Honors Biology Ch. 8 NOTES Mitosis and Meiosis

Honors Biology
Ch. 8 NOTES
Mitosis and Meiosis
Opening Essay
Describe the life-cycle phases of a multicellular
organism. Explain how asexual reproduction can be used
to save a plant species from extinction.
LT #1 a, b Why do Cells Divide?
Connections Between Cell Division and Reproduction
8.1
Compare the parent-offspring relationship in asexual
and sexual reproduction.
 Asexual reproduction produces genetically identical offspring that inherit all of their DNA
from a single parent.
 The offspring of sexual reproduction show a family resemblance, but siblings vary
because they inherit different combinations of genes from the two parents.
8.2 Explain why cell division is essential for eukaryotic and prokaryotic life.
SINGLE-CELLED
PROKARYOTIC
EUKARYOTIC
Reproduction
by binary fission
Reproduction
by mitosis
Meiosis: Egg and sperm (2nn)
Mitosis: Growth, Maintenance,
Repair, Asexual Reprod. (2n2n, nn)
Mitosis: yes
Meiosis: no
MULTICELLED
8.3
CLONES?
Yes
GENETIC
DIVERSITY
ACHIEVED
HOW?
Mutation
Transformation:
(foreign plasmids)
Transduction:
(foreign DNA by viruses)
Conjugation:
(sharing through pili)
Mitosis: by mutation
Meiosis: Mutation
Two sources of DNA (parents)
Independent Assortment of homologues
Segregation of alleles
random fertilization
Explain how daughter prokaryotic chromosomes are
separated from each other during binary fission.
1. As the chromosome is duplicating, one copy moves toward the
opposite end of the cell.
2. Meanwhile, the cell elongates.
3. Plasma membrane pinches double-sized cell into two.
The Eukaryotic Cell Cycle and Mitosis
8.3–8.4 Compare the structure of prokaryotic and eukaryotic
chromosomes.
Prokaryotes:
 Nucleoid Region
 Main chromosome: large, circular
 Plasmids: very small, circular, satellite DNA
 DNA + proteins
Eukaryotes:
 located in:
o nucleus
o mitochondria (bacteria-like)
o chloroplasts (bacteria-like)
 linear
 DNA + proteins, many more than prok., more complex
 Two forms:
o chromatin: diffuse mass of long, thin fibers
o distinct chromosomes: before cell division
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LT #2,3 Chromosomes VOCABULARY OF CELL DIVISION
Chromatin
Chromosome
Chromatids
Centromere
Centrioles
Centrosome
Cytokinesis
Cell plate
diffuse mass of long, thin fibers of DNA when
cell is “reading” DNA to make proteins.
Condensed form of DNA
Identical sister chromatids are result of DNA
Synthesis during the cell cycle
Protein that holds sister chromatids together,
site for spindle fiber attachment. Split apart
in Anaphase (mitosis) / Anaphase II (meiosis)
Animal cell organelle composed of cylinders
of microtubule triplets. Usually has a
centrosome with a pair of centrioles involved
in cell division.
Microtubule organizing center.
Division of the cytoplasm to form two
separate daughter cells. Occurs in
Telophase. Mitosis and cytokinesis make up
the mitotic (M) phase of the cell cycle.
A double membrane across the midline of a
dividing plant cell, between which the new
cell wall forms during cytokinesis.
LT #2 The Cell Cycle
8.5 Identify when DNA is replicated, chromosomes are sorted, and two new
cells are formed.
Describe the stages of the cell cycle. Use the Cell Cycle Activity online.
INTERPHASE:
o Takes up 90% of the cell cycle
o Growing stage
o Cell roughly doubles everything in
cytoplasm
o precisely replicates its DNA.
o Time of very high metabolic function
Subphases
G1:
o “First Gap”
o cell grows
o chromosomes are single
S:
o Chromosome duplication
o cell grows
G2:
“Second Gap”
cell grows
chromosomes are identical sister
chromatids.
LT #4 MITOTIC PHASE:
cell division
10% of cell cycle
Stages: DNA
Mitosis: Nuclear Division (of chromosomes)
Cytokinesis: Cytoplasm Division
o
o
o
Cell Cycle Phase duration: optional
The duration of these cell cycle phases varies considerably in different kinds of
cells. For a typical rapidly proliferating human cell with a total cycle time of 24
hours, the G1 phase might last about 11 hours, S phase about 8 hours, G2
about 4 hours, and M about 1 hour. Other types of cells, however, can divide
much more rapidly. Budding yeasts, for example, can progress through all four
stages of the cell cycle in only about 90 minutes. Even shorter cell cycles (30
minutes or less) occur in early embryo cells shortly after fertilization of the egg
(Figure 14.2). In this case, however, cell growth does not take place. Instead,
these early embryonic cell cycles rapidly divide the egg cytoplasm into smaller
cells. There is no G1 or G2 phase, and DNA replication occurs very rapidly in
these early embryonic cell cycles, which therefore consist of very short S
phases alternating with M phases.
Animation of Mitosis esp. metaphase /
anaphase
(Saved to: MacHD, cschmittloyd, downloads)
[Google: Drew Berry, Astonishing Molecular
Machines. Download and show clip from 5:00
min. -9:30 min.]
Or click the link:http://www.youtube.com/watch?v=dMPXu6GF18M&noredirect=1
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LT #4 MITOTIC PHASE
8.6 Recognize the phases of mitosis from diagrams and
micrographs. fig. 8.6 p. 130-131. Use the Mitosis Video
Activity online.
8.6 List the phases of mitosis and
describe the events characteristic of each
phase.
PROPHASE
1.
2.
3.
4.
Chromatin  Chromosomes
Nucleoli disappear
Mitotic spindle appears
Centrosomes migrate to poles
PROMETAPHASE
1. Nuclear Envelope disappears
2. Spindle fibers attach to
centromere
3. Others attach to each other (pole
to pole)
4. Protein “motors” move
chromosomes to center of cell.
METAPHASE
1. “Chromosomes met at
metaphase”
2. Centromeres of all chromosomes
are lined up on the metaphase
plate (equatorial plane)
3. Sister chromatids face opposite
poles.
4. Microtubules attached to one
sister chromatid all go to one pole.
ANAPHASE
1. Begins when the two centromeres
of each chromosome come apart,
separating identical sister
chromatids.
2. Chromatid  Chromosome.
3. Motor proteins “walk” the daughter
chromosomes, centromere-first,
along the microtubules toward
opposite poles shortening
microtubules.
4. Polar fibers elongate, stretching
the cell.
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TELOPHASE
1. Cell elongation continues.
(Prophase run backwards.)
2. Nuclear envelopes reform.
3. Nucleolus reappears.
4. Chromosomes  chromatin.
5. Mitotic spindles disappear.
CYTOKINESIS
Division of cytoplasm
LT #4d
8.7 Compare cytokinesis in animal and plant cells.
Animals: Cleavage Furrow
Plants: Cell Plate formation.
LT #2d Cancer
8.8–8.9 Explain how anchorage, cell density, and growth factors control
cell division.
#1 cell density-dependent inhibition: fig. 8.8b
o (physical factor)
o density-dependent inhibition: crowded cells stop dividing
o physical contact of cell-surface proteins
#2 growth factors: fig. 8.8a
o protein (chemical factor) secreted by certain body cells that stimulates
other cells to divide.
o At least 50 different
o Example: Injury  blood platelets  protein (p-dgf) which promotes
rapid growth of connective tissue cells that help seal the wound.
#3 anchorage dependence:
o cells must be in contact with a solid surface to divide
Density-dependent inhibition mediated by the availability
of growth factors is the most important regulatory
mechanism controlling cell division.
LT #2d
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8.10 Explain how cancerous cells are different from
healthy cells.
Cancer is a disease of the cell cycle.
o Cancer cells do not respond normally to cell cycle control
system, i.e. G1, G2 checkpoints leading to G0 or “time out.
o Cells divide out of control
o Can invade other tissues preventing normal functioning
o Can kill organism (1 in 5 people in U.S.)
o Cell transformation to abnormal.
o Abnormal cells are killed by immune system
o May evade immune system and multiply
o Tumors are abnormally growing mass of body cells.
LT #2d
8.10 Distinguish between benign and malignant tumors.
Benign Tumor: remains at original site.
Malignant tumor cells spread to other tissues
o Cancer Patients: have malignant tumors
o Metastasis: cancer cells spread by circ. and
lymphatic system
LT #2d
8.10 Explain the strategies behind some common cancer treatments.
Benign tumors
Surgery
Radiation (focused high-energy radiation)
Malignant Tumors:
Chemotherapy:
o disrupts specific steps in cell cycle
o negative affects on tissue with rapid cell division

intestinal cells  nausea

hair follicles  hair loss

immune cells  susceptibility to infection
LT #1b, #4c
8.11 Describe the functions of mitosis.

Growth

Maintenance

Repair: Animation showing the cell process involved
in a newt regenerating an arm.
http://bcove.me/2irbwp7q

Asexual reproduction
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LT #5 Meiosis and Crossing Over
8.12 Explain how chromosomes are paired. Distinguish
between autosomes and sex chromosomes.
Somatic Cells
o body cells
o 23 pairs of chromosomes
o (pairs = 2) (23 = n) (2n = 46)
Homologous Chromosomes
o Each parent donates one set of chromosomes (n)
o Fertilization brings both together: n + n = 2n
o Restores original number.
o Two sets of chromosomes or 2n.
o Example:
#1 chrom. from mom
#1 chrom. from dad
o These are homologous chromosomes.
Autosomes: All the chromosomes except the sex
chromosomes
Sex Chromosomes:
o In humans, the 23rd pair of chromosomes.
o Carry genes for traits other than sex determination.
o XX = female
o XY = male
o Because males have two versions of sex chromosomes
they determine the sex of the offspring.
o
LT#5 MEIOSIS
8.13 Distinguish between somatic cells and gametes and between
diploid cells and haploid cells.
Somatic Cells: body cells (2n = diploid)
Gametes: eggs and sperm (n = haploid or monoploid)
Diploid Cells: 2n (chromosomes as homologous pairs)
Haploid Cells: n (one of each homologous pair)
Fertilization: n + n = 2n (zygote)
Work through the study sheet “Sex Cells, Sex Chromosomes and Somatic
Cells and Autosomes” from Weebly.
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8.14 List the phases of meiosis I and meiosis II and
describe the events characteristic of each phase.
http://www.pbs.org/wgbh/nova/miracle/divi_flash.html
Phases
Events
Meiosis I
(homologs separate)


Prophase I
2 x 2n
Metaphase I
Anaphase I
2 x 1n
Meiosis II
(chromatids
separate / mitotic)
Telophase I &
Cytokinesis
Prophase II
Metaphase II
Anaphase II
1 x 1n
Telophase II &
Cytokinesis
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




90% of time, most complex
Chromatin condenses into distinct
chromosomes
Synapsis & Crossing Over
Nucleoli disappear
Centrosomes move poleward
Spindle forms between centrosomes
Nuclear envelope disappears
Tetrads moved by fibers to middle

 Tetrads move to center
 Form double file
 Spindles attach to each homolog
from opposite poles
 Homologous pairs separate, move to
opposite poles.
 Sister chromatids but only one
homolog
 Chromosomes reach poles.
 Cell Divides
 2 haploid cells result
No S phase
o Spindle forms and moves
chromosomes to middle
o Chromosomes aligned on
metaphase plate
o Single file
o Centromeres of sister chromatids
separate, become daughter
chromosomes.
o Move to opposite poles.
o Nuclei form at the cell poles,
cytokinesis occurs at the same time.
o 4 daughter cells (gametes)
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LT#5A,B Recognize the phases of meiosis from diagrams
and micrographs.
MEIOSIS I
Interphase (S): Synthesis of DNA (chromatids)
Phase Name
Unique Events
Tetrads (mom + dad),
Prophase I
Crossing over, Synapsis
Metaphase I
Fig. 8.16, p.141
Tetrads align, double file, homologues on
opposite sides of metaphase plate,
Independent assortment happens here.
Homologues separate,
Reduction in chromosome number
Anaphase I
MEIOSIS II
Telophase I
/Cytokinesis
no (S) here
Prophase II
Two, non-identical cells result
Metaphase II
Single file of sister chromatids
Anaphase II
Mitotic division (chromatids separate)
Telophase II
/Cytokinesis
4 haploid cells (gametes) result.
(two sets of twin DNA)
The sperm cell that fertilizes the egg is
random.
Random Fertilization
Fertilization
LT
#6a Comparison
8.15 Describe the similarities and differences between
mitosis and meiosis. Explain how the result of
meiosis differs from the result of mitosis.
SIMILARITIES
PURPOSE
To create
Cells from cells
Affect on
Chromosome #
Affect on Diversity
of offspring
Chromosome
Duplications
Divisions
# of cells
resulting
Phases
Metaphase &
Metaphase I
DIFFERENCES
MITOSIS
MEIOSIS
Growth,
Maintenance,
Gametes for sexual
Repair,
reproduction
Asexual Reprod.
2n2n
2nn
Clones
(no affect)
Crossing over
Independent Assortment
Segregation of Alleles
Random fertilization
(increases greatly)
1
2
2
4
once
Same sequence
Align on
Metaphase plate
Single file
Anaphase &
Anaphase I
Sister chromatids
Separate
2 x 2n  1 x 2n
1 cell / 2 cells
Anaphase II
---------
Double file
(tetrads)
Homologues separate
2 x 2n  2 x 1n
Chromatids Separate
2 x 1n  1 x 1n
LT#5D
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8.16–8.18 Explain how independent orientation of
chromosomes at metaphase I, random fertilization,
and crossing over during prophase I of meiosis
contribute to genetic variation in sexually
reproducing organisms.
Independent orientation: fig. 8.16
Random fertilization:
Online Activity: The Origin of Genetic Variation
Crossing over: fig. 8.18a,b
LT #5c
Comparing Male and Female Meiosis
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LT#5C Comparing Male and Female Meiosis
Male
Female
MI before birth,
MII at fertilization
timing in life:
Puberty to death
number of
resulting cells
4
1
LT#6 B,C
contents of
gametes
Nucleus (DNA),
few, if any,
organelles
Nucleus, organelles
mtDNA,
mRNA stockpile.
location in body
testes
ovaries
frequency of
nondisjunction in
relation to age
No correlation
Incidence greatly
increases after age 38,
“biological clock.”
Excellent Review of meiosis
http://www.mhhe.com/biosci/bio_animations/08_MH_Meiosis_Web/
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LT #5e
Alterations of Chromosome Number and Structure
8.19 Explain how and why karyotyping is performed.
Karyotype: An ordered display of magnified images of an
individual’s chromosomes arranged in pairs, starting with the
longest. Also used: centromere position and banding pattern.
How:
1. blood sample taken
2. cultured and treated to arrest mitosis in metaphase
3. centrifuge separates based on density
a. top: liquid discarded
b. bottom: solid treated with hypertonic solution to
burst RBCs but not WBC.
4. centrifuge separates:
a. top: liquid (remains of RBC) from
b. bottom: WBC
5. microscope slide made of WBC with fixative
6. digital camera captures image
7. computer manipulates image to pair up homologues
8. resulting display is a karyotype
LT#6D
Why:
o Errors in meiosis can lead to gametes containing
chromosomes in abnormal numbers or with major
alterations in their structures.
o Fertilization with these gametes results in birth defects.
o Chromosomal abnormalities (not gene-level) can be
detected with a karyotype.
LT #5e
8.20 Describe the causes and symptoms of Down
syndrome.
Cause:
o Nondisjunction of the 21st chromosome during meiosis.
o after fertilization it results in three #21 chromosomes
o also called trisomy 21
o Incidence increases with maternal age
o 1 out of 700 children born
o most common serious birth defect in the US
Symptoms:
o round face
o skin fold at the inner corner of the eye
o flattened nose bridge
o small irregular teeth
o short stature
o heart defects
o susceptible to respiratory infections
o leukemia
o Alzheimer’s
o shorter life span
o varying degrees of mental retardation
o most are sexually under-developed
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LT #5e
8.21 Define nondisjunction, explain how it can occur, and
describe what can result.
Nondisjunction: When the members of a chromosome pair
fail to separate as they should
How can it occur?
Meiosis I:
o A pair of homologous chromosomes does not separate
during meiosis I.
o Even though the rest of meiosis occurs normally, all the
resulting gametes end up with abnormal numbers of
chromosomes.
o Two of the gametes have three chromosomes; the other
two gametes have only one chromosome each.
Meiosis II:
o Meiosis I is normal
o But one pair of sister chromatids fails to move apart during
meiosis II.
o Two of the resulting gametes are abnormal; the other two
are normal.
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LT #5e
8.22 Describe the consequences of abnormal numbers of
sex chromosomes. Table 8.22
Klinefelter’s Syndrome: Males only, 40% survive gestation,
feminization, hypogonadism, sterile.
Turner’s: Females only, short, thin, tissue between shoulders
and head, infertile.
LT #5d
8.23 Explain how new species form from errors in cell
division.
o At least half of all species of flowering plants are
polyploidy, including such useful ones as wheat,
potatoes, apples, and cotton.
o 2n + 2n  4n (polyploidy)
o Polyploid animals are less common than plants.
o fish
o amphibians
o at least one mammal (burrowing rodent)
8.24 Describe the main types of chromosomal changes.
Explain why cancer is not usually inherited.
Alterations of chromosome structure involving one chromosome
or a homologous pair
TEDed: Where Do New Genes Come
From? – Carl Zimmer (4:23min)
http://ed.ted.com/lessons/where-do-genescome-from-carl-zimmer
Chromosomal translocation between nonhomologous
chromosomes.
LT#6 Summary
LT#6 A
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Make a Venn diagram to illustrate the similarities and differences between
mitosis and meiosis.
LT#6 B,C
Tracing maternal and paternal lineages.
Maternal Lineages
 Because sperm are swimmers and need to “travel light,” males do not
contribute mitochondria to their offspring.
 Mitochondria have their own DNA (mtDNA).
 Because mtDNA is inherited only from our mother, maternal lineage can be
traced using mtDNA.
Paternal Lineages
 Males pass on their Y chromosome to sons only.
 Male lineages can be studied using the Y chromosome.
LT#6 D
Predict the result of abnormal mitosis and meiosis.
1. A zygote is a fertilized egg. It becomes an individual made of trillions of cells
by mitosis. A zygote, with a genotype of XY for sex chromosomes,
experienced nondisjunction of the Y chromatids during the very first mitotic
division that creates two cells. Identify the genotypes of the first two cells.
(Hint: one is a monosomy and the other is a trisomy.)
2. Subsequent mitotic divisions occur normally. Describe the impact that this
would have on an individual. (Hint: see the photos of bilateral
gynandromorphs.)
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AUTOSOMAL TRISOMIES OPTIONAL READING
Syndrome: A characteristic set of symptoms
NAME
Trisomy 8
Warkany
Syndrome
FREQUENCY
N0TES
Complete T8 is
very rare
Pre-natally lethal
Mosaicism possible
Trisomy 9
rare
T9 one of the most frequent
autosomal anomalies compatible
with long survival rate.
Mosaicism possible
Trisomy 13
Patau
Syndrome
1/10,000
10% of infants reach 1 year
80% die in the 1st month
Trisomy 21
Down’s
Syndrome
Abnormal skull, nervous system, mental
retardation, abnormal heart, kidneys,
musculoskeletal system, overlapping fingers,
rocker bottom feet, webbed neck.
Cleft lip or palate
Close-set eyes
Decreased muscle tone
Extra fingers or toes
Hernias
Hole, split or cleft in iris
Low-set ears
Severe mental retardation
Scalp defects (absent skin)
Seizures
Skeletal (limb) abnormalities
Small eyes
Small head (microcephaly)
Small lower jaw
Undescended testicle
Most common chromosomal
cause of miscarriage during
1st trimester
Trisomy 16
Trisomy 18
Edward’s
Syndrome
SYMPTOMS
1/6,000
10% of infants reach 1 year
80% die in the 1st month
1/700
Most common trisomy that
infants can survive.
Most common serious
birth defect in the U.S.
kidney malformations
Structural heart defects
Intestines protruding outside the body
Developmental delays
Growth deficiency
Small head
Prominent back portion of head
Low-set malformed ears
Abnormally small jaw
Cleft lip/cleft palate
Widely –spaced eyes
Drooping upper eyelids
Short breast bone
Clenched hands
Absent radius
Characteristic facial features
Round face
A skin fold at the inner corner of the eye
Flattened nose bridge
Small irregular teeth
Short stature
Heart defects
Susceptibility to respiratory infections
Leukemia
Alzheimer’s disease
Shorter than normal life span
Trisomy 22
Cat eye
Syndrome
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