Download Chapter 8 (cont…) Meiosis and Reproduction

Bio100 (Paddack) Lecture 9 (9/26/16)
I. Cell Division: fission & mitosis
A. Why
B. Asexual vs sexual reproduction
C. Prokaryotes: Binary Fission
D. Eukaryotes: Cell Cycle
1. Interphase – DNA replication
2. Mitotic Phases
a. Prophase
b. Prometaphase
c. Metaphase
d. Anaphase
e. Telophase
f. Cytokinesis
E. Control of Cell Cycle
F. When cell cycles go wrong
1. Cancer
2. Mutations
II. Sexual reproduction: Meiosis
A. Sexual reproduction defined
B. Chromosome homologs
C. Gametes
D. Meiosis process
E. How genetic variability arises in meiosis
1. Mutations
2. Random shuffling
3. Random mating
4. Cross over
cell division!
Chapter 8: Cellular Reproduction
Cell division is:
• How we get more
cells.
– growing from a single
cell into us
– cell renewal and repair
• How unicellular
organisms reproduce
Prokaryotes (bacteria, archaea) reproduce
asexually – simple cell division
1
Figure 8.3B
Chromosomes
DNA molecules
Sister
chromatids
Chromosome
duplication
Centromere
Sister
chromatids
Chromosome
distribution
to the
daughter
cells
INTERPHASE
Metaphase
Prophase
Anaphase
2
…and back to INTERPHASE
Telophase and Cytokinesis
http://vcell.ndsu.nodak.edu/animations/mitosis/movie-flash.htm
Mutations: errors in DNA replication
Sexual Reproduction
Cell types with respect to chromosome number:
1. Somatic cells – all body cells; full number of chromosomes
2. Gametes, germ cells – egg and sperm cells; half the number of
chromosomes
1
e.g. 46
+
1
e.g. 46
=
2
e.g. 92
3
• Chromosomes come in pairs
Homologous Chromosomes/Homologues
– One from egg, one from sperm
• Pairs are called Homologous Chromosomes –
they hold the same genes
46 chromosomes
23 pairs of chromosomes
• carry genes for the same traits.
Eye color
Tongue rolling
Result of Meiosis:
4 haploid gametes (1n) are formed from
1 diploid cell (2n)
Meiosis I
Meiosis II
• Alleles = alternative forms of the same gene
Meiosis
Diploid = 2N
Haploid = N
Somatic cells
Gametes
4
Meiosis – the production of gametes
In Meiosis I:
• Homologous chromosomes align
• Pairs of homol. chromosomes are separated
• In Meiosis II:
– Sister chromatids separate (just like mitosis)
Figure 8.13
Figure 8.13
http://vcell.ndsu.nodak.edu/animations/downloads/movies/meiosis/MeiosisWMV.wmv
Mitosis
 functions in growth, tissue repair,
asexual reproduction
 occurs in somatic cells
Meiosis
 functions in sexual reproduction
 occurs only the cells of
reproductive tissues to produce
gametes
 produces daughter cells that are
genetically identical to parent cell
 produces daughter cells that have
only half the genetic material as the
parent cell
 starts with 1 diploid cell  ends
with 2 diploid cells
 starts with 1 diploid cell  ends
with 4 haploid cells
http://www.pbs.org/wgbh/nova/miracle/divi_flash.html
7. What are growth factors and what role do they
play?
8. What happens when mitosis becomes
uncontrolled?
9. Define: genetic mutation.
10. Define meiosis & state how the end result of it
differs from that of mitosis.
11. Define: somatic cell, gamete, diploid, haploid,
homologous chromosomes, egg, sperm, fertilization.
12. Are gametes diploid or haploid?
13. The 3 main stages of meiosis are interphase,
meiosis I, and meiosis II. Briefly describe overall
what happens during each stage.
Lecture 9 (9/26/16): Cell Division Study Questions
1. List 3 reasons for cell division.
2. Do prokaryotes under sexual or asexual
reproduction? Describe their process of binary fission.
3. Define: mitosis, cell cycle, DNA, chromosome,
gene, chromatin, chromatids.
4. There are 2 main stages of mitosis. List them &
state what the overall task of each of the 2 stages is.
5. What are sister chromatids? Why do the look like
an X when condensed?
6. Sketch each of the following phases of Mitosis &
state what is occurring in each: prophase,
prometaphase, metaphase, anaphase, telophase,
cytokinesis.
14. In prophase of Meiosis I, tetrads are formed –
what are they?
15. Crossing over occurs in this stage – what is
this and what is the result?
16. List & briefly describe 4 different sources of
genetic variability.
5