cell division

Audesirk, Audesirk & Byers part of Chapter 11

In second grade, my health teacher read us the book "Mickey the microbe," and I learned that bacteria could "multiply and divide;" I was envious since I was not going to learn how to multiply and divide until 4th grade.

Figure 4-10
Chromosome = colored body.

Figure 11-3
Understand: concepts of 2n is diploid, prophase, metaphase, anaphase.
interphase is when the cell actually functions -
unwound chromatin vs. condensed chromosomes
cell cycle:interphase G1, S, G2, mitosis
G = gap, S = synthesis
arrest in G1 if postmitotic these are the cells which age

Some cells do not divide, others do

In many cell types, for instance brain (CNS Neurons) and heart (myocardial cells) - not divide, which is why stroke and heart attack are so damaging (no new cells replaced by mitosis) vs. in intestines, cells are constantly replaced by mitoses from stem cells since, in that milieu, cells digest themselves.
Centromere (on chromosome) = kinetochore (where microtubules attach)

Figure 11-10
(This figure shows a lot and we will spend some time on it.)
homologues do not line up (contrast with meiosis, next lecture),
DNA had already doubled (S=synthesis)
prophase, centrioles, spindle
Centromere (on chromosome) = kinetochore (where microtubules attach)
later (metaphase) chromosomes line up at metaphase plate, centromeres divide
anaphase, chromosomes separate
telophase when cells separate followed by cytokinesis.

Cell division in eukaryotes to make genetically identical daughter cells
FUNDAMENTAL: multicellular, all cells have same genes (except germ cells)

Human chromosomes

Figure 11-6
observe at metaphase block w drug colchicine
(they are duplicated - sister chromatids.)

Figure 11-9
look different, i.e. where centromere is and size
46 chromosomes (23 pairs [since we are diploid, 2n] one from father and one from mother)
22 pairs of autosomes and 2 sex chromosomes, XX female, XY male
there are two homologues in a pair

Figure 11-13
Progress through cell cycle is controlled

Figure 11-14
Very specific molecules control progress through cell cycle.

Figure 11-15
Many of the signal transduction cascades control this cell cycle.

Figure E11-3
When things go wrong with these controls, cancer occurs.

Questions used in 2007 and 2008 related to this outline

If p53, the tumor suppressor, is mutated,
(a) chromosomes are not divided equally to the two daughter cells.
(b) the homologues never line up next to each other.
(c) chromosomes get stuck at the metaphase plate.
*(d) damaged DNA gets replicated.
(e) cyclin never gets made.

DNA polymerase had already duplicated the DNA to make two identical copies of all the genetic material. Where are these two copies?
(a) in the two kinetochores
(b) in the two centrioles
*(c) in the two sister chromatids
(d) in the two homologues
(e) one in the autosome, the other in the sex chromosome

If a cell exits from the cell cycle to function as a non-dividing cell, from which step does it exit?
*(a) G1, the first gap
(b) S, the synthesis phase
(c) metaphase
(d) cytokinesis
(e) mitosis

Retinoblastoma (Rb) informs us about normal vs abnormal regulation of cell division. When it was stated that cyclin dependent kinase phosphorylates Rb, what is Rb?
(a) some DNA
*(b) a protein
(c) an extracellular growth factor that signals the cell
(d) the centriole
(e) the sister chromatin

The centriole pair organizes a structure for chromosome motility called
(a) interphase.
(b) the metaphase plate.
(c) the karyotype.
(d) colchicine.
*(e) the spindle.

Where did the two homologues come from?
(a) one from the template strand, one from the complementary strand
(b) one from cyclin, one from cyclin dependent kinase
(c) one from the autosome, one from the XY pair
*(d) one from the mother, one from the father
(e) one from p53, one from retinoblastoma

What about mitosis in myocardial (heart muscle) cells?
(a) They undergo mitosis after DNA synthesis is complete.
(b) The p53 molecule cannot block cyclin phosphorylation.
(c) Growth factors present after stroke regulate mitosis in these cells.
*(d) They are in G0.
(e) Colchicine locks them in metaphase.

Why might you want to block mitosis with colchicine?
*A) to prepare a karyotype
B) because of all the DNA damage done by cyclin
C) in situations where p53 does not bind to the membrane growth factor receptor
D) to prevent eye cancer (retinoblastoma)
E) to give the homologues a chance to line up

When does the DNA replicate itself in a eukaryotic cell?
A) prophase
B) metaphase
C) anaphase
D) telophase
*E) interphase

When a eukaryotic cell undergoes mitosis
A) each daughter cell receives exactly half the genetic information in the parent cell.
*B) each daughter cell receives a nearly perfect copy of the parent cell's genetic information.
C) a haploid chromosomal number is passed on to each daughter cell.
D) genetic information is randomly parceled out to the daughter cells.
E) one of each of the two homologues goes to each daughter cell.

The cells of the intestinal epithelium are continually dividing
A) because they are in G0.
B) because p53 is mutated.
*C) to replace dead cells lost from the surface of the intestinal lining.
D) because they do not have autosomes, but they do have sister chromatids.
E) because that is where gametes are made.

If there are 12 chromosomes in an animal cell in the G1 stage of the cell cycle, what is the diploid number of chromosomes for this organism?
A) 6
*B) 12
C) 24
D) 36
E) 48

The microtubules of the mitotic spindle attach to a specialized structure in the centromere region of each chromosome, called the
*A) kinetochore.
B) nucleolus.
C) metaphase plate.
D) chiasma.
E) centriole.

In the human karyotype, you see X-shaped bodies.
A) Each side of the X is one of the strands (template or complementary) of the DNA double helix.
B) This appearance applies to the X chromosome only.
C) This is only the case for XXY (Klinefelter's syndrome) males.
D) At this stage, the genetic material is called "chromatin."
*E) Two copies of one chromosome are still connected at the centromere.

A homologous pair of chromosomes
*A) consists of two chromosomes, one from each parent, with the same genes.
B) consists of two chromosomes having identical alleles.
C) would be one chromosome after it has duplicated before mitosis.
D) might be found in one sperm cell.
E) is found only in haploid cells

Sister chromatids are
A) X chromosomes.
B) specialized gamete-forming cells.
C) inactivated chromosomes (Barr bodies).
D) the same as homologous chromosomes.
*E) duplicated chromosomes held together by a common centromere.

Questions used in 2002 relating to this outline (and other outlines)

Most people have two copies of chromosome 21. These two copies would be called
(a) alleles.
(b) tetrads.
*(c) homologues.
(d) spindles.
(e) centromeres.

A pair of sister chromatids might be X-shaped in the microscope
(a) only for the X chromosome.
(b) during the G2 of interphase.
(c) because of the centriole pair.
(d) in anaphase.
*(e) when they are joined at the centromere.

Karyotypes are produced from
(a) gametes.
*(b) cells arrested in metaphase.
(c) nuclei of myocardial dells.
(d) haploid cells.
(e) cells in meiosis.

A person has 44 autosomes plus one X chromosome plus one Y chromosome. Which statement is true for this person?
*(a) The Y chromosome came from the father.
(b) The X chromosome becomes a Barr body.
(c) The X chromosome could have come from either the father or the mother.
(d) The Y chromosome's inactivation is described by the Mary Lyon hypothesis.
(e) This person has Klinefelter's syndrome.

The kinetochore is most closely associated with
(a) interphase chromatin.
(b) the stamen.
(c) the G protein linked signal transduction cascade.
(d) the part of the gene to which steroid hormone receptors bind.
*(e) the centromere.

What is cytokinesis?
(a) the way useful energy is obtained after light excites an electron
(b) the arrest of neurons in adult human central nervous system in G1
*(c) the final processes of cell division
(d) how cAMP becomes inactivated
(e) a way to test for genetic or chromosomal abnormalities

A protein called p53 is
(a) coded by the C. elegans gene that promotes cell death.
(b) deficient in sickle cell anemia.
(c) the G protein coupled receptor.
(d) obtained from bacteria that live in hot springs.
*(e) a tumor suppressor.

This page was last updated 6/30/09

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