CELLULAR REPRODUCTION

MITOSIS & MEIOSIS

chapter 9 – mitosischapter 10.1 – meiosis

CELL REPRODUCTION=CELL DIVISION

What are the characteristics of living things?

Why is cell division necessary?

How is cell reproduction related to

our other topics of study?

CELL SIZE LIMITATIONSAs cell size increases a cell has difficulty….

o communicatingo obtaining & supplying nutrientso expelling/eliminating wasteo transporting substances - via diffusion, osmosis,

endocytosis

Cells grow until they reach their size limit, then they must stop growing, divide or die.

CELL SIZE LIMITATIONSAs cell size increases… the surface area to volume ratio decreases!!!

The smaller the cell the more efficient it will be!!!

Just as there is a limit to cell size….

there is a limit to the size of living things

In a cell, the DNA is usually present

in a form called CHROMATIN

Before cell division…

the DNA will

replicate (copy)

and

become more compact

forming…

double stranded

CHROMOSOMES

CHROMOSOME STRUCTURE:

A Double-Stranded Chromosome has…

2 identical parts called “sister” chromatids

held together by a centromere (protein disc)

2 TYPES OF EUKARYOTIC CELL DIVISION

MITOSIS makes …. 2 cells body (somatic) cells diploid cells (2n) genetically identical cells maintains chromosome # body cells; somatic cells involves a cell cycle

MEIOSIS makes… 4 cells sex (germ) cells haploid cells (n) genetically different cells reduces chromosome # by ½ sex cells; germ cells; gametes NO cell cycle

2 TYPES OF PROKARYOTIC CELL DIVISION

Prokaryotes are BACTERIA

BINARY FISSION(asexual reproduction)

single, circular chromosome (DNA)

copies itself and the cellsplits into 2 cells

that are genetically identical

.

CONJUGATION(sexual reproduction)

1. Plasmid (loop of DNA) is copied2. Plasmid is exchanged between

bacterial cells (do not need to be the same species)

PLOIDY … refers to the NUMBER OF COMPLETE

SETS OF CHROMOSOMES in a cell

DIPLOID…HAPLOID…POLYPLOID…

DIPLOID CELLS

contain 2 CHROMOSOMES of each homologous pair contain homologous pairs somatic (body) cells = kidney, skin, muscle, bone,… represented 2n (n= # of chromosome pairs)

having 2 sets of chromsomes… 1 set from mother and 1 set from father = 2n

HAPLOID CELLS

contain 1 CHROMOSOME of each homologous pair contain NO homologous pairs sex cells/gametes/germ cells – egg and sperm represented n or 1n (n= # of chromosome

pairs)

having 1 set of chromsomes…

contain 3+ CHROMOSOMES of each homologous pair contain homologous pairs somatic (body) cells represented 3n, 4n, 5n,….

having more than 2 sets of chromosomes chromosome number is greater than 2n

common in plants – wheat, oats, strawberries, lilies,…. exhibit more vigor and size

rare in animals – some fish + amphibians always fatal in humans triploid organism (3n) – has 3 complete sets tetraploid organism (4n) – has 4 complete sets

POLYPLOID CELLS

LET’S PRACTICE – DIPLOID AND HAPLOID

Humans have 46 chromosomes in their body cells….

How many chromosomes do humans have in…. somatic cells? diploid cells? sex cells? haploid cells?

How many chromosome PAIRS do humans have in … somatic cells? diploid cells? sex cells? haploid cells?

Each species has a characteristic chromosome number …

Domestic Cats 38Sheep 54Fruit Fly 8Buffalo 60Corn 20Human 46

Mrs. Dockery’s man crush

THE CELL CYCLE…

3 main phases:Interphase – G1, S,

G2

Mitosis Cytokinesis

Cells don’t go

through the cycle

at the same rate!!!

Cell Division

a repeating series of events in the life of a (somatic)cell

Animation - How the Cell Cycle Works – 1 minutehttp://highered.mcgraw-hill.com/sites/0072495855/student_view0/chapter2/animation__how_the_cell_cycle_works.html

INTERPHASE the time between divisions the majority of the cell’s lifetime divided into 3 phases….

G1 phase – cell growth, maturation + metabolism

normal cellular activities (photosynthesis, active transport, lipid synthesis,…) S phase – DNA is replicated (copied)

G2 phase – preparation for cell division

SOME CELLS REMAIN IN INTERPHASE THEIR ENTIRE LIFETIME….

These cells enter a state called G0 phase

These cells…. do not copy their DNA do not go through cell division

cells in the central nervous system (brain and spinal cord) do not go through cell division after maturity

BUT..OTHER CELLS MAY GO THROUGH INTERPHASE AND THE CELL CYCLE RAPIDLY AND UNREGULATED

CANCER…

MITOSIS

division of the nucleus (genetic material/DNA) into 2 genetically identical nuclei

4 steps/phases - PMATProphaseMetaphaseAnaphaseTelophase

Animation – Mitosis – 1 minute http://www.youtube.com/watch?v=-G-3BDlnK58

CYTOKINESIS

Immediately follows mitosis division of the cytoplasm into 2 “daughter”

cells (genetically

identical)

Animation - Mitosis and Cytokinesis – 1 minutehttp://highered.mcgraw-hill.com/sites/0072495855/student_view0/chapter2/animation__mitosis_and_cytokinesis.html

PROCESS OVERVIEW

WHY IS CELL DIVISION (BY MITOSIS) NECESSARY?

3 reasons….. GROWTH – adds new cells REPAIR – of damaged tissues and parts MAINTENANCE – cells are always dying

and need to be replaced

HOW IS MITOSIS DIFFERENT AS WE AGE?

occurs very quickly when we are young in adulthood and into old age the process

slows

Live Video – Pig Epithelial Cells Undergoing Mitosis – 1 minutehttp://www.youtube.com/watch?v=P7m3WfzgZdI&feature=player_detailpage

Cells Alive – Animal Cell Mitosis http://www.cellsalive.com/mitosis.htm

Mitosis – Video – 4 minuteshttp://vcell.ndsu.nodak.edu/animations/mitosis/movie-flash.htm

CELL CYCLE REGULATION

NORMAL CELL CYCLE the timing and rate of cell division is important

Red blood cells live about 3-4 months and then must replace themselves, but some white blood cells live for years before replacement

regulated by proteins called CYCLINS

DURATION OF THE CELL CYCLE…VARIES…

depending on the (type) of cell that is dividing….

some eukaryotic cells might complete the cycle in

as few as 8 minutes, others might take up to 1 year

for most normal, animals cells, the cell cycle takes approximately 12-24 hours

ABNORMAL CELL CYCLES…. Cancer Apoptosis Stem Cells

CANCER uncontrolled growth and division of cells cells spend little time in interphase and

therefore undergo mitosis more rapidly cancer is due to A FAILURE TO REGULATE THE CELL CYCLE

CANCER

caused by carcinogens, radiation, genetics

carcinogens - cancer causing agents UV radiation - more exposure the greater the

risk genetics – may predispose you to develop

cancer

the risk of cancer - increases with age

CANCER

Video Segment – Differences between healthy and cancer cells

http://app.discoveryeducation.com/search?Ntt=differences+between+healthy+and+cancer+cells

3D Medical Animation – What is Cancer?

http://www.youtube.com/watch?v=LEpTTolebqo

Animation – Cancer: Unregulated Cell Division

http://www.youtube.com/watch?v=IeUANxFVXKc&feature=related

MASSES OF CELLS ARE CALLED TUMORS

Malignant Tumors (CANCER) invasive destroy nearby tissues life-threatening progressive

Benign Tumors non invasive not life-threatening

APOPTOSIS…programmed cell death

not every cell is destined to survive cells shrink and shrivel in a controlled process

helpful because ….it can help protect organisms from developing cancerous growths

2 examples:fingers and toesleaves

STEM CELLS

2 types:

Embryonic Stem Cells Adult Stem Cells

unspecialized (“blank”)cells; not specialized in structure and function

WHAT IS SPECIAL ABOUT STEM CELLS?

Have the ability to renew themselves develop into many different cell types have potential medical uses because they are UNSPECIALIZED

EMBRYONIC STEM CELLS

taken from an embryo embryo = up to 8th week can differentiate into MANY cell types

ADULT STEM CELLS

taken from a growing human even infants have “adult” stem cells found in bone marrow, believed to be in brain and heart NOT ABLE TO differentiate into all cell types

ADULT STEM CELLS

WHAT ARE SOME POTENTIAL USES OF STEM CELLS?

repair of damaged or degenerating tissues may have medical applications in….

Parkinson's disease, genetic disorders, diseases of degeneration, endocrine abnormalities, congenital disorders, spinal cord injuries and paralysis,…

MEIOSIS…process that….

REDUCES the amount of genetic material (DNA) and

the chromosomes by 1/2

meiosis, like mitosis must befollowed by CYTOKINESIS – in

order for the process of cell division to be complete

MEIOSIS… follows interphase…..a period of cell growth,

DNA replication and preparation for division

produces gametes/sex cells/germ cells…..that are genetically different from each other and will be used in sexual reproduction

does not follow a cell a “cell cycle” as mitosis does

2 nuclear divisions – Meiosis 1 and Meiosis II

OVERVIEW OF

MEIOSIS

MEIOSIS I – THE FIRST NUCLEAR DIVISION4 stages (followed by cytokinesis) –

Prophase 1 = P1Metaphase 1 = M1Anaphase 1 = A1Telophase 1 = T1

SYNAPSIS occurs - the pairing of homologous chromosomes and the formation of tetrads

CROSSING-OVER occurs - the exchange of genetic material between homologous chromosomes

SYNAPSIS AND

CROSSING OVER

MEIOSIS II – THE SECOND NUCLEAR DIVISION

occurs simultaneously in 2 cells

4 stages (followed by cytokinesis) Prophase 2 = P2Metaphase 2 = M2Anaphase 2 = A2Telophase 2 = T2

Phases of Meiosis – Animation http://highered.mcgraw-hill.com/olc/dl/120074/bio19.swf

MEIOSIS IN MALES

CALLED SPERMATOGENESISOCCURS IN THE TESTES

MALE GAMETES ARE…. SPERMATOZOA = SPERM

PRODUCE 4 HAPLOID SPERM (FROM EACH DIPLOID CELL)

MEIOSIS IN FEMALES

CALLED OOGENESISOCCURS IN THE OVARIES

FEMALE GAMETES ARE…. EGG(S) = OVUM (OVA) PRODUCE 1 HAPLOID EGG AND 3 POLAR BODIES (FROM EACH DIPLOID CELL)

COMPARISON - MEIOSIS IN MALES AND FEMALES

Are there other difference in the process of meiosis in males and females? Why?

ASEXUAL SEXUAL REPRODUCTION REPRODUCTION 1 parent 1set of genes no union of

gametes offspring is

genetically identical to the parent

I cell 2 identical cells

2 parents 2 sets of genes fusion of haploid

(1n) gametes offspring is

genetically different from the parents

2 different cells 1 unique zygote

What are the advantages of asexual reproduction? sexual reproduction?

IN SEXUAL REPRODUCTION •two haploid (1n) gametes fuse in a process called FERTILIZATION •their union forms a diploid cell (2n) called a ZYGOTE

IN fertilization …

Haploid (n) + Haploid (n) = Diploid (2n)

EGG + SPERM = ZYGOTE

GENETIC RECOMBINATION

OCCURS DURING CROSSING OVER OF MEIOSIS

allows for variety among organisms

THE MORE VARIETY WITHIN A SPECIES THE MORE LIKELY THAT SPECIES WILL SURVIVE

MITOSIS VS. MEIOSIS

Interactive Table A (open hyperlink)

Interactive Table B (open hyperlink)

Comparison Mitosis and Meiosis – Animation http://highered.mcgraw-hill.com/sites/0072495855/student_view0/chapter2/

animation__comparison_of_meiosis_and_mitosis__quiz_2_.html

MITOSIS….LET’S REVIEW….

What occurs in mitosis? Why is this processes used by living things? What types of cells are produced? Are they haploid or diploid? How many cells are produced?

MEIOSIS….LET’S REVIEW….

What occurs in meiosis? Why is this processes used by living things? What types of cells are produced? Are they haploid or diploid? How many cells are produced? What is synapsis? What is crossing over? How does meiosis differ in males and females?