bio test three

Name the steps of Prophase.

1. Chromosomal material condenses to form compact mitotic chromosomes (chromosomes are two chromatids attached at the centromere).
2. Cytoskeleton dissembles and mitotic spindle is assembled.
3. Golgi complex and ER fragment, nuclear envelope disperses.

Name the steps of Prometaphase.

1. Chromosomal microtubules attach to kinetochores of chromosomes.
2. Chromosomes are moved to spindle equator.

Name the steps of Metaphase.

1. Chromosomes align along metaphase plate, and they are attached by chromosomal microtubules to both poles.

Name the steps of Anaphase.

1. Centromeres split and chromatids separate.
2. Chromosomes move to opposite spindle poles.
3. Spindle poles move farther apart.

Name the steps of Telophase.

1. Chromosomes cluster at opposite spindle poles.
2. Chromosomes become dispersed.
3. Nuclear envelope assembles around chromosome clusters.
4. Golgi complex and ER reform.
5. Daughter cells formed by cytokinesis.

What is required for mitosis and therefore occurs during G1 to G2?

centrosome duplication

Name five components of the mitotic spindle.

1. a pair of centrioles
2. the associated matrix of the centrioles
3. astral microtubules
4. chromosomal (kinetochore) microtubules
5. polar microtubules

What is the exception of polar spindle complex formation?

They can form in the absence of centromeres through the action of (-) end directed microtubule motors

What is the kinetochore and what level of activity does it have?

it's the junction between mitotic microtubules and the chromosomes and it's a highly active zone

What do labeling studies demonstrate?

that mitotic microtubules are not stable but rather are constantly cycling tubulin subunits in a process known as tubulin flux (~1um/min)

Give three details of metaphase chromosomes. Draw a metaphase chromosome.

1. tightly would complex of DNA and protein (chromatin)
2. DNA content of each sister chromatid is identical
3. cohesion between sisters is established in S-phase

What does the regulation of APC activity control?

degradation of cyclin B and entry to anaphase to end mitosis

What does full APC activiation require?

MPF phosphorylation of several APC subunits that are low affinity target thereby requiring peak levels of MPF

What blocks anaphase entry?

the presence of free (unattached) kinetochores => drugs that disassemble spindle (colchicine) will arrest mitosis

What is Cdh1 and what is its function? What activates it? What deactivates it?

It's an APC adaptor protein (specificity factor) that directs APC activity to M-Cyclins. Activation = Cdc14 phosphatase Deactivation = G1 CDK kinase

What initiates anaphase?

anaphase promoting complex (APC)-dependent unlinking of sister chromatids

What does APC do?

acts to degrade anaphase inhibitor that otherwise block inactivation of cohesins

What does MPF do to SMC?

targets and destabilizes SMC proteins that are part of the cohesin complexes

What is phosphatase activity required for?

the reassembly of the nuclear envelope

What is chromosomal material required for?

to nucleate formation of nuclear membrane (any chromosome will do, even from another species)

What does cytokinesis depend on?

actin/myosin based contractile ring apparatus

What is the net result of DNA packaging/chromosome creation?

DNA is packaged into a mitotic chromosome that is 10,000 fold shorter than the extended length of DNA

Name the six steps of DNA packaging/chromosome creation.

1. short region of DNA double helix
2. "beads-on-a-string" form of chromatin
3. 30 nm chromatin fiber of packed nucleosomes
4. section of chromosome in an extended form
5. condensed section of chromosome
6. entire miotic chromosome

How many times is a strand of DNA wound, how is it wound, and what does it wind around?

~twice in a left-handed coil / a histone octamer

What is the equation for a histone octamer?

[H2A+H2B]2+[H3+H4]2

What does histone H1 do?

it associates with DNA at entry and exit site from nucleosome in two alternate positions

What are histones and what is their basic purpose?

they're small basic proteins that neutralize the negative charge on the phosphate backbone of DNA

Describe the positioning of the nucleosome structure.

[H3+H4]2 sits with one heterodimer of [H2A+H2B] above it and another [H2A+H2B] below it

What is within a histone?
What extends out of a histone?
What is on the outside of a histone?

3 a-helices
N-terminal tails
two turns of DNA

Name the two types of chromatin.

1. Eu:euchromatin = diffuse chromatin (active)
2. He:heterochromatin = compacted chromatin (silent)

Name the two types of heterochromatin.

constitutive (very silent) and facultative (specifically silent)

What is required for x-chromosome inactivation? How does this inactive chromosome exist? When does it occur?

a form of dosage compensation / in the form of highly condensed heterochomatin that is visible at the nuclear envelope called Barr Body / early in development

Is inactivation of the x chromosome selective or random? Reversible or irreversible?

random and irreverible

What controls inactivation?

histone methylation status of Xist gene part of x-chromosome inactivation center which generates a non-coding RNA that specially targets and inactivates x-chromosome in cis

Where and why does reactivation of x-chromosome?

occurs in primordial germ cells so that both x chromosomes are active and all gametes receive an active euchromatized x.

Name the three components of a nucleotide.

1. a 5-carbon ribose sugar
2. a 5' phosphate group
3. a 1' base pair

What is the difference between a ribose sugar and a deoxyribose sugar?

ribose has a 2' OH and deoxyribose has a 2' H

Describe what a purine is and name them.

A nitrogenous base with a pentagon and a hexagon / adenine and guanine

Describe what a pyrimidine is and name them.

A nitrogenous base with a single hexagon / cytosine, thymine and uracil

Name the nucleobases.

adenine, guanine, uracil, thymine, and cytosine

Name the nucleosides.

ribonucleosides: adenosine, guanosine, uridine, and cytidine
deoxyribonucleosides: deoxyadenosine, deoxyguanosine, deoxyuridine, deoxycytidine, thymidine

Name the nucleotides.

ribonucleotides:
monophosphates = AMP, GMP, UMP, CMP
diphosphates = ADP, GDP, UDP, CDP
triphosphates =ATP, GTP, UTP, CTP
deoxyribonucleotide:
mono = dAMP, dGMP, dUMP, TMP, dCMP
di = dADP, dGDP, TDP, dCDP
tri = dATP, dGTP, TTP, dCTP
cyclic nucleotide:
cAMP, cGMP, c-di-GMP, cADPR

What does the assembly of nucleic acid strands involve?

the formation of a phosphodiester bond between the 5' phosphate group of one nucleotide/side and the 3' hydroxyl group of another nucleotide/side

Name the bonding pairs of bases and how many hydrogen bonds they have.

adenine and thymine / adenine and uracil (2 H bonds) // cytosine and guanine (3 H bonds)

Name the four arrangements of DNA and describe them.

1. B DNA: normal
2. A DNA: wider and shorter than normal
3. Z DNA: thinner and longer than normal
4. Triple-Helical DNA: three strands instead of the normal two

What type of topology can circular DNA adopt?

supercoiled

Name the type of DNA that migrates the fastest and the type that migrates the slowest through a gel.

supercoiled = faster, circular = slower

When is DNA underwound? Overwound?

>10bp per turn ->(-)SC
<10bp>(+)SC

Give steps of DNA creation.

1. three entities (phosphate group, deoxyribose sugar, and nitrogenous bases)
2. combine entities into a deoxyribonucleotide
3. combine two nucleotides based on bases
4. combine these pairs together through phosphodiester bonds

Give steps of RNA creation.

1. three entities (phosphate group, ribose sugar, and nitrogenous bases [U instead of T])
2. combine entities into a ribonucleotide
3. combine ribonucleotides to form a single strand of ribonucleotides

What do catalytic RNA's form?

ribozymes

Name the three theories of DNA replication and describe them.

semiconservative: one black ->two black and red->two black and red, two red
conservative: one black -> one black, one red -> one black, three red
dispersive: one black -> two black and red mixed -> four black and red mixed

Name the experiment that proved that the semiconservative theory for DNA replication was correct. What mediums were used?

Meselson-Stahl experiment / N14 and N15

In oder for DNA replication to occur, what two things must be present?

an open template and an open 3'OH

What is helicase's job? Topoisomerase's job?

unwinds DNA / twists DNA and cuts DNA backbones to remove knots and other entanglements

What happens when M cells and G1 cells combine?

mitotic pathways starts indicating that there's a diffusible factor in M-phase cells

What happens when S cells and G1 cells combine?

the new cell will replicate both DNA's because S-phase cells have activators that influence the nuclei of G1 cells (if more S cells than G1 cells are used, then G1 cell DNA will enter replication faster)

What happens when S cells an G2 cells combine?

only S-phase DNA is replicated while G2 remains refractory to S-activator (which indicates that S-phase CdkC can't find any pre-replication complexes on DNA). This ensures that DNA is only replicated once.

What happens when G1 cells and G2 cells combine?

neither replication nor mitosis is induced, which indicates that both S and M inducers are transient.

What inhibits CDK?

Wee1

What activates CDK?

Cdc25

What happens with a deficiency of Cdc25 and an excess of Wee1?

elongated cells and increased G2

What happens with a deficiency of Wee1 and an excess of Cdc25?

small cells and decreased G2