1. Reproduction and Inheritance
CH 8
Reproduction and Inheritance

2. Reproduction
Asexual Reproduction
Sexual Reproduction
LM 340

3. Prokaryotes are asexual
Via binary fission
Recall that Prokaryotes have circular DNA
Plasma membrane
Prokaryotic chromosome
Cell wall
Duplication of chromosome and separation of copies 1
Continued elongation of the cell and movement of copies 2
Prokaryotic chromosomes
Division into two daughter cells 3
Figure 8.3A

4. Eukaryotes Complex cell division
Chromosomes occur as chromatin unless dividing
Individual chromosomes visible when cell is dividing
LM 600

5. Cell cycle
Ordered sequence of events from time a cell is first formed until its own division
Growth phase
Division phase (mitotic phase)
Mitosis
Cytokinesis

6. INTERPHASE S (DNA synthesis) G1 G2 MITOTIC
Fig. 8-5
INTERPHASE S
(DNA synthesis) G1 G2
Cytokinesis
Mitosis
MITOTIC
PHASE (M)

7. Interphase Synthesizes new organelles and molecules Growth phase
Chromosomes duplicated
Not individually distinguishable
Loosely packed into chromatin
Contains nucleoli indicating cell is making proteins

8. Prophase Chromatin fibers more tightly coiled and folded
Form discrete chromosomes
Nucleoli disappear
Duplicated chromosomes appear and joined at centromere
Mitotic spindle forms in cytoplasm

9. Prometaphase Nuclear envelope fragments and disappears
Microtubules emerge from centrosome at poles ad reach chromosomes
Chromosomes tightly condensed
Kinetochore sppears

10. Metaphase Mitotic spindle formed
Chromosomes line up at metaphase plate
Centromeres of chromosomes line up

11. Anaphase Two centromeres of each chromosome come apart
Sister chromatids separate
Poles move farther apart, elongating cell
Complete collection of chromosomes at each pole

12. Telophase and Cytokinesis
Nucleear envelope reforms
Chromosomes uncoil into chromatin
Nucleoli reappear
Cytokinesis
Cell divides in two

13. INTERPHASE PROPHASE PROMETAPHASE
Fig. 8-6a
INTERPHASE
PROPHASE
PROMETAPHASE
Centrosomes
(with centriole pairs)
Chromatin
Early mitotic
spindle
Centrosome
Fragments
of nuclear
envelope
Kinetochore
Centromere
Nuclear
envelope
Plasma
membrane
Spindle
microtubules
Chromosome, consisting
of two sister chromatids
Nucleolus

14. TELOPHASE AND CYTOKINESIS
Fig. 8-6b
METAPHASE
ANAPHASE
TELOPHASE AND CYTOKINESIS
Nucleolus
forming
Metaphase
plate
Cleavage
furrow
Nuclear
envelope
forming
Daughter
chromosomes
Spindle

15. Cytokinesis Cleavage Cell wall Starts in telophase or late anaphase
Cleavage furrow
Shallow groove on cell surface
Microfilaments draw together and split cell in two
Cell wall
Vesicles containing cell wall material form cell plate
Telophase
Form cell plate that grows out to fuse with existing wall

16. Cytokenesis Cleavage furrow Microfilaments contract Cleavage furrow
Contracting ring of
microfilaments
Daughter cells

17. Cell plate
forming
Daughter
nucleus
Wall of
parent cell
New cell wall
Cell wall
Vesicles containing
cell wall material
Cell plate
Daughter cells

18. Cell Division Growth factors Density-Dependent inhibition
Proteins that stimulate cell to divide
Density-Dependent inhibition
Stop cells from dividing under crowded conditions
Anchorage dependence
Need surface on which to divide

19. Growth Cell cycle control system
Set of molecules that triggers and coordinates key events in cell cycle
Checkpoints
Cell is set to STOP until told to GO

20. Growth Cell cycle control system
Set of molecules that triggers and coordinates key events in cell cycle
G1 checkpoint G0
Control
system S G1 M G2
M checkpoint
G2 checkpoint

21. Growth factor Plasma membrane Relay proteins Receptor protein
Fig. 8-9b
Growth factor
Plasma membrane
Relay
proteins
Receptor
protein
G1 checkpoint
Signal
transduction
pathway
Control
system G1 S M G2

22. Out of control Cancer Do not respond to cell control system
No density-dependent inhibition
Divide indefinitely
No anchorage dependence

23. Meiosis terms Somatic cells Homologous chromosomes Sex chromosomes
Autosomes
Diploid
Haploid

24. Haploid gametes (n = 23) n Egg cell n Sperm cell Meiosis Fertilization
Fig. 8-13
Haploid gametes (n = 23) n
Egg cell n
Sperm cell
Meiosis
Fertilization
Diploid
zygote
(2n = 46) 2n
Multicellular
diploid adults
(2n = 46)
Mitosis and
development

25. Meiosis Produces haploid gametes in diploid organisms
Duplication of chromosomes
Two cell divisions

26. MEIOSIS I: Homologous chromosomes separate
Fig. 8-14a
MEIOSIS I: Homologous chromosomes separate
INTERPHASE
PROPHASE I
METAPHASE I
ANAPHASE I
Centrosomes
(with centriole
pairs)
Microtubules
attached to
kinetochore
Metaphase
plate
Sister chromatids
remain attached
Sites of crossing over
Spindle
Nuclear
envelope
Sister
chromatids
Tetrad
Centromere
(with kinetochore)
Homologous
chromosomes separate
Chromatin

27. MEIOSIS II: Sister chromatids separate
Fig. 8-14b
MEIOSIS II: Sister chromatids separate
TELOPHASE II
AND CYTOKINESIS
TELOPHASE II
AND CYTOKINESIS
PROPHASE I
METAPHASE II
ANAPHASE II
Cleavage
furrow
Sister chromatids
separate
Haploid daughter
cells forming

28. (before chromosome duplication) Daughter cells of meiosis II
Fig. 8-15
MITOSIS
MEIOSIS
Parent cell
(before chromosome duplication)
Site of
crossing over
MEIOSIS I
Prophase I
Prophase
Tetrad formed
by synapsis of
homologous
chromosomes
Duplicated
chromosome
(two sister
chromatids)
Chromosome
duplication
Chromosome
duplication
2n = 4
Chromosomes
align at the
metaphase plate
Tetrads
align at the
metaphase plate
Metaphase
Metaphase I
Anaphase
Telophase
Anaphase I
Telophase I
Sister chromatids
separate during
anaphase
Homologous
chromosomes
separate
(anaphase I);
sister chroma-
tids remain
together
Haploid
n = 2
Daughter
cells of
meiosis I
No further
chromosomal
duplication;
sister
chromatids
separate
(anaphase II) 2n 2n
MEIOSIS II
Daughter cells
of mitosis n n n n
Daughter cells of meiosis II

29. Diversity Random arrangement of homologous chromosomes
Different gene versions
Genetic recombination
“Crossing over”

30. Error Abnormal sex chromosomes Trisomy 21 Nondisjunction in meiosis I
meiosis II
Gametes
n + 1
n + 1
n – 1
n – 1
Number of chromosomes

31. Error
Down syndrome
Extra copy of chromosome 21