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• First 2 billion years
Advantages:
• One parent (quick and easy)
• Increase numbers quickly
• Favorable in stable environment
Disadvantages:
• Offspring identical (clones)
• Slow evolution/ less diversity (extinction)
• Division into two or more
• Equal= binary
• Can be along any plane
• Group of cells on parent develops into
new individual
Frag men ta tion
• Body parts regenerate
• “Virgin birth”
• Egg develops without fertilization- some
diploid/ some haploid
• Uncommon- role in social organisms
• Gametes produced (sperm and ova)
Advantages:
• Genetic diversity (withstand environmental
pressure)
Disadvantages:
• Complicated-- time, energy requirement
• “Cost of meiosis”-- only half genes passed
• Wastage in the production of males
Somatic
cell
Gamete
or
Germ cell
Necessary for ANY cell to divide:
• reproductive signal
• replication of DNA
• segregation of DNA
• cytokinesis of cytoplasm
Nucleoid region
(protein scaffold)
(p)
(q)
53 rule: always
copies 5’-3’
link
1 interphase
4 mid prophase
7 early anaphase
10 late telophase (cytokinesis)
2 interphase
5 late prophase
8 anaphase
3 early prophase
6 metaphase
9 early telophase
link
link
animation
Down's Syndrome: 47 chromosomes
with 3 #21 chromosomes.
Triple-X Syndrome: 47 chromosomes
caused by 3 X chromosomes.
Klinefelter's Syndrome: 47
chromosomes caused by 2 X
chromosomes and 1 Y chromosomes.
Turner's Syndrome: 45 chromosomes
with 1 X chromosome (caused by the
absence of one of the X chromosomes or
a Y chromosome).
Leads to aneuploidy
• Too much mitosis or too little apoptosis
All cancers are of
genetic origin
• Germ lineMendelian
inherited- (single
gene)- 5-10%
• Non-inherited- somatic mutations
• Familialinherited
–Increase of
susceptibility
–Multifactorialmany genes
• Environment
• Other genes
(repair)
Normal
Genes
“Go”
Proto
Oncogenes
2. “Stop”
Suppressor
genes
1.
Mutation
Mutation
Mutation
Cancer
Genes
(1)
Oncogenes
(2)
mutant
suppressor
3. Genes that recognize DNA errors and repair or halt cell
cycle (apoptosis)
Repair
Genes
Mutation
(3)
abnormal
repair
genes
Examples of “cancer genes”
• 1993- APC
P53
• 1994 P16
• 1995 HNPCC
AT
• 1996 HPC1
BRCA1-2
• 1997 B-CAT
PTEN
Suppressor
Supressor
Suppressor
Repair
Repair
Oncogene
Suppressor
Oncogene
Suppressor
• 1998 P73
Suppressor
link
Colon
Various
Melanoma
Colon
Various
Prostate
Breast
Colon
Brain
Breast
Colon
Nerve
hhmi
2004- Question 1
Meiosis reduces chromosome number and rearranges genetic
information.
(a) Explain how the reduction and rearrangement are
accomplished in meiosis.
(b) Several human disorders occur as a result of
defects in the meiotic process. Identify one such
chromosomal abnormality; what effects does it have on
the phenotype of people with the disorder? Describe
how this abnormality could result from a defect in
Turner
meiosis.
Klinefelter
(c) Production of offspring by parthenogenesis or Down
cloning bypasses the typical meiotic process. Describe
either parthenogenesis or cloning and compare the
genomes of the offspring with those of the parents.