CELL DIVISIONChapter 6

CELL DIVISION

Before cells can divide, DNA has to replicate itself so there are 2 copies

DNA REPLICATION 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

TELOMERES – TICKING CLOCK

Hutchinson-Gilford ProgeriaSyndrome

MUTATIONS Sometimes the errors result in proteins that

don’t work or don’t work as well What causes a mutation?

Spontaneous Radiation-induced mutations Chemical-induced mutations

Sphinx mutation

ANIMAL CELLS HAVE “COUNTERS” THAT KEEP TRACK OF HOW MANY TIMES A CELL HAS DIVIDED. THESE COUNTERS ARE CALLED:

A) odometers.B) telomeres.C) chromosomes.D) nuclei.E) centromeres.

IN 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.

WITHIN INTERPHASE, WHICH OF THE STAGES IS DEFINED BY THE ACTIVE REPLICATION OF THE CELL’S GENETIC MATERIAL?

A) the Gap 2 phaseB) the mitotic phase C) the Gap 1 phaseD) the replitosis phaseE) the DNA synthesis phase

2 DIFFERENT FORMS OF CELL DIVISION 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

DIFFERENT FORMS OF CELL DIVISION 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 ***

MITOSIS

2 cellsIdentical to Parent

THE 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.

LET’S SEE THAT AGAIN - MITOSIS

End with 2 cells that are genetically identical to the parent and to each other.

THIS FIGURE DEPICTS:

A) mitotic anaphase.B) mitotic prophase.C) mitotic metaphase.D) mitotic telophase.E) meiotic anaphase I.

SEXUAL REPRODUCTION & MEIOSIS

What would happen if these cells were formed by mitosis?

MEIOSIS - AGAIN 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

= 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.

GENETIC RECOMBINATION – THE REASON FOR SEX

PROJECT 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.

KARYOTYPE

WHAT IS DIFFERENT ABOUT THIS KARYOTYPE?

DOWN’S SYNDROME

Why are only smaller chromosomes ever seen in trisomy?

WHICH 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.

A DIPLOID (2N) CELL UNDERGOES MEIOSIS. WHAT ARE THE PRODUCTS OF THIS DIVISION?

A) one polyploid gameteB) four haploid cellsC) four diploid cellsD) two haploid cellsE) two diploid cells

THE EGG CELLS OF A HORSE CONTAIN 32 CHROMOSOMES. HOW MANY CHROMOSOMES ARE IN THE HORSE’S LIVER CELLS?

A) 32B) 16C) 128D) 64E) 8

READ CHAPTER 7 ON INHERITANCE OF TRAITS