Download Chromosome

Q: What is the difference between a
diploid and a haploid cell?
A haploid cell has half the number of chromosomes in a diploid cell.
Today: Beginning Unit on Cell
Reproduction
Power Point Notes: Chromosomes
Homework: 8.2 Section Review
1-6, 8
Fluorescent In-Situ Hybridization (FISH) identification of human chromosomes
Cell Reproduction: Chromosomes
Chromosome
- replicated
DNA that is
condensed,
coiled and
wrapped around
histone proteins
- replicates and
condenses when
the cell is about
to divide
Histones
- Proteins that help
maintain the shape
of the
chromosome.
- Aid in tight
packing of DNA.
Chromosome Structure
Chromatid - each half of
the chromosome
Centromere – point
where chromatids attach
Chromatin
– Thin, uncoiled strands of
DNA and protein
– This form of DNA is
found during interphase
of the cell cycle
Chromosome Numbers
Autosomes
- all non-sex chromosomes.
- Humans have 22 pairs of autosomes
Sex Chromosomes
- Genetic information that determines gender of an
organism
- In humans, Females have XX chromosome pair; males
have an XY pair
- 1 pair of sex chromosomes
- Humans have a total of 23 pairs of chromosomes.
2n Chromosomes
Honeybee (female) – 32 Adder’s Tongue Fern - 1262
Human - 46
Cat - 38
Common Frog - 26
Maize - 20
Does more chromosomes
bigger
Chromosome
number mean
doesanot
or more complicated
organism?
determine
complexity
of organism
Animal
Chromosome number (2n)
1.
Ascaris megalocephala (horse roundworm)
2
2.
Drosohila melanogaster (fruit fly)
8
3.
Musca domestica (house fly)
12
4.
Rana hexadactyla (frog)
26
5.
Apis mellifera (honey bee — female)
32
6.
Hydra vulgaris
32
7.
Fells domestica (cat)
38
8.
Pattus rattus (rat)
42
9.
Homo sapiens (man)
46
10.
Bos indicus (cow)
60
11.
Canis familiaris (dog)
78
12.
Columbia livia (pigeon)
80
13.
Amoeba proteus
250
14.
Aleucantha (radiolarian)
1600
Plant
Chromosome number (2n)
1.
Mucorheimalis (bread mold fungus)
2
2.
Penicillium notatum (fungus)
4
3.
Pisum sativum (pea)
14
4.
Zea mays (maize)
20
5.
Oryza sativa (rice)
24
6.
Lycopersicon (Tomato)
24
7.
Solanum tuberosum (potato)
48
8.
Saccharum offtinalis (sugarcane)
80
9.
Ophioglossum (Adder’s tongue fern)
1262
Chromosome Numbers cont.
• HOMOLOGOUS CHROMOSOMES
– Two chromosomes that are the same size,
shape and DNA makeup
• DIPLOID – contain both chromosomes of
a homologous pair. “2N”
• HAPLOID – contain only one of the
chromosomes of a homologous pair. “1N”
Karyotype
A photomicrograph
of the chromosomes
in a normal dividing
cell found in a
human.
Does this karyotype
appear to be male
or female?
karyotyping
Trisomy 21, a chromosomal abnormality indicative of down syndrome
Karyotyping Questions:
•
•
•
•
•
What characteristics did you use to pair up the
Chromosomes?
How many autosomes are there? How many
sex chromosomes?
Is the organism male or female? What sex
chromosomes do females have? Males?
Why are Karyotypes impt for geneticists?
What disease would be caused if you had
three chromosomes on 21?
Q: What is the difference chromatids,
centromeres, and chromatin?
Chromatids are the halves of the chromosomes,
centromeres are where the chromatids are joined,
chromatin is the coiled up DNA that makes up the chromatids/chromosomes
Today
Power Point Notes: Cell Division
Prokaryotes vs. Eukaryotes
Homework: draw binary fission p
154, and cell cycle with bulleted
notes p 155.
Cell Division In Prokaryotes
- Prokaryotes use binary fission, the division
of a prokaryotic cell into two offspring cells
- Cell membrane divides
- Prokaryotes do no have a nucleus
Cell Division in Eukaryotes
Mitosis – results in new cells with genetic
material identical to the original cell
Asexual reproduction – the production of
offspring from one parent
Meiosis – occurs during the formation of
gametes
Gametes – haploid reproductive cells
Q: What are the stages of the cell cycle
(included in interphase and cell division)
in order?
G1, S, G2, Mitosis, and Cytokinsis. Also G0
Today: Cell Cycle, Mitosis
Homework: Draw and label stages of Mitosis
and Cytokinesis, with 3-4 notes for each.
Print: Graphic organizer for Thurs, Meiosis
flipbook for Fri.
Cell Cycle
Interphase
- the time between
divisions
- the cell spends
most of its time in
interphase
Cell Division
- mitosis and
cytokinesis
How long does
mitosis take?
It depends on cell
type and culture
conditions.
Cell Cycle Interphase
• G1 stage of interphase
– Cell grows to normal size
– Cell carries out regular functions (protein synthesis,
etc…)
• S stage
– DNA is synthesized
• G2 stage
– Organelles are replicated, preparing for cell division
• G0 stage
– Cells stop dividing, sometimes permanently (ex:
nerve cells)
G1 → S → G2
OR
G1 → G 0
Mitosis
Division of the cell nucleus in which
chromosomes of the parent cell divide into
two identical daughter cells
http://www.johnkyrk.com/mitosis.html
http://www.cellsalive.com/mitosis.htm
Prophase
1. Nucleolus and nuclear
membrane disappear
2. Chromatin condenses to
form chromosomes
3. Centrioles and spindle
fibers appear
- Centrioles are not in plants.
Metaphase
1. Kinetochore fibers
move the
chromosomes to the
center of the cell
2. Chromosomes line
up along the center
of the cell
3. kinetochore fibers
hold chromosomes
in place
Anaphase
1. Chromatids separate at
the centromere
2. Chromatids move,
centromere first, toward
opposite poles
3. Chromatids are
considered to be
individual
chromosomes after
separation.
One chromosome (unduplicated)
one chromatid
one chromatid
One chromosome (duplicated)
two sister
chromatids
Telophase and Cytokinesis
1.
2.
3.
4.
5.
Centrioles and spindle
fibers disappear
chromosomes unwind into
chromatin “spaghetti”
nuclear membrane forms
around set of chromatin
and the nucleolus appears
Cytoplasm divides
(cytokinesis), forming two
new cells
Organelles are separated
into two new cells
Control of Cell Division
• signals from the cell can
trigger the next phase of
the cell cycle
• 3 checkpoints:
– Cell growth (G1) checkpoint
• decide whether cell should
divide or not.
– Yes - cell begins G2 phase
– No - cell goes into G0 phase
– DNA synthesis (G2)
checkpoint
• signal the cell to enter mitosis
– Mitosis checkpoint
• signal the cell to exit mitosis
Application
1. Growth
2. Self Healing
3. Cancer
- uncontrolled growth of cells
- error at G1 checkpoint
Which stage?
Mitosis
• http://www.biologycorner.com/flash/mitosis
.html
Mitosis vs. Meiosis
MEIOSIS
– Takes place in two sets of divisions, meiosis I
and meiosis II
– Occurs in Germ cells found in the ovaries and
testes
• Meiosis I
– Reduces the number of chromosomes from
diploid to haploid
• Meiosis II
– Produces four haploid daughter cells
http://www.johnkyrk.com/meiosis.html
Prophase I
• Like Mitosis:
–DNA is coiled into
chromosomes
–Spindle fibers appear
–Nucleolus and nuclear
membrane disassemble
• Different than Mitosis
• Synapsis - homologous
chromosomes pair up
• Crossing over - exchange
genetic information, or
genetic recombination
Meiosis I continued
Metaphase I:
tetrads line up at the
nucleus
tetrad – a pair of
homologous chromosomes
Anaphase I:
Independent assortment
- tetrads move to opposite
sides of the cell (random)
Telophase I and
Cytokinesis:
chromosomes reach
opposite sides of the cell
and the cell divides
Meiosis II
-
Begins with the two cells
formed in Meiosis I
DNA is NOT copied
before Meiosis II
Meiosis I
Prophase II, Metaphase II,
and Anaphase II – similar to
Meiosis I, but each half
receives only half of the
genetic information
Telophase II and
Cytokinesis II - Like
Meiosis I
-
Ends with four cells
instead of two
Cells are haploid instead
of diploid
Meiosis II
Gametes
• In animals, gametes
are the only cells
that use meiosis.
• Spermatogenesis –
produces 4 sperm
cells
• Oogenesis –
produces 1 egg cell,
or ovum, and three
polar bodies, which
degenerate.
What is crossing over?
Crossing over occurs when pieces of
chromatids break off and attach to the
homologous chromosome by it.
What are some key differences and
similarities between mitosis and
meiosis?
• Mitosis is used by regular cells, meiosis is
used by reproductive cells
• There is one division in Mitosis, and two
divisions in Meiosis
• Mitosis ends with two diploid cells, Meiosis
ends up with four haploid cells
• In both Mitosis and Meiosis DNA is
doubled just once.