Chapters 11 & 12 – Mitosis, Meiosis, and Sexual Reproduction
Chapter 11
Cell Division in Prokaryotes
• Prokaryotic cell division occurs as ____________________ in which cell divides
into two halves.
– Genetic information exists as a _________________________________
___________________
 Copying begins at _____________________, and proceeds
____________.
 One genome ends up in each __________________.
Binary Fission
Discovery of Chromosomes
All eukaryotic cells store genetic __________________________.
– Most eukaryotes have between 10 and 50 chromosomes in their body cells.
 Human cells have 46 chromosomes.
 23 nearly-identical pairs
Structure of Chromosoms
• Chromosomes are composed of a __________________________________.
– ________________ - not expressed
– ________________ - expressed
• DNA exists as a _________________________________________________
________________________________--.
– forms nucleosome every 200 nucleotides
 DNA coiled around ________________________________
Eukaryotic Chromosomal Organization
Structure of Chromosomes
• Karyotype - _________________________________________.
– diploid - A cell possessing ______ copies of each chromosome (human
body cells).
 Homologous chromosomes are made up of __________________
joined at the _______________.
– haploid - A cell possessing a _________ copy of each chromosome
(human sex cells).
Karyotype and Chromosomes
Phases of the Cell Cycle
• Five phases of cell division:
– __ - primary growth phase
– __ - genome replicated
– __ - secondary growth phase
 collectively called interphase
-- M - _________________
-- C- __________________
Cell Cycle
Interphase
• G1 - _______________________________
• S - ________________________________
_____________________
– attached at ________________
 contains attachment site
(___________)
• G2 - _________________________
– assemble machinery such as centrioles
Mitosis
• Prophase
– _______________________________
 Microtubules connect _________________ on each pair of sister
______________ to the spindle poles.
– nuclear envelope breaks
________________________________
________________________________
________________________________
________________________________
________________________________
________________________________
• Metaphase
– chromosomes align in
cell’s center
 metaphase plate
 spindle
______________________________________
______________________________________
______________________________________
______________________________________
______________________________________
• Anaphase
– sister ________________________
 poles move apart
 centromeres move toward ____________
 microtubules shorten
• Telophase
– ________________________
– nuclear envelope forms around ________ set of sister chromatids
Cytokinesis
• Cleavage of cell into ___________
– animal cells
 constriction belt of ___________
– plant cells
 cell plate
– fungi and protists
 mitosis occurs within the ______
Cell Cycle Control
• Two __________________ in cell cycle:
– replication of _______________
– separation of _________________
• Cell can be put on hold at specific checkpoints.
• G1 / S - _______________________________
• G2 / M - ______________________________
• Spindle checkpoint - all chromosomes are attached to spindle
Growth Factors and the Cell Cycle
• Each growing cell binds minute amounts of positive regulatory signals (growth
factors) that stimulate cell division.
– If neighboring cells use up too much growth factor, there is not enough left to
trigger cell division.
 Growth factors trigger intercellular signaling systems
Chapter 12
Reduction Division
• In sexual reproduction, gametes ________(___________) to produce a _________.
– Gamete formation involves a mechanism (____________) that ________ the
number of ____________________________ that found in other cells.
 Adult body cells are ____________.
 Gamete cells are _______________.
 ___________________________
Sexual Life Cycle
Meiosis
• Synapsis
– Homologues _________________________.
• Homologous recombination
– Genetic exchange (_________________________) occurs between
_________________________________.
• Reduction division
– Meiosis involves two ______________________-, with no _____________ of
genetic material between them.
Prophase I
• Homologous chromosomes become ___________________ in synapsis, exchange
segments via __________________, and then _______________.
– Presence of a _______________ indicates ________________ has occurred
Metaphase I
• Terminal ________________ holds ______________________ together.
– Spindle microtubules attach to ______________________ on the outside of
each ___________________.
• Joined pairs of ____________________ lines up on _____________________.
– orientation of each pair is ________________________
Completing Meiosis
• Anaphase I
– Spindle fibers begin to _________________ whole centromeres toward poles.
 Each pole receives a _____________________ homologous pair.
 complete set of ______________________
 random orientation results in ________________________
Completing Meiosis
• Telophase I
– Chromosomes are _______________________; one at _______________.
 ______________________ re-forms around each daughter cell.
 Sister chromatids are __________________ due to ___________.
Second Meiotic Division
• Meiosis II resembles ___________________.
– prophase II - ______________ breaks down and second meiotic
division begins
– metaphase II - spindle fibers _________________ of centromere
– anaphase II - spindle fibers _________ and sister chromatids
move to ______________________
– telophase II - nuclear envelope ______________
• Final result - four haploid cells
Sex
• Asexual reproduction - individual inherits ________________ from a
single parent
– ____________________ - development of an adult from an
_______________________
• __________________________ - produces genetic _______________.
– Segregation of chromosomes tends to disrupt _________________
___________________.
 Only _________ progeny maintain _____________________
Origin and Maintenance Of Sex
• Theories
– DNA repair hypothesis
 Only diploid cells ____________________________________
______________________.
– Contagion hypothesis
 A secondary _______________________________________
_______________________________.
• Red Queen hypothesis
– Current ________________ can be stored in reserve for ________.
• Miller’s Ratchet
– __________________ may be a method of keeping the _________
____________.
Evolutionary Consequences of Sex
• Evolutionary process is ________________ and ________________.
– pace of evolutionary change is _____________ by
___________________
– ___________________ not always favored by _________________
 may act to preserve ______________________