Transcript Teacher quality grant

Biology Partnership
(A Teacher Quality Grant)
Cell Cycle
Mitosis & Meiosis
Nancy Dow
Jill Hansen
Tammy Stundon
December 1, 2012
Gulf Coast State College
Panhandle Area Educational Consortium
5230 West Highway 98
753 West Boulevard
Panama City, Florida 32401
Chipley, Florida 32428
850-769-1551
877-873-7232
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www.gulfcoast.edu
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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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
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or spores.
Content Limits
• Items addressing mitosis or meiosis are limited to
identification of phases, structures, and major
events of each phase.
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The cell cycle has four main stages.
• The cell cycle is a regular pattern of growth,
DNA replication, and cell division.
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Mitosis and cytokinesis produce two
genetically identical daughter cells.
Parent cell
• Interphase
prepares the cell
to divide.
• During
interphase, the
DNA is
duplicated.
centrioles
spindle fibers
centrosome
nucleus with
DNA
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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
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Mitosis divides the cell’s nucleus in four phases.
– During metaphase, chromosomes line up in the
middle of the cell.
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Mitosis divides the cell’s nucleus in four phases.
– During anaphase, sister chromatids separate to
opposite sides of the cell.
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Mitosis divides the cell’s nucleus in four phases.
– During telophase, the new nuclei form, spindle fibers
break down and chromosomes begin to uncoil.
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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
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Number of chromosomes
KEY CONCEPT
Gametes have half the number of chromosomes
that body cells have.
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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.
• 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.
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body cells
sex cells (sperm)
sex cells (egg)
INHERITANCE OF GENES
Maternal
chromosome pair
Paternal
chromosome pair
Gene
Maternal gamete: egg
Paternal gamete: sperm
Humans have
23 pairs of
chromosomes
(46 individual
chromosomes)
and, thus, two
copies of each
gene.
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
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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
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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.
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Haploid (n) cells have one copy of
every chromosome.
– Gametes are haploid.
– Gametes have 22 autosomes and 1 sex chromosome.
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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 makes
more diploid cells
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Meiosis makes haploid cells from
diploid cells.
– Meiosis occurs in sex cells.
– Meiosis produces gametes.
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Compare and Contrast
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KEY CONCEPT
During meiosis, diploid cells undergo two cell
divisions that result in haploid cells.
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Meiosis Square Dance
Cells go through two rounds of division in meiosis.
• Meiosis reduces chromosome number and
creates genetic diversity.
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• 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.
homologous chromosomes
sister
chromatids
sister
chromatids
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HOMOLOGUES AND SISTER CHROMATIDS
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
Paternal
chromosome
Sister
chromatids
Sister
chromatids
• Meiosis I occurs after DNA has been replicated.
• Meiosis I divides homologous chromosomes in four phases.
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INTERPHASE
Centromere
Replicated
chromosome
Nuclear
membrane
INTERPHASE
• Chromosomes replicate in
preparation for meiosis.
INTERPHASE
Centromere
MEIOSIS DIVISION 1:
HOMOLOGUES SEPARATE
Replicated
chromosome
Homologues
Homologues
cross over
Nuclear
membrane
INTERPHASE
• Chromosomes replicate
in preparation for
meiosis.
Spindle
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PROPHASE I
• Replicated chromosomes condense.
• Spindle apparatus is formed.
• Homologous pairs of sister chromatids
come together and cross over.
• Nuclear membrane disintegrates.
Prophase I
• Biology Media Gallery Clip – Meiosis (2 min)
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MEIOSIS DIVISION 1:
HOMOLOGUES SEPARATE
Homologues
Homologues
cross over
Spindle
1
PROPHASE I
• Replicated chromosomes condense.
• Spindle apparatus is formed.
• Homologous pairs of sister chromatids
come together and cross over.
• Nuclear membrane disintegrates.
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METAPHASE I
• Homologues move toward
the center of the cell and
line up.
MEIOSIS DIVISION 1:
HOMOLOGUES SEPARATE
Spindle fiber
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METAPHASE I
• Homologues move toward
the center of the cell and
line up.
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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
Spindle fiber
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.
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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.
• Meiosis II divides sister chromatids in four phases.
• DNA is not replicated between meiosis I and meiosis II.
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MEIOSIS DIVISION 2:
SISTER CHROMATIDS SEPARATE
Daughter cell 1
Sister
chromatids
Daughter cell 2
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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.
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PROPHASE II
6 METAPHASE II
• Chromosomes
• Sister chromatids
in daughter cells
line up at the
condense.
center of the cell.
There is a brief interphase prior to
prophase II. Chromosomes are
not replicated again at this
stage.
7 ANAPHASE II
• Sister chromatid pairs
are pulled apart by the
spindle fibers toward
opposite cell poles.
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?
• 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
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.
– 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
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Haploid cells develop into mature gametes.
• 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.
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Mitosis vs. Meiosis
• 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
• 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
Topic
Mitosis
Meiosis
Location
Somatic cells
Sex cells
Description
2N  2N
2N  N
# of cells produced
2
4
Purpose
Growth/repair
Produce gametes
Number of divisions
1
Side by side comparison of Mitosis and Meiosis
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• Foldable
Mitosis vs. Meiosis Manipulative
Meiosis Simulation with pop-beads
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HOW SEX IS DETERMINED IN HUMANS
Individuals have two copies of the sex chromosomes in every cell.
Females have two
copies of the X
chromosome ( XX)
X
X
Males have one X
chromosome and one Y
chromosome. (XY)
X
Y
Males determine the sex of the child.
Mistakes during meiosis
• 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
DOWN SYNDROME (TRISOMY-21)
--Usually due to a problem with the
egg
Characteristics:
Short stature, stubby fingers, round head,
fissured tongue, often mental retardation
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2
3
6
7
8
13
14
15
19
20
21
4
9
10
16
22
X
5
11
12
17
18
Y
Autosomes – for humans, chromosomes 1-22, non-sex chromosomes
Examples of autosomal non-disjunction
• 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 nondisjunction is the same throughout life.
Examples of autosomal non-disjunction
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
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
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
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

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
Fragile X Syndrome
Characteristics:
Short in stature with long
face with prominent jaw
and large ears, delayed
speech development,
often heart defects
Karyotype Lab
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
• 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
• Web Quest Mitosis and Meiosis
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Additional Resources
• 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
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Follow up
• Q&A
• Post Test
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