & sperm)

• Meiosis occurs in sex organs (testes & ovaries)

• Still part of cell cycle (simply replace mitosis with meiosis)

You have somatic cells and germ cells. (body cells) (sex cells)

• Germ cells develop into gametes (sperm & eggs)

• Germ cells are located in the reproductive organs.– Gametes have DNA that can be passed to offspring.

body cells (muscle cells) sex cells (sperm) sex cells (egg)

Your body cells have a total of 23 pairs of chromosomes.

That is ___ total chromosomes.

– Chromosome pairs # 1-22 are autosomes. (=44 chromosomes)

– Pair # 23 are the Sex chromosomes, X and Y, (determine gender)

Each of your cells have: 1. autosomes (regular ones)

2. sex chromosomes

Girl = X XBoy = X Y

Quick Check / Review1. Meiosis is a type of cell division that makes

______ cells in the ______ & _______ (organs) of our bodies.

2. Somatic (body) Cells reproduce through ____________ (mitosis or meiosis).

3. Sex Cells reproduce through __________. (mitosis or meiosis)

4. How many total chromosomes are in your body cells???? _______ (hint: 23 pairs)

Body cells are diploidBody cells are diploid Gametes (sperm & eggs) are haploidGametes (sperm & eggs) are haploid

• Fertilization joining of egg and sperm; occurs in sexual reproduction, results in a diploid zygote

• Diploid (2n) cells have two copies of every chromosome. = 46 chromosomes

– Body cells are diploid*– Total = 46 Chromosomes(A set of chromosomes (23) come from each parent)

Haploid (n) cells have only one copy of every chromosome (or ½ the normal amount)

– Gametes (sperm & eggs) are haploid.

– Total = 23 chromosomes (that’s ½ of 46!!)

Diploid (2n) vs. Haploid (n) Cells

•Body Cells

•Contain 2 copies of each chromosome

•Total = 46 chromosomes(44 autosomes & 2 sex)

• Reproduce through mitosis

•Sex Cells

•Contain 1 copy of each chromosome

•Total = 23 chromosomes(22 autosomes & 1 sex)

• Reproduce through meiosis

Meiosis results in 4 haploid gamete cells– Meiosis occurs in reproductive organs (testes &

ovaries) – Involves 2 cell Divisions = (meiosis 1 & meiosis 2)

– Meiosis produces 4 haploid (n) gametes*

Meiosis 1

Meiosis 2

4 haploid gametes

Parent Germ Cell

During interphase

2n

2n

n n

n n nn

Mitosis vs. MeiosisMitosis and meiosis are types of nuclear division

that make different types of cells.

Final product: 2 diploid (2n) cells

Mitosis occurs in body cells

Final product: 4 gametes (haploid (n) cells)

Occurs in testes & ovaries

How do we get genetic variation?

During Prophase 1 (of Meiosis 1)…

homologous chromosomes, while paired in “tetrads” undergo

“Crossing Over” and swap genes for traits.

This creates genetic variation in populations!!!

Crash Course - Meiosis

• Meiosis: Where the Sex Starts - Crash Course Biology #13 - YouTube

Meiosis video clip

Meiosis review clip

Let’s play a review GAME!

http://hrsbstaff.ednet.ns.ca/bfougere/Science%20Jeopardy_files/frame.htm