Transcript Asexual vs. sexual reproduction

Cellular Reproduction
Asexual vs. sexual reproduction
• Making the next generation
• Asexual
– One parent
– Offspring are genetically identical to parent
• Sexual
– Two parents
– Offspring contain genes from both parents
and are genetically unique
Fig. 8-1a
Prokaryotic asexual reproduction
BINARY FISSION
• Prokaryotes have a single
circular chromosome
• Chromosome replicates
• Cell adds new membrane
and cell wall between the
chromosomes– cell
elongates
• Cell splits between two
chromosomes
Fig. 8-3b
Prokaryotic chromosomes
Fig. 8-5
CELL CYCLE IN EUKARYOTIC
CELLS
INTERPHASE
G1
First gap phase
-growth
-normal cell activities
S
(DNA synthesis)
-DNA copies (replicates)
itself
G2
Second gap phase
-growth
-cell prepares for mitosis
Mitosis = division of the nucleus
Cytokinesis = division of the cytoplasm
Fig. 8-4bc
What happens to a chromosome during the cell cycle
Sister chromatids
Single, replicated chromosome
(G1)
Chromosome is replicated/
sister chromatids (identical
copies) attached at centromere
Centromere
Sister
chromatids
Replicated chromosome
splits, each chromatid
going to a separate cell
What’s wrong with this????
Fig. 8-9a
G1 checkpoint
Cells can’t get past unless they
get a signal from outside
G0
G0 is a nondividing state
Ex: brain, muscle
Control
system
G1
M
S
G2
G2 checkpoint  size and
DNA checked
M checkpoint in metaphase all c’somes attached to spindle
Fig. 8-9b
Growth factor
-outside “signal” that it’s time to divide.
-gets a cell to move past the G1 checkpoint
Plasma membrane
Receptor
protein
Relay
proteins
G1 checkpoint
Control
system
G1
M
G2
S
Fig. 8-12
Your chromosomes are organized into homologous pairs
One from mom
One from dad
Have genes for the
same traits
May be different
forms of the gene
however
Homologous pair of
chromosomes
Centromere
Sister chromatids
One duplicated
chromosome
Life cycle of humans
Haploid gametes (n = 23)
Adults produce
gametes (sex cells) by
meiosis
-these are haploid
cells
n
n
Meiosis
Haploid gametes fuse
during fertilization
-forming a
zygote that is diploid
Zygote divides by
mitosis, cells
differentiate during
development 
creating the adult
Egg cell
Sperm cell
Fertilization
Diploid
zygote
(2n = 46)
2n
Multicellular
diploid adults
(2n = 46)
Mitosis and
development
In Meiosis I,
duplicated
homologous
chromosomes
pair up and then
are separated
into separate
cells
Diploid
Haploid
In Meiosis II,
duplicated
chromosomes
are split, each
chromatid going
into a separate
cell
Haploid
Stages of Mitosis
• Before mitosis can occur what has to
happen to the chromosomes
Cancer
• Cells that undergo uncontrolled cell
division
• Invade surrounding tissue
• Move by way of circulatory or
lymphatic system to new location
– Metastisis
– Benign vs. malignant
DNA Polymerase
• Adds nucleotides to a growing
nucleic acid chain
• Can ONLY add to the 3’ end of
the chain
–Result:
–The two sides of the DNA molecule
are copied differently
Role of ligase