Mtc: Jan 4 Part 2- Chromosome Function And Cell Cycle Dynamics

Front 1

What are the minimum requirements of 3 functional elements that turns a simple DNA molecule into a chromosome.

Back 1

1)Centromere
2) Telomere
3) Origin of Replication (aka Autonomous Replicating Sequence (ARS))

Front 2

Why are centromeres essential?

Back 2

-Spindle formation
-Chromosomal segregation
-Control of chromosome copy number

Front 3

Describe the physical components of a centromere?

Back 3

-Protein complex (kinetochore) for attachment of mitotic spindle
-Human centromeric sequence 171 bp repeated thousands of times (α-satellites)
-Bounded by non- α-satellites centric heterochromatin

Front 4

How can a neocentromere form?

Back 4

centromeres that appear in chromosomal regions without any alpha-satellite repeats

Front 5

How many active centromeres per chromosome?

Back 5

One

Front 6

Generally Describe Telomeres.

Back 6

-TTAGGG]n (highly conserved)
-Telomere associated protein protects Uneven 3’ single stranded “over-hang”
-Telomere-associated proteins
-Stabilize chromosome ends
-Facilitate pairing of homologous chromosomes during meiosis
-Ensure complete DNA replication
-Localize chromosomes within the nucleus

Front 7

What have been identified to either forms he kinetochore or mediate its function?

Back 7

Centromeric proteins (CENP)

Front 8

Patients with what connective tissue disorder have high levels of antibodies against centromeric proteins?

Back 8

Scleroderma

Front 9

Chromosomal Non-disjunction (Give an example)

Back 9

A condition where abnormal recombination around the centromeric region results in chromosomal rearrangements such as Robertsonian translocations

Front 10

Describe the Origin of Replication.

Back 10

-Initiation of DNA replication
-No consensus sequence identified in human
-Large number of origins of replication per chromosome
-Euchromatin regions replicate early in cell cycle
-Heterochromatin regions replicate late in cell cycle

Front 11

_______ _____ is expected after each round of DNA replication, and is a hallmark of aging cells.

Back 11

Telomeric shortening

Front 12

What regenerates telomeric length and helps maintain length of young cell when increased in regards to cancer cells and stem cells?

Back 12

Telomerase

Front 13

______ strand synthesis during DNA replication results in truncation of telomeres with each cycle of DNA replication

Back 13

Lagging

Front 14

What are the components of the Human Artificial Chromosome?

Back 14

-Random Large Human DNA fragments
-Human Centromeric sequences
-Human Telomeric sequences

Front 15

At the end of the S-phase, sister chromatids bound together by ______.

Back 15

Cohesins

Front 16

What phase requires the presence of condensins? What does it require?

Back 16

-Metapahse
-Energy (ATP)

Front 17

What happens during prophase with the cohesins?

Back 17

-Cohesins along the chromosomal arms become phosphorylated and dissociated form the chromatins
-Cohesins at the centromeres stay intact and the sister chromatids are thus bound at the centromere

Front 18

Centrosome

Back 18

Microtubule organizing center of the cell

Front 19

Where are centrosomes located?

Back 19

Located near the nucleus during interphase

Front 20

What centrosomes surrounded by?

Back 20

Orthogonally arranged centrioles surrounded by a haze of pericentriolar material from which an array of microtubules extends out to the cell periphery

Front 21

What is the relationship between centrioles and microtubules?

Back 21

-Microtubules extend from the pericentriolar region to the cell periphery during interphase
-Microtubules have polarity (+end away from centrosome)

Front 22

Describe microtubules

Back 22

Cylindrical molecules or α- and β-tubulin

Front 23

Where does nucleation occur for a microtubules? What is carried out by?

Back 23

Nucleation event occurs at the centriole, carried out by γ-tubulin complex on the centrosome

Front 24

Where does assembly and dis-assembly occur for a microtubule occur?

Back 24

-Assembly and dis-assembly occur at the +end

Front 25

Describe what occurs at assembly and dis-assembly of microtubules.

Back 25

-High turnover rate
-GTP-dependent polymerization at the +end leads to growth (rescue)
-Depolymerization at the +end leads to shrinkage (catastrophe)
-Dynamic equilibrium
-Microtubules inhibitors (colchicines, vinblastine, vincristine, paclitaxel)

Front 26

Centrosome Cycle

Back 26

-Centrosome duplication
-Poorly understood
-Disassembly of interphase microtubules and assembly
-New microtubules formed from both centrosomes (asters)
-Aster migration to opposite sides of nucleus
-Bipolar mitotic spindle

Front 27

What are the 3 types of microtubules in mitosis?

Back 27

-Astral Microtubules (centrosome to 2 poles of cell=orientation)
-Kinetochore microtubules (Centromere to kinetochore-->seeking and capturing chromosomes)
-Polar microtubules

Front 28

Role of Astral microtubules (mitotic spindle)

Back 28

-CEntrosome orientation

Front 29

Role of Kinetochore microtubules (mitotic spindle)

Back 29

Seeking and capturing kinetochore

Front 30

Role of Polar microtubules (mitotic spindle)

Back 30

-Zone of interdigitation
-Pushing centrosomes apart

Front 31

What is the name of the process in which microtubules are constantly gaining tubulin dimers at the +end and losing them at the -end?

Back 31

Microtubules treadmilling

Front 32

Microtubules are in _____ ______ at the +end, with alternating ____ and _____ events.

Back 32

-Dynamic equilibrium
-Catastrophe and rescue events

Front 33

(Mitotic spindle) There is a _____ force applied at the -end of the kinetochore microtubules, and an ______ force applied by the +end of the polar microtubules on the telomeric region

Back 33

-Pulling
-Pushing

Front 34

What is the spindle-attachment checkpoint?

Back 34

-A ready state in which anaphase cannot ensue until all kinetochores have been properly attached

Front 35

What is the tension of the mitotic spindle believed to set up by molecular events?

Back 35

-Results in a state of quasi-stabiliy of the spindle that is poised to be changed when cellular signals for entry into anaphase is delivered

Front 36

What for bivalent chromosomes (tetrads)? (Meiosis)

Back 36

Homologous chromosomes that have synapsed with each other=4 sister chromatids

Front 37

Where does the pairing of homologous chromosomes begin at? (Meiosis I)

Back 37

Telomeres

Front 38

Synaptonemal Complex (Meiosis I)

Back 38

Large protein complex that helps facilitate a homolog search and subsequent pairing

Front 39

Where do microtubules from one centrosome attach? (Meiosis I)

Back 39

To sister kinetochores of the same homolog

Front 40

How do sister chromatids of the same homolog bind together? Exactly where do they stay intact?

Back 40

-By Cohesins
-Remain intact between point of recombination and telomere

Front 41

In meiosis I what types of chromatids does recombination occur between?

Back 41

Non-sister chromatids

Front 42

When are the remaining cohesins cleaved?

Back 42

During Anaphase I

Front 43

What are the functions of Meiotic Recombination?

Back 43

-Holds homologous chromosomes together during metaphase I
-Contributes to genetic diversity among gametes

Front 44

Males with _____ recombination frequency toward _______region are non-randomly distributed.

Back 44

-Higher
-Telomeric

Front 45

Females with _____ recombination frequency near _______ region are non-randomly distributed.

Back 45

-Higher
-Centromere

Front 46

What is the basic molecule of inheritance?

Back 46

Chromosome

Front 47

Kinetochore

Back 47

Site of Attachment for the mitotic spindle during cell division

Front 48

______ contains RNA template that can extend the longer parent strand to provide extra bases upon which the _____ strand can be synthesized.

Back 48

-Telomerase
-Lagging

Front 49

What process is essential for correct chromosomal segregation?

Back 49

Binding of sister chromatids together by cohesins

Front 50

Nucleation

Back 50

An initiation event for the assembly of microtubules

Front 51

Rescue

Back 51

Growth of the microtubules=Continued GTP-dependent polymerization at the +ends

Front 52

Catastrophe

Back 52

Shrinkage of the microtubules=depolymerization results

Front 53

Dynamic Equilibrium

Back 53

alternating behavior of growth and shrinkage for microtubules

Front 54

When does the nuclear envelope disassemble?

Back 54

Prometaphase

Front 55

What is the dissolution of the nuclear envelope triggered by?

Back 55

-Phosphorylation of lamin proteins by the enzyme lamin kinase

Front 56

What must happen before the attachment of kinetochore to microtubules?

Back 56

Disassembly of the nuclear envelope

Front 57

When do the nuclear envelope fragments reassemble?

Back 57

-During early telophase

Front 58

When is the reassembly of the nuclear envelope complete?

Back 58

-Late telophase

Front 59

Zone of interdigitation

Back 59

Polar microtubules from one pole extend toward polar microtubules of the opposite pole and overlap to form this

Front 60

What is meiotic recombination mediated by?

Back 60

A protein complex that is highly conserved over evolution

Front 61

Where are meiotic recombination sites?

Back 61

-Non-randomly distributed along chromosomes
-More frequent at some regions=recombination hot spots
-less so in others (recombination cold spots)

Front 62

What does entry into anaphase require?

Back 62

Anaphase Promoting Complex (APC)

Front 63

Function of Anaphase Promoting Complex (APC)

Back 63

-Initiates cascade of events resulting in the cleavage of centromeric cohesins that bind the sister chromatids together

Front 64

2 Independent Processes that Move the Sister Chromatids Apart

Back 64

-During early anaphase (anaphase A): shortening of kinetochore microtubules at both ends predominates=initial seperation of sister chromatids (continued through anaphase)
-Latter Part of Anaphase (Anaphase B): polar microtubules elongate but at the same time begin to poleward sliding movement relative to the microtubules from the opposite pole that they overlap with=pushes centromeres apart

Front 65

Contractile Ring

Back 65

During late telophase, a group of cytoskeletal proteins including actins, myosins, and associated regulatory proteins begins to form this

Front 66

Where is the contractile ring located?

Back 66

-Plane of ring is perpendicular to the mitotic spindle
-Located where the metaphase plate once was

Front 67

What corresponds with the progressive tightening of the contractile ring?

Back 67

Cleavage furrow appears at the onset of cytokinesis

Front 68

How do microtubules relate to the contractile ring?

Back 68

-Play a role in localization of the contractile ring
-Maintains stability of the advancing cleavage furrow

Front 69

What organelles undergo fragmentation and reassembly during mitosis?

Back 69

-Endoplasmic Reticulum
-Golgi Apparatus

Front 70

What organelle does not undergo fragmentation and reassembly during mitosis?

Back 70

-Mitochondria=maintains intact

Front 71

Chiasma

Back 71

The location where the crossing over occurs in meiotic chromosomes