Chapter 8: Cell
Reproduction
Review
Organelles
Centrioles
Made of microtubules
Acts as anchors in cell division
Mitotic Spindle fibers
Two Main types
Kinetochore Fibers- Attach from centriole to centromere of
chromosomes and assists in movement of chromosomes
Polar Fibers – Extend from pole to pole and keep the shape of
the cell during cell division
Nuclear envelope
Double Phospholipid bilayer surrounding nucleus
Allows selective passage of RNA and other material
Nucleolus
Dense area where DNA is concentrated in the nucleus
Section 8.1
Chromosomes
Chromosome Structure
Rod-shaped and made of DNA and proteins called histones
Two full copies of DNA
Form it takes before cell division
Has two identical halves called chromatid
Chromatid
Half of the chromosome
One full copy of DNA
Attached in the center
Centromere
Center where chromatids are
held together
Chromatin
Less tightly coiled DNA-protein complex
Tin = thin *Think spaghetti
Form taken during transcription
Section 8.1
Sex Chromosomes
Determine gender of the organism
May carry genes for other characteristics
Either X or Y
Female = XX Male = XY
One pair (or two chromosomes)
Autosomes
Remaining chromosomes
Contain genes for many traits
22 pairs (or 44 chromosomes)
Section 8.1
Homologous Chromosomes
Two copies of each autosome
One copy from each parent
Same size and shape
Carry genes for the same trait
Karyotype
Photomicrograph of chromosomes
Notice there are 22 pairs of
autosomes and 1 pair of sex
chromosomes
What is the gender of this
organism?
Section 8.1
Diploid
Cells that are diploid contain two autosomes from each
homologous pair and two sex chromosomes
Abbreviated as 2n
Memory key * di = two
Occurs in all cells except sperm and egg cells
Haploid
Cells contain only one set of chromosomes
Therefore, half the number of chromosomes of a diploid
cell
Abbreviated as 1n
Memory key * hap = half
Sperm cell (1n) and egg cell (1n) create a diploid cell (2n)
Section 8.1
Notice high number
of chromosomes
in fern compared
to humans!
Section 8.1
Activity
Create a karyotype!
Arrange in pairs according to length, centromere
position, and banding pattern
Questions
1. How many autosomes are there? How many sex
chromosomes?
2. Is the organism a male or female?
3. Why are karyotypes important tools for geneticists?
Homework
Review questions on p. 153 #1-5
Section 8.1 Review Answers
1.
Name the proteins that DNA wraps around to form a
chromosome in eukaryotic cells.
•
Histones.
2. How do the structure and location of a prokaryotic
chromosome differ from that of a eukaryotic
chromosome?
•
A prokaryotic chromosome consists of a circular DNA
molecule. Eukaryotic chromosomes are rod-shaped,
associated with histone and nonhistone proteins, and found
within the cell’s nucleus.
3. Does chromosome number indicate whether an organism
is a plant or animal? Explain.
•
No. For example, chimpanzees have the same number of
chromosomes as potatoes or plums.
Section 8.1 Review Answers
4. Contrast sex chromosomes with autosomes.
•
Sex chromosomes determine the gender of an organism.
Autosomes are all of the other chromosomes in an
organism.
5. Using Table 8-1, list the haploid and diploid number of
chromosomes for each organism.
Section 8.1 Review Answers
Organism
Diploid # Chromosomes
Haploid # Chromosomes
Adder’s tongue fern
1262
631
Carrot
18
9
Cat
32
16
Chimpanzee
48
24
Dog
78
39
Earthworm
36
18
Fruit fly
8
4
Garden pea
20
10
Gorilla
48
24
Horse
64
32
Human
46
23
Lettuce
18
9
Orangutan
48
24
Sand dollar
52
26
Section 8.2
Cell Cycle
Repeating set of events in the life of
a cell
Interphase
Time between cell divisions
Three phases
G1 – Cell growth
S – DNA is copied
G2 – Growth and prep for cell division
Cell division
Two phases
Mitosis – Nucleus of the cell divides
Cytokinesis – Division of the cell’s cytoplasm
Section 8.2
Cell Division
Prokaryotes
Remember: Has cell wall, no nuclei, no membrane-bound
organelles
Binary fission
Division of prokaryotic cell into two offspring cells
Section 8.2
Cell Division (cont’d)
Eukaryotes
Mitosis
Division of the nucleus
Four stages (Prophase, Metaphase,
Anaphase, Telophase)
Cytokinesis
In animal cells, pinching of cell
membrane occurs
Cleavage furrow
In plants, cell plate formation
Section 8.2
Control of Cell Division
Checkpoints = traffic signal
Three main checkpoints
G1 checkpoint
G2 checkpoint
Mitosis checkpoint
Section 8.2
Activity
Venn diagram: Cell division in Prokaryotes vs Eukaryotes
Karyotype Part 2
Homework
Create the cell cycle
Section 8.2 (cont’d)
Mitosis
Prophase
Tight coiling of DNA into chromosomes
Nucleolus and nuclear membrane break down
Centrosomes appear and move to opposite ends
of the cell
Kinetochore fibers extend from kinetochore
from each chromatid to centrosome
Metaphase = Middle
Kinetochore fibers move chromosomes to center
of cell
All chromosomes line up in a single file line
Section 8.2
Anaphase
Chromosomes separate at the centromere and
chromatids move to opposite poles
Chromatids are now considered individual
chromosomes
Telophase
Spindle fibers disassemble
Chromosomes return to less tightly coiled
chromatin state
Nuclear envelope forms around each set of
chromosomes
Nucleolus forms in each of the newly forming cells
Animation
Mitosis vs Meiosis
Where do they occur?
Mitosis – in the body cells
Meiosis – in the germ cells
Why does it occur?
Mitosis
Asexual reproduction
Growth and development
To replace old cells
Meiosis
Formation of gametes (egg and sperm cells) that will be
used in sexual reproduction
Mitosis vs Meiosis
End result?
46
46
23
23
46
46
23
MITOSIS
23
23
MEIOSIS
23
Meiosis
Also known as reduction division
Occurs in germ cells found in the ovaries and testes
Produces sex cells which are haploid
Occurs in two phases
Meiosis I
Reduces the number of chromosomes from diploid to
haploid
Meiosis II
Produces four haploid daughter cells
Meiosis I
Meiosis I
Prophase I
DNA coils tightly into chromosomes
Spindle fibers appear
Nucleolus and nuclear envelope
disassemble
Synapsis =Pairing of homologous
chromosomes
Tetrad =Pair of homologous
chromosomes twisted around each
other
Crossing over may occur
Genetic recombination
Meiosis I
Metaphase I
Spindle fibers attach to centromere of tetrads
Tetrads line up along midline
Anaphase I
Homologous chromosome pairs are separated and
move to opposite poles
Independent assortment occurs
Telophase I
Chromosomes reach opposite ends of cell
Spindle Fibers disappear
Cytokinesis begins
Meiosis II
Meiosis II
Prophase II
Spindle fibers form and attach to the centromeres of the
double stranded chromosomes
Metaphase II
Chromosomes are moved to the midline of the dividing cell
Anaphase II
Chromatids separate and move toward opposite poles
Telophase II
Nuclear membrane forms in each of the four new cells
Cytokinesis II occurs resulting in four new cells, each with half
the original cell’s number of chromosomes
Section 8.3
Results of mitosis vs. meiosis
Section 8.3
Development of
Gametes
Spermatogenesis
Oogenesis
Polar bodies
Sexual
reproduction