CHAPTER 8 Cellular Reproduction: Cells from Cells.

CHAPTER 8CHAPTER 8

Cellular Reproduction:Cells from Cells

You began life as a single cell, but there are now more cells in

your body than stars in the milky way.

THE BIG PICTURE:

BIOLOGY IS THE STUDY OF LIFE

ALL life is made of cells.

Cells divide and reproduce by using the information of DNA.

Figure 8.1

This was YOUR “baby” picture

You couldn’t do much

AND LOOK AT YOU NOW !

In this chapter, we will discuss how

cells divide, a topic that has fascinated

scientists since they first observed

it through a microscope more

than 100 years ago.

and just like carefully

watching a game played repeatedly,

they have been able to figure out the rules

of cell division

ALL LIFE IS MADE OF CELLS

There are WELL over 50 TRILLION CELLS IN A HUMAN BODY

Perspective on 50 trillion

And all those cells divided from just 1 fertilized egg cell

There are two kinds of cell division:

1.Mitosis - making a “photocopy” of a cell

• (for growth and maintenance)

2.Meiosis – taking a cell & “halving” it

• (for sexual reproduction)

MITOSIS

MEIOSIS-testicles-ovaries

MITOSIS

PARENT CELL

“DAUGHTER” CELL

START > > > > > END

MEIOSIS – IN MALES

MEIOSIS – IN FEMALES

START > > > > > END

MITOSIS HAPPENS IN YOUR TOES, TOO

Mitosis:- Happens everywhere BUT sex cells (testicles

or ovaries)

- Produces 2 genetically identical "daughter" cells from a single "parent" cell.

- Grew you from a single fertilized cell to the person you are today.

- Repairs / Replaces cells lost through everyday wear and tear- ex: skin cells

MeiosisMeiosis, on the other hand, is quite different.

It shuffles the genetic deck, generating “daughter” cells that are distinct from one another and from the original parent cell.

only a few special cells (sex cells) are capable of meiosis:

- Female > eggs - males > sperm

So, basically, mitosis is for growth and maintenance, while meiosis is for sexual reproduction.

A QUICK CHECK

What is the cellular process that produces identical “daughter” cells? ___________________

What is the cellular process that takes place everywhere in your body but your sex cells? __________________

What is the cellular process that made you grow from a single cell to the person you are today?

______________

What is the cellular process that only produces sex cells? ______________________

Who lives in a pineapple under the sea? ___________

MITOSIS

MEIOSIS

S.B.S.P.

THE CELL CYCLE

Phases of CELL DIVISIONINTERPHASE

PROPHASE

PROMETAPHASE

METAPHASE

ANAPHASE

TELEPHASE CYTOKINESIS

MITOSIS

NOT MITOSIS

Phases of CELL DIVISION

INTERPHASE – cell grows to make room (G1), makes a copy of each chromosome(S), but the old copies of the chromosomes are stuck to the copied ones (G1, S, & G2)

PROPHASE - In the nucleus, copied chromosomes condense and become visible. Outside the nucleus in the cytoplasm, the spindles forms.

PROMETAPHASE – Nuclear membrane breaks up, spindle fibers begin to interact with newly copied chromosomes

METAPHASE – Chromosomes pushed by spindle fibers to the metaphase plate ready to be separated

ANAPHASE –Chromosomes separate into two genetically identical groups, move to opposite ends of the cell.

TELEPHASE - Nuclear membranes form around each of the two sets of chromosomes, the chromosomes begin to spread out, and the spindle fibers begins to break down

CYTOKINESIS –

cell divides into 2 (READY TO START AGAIN)

http://www.youtube.com/watch?v=nPG6480RQo0&feature=related

http://www.youtube.com/watch?v=VlN7K1-9QB0

QUICK REVIEW

An in-between time in a cells life where it doubles its DNA and grows ______________

A time in a cells life when the chromosomes condense and become visible also the spindles start to form ____________________

A time in a cells life cycle when spindle fibers finally get to interact with the newly condensed chromosomes because the nucleus just dissolved __________________

interphase

prophase

prometaphase

QUICK REVIEW

When chromosomes are pushed to the middle of the cell. ____________________

Chromosomes begin moving AGAIN but this time away from each other and towards the opposite sides of the cell. ____________

Nuclear membranes form around each of the two new sets of chromosomes, this is the END of the line ____________

Cells move away from each other _________

metaphase

anaphase

telophase

cytokenisis

QUICK REVIEW

This phase is NOT part of mitosis ________interphas

A TOUR OF DNA

Here is a eukaryotic cell (animal cell)

The DNA in a cell is packed into an elaborate, multilevel system of coiling and folding.

DNA Packing

THE CHROMOSOME

THE CENTROMERE

It’s like a

super belt

A Chromosome

- (1 continuous piece of DNA)

- (a single chromatid)

ALSO a chromosome

- (2 identical continuous pieces of DNA connected at centromere)

-(made of 2 sister chromatids)

QUICK REVIEW

DNA DOUBLE HELIX

HISTONE

NUCLEOSOME

QUICK REVIEW

= a chromosome

2 identical sister ……

chromatids

• Genes = a unit of heredity passed on from a parent to its offspring

– are written in the language of DNA

WHERE IS A GENE?!?!?!?!

• Chromosomes:

– Are made of DNA and histones (protein to wrap DNA around)

– Are not visible in a cell until the chromatin condenses (folds) to the stereotypical chromosome shape.

ORGANIZE FROM THINNEST (1) TO THICKEST (5)

histones

DNA double helix

Super coil

Chromosomes (coiled)

Nucleosomes

Eukaryotic Chromosomes

The number of chromosomes in a

eukaryotic cell depends on the species.

RED VISCACHA RAT

Karyotype = A picture of your

condensed chromosomes

A karyotype

Remember: this picture is of condensed chromosomes

we know, from mitosis, that chromosomes don’t condense unless they were first doubled

(during S of interphase)

Look close. . .

Each chromosome is really made up of it’s “identical twin” from when

it doubled in S of interphase

For example: If this is mom’s #1 chromosome with information on how her childs eyes will be colored

Your dad has the same #1 chromosome with his version of how to color his child’s eye color

CLOSER INSPECTION

Each “identical twin” joined at the centromere is known as a chromatid

Here we see 4 chromatids in total, of 2 chromosomes

2 chromatids on the left chromosome (from mom) & 2 chromatids on the right chromosome (from dad)

Sister chromatids = 2

chromatids joined at

the centromere

Here we see ________ pairs of sister chromatids.

Homologous chromosomes = moms version of chromosome next to dads version of that same chromosome

22 PAIRS OF CHROMOSOMES

(44 CHROMOSOMES + 2 sex chromosomes ) = 46

total chromosomes

A healthy human has a total of 46 chromosomes

___ pairs of chromosomes & 2 sex chromosomes

A healthy human has 2 kinds of chromosomes:

1)Autosome = any chromosome that is not related to gender

(chromosome #’s 1 - 44)

2)Sex chromosome = the 2 chromosomes that are related to gender

(chromosome #’s 45 & 46 or x & y)

MEIOSIS

WHAT IS MEIOSIS? (NOT MITOSIS)

• meiosis (pronounced my-o-sis) is a process that reduces the number of chromosomes per cell in half. (46 -> 23)

• Meiosis always results in the formation of gametes, (sperm or egg)

Q – What is the point of meiosis? EXPLAIN!!

Q – What happens to the future cells if a sex cell undergoes mitosis instead of meiosis? EXPLAIN!!

Q: What is the point of Meiosis?

A: To prepare for sexual reproduction

Q: But why does meiosis have to be different than mitosis?

Every person is made of cells

Each cell in our body has 46 chromosomes

A SEXUALLY MATURE MALE AND FEMALE

WANT TO HAVE A BABY

•He has 46 chromosomes

per cell

FEMALE

•She has 46 chromosomes

per cell

Without meiosis, a baby would have 92

chromosomes (46 from mom & 46 from dad)

Remember: meiosis is a process that

cuts the number of chromosomes in

half (46 -> 23)

QUICK REVIEW

How many chromosomes does a body cell have? _______

How many chromosomes does a cell have before MITOSIS? __________

How many chromosomes does a cell have after MITOSIS? __________

How many chromosomes does a cell have before MEIOSIS? __________

How many chromosomes does a cell have after MEIOSIS? __________

Fertilization

• Dad’s sperm = ___ chromosomes

• Mom’s egg = ___ chromosomes

FERTILIZATION = fusion of sperm and egg

46 total

MOM (23 chrom) DAD (23 chrom)

YOU (46 chromosomes per cell)

The instant just before YOU (becoming 46 chrom’s)

23 chromosomes

And ever since this moment each cell in you has been copied

through the process of _________

mitosis

You divided … and divided…. And divided

MEIOSIS

(ABREVIATED)

MEIOSIS VIDEO

http://www.youtube.com/watch?v=D1_-mQS_FZ0

* REMEMBER *

• Meiosis = reduces the number of

chromosomes per cell in half. (46 -> 23)

What meiosis looks like

I P P M A T C P P M A T CMEIOSIS I MEIOSIS III I I I I

II II II II II II

STARTS WITH ENDS WITH

MITOSIS

•1 CELL

•46 CHROMOSOMES PER CELL

•2 CELLS

MEIOSIS

•1 CELL

•4 CELLS

ABREVIATED REVIEW

OF MITOSIS

ABREVIATED REVIEW OF

MEIOSIS

MEIOSIS I

IINTERPHASE (G1)

23 chromosomes from mom

23 chromosomes from dad

46 total

* Note = chromosomes are not really condensed *

IINTERPHASE (S)

46 total

S = synthesis (each chromosome copies itself)

IINTERPHASE (G2)

46 total

G2 = gap 2

IMEIOSIS I - ( Prophase I )

46 total

Centrosomes begin to form

IMEIOSIS I – ( Prometaphase I )

46 total

Nucleus breaks up and spindle fibers rush in

IMEIOSIS I – (Metaphase I )

46 total

Tetrad’s (homologous chromosomes) line up side by side

ZOOMING IN

Tetrad = the combination of 2 homologous chromosomes lined up RIGHT next to each other

Dad’s #1 chromosome

Mom’s #1 chromosome

Dad’s #2 chromosome

Mom’s #2 chromosome

Also, when the homologous chromosomes get this close (a tetrad) some of their information gets switched or CROSSES OVER.

IMEIOSIS I – (Anaphase I )

23 chromosomes

to the left

CBecause of all the “crossing over” it is impossible to

call one side mom’s and one side dad’s

23 chromosomes

to the right

IMEIOSIS I – (Telophase I )

23 chromosomes

to the left

CNote: chromosomes begin to unwind (not shown)

and nucleus reforms

23 chromosomes

to the right

IMEIOSIS I – (Cytokenisis I )

23 chromosomes to the left cell

CEnd of meiosis I

23 chromosomes to the right cell

MEIOSIS II

IIMEIOSIS II – (Prophase II )

CCentrosomes begin to form (NO INTERPHASE!)

IIMEIOSIS II – (Prometaphase II )

CSpindle fibers make first contact with

chromosomes as nucleus breaks up

IIMEIOSIS II – (Metaphase II )

CChromosomes line up at metaphase plate

IIMEIOSIS II – (Anaphase II )

23 chrom’S

CSNAP!!!

23 chrom’S

ZOOMING IN ON METAPHASE II

3 CENTROMERES = 3 CHROMOSOMESor 6 chromatids or 6 sister chromatids

ZOOMING IN ON ANAPHASE II

6 CENTROMERES = 6 CHROMOSOMESor 6 chromatids

IIMEIOSIS II – (Telophase II )

23 chrom’s

CChromosomes unwind and nucleus reforms

23 chrom’s

IIMEIOSIS II – (Cytokenesis II )

23 chrom’s

CChromosomes unwind

23 chrom’s

If you’re a male this happens

If you’re a female this happens

SO…… HERE IS A COMPARISON OF THE TWO

STARTS WITH ENDS WITH

MITOSIS

______ CELL

____ CHROMOSOMES . PER CELL

_____ CELLS

MEIOSIS_____ CELL

_____ CELLS

All non-sex cells are called somatic cells

Sperm and egg cells are called gametes

Lets simplify

Lets simplify….. even more

n = information

23 chromosomes = n (or haploid)

46 chromosomes = 2n (or diploid)

OR HALF THE INFORMATIONO

OR DOUBLE THE INFORMATION

MOM (23 chrom) DAD (23 chrom)

“n” or haploid “n” or haploid

YOU (46 chromosomes per cell)

“2n” or diploid

Parent cell 46 (chromosomes)

mitosis

Meiosis I

23 23 23 23

Meiosis II

DIPLOID CELLS (2n)

HAPLOID CELLS (n)

Parent cell 46 (chromosomes)

mitosis Meiosis I

Meiosis II

( Diploid 2n)

HAPLOID (n) = 3

HAPLOID (n) = 8

HAPLOID (n) = 11

HAPLOID (n) = 15

HAPLOID (n) = 20

HAPLOID (n) = 23

HAPLOID (n) = 27

THE BIG DIFFERENCES

1. THE OUT COME

A. MITOSIS = 2 IDENTICAL DAUGHTER CELLS

B. MEIOSIS = 4 DIFFERENT DAUGHTER CELLS (WITH HALF THE GENETIC INFO AS PARENT CELL)

2. METAPHASE I (OF MEIOSIS I)

A. TETRADS LINE UP & CROSSING OVER OCCURS

3. THE NUMBER OF TIMES “PPMAT” HAPPENS

Genetic Variation

• Without CROSSING OVER offspring of the parents would not be a blend of both parents but a clone !!!

This is not the adult

dog’s puppy

IT IS ITS

CLONE ! ! ! !

Crossing Over

• In crossing over,

– Homologous chromosomes exchange genetic information.

– Genetic recombination occurs.

Crossing Over

Nondisjunction

• nondisjunction = not separate

– a chromosome pair fail to separate during an anaphase.

– The result is gametes (sex cells) with an incorrect number of chromosomes (too much or too few).

METAPH

THE END RESULT ARE 2 CELLS THAT SUCK AND ARE ULTIMATELY DESTROYED

Figure 8.20

Figure 8.21

The result of nondisjunction in (meiosis)

Down Syndrome: An Extra Chromosome 21

• Down Syndrome

– a condition where an individual has an extra chromosome 21.

– also called trisomy 21.

Figure 8.22

• The incidence of Down Syndrome increases with the age of the mother.

Figure 8.23

Abnormal Numbers of Sex Chromosomes

• Nondisjunction

– Also affects the sex chromosomes.

Karyotype = A picture of your

condensed chromosomes

A karyotype

A human male karyotype

MALES ARE “XY”

FEMALES ARE “XX”

A human female karyotype

Remember: this picture is of condensed chromosomes

we know, from mitosis, that chromosomes don’t condense unless they were first doubled

(during S of interphase)

Look close. . .

Each chromosome is really made up of it’s “identical twin” from when

it doubled in S of interphase

CLOSER INSPECTION

But some times accidents can happen during

cellular reproduction

Table 8.1

Mind Blow

Cancer

What Is Cancer?

• Cancer = a disease of the cell cycle.

• Cancer cells do not respond normally to the cell cycle control system.

THE CELL CYCLE

• Cancer cells can form tumors,

TUMORS = Abnormally growing masses of body cells.

–can spread to other parts of the body.

Cancer Treatment

• Cancer cells are often grown in culture for study.

BRAIN GAME

Imagine a cell with 2 information pieces called chromosomes

CHAPTER 8 Cellular Reproduction: Cells from Cells.

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