Before cells can divide, DNA has to replicate itself so there
are 2 copies
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DNA R EPLICATION DNA strand opens up and DNA polymerase
attaches The exposed unpaired bases find new partners Growth of the
DNA replicates is always in one direction This means while one side
can grow as the DNA unzips The other side grows in pieces that then
must be glued together Errors are edited
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T ELOMERES TICKING CLOCK Hutchinson-Gilford Progeria
Syndrome
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M UTATIONS Sometimes the errors result in proteins that dont
work or dont work as well What causes a mutation? Spontaneous
Radiation-induced mutations Chemical-induced mutations Sphinx
mutation
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A NIMAL CELLS HAVE COUNTERS THAT KEEP TRACK OF HOW MANY TIMES A
CELL HAS DIVIDED. T HESE COUNTERS ARE CALLED : A) odometers. B)
telomeres. C) chromosomes. D) nuclei. E) centromeres.
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I N DNA REPLICATION, WHEN THE DNA MOLECULE SEPARATES INTO TWO
STRANDS : A) it is possible to reconstruct perfectly all the
information on the missing strand because one strand carries all
the information needed to construct its complementary strand. B)
the rebuilding process begins, in which an enzyme connects the
appropriate complementary base to the exposed base. C) the mitotic
phase of cell cycle begins. D) All of the above are correct. E)
Only a) and b) are correct.
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W ITHIN INTERPHASE, WHICH OF THE STAGES IS DEFINED BY THE
ACTIVE REPLICATION OF THE CELL S GENETIC MATERIAL ? A) the Gap 2
phase B) the mitotic phase C) the Gap 1 phase D) the replitosis
phase E) the DNA synthesis phase
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2 D IFFERENT F ORMS OF C ELL D IVISION Asexual reproduction and
cell division of body cells Prokaryotes and some single celled
Eukaryotes Binary fission All growing or repairing multi-cellular
organisms Mitosis Sexual reproduction Some single celled Eukaryotes
Conjugation Eukaryotes Meiosis
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D IFFERENT F ORMS OF C ELL D IVISION Asexual reproduction and
cell division of body cells Prokaryotes and some single celled
Eukaryotes Binary fission All growing or repairing multi-cellular
organisms Mitosis *** Sexual reproduction Some single celled
Eukaryotes Conjugation Eukaryotes Meiosis ***
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M ITOSIS 2 cells Identical to Parent
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T HE PURPOSE OF MITOSIS IS TO ENABLE EXISTING CELLS : A) to
generate gametes. B) to grow. C) to die on purpose. D) to generate
new, genetically identical cells. E) to generate new, genetically
diverse cells.
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L ET S SEE THAT AGAIN - M ITOSIS End with 2 cells that are
genetically identical to the parent and to each other.
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T HIS FIGURE DEPICTS : A) mitotic anaphase. B) mitotic
prophase. C) mitotic metaphase. D) mitotic telophase. E) meiotic
anaphase I.
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S EXUAL R EPRODUCTION & M EIOSIS What would happen if these
cells were formed by mitosis?
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M EIOSIS - A GAIN Only during the formation of eggs or sperm
Two divisions in one At start homologous chromosomes with their
replicates come together to form a tetrad (4) Genetic recombination
First division homologous chromosomes separate Second division
replicates separate End up with 4 cells that are all genetically
different
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= Oogenesis Spermatogenesis produces 4 cells all the same size
that then go on to lose most of the cytoplasm and get a tail for
swimming.
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G ENETIC R ECOMBINATION THE REASON FOR S EX
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P ROJECT 3 Use the hand out or compare figures 6-11 and 6- 20.
List all of the features that the two forms of division have in
common and explain these. List all of the features found only in
meiosis. Explain your answers. You may work in groups to develop
your lists, but hand in your own write-up either at the end of
class or at the start of the next class period.
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K ARYOTYPE
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W HAT IS DIFFERENT ABOUT THIS KARYOTYPE ?
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D OWN S SYNDROME
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Why are only smaller chromosomes ever seen in trisomy?
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W HICH OF THE FOLLOWING ARE FEATURES THAT DISTINGUISH CANCER
CELLS FROM NORMAL CELLS ? A)Normal cells undergo cytokinesis;
cancer cells do not undergo cytokinesis. B) Normal cells have
contact inhibition; cancer cells have no contact inhibition. C)
Normal cells metastasize; cancer cells do not metastasize. D)
Normal cells can divide a finite number of times; cancer cells can
divide indefinitely. E) Both b) and d) are correct.
Slide 42
A DIPLOID (2N) CELL UNDERGOES MEIOSIS. W HAT ARE THE PRODUCTS
OF THIS DIVISION ? A) one polyploid gamete B) four haploid cells C)
four diploid cells D) two haploid cells E) two diploid cells
Slide 43
T HE EGG CELLS OF A HORSE CONTAIN 32 CHROMOSOMES. H OW MANY
CHROMOSOMES ARE IN THE HORSE S LIVER CELLS ? A) 32 B) 16 C) 128 D)
64 E) 8