Cell cycle mitosis meiosis nancy dow jill hansen tammy stundon december 1 2012
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Biology Partnership (A Teacher Quality Grant). Cell Cycle Mitosis & Meiosis Nancy Dow Jill Hansen Tammy Stundon December 1, 2012. Pre-test Q and A board. What is Mitosis? What is Meiosis?. When do they happen?. What is alike and what is different about them?.

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Cell cycle mitosis meiosis nancy dow jill hansen tammy stundon december 1 2012

Biology Partnership

(A Teacher Quality Grant)

Cell Cycle

Mitosis & Meiosis

Nancy Dow

Jill Hansen

Tammy Stundon

December 1, 2012


Pre-test

Q and A board

What is Mitosis?

What is Meiosis?

When do they happen?

What is alike and what is different about them?


Florida next generation sunshine state standards
Florida Next Generation Sunshine State Standards

BENCHMARK

SC.912.L.16.16 Describe the process of meiosis, including independent assortment and crossing over. Explain how reduction division results in the formation of haploid gametes or spores. (MODERATE)

SC.912.L.16.17* Compare and contrast mitosis and meiosis and relate to the processes of sexual and asexual reproduction and their consequences for genetic variation. (HIGH)

Clarifications

Students will differentiate the processes of mitosis and meiosis.

Students will describe the process of meiosis, including independent assortment and crossing over.

Students will explain how meiosis results in the formation of haploid gametes or spores.


Content Limits

  • Items addressing mitosis or meiosis are limited to identification of phases, structures, and major events of each phase.


The cell cycle has four main stages
The cell cycle has four main stages.

The cell cycle is a regular pattern of growth, DNA replication, and cell division.


Mitosis and cytokinesis produce two genetically identical daughter cells

Interphase prepares the cell to divide.

During interphase, the DNA is duplicated.

Mitosis and cytokinesis produce two genetically identical daughter cells.

Parent cell

centrioles

spindle fibers

centrosome

nucleus with

DNA


Mitosis divides the cell’s nucleus in four phases.

  • During prophase, chromosomes condense and nuclear membrane breaks down.

  • centrioles ‘move’ to the poles and spindle fibers form


Mitosis divides the cell’s nucleus in four phases.

  • During metaphase, chromosomes line up in the middle of the cell.


Mitosis divides the cell’s nucleus in four phases.

  • During anaphase, sister chromatids separate to opposite sides of the cell.


Mitosis divides the cell’s nucleus in four phases.

  • During telophase, the new nuclei form, spindle fibers break down and chromosomes begin to uncoil.


Cytokinesis differs in animal and plant cells.

  • In animal cells, the membrane pinches closed.

  • In plant cells, a cell plate forms.

It's Mitosis---My-Sharona


For sexual

reproduction



KEY CONCEPT Gametes have half the number of chromosomes that body cells have.


Two types of cell divisions
Two types of cell divisions

Mitosis – one cells divides to form TWO identical cells.

Occurs for growth and repair

Meiosis – a cell in the testes or ovaries divides into four cells which contain half the number of chromosomes.

Occurs for reproduction (make gametes)


You have body cells and gametes
You have body cells and gametes.

Body cells are also called somatic cells.

Germ cells develop into gametes.

Germ cells are located in the ovaries and testes.

Gametes are sex cells: egg and sperm.

Gametes have DNA that can be passed to offspring.

sex cells (egg)

body cells

sex cells (sperm)

Diploid (2n)

Haploid (n)


INHERITANCE OF GENES

Maternal chromosome pair

Paternal chromosome pair

Humans have 23 pairs of chromosomes (46 individual chromosomes) and, thus, two copies of each gene.

Gene

Maternal gamete: egg

Paternal gamete: sperm

Each human gamete has just one copy of each chromosome and, thus, one copy of each gene.

Gametes unite during fertilization.

Child inherits one set of chromosomes from each parent and, thus, two copies of each gene.

ALLELES


Your cells have autosomes and sex chromosomes
Your cells have autosomes and sex chromosomes.

  • Your body cells have 23 pairs of chromosomes.

    • Homologous pairs of chromosomes have the same structure.

    • For each homologous pair, one chromosome comes from each parent.

  • Chromosome pairs 1-22 are autosomes.

  • Sex chromosomes, X and Y, determine gender in mammals.

Karyotype


Body cells are diploid gametes are haploid
Body cells are diploid; gametes are haploid.

Fertilization between egg and sperm occurs in sexual reproduction.

Diploid (2n) cells have two copies of every chromosome.

Body cells are diploid.

Half the chromosomes come from each parent.


Haploid (n) cells have one copy of every chromosome.

  • Gametes are haploid.

  • Gametes have 22 autosomes and 1 sex chromosome.


Chromosome number must be maintained in animals.

  • Many plants have more than two copies of each chromosome.

  • Mitosis and meiosis are types of nuclear division that make different types of cells.

  • Mitosis makesmore diploid cells


Meiosis makes haploid cells from diploid cells.

  • Meiosis occurs in sex cells.

  • Meiosis produces gametes.



KEY CONCEPT During meiosis, diploid cells undergo two cell divisions that result in haploid cells.



Cells go through two rounds of division in meiosis
Cells go through two rounds of division in meiosis.

Meiosis reduces chromosome number and creates genetic diversity.


Meiosis I and meiosis II each have four phases, similar to those in mitosis.

  • Pairs of homologous chromosomes separate in meiosis I

  • Homologous chromosomes are similar but not identical.

  • Sister chromatids divide in meiosis II.

  • Sister chromatids are copies of the same chromosome.

homologouschromosomes

sister

chromatids

sister

chromatids


HOMOLOGUES AND SISTER CHROMATIDS those in mitosis

Homologues are the maternal and paternal copies of a chromosome. A sister chromatid is a chromosome and its identical duplicated version held together at a centromere.

Homologues

Homologues

Replication (S Phase)

Centromere

Maternal chromosome

Sister chromatids

Paternal chromosome

Sister chromatids


  • Meiosis I divides homologous chromosomes in four phases.


INTERPHASE those in mitosis

Replicated

chromosome

Centromere

Meiosis I

Nuclear

membrane

INTERPHASE

• Chromosomes replicate in preparation for meiosis.


MEIOSIS DIVISION 1: HOMOLOGUES SEPARATE those in mitosis

INTERPHASE

Replicated

chromosome

Homologues

Centromere

Meiosis I

Homologues

cross over

Nuclear

membrane

Spindle

1

INTERPHASE

• Chromosomes replicate in preparation for meiosis.

PROPHASE I

• Replicated chromosomes condense.

• Spindle apparatus is formed.

• Homologous pairs of sister chromatids come together and cross over.

• Nuclear membrane disintegrates.


Prophase i
Prophase I those in mitosis

Biology Media Gallery Clip – Meiosis (2 min)


MEIOSIS DIVISION 1: HOMOLOGUES SEPARATE those in mitosis

Homologues

Meiosis I

Homologues

cross over

Spindle

2

1

PROPHASE I

• Replicated chromosomes condense.

• Spindle apparatus is formed.

• Homologous pairs of sister chromatids come together and cross over.

• Nuclear membrane disintegrates.

METAPHASE I

• Homologues move toward

the center of the cell and

line up.


MEIOSIS DIVISION 1: HOMOLOGUES SEPARATE those in mitosis

Spindle fiber

Meiosis I

2

METAPHASE I

• Homologues move toward

the center of the cell and

line up.

3

ANAPHASE I

• Homologues separate and are pulled to opposite poles. Sister chromatids going to each side are a mix of maternal and paternal genetic material.


Daughter cell 1 those in mitosis

Spindle fiber

Meiosis I

Daughter cell 2

3

ANAPHASE I

• Homologues separate and are pulled to opposite poles. Sister chromatids going to each side are a mix of maternal and paternal genetic material.

4

TELOPHASE I AND CYTOKINESIS

• Sister chromatids arrive at the

cell poles and the nuclear membrane reassembles around them.

• The cell pinches into two

daughter cells.

• Chromosomes may unwind slightly.


  • DNA is not replicated between meiosis I and meiosis II.


MEIOSIS DIVISION 2: SISTER CHROMATIDS SEPARATE

Daughter cell 1

Sister chromatids

Daughter cell 2

4

TELOPHASE I AND CYTOKINESIS

• Sister chromatids arrive at the

cell poles and the nuclear membrane reassembles around them.

• The cell pinches into two

daughter cells.

• Chromosomes may unwind slightly.

5

PROPHASE II

• Chromosomes

in daughter cells

condense.

6

METAPHASE II

• Sister chromatids

line up at the

center of the cell.

7

ANAPHASE II

• Sister chromatid pairs are pulled apart by the spindle fibers toward opposite cell poles.

There is a brief interphase prior to prophase II. Chromosomes are notreplicated again at this stage.


MEIOSIS DIVISION 2: SISTER CHROMATIDS SEPARATE

Daughter cell 1

Daughter cell 2

Daughter cell 3

Daughter cell 4

7

ANAPHASE II

• Sister chromatid pairs are pulled apart by the spindle fibers toward opposite cell poles.

8

TELOPHASE II AND CYTOKINESIS

• The two daughter cells pinch into four haploid daughter cells.

• The nuclear membrane reassembles around the chromosomes.


Why is meiosis so important
Why is meiosis so important? SEPARATE

The chromosome number of the species remains the same generation after generation.

The sperm and egg produced are NOT identical to the cells of the parents and this increases genetic diversity.

Crossing over and independent assortment assure genetic diversity.


SOURCES OF GENETIC VARIATION SEPARATE

There are multiple reasons why offspring are genetically different from their parents and one another.

CROSSING OVER Crossing over during meiosis produces a mixture of maternal and paternal genetic material on each chromatid.

REASSORTMENT OF HOMOLOGUES The homologues and sister chromatids distributed to each daughter cell during meiosis are a random mix of maternal and paternal genetic material.

ALLELES COME FROM TWO PARENTS Each parent donates his or her own set of genetic material.


Meiosis differs from mitosis in significant ways. SEPARATE

  • Meiosis has two cell divisions while mitosis has one.

  • In mitosis, homologous chromosomes never pair up.

  • Meiosis results in haploid cells; mitosis results in diploid cells


Haploid cells develop into mature gametes
Haploid cells develop into mature gametes. SEPARATE

Gametogenesis is the production of gametes.

Gametogenesis differs between females and males.

  • Sperm become streamlined and motile.

  • Sperm primarily contribute DNA to an embryo.

  • Eggs contribute DNA, cytoplasm, and organelles to an embryo.

  • During meiosis, the egg gets most of the contents; the other cells form polar bodies.


Mitosis vs meiosis
Mitosis vs. Meiosis SEPARATE

Mitosis

Occurs in every cell of the body (Somatic cells = body cells)

One cell divides to form 2 identical cells

Meiosis

Occurs only in the testes and ovaries (sex cells)

One cell divides TWICE to form 4 cells with half the number of chromosomes

There are some small differences in the individual steps of both cycles… make note!


Chromosome number in humans
Chromosome number in humans SEPARATE

2n 46 chromosomes (23 pairs)

 Diploid

 mitosis produces diploid cells

1n  23 chromosomes

 Haploid

 meiosis forms haploid cells

side by side comparison


Comparison of the cell cycles SEPARATE

Group activity

Side by side comparison of Mitosis and Meiosis





15 minutes!! SEPARATE


HOW SEX IS DETERMINED IN HUMANS SEPARATE

Individuals have two copies of the sex chromosomes in every cell.

Females have two copies of the X chromosome ( XX)

Males have one X chromosome and one Y chromosome. (XY)

X

X

X

Y



Mistakes during meiosis
Mistakes during meiosis SEPARATE

Non-disjunction

Uneven splitting of chromosomes during meiosis (problem with spindle fibers)

occurs during meiosis I when homologous chromosomes do not separate or during meiosis II when duplicated chromosomes do not separate

The end result is a sperm or egg with too many or too few chromosomes


Examples of Autosomal non-disjunction SEPARATE

DOWN SYNDROME (TRISOMY-21)

--Usually due to a problem with the egg

Characteristics:

Short stature, stubby fingers, round head, fissured tongue, often mental retardation

1

2

3

4

5

6

7

8

9

10

11

12

13

14

15

16

17

18

19

20

21

22

X

Y

Autosomes – for humans, chromosomes 1-22, non-sex chromosomes


Examples of autosomal non disjunction
Examples of autosomal non-disjunction SEPARATE

Down’s syndrome

The frequency of non-disjunction in women increases with age.

1 in 800 births for women under 40 and 1 in 80 births for women over 40

In men, the frequency of non-disjunction is the same throughout life.


Examples of autosomal non-disjunction SEPARATE

Cri Du Chat Syndrome

(Cats’s Cry Syndrome)

-Part of chromosome #5 is missing while other chromosomes are normal

Characteristics:

Malformed larynx so cry sounds like cat, moon face, small head, severe mental retardation


Examples of sex-linked non-disjunction SEPARATE

Turner Syndrome

-the female only has one X chromosome (XO)

-occurs 1 in 6000 births

Characteristics

-short, broad chest, webbed neck, no puberty, infertile, normal intelligence, small finger nails, deformed elbows, low hairline


Examples of sex-linked non-disjunction SEPARATE

Klinefelter Syndrome

-the male has an extra X chromosome (XXY)

-occurs one in 1500 births

Characteristics:

No facial hair, male reproductive glands not fully developed, sterile, some female development,


Examples of sex-linked non-disjunction SEPARATE

Poly-X syndrome

-has more than 2 X chromosomes (XXX)

-occurs 1 in 1500 births

-no abnormalities except sometimes menstrual irregularities (ex. early menopause)

Jacob Syndrome

-males have extra Y chromosome (XYY)

-1 in 1000 births

-taller, persistent acne; speech/reading problems


Examples of sex-linked non-disjunction SEPARATE

  • Fragile X Syndrome

    • The X chromosome is broken with a piece hanging off

    • Occurs in 1 in 1000 male births and 1 in 2500 females


Examples of sex-linked non-disjunction SEPARATE

  • Fragile X Syndrome

  • Characteristics:

  • Short in stature with long face with prominent jaw

  • and large ears, delayed

  • speech development,

  • often heart defects



Cross dressing or crossing over sex testing of women athletes
Cross-Dressing or Crossing-Over: Sex Testing of Women Athletes

Maureen Knabb, Department of Biology, West Chester University, and Joan Sharp, Biological Sciences, Simon Fraser University


Case studies
Case studies Athletes

  • http://sciencecases.lib.buffalo.edu/cs/

    collection of case-studies problem based learning lessons

  • Cross-Dressing or Crossing-Over?

    Sex Testing of Women Athletes

    In this “clicker case,” students learn about sex determination, meiosis, and chromosomal “crossing over” through the story of Santhi Soundararajan, an athlete from Kathakkurichi, India, who was stripped of a medal at the 2006 Asian Games after failing to pass a sex test. 


Computer lab
Computer Lab Athletes

  • Web Quest Mitosis and Meiosis


Additional resources
Additional Resources Athletes

  • Meiosis Tutorial

  • Mitosis and Meiosis Simulation with Beads

  • Side by side animation of mitosis and meiosis

  • http://learn.genetics.utah.edu/content/begin/tour/mitosis.swf mitosis to meiosis tutorial


Follow up
Follow up Athletes

  • Q & A

  • Post Test


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