Transcript Chromosomes - Haiku Learning

Chapter 8: Cell Reproduction
Essential Question: How do
organisms grow? How do cells
reproduce by cell division?
I.
Chromosomes: rod-shaped structures made of
DNA and proteins
A. Chromosome structure
1. Each chromosome is a single DNA molecule
associated with proteins that is tightly coiled
2. Chromosomes are visible during cell division
under a microscope
3. Histones: proteins that help maintain the shape
of chromosomes
a) DNA wraps around the proteins
b) Helps to package DNA tightly
4. Nonhistone: proteins that do not participate in
the packing of DNA but control the activity of
specific regions of the DNA
5. Chromatid: one of the two identical
parts of the chromosome
a) chromatids form as the DNA makes a copy of
itself before cell division
b) when the cell divides, each of the two new
cells will receive one chromatid from each
chromosome
6. Centromere: holds the two chromatids together
until they separate during cell division
7. When the cell is not dividing the DNA is not so
tightly coiled and is called chromatin
Chromosome
B. Chromosome numbers: each species has a
characteristic number of chromosomes in each cell
Adder’s tongue fern = 1,262
Organism with the MOST
chromosomes
1. Sex chromosomes: chromosomes that
determine the sex of an organism and may
carry genes for other characteristics
a) Humans: sex chromosomes are X and Y
b) females have two X chromosomes
c) males have X and Y
2. Autosomes: chromosomes that are not sex
chromosomes
a) humans have 44 autosomes
b) humans have 2 sex chromosomes
3. Every cell produced by sexual reproduction
has two copies of each autosome (one from
each parent)
4. Homologous chromosomes: two
copies of each autosome
a) same size and shape
b) carry genes for the same traits (eye color)
5. Karyotype: photomicrograph of the
chromosomes found in a normal human and shows
the 46 human chromosomes exist as 22 homologous
pairs of autosomes and two sex chromosomes
Down Syndrome (trisomy 21)
- Fold of skin above the eye
- Varying degrees of mental retardation
- Short stature
- Cardiac deformities
What is the difference in an individual that is
“normal” or an individual that has Down
Syndrome?
Turner syndrome
- Only an XO
- Short stature, webbed neck, stocky build
- Ovaries degenerate in late embryonic life, leading to rudimentary
sexual characteristics
Klinefelter syndrome
- Has an XXY
- Male, enlarged breast tissue
XYY karyotype:
- Tall male with heavy acne
- Some tendency to mental retardation
Triplo-X:
- Has an XXX
- Fertile females with normal
intelligence
Genetic Disorders
http://learn.genetics.utah.edu/content/disorders/c
hromosomal/turner/
http://learn.genetics.utah.edu/content/disorders/c
hromosomal/klinefelter/
http://learn.genetics.utah.edu/content/disorders/c
hromosomal/down/
C. Diploid and Haploid cells
1. Diploid: cells having two sets of chromosomes
a) Have both chromosomes for each homologous pair
b) Have 2 sex chromosomes
c) All normal human cells except reproductive cells
(sperm and egg cells) are diploid
d) Abbreviates as 2n
e) 2n number in humans is 46 (22 pairs of homologous
chromosomes and 2 sex chromosomes)
2. Haploid: cells that contain only one set of
chromosomes
a) sperm cells and egg cells
b) Have half the number of chromosomes that are
present in diploid cells
c) Have only one chromosome of each
homologous pair and only one sex chromosome
d) Abbreviated as 1n
3. When a sperm cell (1n) and egg cell (1n)
combine to create the first cell of a new
organism the new cell will be diploid (2n)
II. Cell Division: process by which cells produce offspring cells
A. Cell division in Prokaryotes
1. Binary fission: division of prokaryotic cell into two
offspring cells
2. Three general stages
a) Chromosome makes a copy of itself and attaches to the
inside of the cell membrane
b) Cell grows until it is twice the original size
c) Cell wall forms between the two chromosomes and the
cell splits into two new cells
B. Cell Division in Eukaryotes
1. Two types
a) Mitosis: new cells with genetic material that is
identical to that of the original cell
b) Meiosis: reduces the chromosome number by
half in the new cells
2. Cell cycle: repeating set of events that make up
the life of a cell include interphase and cell division
Concept Map
Cell Cycle
includes
G1 phase
Interphase
M phase
(Mitosis)
is divided into
is divided into
S phase
G2 phase
Prophase
Metaphase
Anaphase
Telophase
Section 10-2
The Cell Cycle
G1 phase
M phase
S phase
G2 phase
3. Interphase: time between cell division
a) G1 phase (gap): cell growth
b) S phase (synthesis): DNA is copied
c) G2 phase: preparation for cell division
4. Cell can exit the cell cycle and enter G0 phase,
stop dividing (nervous system cells)
https://www.youtube.com/watch?v=Wy3N5NCZBHQ
C. Control of Cell Division
1. Proteins regulate the progress of cell division
at certain checkpoints (traffic signals)
a) green light: go to next stage
b) red light: halt or stop
2. Three checkpoints
a) Cell growth (G1) checkpoint: if cell is
healthy and large enough it will go to S
phase
b) DNA synthesis (G2) checkpoint: DNA
repair enzymes check the results of DNA
replication and if everything is correct, it can
move to the next step
c) Mitosis checkpoint: signals the cell to exit
mitosis and enter G1 phase
3. When control is lost: Cancer
a) Proteins that control cell growth and division are
coded for by genes
b) If a mutation occurs in the genes, the proteins
may not work properly
c) Cell growth and division may not work correctly
d) Cancer: uncontrolled growth of cells
D. Mitosis: division of the nucleus and is divided into
four phases
1. Prophase
a) DNA becomes visible as tight coils
b) Nuclear membrane breaks down
c) Centrosomes appear and move to opposite
poles of the cell: two dark spots containing
centrioles
d) Spindle fibers: microtubules that come out of
the centrosomes
e) Mitotic spindle: made of spindle fibers and is
used to equally divide the chromatids between the
two cells
Prophase
Spindle
forming
Centrioles
Nuclear
envelope
Chromatin
Interphase
Centromere
Chromosomes
(paired chromatids)
Prophase
Cytokinesis
Spindle
Centriole
Telophase
Nuclear
envelope
reforming
Centriole
Individual
chromosomes
Anaphase
Metaphase
2. Metaphase
a) spindle fibers move the
chromosomes to the center of the dividing cell
b) held in place at the center of the cell
3. Anaphase
a) chromatids of each chromosome separate at the
centromere
b) move towards opposite poles of
the cell
Metaphase
Spindle
forming
Centrioles
Nuclear
envelope
Chromatin
Interphase
Centromere
Chromosomes
(paired chromatids)
Prophase
Cytokinesis
Spindle
Centriole
Telophase
Nuclear
envelope
reforming
Centriole
Individual
chromosomes
Anaphase
Metaphase
Anaphase
Spindle
forming
Centrioles
Nuclear
envelope
Chromatin
Interphase
Centromere
Chromosomes
(paired chromatids)
Prophase
Cytokinesis
Spindle
Centriole
Telophase
Nuclear
envelope
reforming
Centriole
Individual
chromosomes
Anaphase
Metaphase
4. Telophase
a) spindle fibers break apart
b) chromosomes begin to uncoil and become
invisible
c) nuclear envelope forms
Telophase
Spindle
forming
Centrioles
Nuclear
envelope
Chromatin
Interphase
Centromere
Chromosomes
(paired chromatids)
Prophase
Cytokinesis
Spindle
Centriole
Telophase
Nuclear
envelope
reforming
Centriole
Individual
chromosomes
Anaphase
Metaphase
E. Cytokinesis: cytoplasm of the cell divides
1. Animal cells: cell membrane pinches inward
between the dividing cell’s two poles
a) cleavage furrow: area of the cell membrane
that pinches in
b) cell is split into two cells
2. Plant cells: cell plate: membrane-bound
cell wall that forms in between the dividing
cell and forms two cells
Mitosis Video Clip
Cytokinesis
Spindle
forming
Centrioles
Nuclear
envelope
Chromatin
Interphase
Centromere
Chromosomes
(paired chromatids)
Prophase
Cytokinesis
Spindle
Centriole
Telophase
Nuclear
envelope
reforming
Centriole
Individual
chromosomes
Anaphase
Metaphase
III. Meiosis
A. Meiosis: process of nuclear division that
reduces the number of chromosomes in new cells to
half the number in the original cell
1. Gametes: haploid reproductive cells
a) sperm cells and egg cells that are (1n)
b) contain 23 chromosomes
2. Sperm and egg cell together form a zygote that
contains 46 chromosomes (2n)
B. Stages of Meiosis
1. Cells undergoes G1, S, and G2 phases so there is
a duplicate set of chromosomes, so cells need to
divide twice
2. First division is called meiosis I and creates 2n
cells
3. Second division is called meiosis II and creates
1n cells
C. Meiosis I
1. Prophase I: DNA tightly coiled and spindle
fibers appear
a) synapsis: every chromosome lines up next to
its homologue
b) tetrad: each pair of homologous
chromosomes
c) crossing over: chromatids twist around one
another and sometimes a portion may break off
and attach to adjacent chromatids ( permits
exchange of genetic material)
d) genetic recombination: new mixture of
genetic material
2. Metaphase I: tetrads line up randomly along the
midline of the cell
a) spindle fibers from one pole attach to the
centromere of one of the homologous chromosomes
b) spindle fibers from the other pole attach to the
centromere of the other homologous chromosome
3. Anaphase I: each homologous chromosome (2
chromatids attached by a centromere) moves to an
opposite pole
a) independent assortment: random separation
of the homologous chromosomes
4. Telophase I: chromosomes reach the opposite
ends of the cell and cytokinesis begins
a) two new cells are formed
b) each cell has 46 chromosomes
5. During meiosis I: two new cells produced each
containing one chromosome from each homologous
pair
a) Each new cell contain two copies of the
chromosome because the original cell copied its
DNA before meiosis I
Meiosis I
Section 11-4
Interphase I
Prophase I
Metaphase I
Anaphase I
Cells undergo a round of
DNA replication, forming
duplicate Chromosomes.
Each chromosome pairs with
its corresponding
homologous chromosome to
form a tetrad.
Spindle fibers attach to the
chromosomes.
The fibers pull the
homologous chromosomes
toward the opposite ends of
the cell.
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Section:
D. Meiosis II: occurs in each cell formed during
meiosis I and the DNA is not copied
1. Prophase II: spindle fibers form and move the
chromosomes toward the middle
2. Metaphase II: chromosomes move to the
middle and face opposite poles
3. Anaphase II: chromatids separate and move
toward opposite poles
4. Telophase II: nuclear membrane forms
Meiosis II
Meiosis II
Prophase II
Metaphase II
Anaphase II
Meiosis I results in two
The chromosomes line up in a The sister chromatids
haploid (N) daughter cells,
similar way to the metaphase separate and move toward
each with half the number of stage of mitosis.
opposite ends of the cell.
chromosomes as the original.
Telophase II
Meiosis II results in four
haploid (N) daughter cells.
5. Cytokinesis II: creates 4 new cells each
containing half of the original cell’s number of
chromosomes
E. Formation of Gametes
1. Meiosis produces haploid reproductive
cells (gametes)
2. Meiosis only occurs in reproductive
organs (testes and ovaries)
3. Male gametes: sperm cells or spermatozoa
a) spermatids: diploid reproductive cell divides
by meiosis to form four haploid cells
b) spermatogenesis: production of sperm when
spermatids develops into a mature sperm cell
4. Female gametes: egg cells or ova
a) ovum: diploid reproductive cell divides by
meiosis to form one egg cell (uneven dividing of
the cell during cytokinesis I and II)
b) polar bodies: three other products that
degenerate
c) oogenesis: production of mature egg
cells
F. Asexual and Sexual Reproduction
1. Asexual reproduction: production of
offspring from one parent
a) does not involve meiosis or union of gametes
b) unicellular organisms: binary fission or
mitosis
c) multicellular organisms: budding off of
portions of their bodies
d) offspring are genetically identical to parents
2. Sexual reproduction: production of offspring
through meiosis and the union of a sperm and egg
a) offspring are genetically different from the
parents because genes are combined in new ways
in meiosis
b) offspring contain a unique combinations of
their parents genes
c) sexual reproduction enables species to adapt to
new conditions