REPRODUCTION

• All cells come from cells.All cells come from cells.

• Essential for the continuation of a species

Why do cells divide?Cells need to remain small. A greater surface area to

volume ratio is needed to maintain homeostasis

• for reproduction

– one celled organisms (clones)

• for growth & development– from fertilized egg to multi-celled

organism

• for repair– replace cells that die from

normal wear & tear or from injury

Asexual Reproduction

Types of Reproduction

Parents Variation Mate Selection

ASEXUAL

One parent

Results in clones (genetically identical)

Very little or no variation in offspring

No mate selection needed

SEXUAL

Two parents –

egg and sperm sex cells (gametes)

Great variation Great variation (diversity) (diversity) due to crossing over (exchanging genetic info)

Varying degrees of mate selection

METHODS OF ASEXUAL REPRODUCTIONMETHODS OF ASEXUAL REPRODUCTION

1. BINARY FISSION– DNA copies itself and then

cell divides in half– results in 2 identical, equally

sized offspring (cells) – EX: bacteria, amobea

http://www.brainpop.com/science/cellularlifeandgenetics/asexualreproduction/

AMOBEA

2. BUDDING•NUCLEUS DIVIDES EQUALLY, CYTOPLASM DOES NOT•RESULTS IN different sized “BUDS” offspring

• EX: YEAST, HYDRAYEAST, HYDRA

Hydra

3. SPORULATION 3. SPORULATION “SPORE SPORE FORMATIONFORMATION”•single specialized cells made by mitosis that grow (germinategerminate) into a new organism under proper conditions (WATERWATER AND FOOD)!•EX: OCCURS IN MOLD MOLD AND OTHER FUNGI FUNGI

Spores

4. REGENERATION4. REGENERATION:: is the ability to replace body parts.•Example – Starfish, worms, hydras

• To what extent can regeneration occur in humans? Why?

Humans can regenerate certain organs like the skin but not old body parts

5. VEGETATIVE PROPAGATION can be produced asexually from the roots,

stems and leaves of an existing plant. a) Natural:

– Bulbs – tulips, onions and lilies

– Runners– Grass and strawberries

– Tuber -potato

b) Artificial:– Cuttings – segments separated from the

plant and placed in soil to grow a new plant

– Grafting – attaching a branch or stem of one plant on to another

Vegetative Propagation

PROS CONS• Plants are

identical –good if productive & strong

• Faster than planting a seed

• Producing Producing Seedless Seedless fruitfruit

• Can be wiped out by disease or a disaster (flooding or a drought)

• Can be more Can be more susceptible to susceptible to insecticidesinsecticides 

Cell Reproduction: Vocabulary

1. DNA: instructions for making proteins

2. Genes: a segment of DNA that tells the ribosome to make ONE specific protein

3. Chromosome: a tightly packed piece of DNA containing over a 1000 different genes

4. Chromatin: chromosomes all stretched out; thread-like DNAthread-like DNA

5. Homologous chromosomes: a pair of chromosomes carrying the same genes (one from each parent)

6. Centromere: the point where the chromosomes

join together

nucleus

Sister Chromatids

CentromereChromatid

Mitosis - HOW “NORMAL” CELLS DIVIDEA. What is Mitosis?

• The process of distributing exact copies of genetic information.

Malfunction of Cell Reproduction: Uncontrolled mitosis:•Production of numerous, nonfunctional cells •Force out functional cells by stealing their nutrients•Very dangerous when cancer cells enter the endocrine

or circulatory systems.•Results:   Cancers and Tumor Growth

Thyroid Cancer

http://www.brainpop.com/science/cellularlifeandgenetics/mitosis/ (2:09)

http://www.iteachbio.com/Life%20Science/LifeFunctionsandTheCell/Mitosis.mov

B. What is Mitosis used for?1. Growth & development

• from fertilized egg to multi-celled organism

2. Repair of the body• Replace cells that die from normal

wear & tar or from injury3. Asexual reproduction • Mitosis (nuclear division)

C. How does Mitosis happen? 1. Genetic material within the nucleus makes an exact

copy of itself.2. It is then packaged and separated into two new nuclei.3. Each daughter cell gains exactly one copy of the

genetic material.

Mitosis

InterphaseProphaseMetaphaseAnaphaseTelophaseCytokinesis

Mito

sis

The Cell Cycle

• Interphase• Prophase• Metaphase• Anaphase• Telophase• Cytokinesis

STAGES/PHASES OF THE CELL CYCLE

MITOSIS

Pneumonic Pneumonic DeviceDevice

II PPrayray MMore ore AAtt TThe he CChurchhurch Cell cycle video http://www.youtube.com/watch?v=3k

pR5RSJ7SA&feature=related

18

http://www.cellsalive.com/mitosis.htm

IPMATC

Mitosis: Animal v. PlantMitosis: Animal v. Plant

Overview of mitosis

Copy DNA

Line Up Separate Divide

http://www.sumanasinc.com/webcontent/animations/content/mitosis.html

KEYS TO MITOSISKEYS TO MITOSIS Original cell has complete set of chromosomesOriginal cell has complete set of chromosomes

This is known as This is known as DIPLOID DIPLOID or 2Nor 2N One division results in One division results in 2 DAUGHTER CELLS

No genetic material exchangedNo genetic material exchanged Cells are Cells are GENETICALLY IDENTICALGENETICALLY IDENTICAL DaughterDaughter Cells are also DIPLOID or 2NCells are also DIPLOID or 2N

Ex. Original cell has 46 chromosomes, daughter cells will Ex. Original cell has 46 chromosomes, daughter cells will have 46 chromosomeshave 46 chromosomes

IN SINGLE CELLED ORGANISMS:IN SINGLE CELLED ORGANISMS: Method of reproduction Method of reproduction (ASEXUAL)(ASEXUAL)

ProtistsProtists, some Algae, and , some Algae, and MoldsMolds IN MULTI-CELLED ORGANISMS:IN MULTI-CELLED ORGANISMS:

Mitosis used for Mitosis used for GROWTH and REPLACEMENTGROWTH and REPLACEMENT of of BODYBODY (somatic)(somatic) CELLSCELLS (skin, liver, heart etc…) (skin, liver, heart etc…)

Turn in article reviews on Stem Cells and Telomeres

Never Say Die Scientific American Frontiers - Season 10 The Clock of Life- http://chedd-angier.com/frontiers/season10.html (start at 15:11minutes) (9 minutes)

Your turn: Complete the 2 article reviews on TELOMERES

WHAT ARE STEM CELLS” https://www.youtube.com/watch?v=jF2iXpoG5j8

Your turn: Complete the article review on Stem Cells

Complete Pearson activity on mitosisHW: complete RB worksheet BQuiz Monday on Mitosis

SEXUAL REPRODUCTION

Meiosis – A Source of DistinctionMeiosis – A Source of Distinction

Why do you share some but not all characters of each parent?

At one level, the answers lie in meiosis.

What is meiosis? It is a special type of cell division that makes egg and sperm

How? Chromosomes replicate Each cell divides twice

This provides each cell with half the number of chromosomes

Why? Meiosis is necessary to halve the number of chromosomes

going into the sex cells Why halve the chromosomes in gametes?

At fertilization the male and female sex cells will provide ½ of the chromosomes each – so the offspring has genes from both parents

This makes for a lot of genetic diversity. Genetic diversity is important for the evolution of

populations and species.

Let’s review some vocabulary first:

1. Homologous chromosomes (homologs):

A PAIR of chromosomes carrying the SAME GENES (ONE from each parent)

HOMOLOGOUS = same information

Humans have 23 PAIRS

2. Sister CHROMATIDS: 2 “identical” strands of

DNA that make up each member of a homologous pair

Draw and label this diagram in the box of your notes

23

2346

egg

sperm

46meiosis

Haploid (n)Diploid (2n)

3. DIPLOID (2N): having 2 of each chromosome type

ex. mitosis always STARTS and RESULTS in a diploid number (46)

ex. meiosis always STARTS with diploid number (46)

4. HAPLOID (N): A cell (always a gamete) that contains ½ the number of

CHROMOSOMES Meiosis results in cells with ½ NUMBER OF CHROMOSOMES

(23)!

5. Fertilization - THE JOINING OF SEX CELLS½ genetic (egg) + ½ genetic (sperm) = 1 genetically whole organism

(n=23) (n=23) = (2n=46)

egg + Sperm zygote.

=

n=23egg sperm

n=23

2n=46zygote

6. Zygote6. Zygote

is a FERTILIZED

egg

MitosisMitosis

FertilizationFertilization

ZygoteZygoteEmbryoEmbryo

Draw and label this diagram in the box of your notes

•A method of organizing A method of organizing the the chromosomeschromosomes of a of a cell in relation to cell in relation to number, size, and type.number, size, and type.

•There are two categories There are two categories of chromosomes:of chromosomes:

•Sex chromosomesSex chromosomes

•X, YX, Y

•AutosomesAutosomes – 1, 2, 3, – 1, 2, 3,….. (numbers 1-22 in ….. (numbers 1-22 in humanshumans))

7.7. KARYOTYPE KARYOTYPE - -

XX chromosome - femaleXY chromosome - male

8. CROSSING-OVER:•Process when homologous Process when homologous chromosomes “cross” each chromosomes “cross” each other andother and EXCHANGE EXCHANGE genesgenes

•SOURCE OF VARIATION-SOURCE OF VARIATION-givesgives NEW COMBINATIONS NEW COMBINATIONS of mom of mom and dad’s genes in one and dad’s genes in one chromosomechromosome

Images of Chromosomes crossing over

How does this explain:family resemblance & differences!

Why are the kids so similar to the parents but not exact?

Martin & Charlie Sheen, Emilio Estevez

Michael & KirkDouglas

Baldwin brothers

MEIOSIS: Cell Division to MEIOSIS: Cell Division to form Gametesform Gametes

Meiosis Animation

Meiosis: Meiosis: SEXSEX!!!!!!!!!! A form of CELL DIVISIONCELL DIVISION by which sex cells called

GAMETESGAMETES (egg and sperm), (egg and sperm), are produced. Takes place in reproductive structures called GONADS

(ovaries and testes) Diploid Diploid (2n) (2n) haploid haploid (n)(n) EACH CELL DIVIDES TWICE EACH CELL DIVIDES TWICE - - (meiosis I meiosis I and meiosis IImeiosis II)

Each sex cell has halfhalf the number of CHROMOSOMESCHROMOSOMES ALLOWS FOR GENETIC VARIATION OF OFFSPRING gametes of offspring do not have same genes as gametes from parents

offspring

from Dad

from Mom new gametes made by offspring

variation

We’remixing things

up here!

PRIOR TO MEIOSIS MEIOSIS I

Sister chromatids

Tetrad (4 chromatids from homologous chromosomes)

1. Chromosomesreplicate inparent cell.

2. Synapsis (joining) of homologous (sister) chromosomes. Crossing over of non-sister chromatids – brings about Variation

3. Tetrads migrate to middle of cell. Independent Independent assortment assortment (random line (random line up)- more up)- more variation!variation!

4. Homologsseparate.

MEIOSIS I: HOMOLOGOUS CHROMOSOMES SEPARATE

MEIOSIS II

5. Cell divides into 2 haploid (N) daughter cells.

6. Chromosomes begin moving to

middle of cell.

7. Chromosomes line up at middle of cell.

8. Sister chromatids separate.

9. Cell division results in four haploid daughter cells. Leads to random fertilization.

MEIOSIS II: SISTER CHROMATIDS SEPARATE

Learning Target: I can illustrate meiosis from a diagram and explain the possible outcomes and the source of variation amongst the cells..

Individually observe Figure 11-15 in textbook and read pages 276-277.

As a group complete the condensed meiosis diagram on the mitosis –meiosis summary sheet. Use colored pencils to represent the homologous chromosomes. Discuss the best way to illustrate the process. When you agree fill in sheet. Label where homologous chromosomes separate and where sister chromatids separate. Use page 278 for help as well.

When finished answer the questions on the back as a group. I expect all to be participating!!

9. Gametogenesis9. Gametogenesis

Making gametes (sex cells- Making gametes (sex cells- EGGEGG and and SPERMSPERM)) Spermatogenesis:

Formation of 4 FUNCTIONAL sperm

Oogenesis:Formation of egg cells (1 functional CELL and 3 polar bodies)

Basic diagram of Meiosis- OvaBasic diagram of Meiosis- Ova

Female Human Female Human Pre-GametePre-Gamete

4646chromosomechromosome

ss

4646differentdifferent

chromosomechromosomess

4646differentdifferent

chromosomechromosomess

Replication Replication and Crossing-and Crossing-

OverOver

2323

1 functional

ovum and 3 polar bodies

First cell First cell divisiondivision

Oogenesis:• Formation of egg cells (ova)• Results in 1 functional gamete and 3 polar bodies

Basic diagram of Meiosis- SpermBasic diagram of Meiosis- Sperm

Male Human Male Human Pre-GametePre-Gamete

4646chromosomechromosome

ss

4646differentdifferent

chromosomechromosomess

4646differentdifferent

chromosomechromosomess

Replication Replication and Crossing-and Crossing-

OverOver

2323 2323 2323 2323

44 functional functional spermsperm

After 2After 2ndnd cell cell divisiondivision

First cell First cell divisiondivision

Spermatogenesis:•Formation of sperm cells•Results in 4 functional gametes

ADVANTAGES OF SEXUAL REPRODUCTION

1. Sexual reproduction increases individual VARIATION within a SPECIES

Asexual Reproduction (Mitosis):

Results in offspring = to parents

Sexual Reproduction (Meiosis):

Results in offspring that are not = to parents

2. GENETIC DIVERSITY may produce some organisms that are ADAPTABLE to non favorable conditions:

Susceptibility to PATHOGENS

ENVIRONMENTAL changes

VariationVariation

Important to population as the raw material Important to population as the raw material for for natural selectionnatural selection..

Genetic diversity is important for the Genetic diversity is important for the evolution of populations and speciesevolution of populations and species

Question:Question:

What are the three sexual sources ofWhat are the three sexual sources of

genetic variation? genetic variation?

Write this down

Answer:Answer:

1. crossing over (prophase I)1. crossing over (prophase I)

2. independent assortment (metaphase I)2. independent assortment (metaphase I)

3. random fertilization3. random fertilization

Remember: variation is good!

Write this down

HYPOTHETICAL EXAMPLE OF INDEPENDENT ASSORTMENT

Eye color

Gene thatcontributes to browneyes

Gene thatcontributes to blueeyes

Maternalchromosome

Paternalchromosome

Hair color

Gene thatcontributes to black hair

Gene thatcontributes to red hair

Maternalchromosome

Paternalchromosome

During meiosis I, tetrads can line up two different waysbefore the homologs separate.

OR

Brown eyesBlack hair

Blue eyesRed hair

Blue eyesBlack hair

Brown eyesRed hair

HYPOTHETICAL EXAMPLE OF INDEPENDENT ASSORTMENT

MEIOSIS & GENETIC VARIATION

Random Fertilization: Each human can produce an

nearly 8.4 million different kinds of gametes

Crossing over not taken into account!!!

Sex yields: 8.4 mill x 8.4 mill = 70.6 x 10 12

genetically distinct offspring can be produced

DISADVANTAGES OF SEXUAL REPRODUCTION

1. Sex SLOWS RATE of Reproduction!

Sexual reproduction should decline in frequency relative to asexual reproduction

Sexual Reproduction: Only FEMALES

produce offspring, therefore fewer are produced

Asexual Reproduction:

All individuals can produce offspring

2. Errors In Inheritance:

Genetic disorders occur for various reasons:NONDISJUNCTION:

Failure of a pair of chromosomes to separate during gamete formation

ABNORMAL numbers of one or more chromosomes is usually, but not always, fatal

Includes Genetic Disorders Like: DOWN’S SYNDROME (chromosome #21)

Comparing Mitosis & Meiosis – 1 min

AnimationAnimation

KEYS TO MEIOSISKEYS TO MEIOSIS

Original cell has complete set of chromosomes Original cell has complete set of chromosomes (Diploid or 2N)(Diploid or 2N)

2 divisions2 divisions result in result in 4 DAUGHTER CELLS (gametes: 1 ova 4 DAUGHTER CELLS (gametes: 1 ova or 4 sperm)or 4 sperm) Genetic material is exchanged during Genetic material is exchanged during CROSSING OVERCROSSING OVER

CHROMOSOMES CHROMOSOMES “criss-cross” “criss-cross” EXCHANGING GENESEXCHANGING GENES Daughter cells (gametes) are genetically differentDaughter cells (gametes) are genetically different Daughter cells (gametes) are now Daughter cells (gametes) are now HAPLOID HAPLOID or N ( ½ the or N ( ½ the

original # )original # ) Ex.Ex. If original cell has 46 chromosomes, gametes that If original cell has 46 chromosomes, gametes that

result from meiosis will have 23 chromosomesresult from meiosis will have 23 chromosomes OCCURS OCCURS ONLYONLY IN IN MULTICELLUARMULTICELLUAR, SEXUALLY , SEXUALLY

REPRODUCING ORGANISMSREPRODUCING ORGANISMS

I II – like mitosis BUT twice

Crossing over occurs

• Crossing over (during prophase I) brings about VARIATION!!!!!Crossing over (during prophase I) brings about VARIATION!!!!!

Parent cell

DNA Synthesis

Mitosis & Cytokinesis

Parent cell and daughter cells contain thesame complement of chromosomes.

A REVIEW OF MITOSIS

Two daughter cells

Note: Mitosis Is Part Of The Cell Cycle!!

COMPARISON OF MITOSIS AND MEIOSIS

Characteristic

Mitosis Meiosis (SEX)

Function GROWTH, DEVELOPMENT, REPLACEMENT, REPAIR

Make GAMETES (egg and sperm)

Occurs in BODY (Somatic) cells Immature REPRODUCTIVE cells

Results in 2 daughter cells (clones of each other)

4 daughter cells (all different)

Chromosome #

Daughter cells are DIPLOID

(2n) = 46 chromosomes

Daughter cells are HAPLOID (1n) = 23 chromosomes

Reproduction Type

ASEXUAL – 1 parent SEXUAL – 2 parents

Stages

Drawing

1 cell division (IPMAT) 2 cell divisions (PMAT x 2)

464646

46 2323

232346

46