Download Chromosomes and Cell Reproduction Notes

Chromosomes and Cell
Reproduction
Chapter 6 & 7
I. Chromosomes
Chromosome- made of 2 exact copies of DNA
coiled around proteins
(*this is after replication but before cell division)
B. Chromatid- each copy of the DNA on a
chromosome
C. Centromere- place where the chromatids
attach to make a chromosome
D. Genes- Segments of DNA on a chromosome
that code for a specific protein/trait
A.
*Draw a chromosome
and label chromatids,
centromere and gene
II. Chromosome Number
A.
B.
C.
Each human somatic cell (body cell) has 2
copies of 23 different chromosomes for a total
of 46 chromosomes
We inherit 1 of each chromosome from mom
and 1 from dad
Homologous Chromosomes- similar in size,
shape and genetic content
D. Diploid cells- contain 2 sets of chromosomes,
all somatic cells are diploid
(ex. Somatic cells in humans have a total of 46
chromosomes)
E. Haploid Cells- contain only 1 set of
chromosomes, only gametes can be haploid
(ex. Gametes in humans have 23 chromosomes)
III. Karyotypes
A.
B.
C.
A picture of the chromosomes of an organism
arranged by size
Used to examine an individuals chromosomes:
Karyotypes can determine only 2 things about
the organism:
1.
2.
Sex of individual
Any abnormalities in the chromosomes (number
or shape
C. Humans have 1 pair of sex chromosomes and 22
pairs of autosomal chromosomes (non sex
chromosomes)
D. Sex ChromosomesXX= Female
XY= Male
(the sex chromosomes are the last pair of chromosomes shown
in a karyotype)
Trisomy – when there is three of a certain chromosome instead of the normal 2
IV. Cell Cycle
A.
B.
C.
D.
E.
G1 Phase- period of cell growth
S Phase- when DNA replication occurs
G2 Phase- cell growth and preparation for
mitosis
Mitosis- division of the nucleus
Cytokinesis- division of the cytoplasm
Cell Cycle Animations
http://www.cellsalive.com/cell_cycle.htm

http://iknow.net/cell_div_education.html
V. Mitosis
A.
B.
C.
D.
The division of the nucleus in somatic cells
Chromosomes have replicated prior to the
start of mitosis
Produces 2 identical daughter cells
4 phases
1. Prophase chromatin coils into
chromosomes
 Nuclear envelope
dissolves
 Spindle fibers form
2. Metaphase (middle)
 Chromosomes line up
in the middle of the
cell
 Centrioles move to
opposite poles
 Spindle fibers attach
to chromosomes
3. Anaphase (apart)
 Spindle fibers shorten
and pull chromatids
toward opposite poles
4. Telophase (opposite of
prophase)
 Nuclear envelope
forms around
chromatids
 Chromatids uncoil
 Cleavage is formed
 Spindle fibers dissolve
E. Cytokinesis
 Occurs after Mitosis
 Cytoplasm is divided
in half
 Cell membrane
encloses each cell
**New cells are now in interphase and the
cell cycle starts over.
Mitosis Animation

http://iknow.net/cell_div_education.html
http://www.loci.wisc.edu/outreach/bioclips/CDBio.html
VI. Meiosis
A.
B.
C.
Two divisions of the nucleus
Results in the formation of 4 gametes (egg,
sperm)
Halves the number of chromosomes (in
humans from 46 to 23)
Stages of Meiosis I
1.*Prophase I- crossing over occurs,
(portions of one chromosome are broken and
exchanged with portions of the other
homologue)**results in genetic variability
2. Metaphase I- homologous chromosome
pair up together at the equator
3. Anaphase I- centromeres do not divide
4. Telophase I and Cytokinesis
Meiosis II
1. Prophase II
2. Metaphase II
3. Anaphase II
4. Telophase II & Cytokinesis
Interphase
P2
P1
M2
M1
A2
http://www.tokresource.org/tok_
classes/biobiobio/biomenu/meios
is/
A1
T2
T1 & C
Cytokinesis
Females- called oogenesis, forms 1 ovum and 3
polar bodies
Males- called spermatogenesis, forms 4 sperm cells
http://www.biologyexams
4u.com/2013/06/differen
ce-betweenspermatogenesis-and.html
Meiosis Animations

Meiosis Animation

Meiosis Square Dance Video