Transcript File - Biology with Radjewski

Rod shaped structures inside the nucleus
of Eukaryotic cells
 Made of DNA and proteins
 Contain the genes that make you, you!
 Shape of the chromosome is maintained
by histones


3 forms of a
chromosome
› Chromatin – ball of
yarn
› Chromatid – half of
an x, sometimes
bent
› Chromosome – X
 Center of X is called
a centromere

Sex Chromosomes
› Determine the sex of the organism
› Males XY
› Females XX
› 2 out of 46 in the human cell

Autosomes
› All the other chromosomes
› 44 out of 46 in the human cell
Chapter 8
Section 1 Chromosomes
Sex Chromosomes and Autosomes
Click below to watch the Visual Concept.
Visual Concept
Also called homologues
 2 copies of the
chromosome

› One from Mom; One from
Dad
Have the same size
 Have the same shape
 Have the same
information (genes)


Diploid
› Cells that have
chromosomes in
pairs
› Symbol 2n
› Somatic cells or
body cells are like
this
› Humans diploid
number is 46.

Haploid
› Cells that do not
have chromosomes
in pairs
› Symbol 1n
› Gametes are like
this
 Sex cells
 Sperm and egg cells
› Humans haploid
number is 23.
Chapter 8
Section 2 Cell Division
Cell Division in Prokaryotes, continued
• Binary fission is the process of cell division in
prokaryotes.

Asexual
Reproduction
› Production of
offspring from one
parent
› Mitosis

Sexual Reproduction
› Production of
offspring from 2
parents
› Meiosis
How do little elephants grow up to be BIG
elephants?
The process of asexual
reproduction begins after a
sperm fertilizes an egg.
Skin cancer - the abnormal growth of
skin cells - most often develops on skin
exposed to the sun.
Cell that reproduce by asexual
reproduction reproduce constantly.
Animated Mitosis Cycle
http://www.cellsalive.com/mitosis.htm
• Interphase
• Prophase
• Metaphase
• Anaphase
• Telophase & Cytokinesis
•
3 phases
• G1 – cell is growing
Nuclear Membrane
And nucleolus are
visible
• S – DNA is being copied
CHROMATIN!
• G2 – cell is preparing for mitosis
Nucleus
CELL
MEMBRANE
Cytoplasm
Animal Cell
Plant Cell
Photographs from: http://www.bioweb.uncc.edu/biol1110/Stages.htm
Nuclear
membrane &
nucleolus
disappear by
end of
prophase
Mitosis begins (cell begins to divide)
• Chromosomes are visible
• Centrioles (or poles) appear and begin to
move to opposite end of the cell.
• Spindle fibers form between the poles.
•
Centrioles
Sister chromatids
Spindle fibers
Animal Cell
Plant Cell
Spindle fibers
Centrioles
Photographs from: http://www.bioweb.uncc.edu/biol1110/Stages.htm
•
Chromosomes attach to the spindle fibers at
the centromere
CHROMOSOME
Centrioles
Spindle fibers
Animal Cell
Plant Cell
Photographs from: http://www.bioweb.uncc.edu/biol1110/Stages.htm
•
Chromatids (or pairs of chromosomes)
separate and begin to move to opposite
ends of the cell.
Centrioles
Spindle fibers
Animal Cell
Plant Cell
Photographs from: http://www.bioweb.uncc.edu/biol1110/Stages.htm
•
•
•
Nuclear
membrane
& nucleolus
are visible
by end of
telophase
Two new nuclei form.
Chromosomes appear as chromatin (threads
rather than rods).
Overlaps with cytokinesis!
Mitosis ends.
Nuclei
Chromatin
Nuclei
Animal Cell
Plant Cell
Photographs from: http://www.bioweb.uncc.edu/biol1110/Stages.htm
•
•
•
•
Division of the cytoplasm
Cell membrane moves inward to create two
daughter cells – each with its own nucleus
with identical chromosomes.
Animal cells – form a cleavage furrow
Plant cells – form a cell plate, which becomes
the cell wall.
Animal Mitosis -- Review
Interphase
Prophase
Metaphase
Anaphase
Telophase
Interphase
Plant Mitosis -- Review
Interphase
Prophase
Metaphase
Anaphase
Telophase
Interphase
Interphase
Prophase
Metaphase
Anaphase
Telophase
Cytokinesis
IPMATC
I Pray More At The Church
32
http://www.cellsalive.com/mitosis.htm
Chapter 8
Section 2 Cell Division
Control of Cell Division
• Cell division in eukaryotes is controlled by many
proteins.
• Control occurs at three main checkpoints.
1. G1 checkpoint – check to see whether the cell is
healthy and is large enough to divide
2. G2 checkpoint – check to make sure DNA is
copied correctly
3. Mitosis checkpoint – if cell divided correctly, then
signals are made to exit mitosis
Chapter 8
Section 2 Cell Division
Control of the Cell Cycle
Click below to watch the Visual Concept.
Visual Concept
Chapter 8
Section 2 Cell Division
Control of Cell Division, continued
• When Control is Lost: Cancer
– Cancer is uncontrolled growth of cells
– Cancer may result if cells do not respond to
control mechanisms.
– Can be caused by mutations in DNA
Chapter 8
Section 3 Meiosis
Formation of Haploid Cells
• Meiosis is a process of nuclear division that reduces
the number of chromosomes in new cells to half the
number in the original cell.
• Start with 46 and end with 23
• Meiosis leads to four haploid cells (gametes) rather
than two diploid cells as in mitosis.
• Done by germ cells
• Meiosis produces haploid gametes.
• Is considered sexual reproduction
• Creates genetic diversity
• Two divisions
Chapter 8
Section 3 Meiosis
Meiosis I
• Meiosis I includes prophase I, metaphase I,
anaphase I, and telophase I.
• Crossing-over, which is when portions of
homologous chromosomes exchange genetics
material, occurs during prophase I and results in
genetic recombination.
Homologous
chromosomes (paired
chromosomes) become
visible
 Nuclear membrane and
nucleolus disappear
 Spindle fiber starts to
appear
 Crossing over occurs –
portions of the chromatid
break off and attach to
other homologous
chromosome

Chapter 8
Section 3 Meiosis
Tetrads and Crossing-over of Genetic Material
Click below to watch the Visual Concept.
Visual Concept

Homologous
chromosomes
(tetrads) line up at
the equator and
connect to spindle
fibers at their
centromeres
Homologous
chromosomes split
and individual
chromosomes move
to poles
 They assort
independently of
one anotherindependent
assortment

There are 2 new
cells at this point
 Each new cell has
half the number of
chromosomes as
the parent germ
cell
 So they are now
haploid

Has prophase II, metaphase II, anaphase
II and telophase II
 Exactly like mitosis
 Four new haploid cells result

› Four gametes
› Depends on whether it is an animal or a
plant cell
Chapter 8
Section 3 Meiosis

Spermatogenesis
› Making of sperm
cells
› Meiosis will result in 4
mature sperm cells
or spermatozoa

Oogenesis
› Making of mature
egg cells, or ova
› Meiosis will result in 1
mature egg cell
and 3 polar bodies
that die