Exam 3- Mitosis and Chromosomes Flashcards by michelle yanez

What is the cell cycle?

Orderly set of stages and substages between one division and the next

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What happens prior to the next division?

cell performs normal activities
cell grows larger
The number of organelles doubles
DNA is replicated

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What are the two major stages of the cell cycle?

Interphase ( 90%)
mitotic phase

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What is the order of interphase?

G1 —> S—> G2

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Do all cells turn over/ go through mitosis at the same rate?

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Why do cells go through the cell cycle?

growth, cell replacement, Asexual reproduction

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What are the different kinds of rates that cells could go through?

constantly cycling: always cycling
inducible: can cycle when signaled
non-cycling ( G0) - never cycle

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what is an example of non-cycling cells?

skeletal and neurons

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What happens during G1 ( specific)?

GROWTH
- recovery from previous division
- cell doubles organelles
- make raw materials for DNA synthesis
- the longest part of the interphase

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What happens during the S phase?

SYNTHESIS
- DNA replication
- Chromosomes enter w/ 1 chromatid each
- Chromosomes leave w/ 2 identical chromatids each
- shorter than G1

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What happens in G2?

GROWTH
- between DNA replication and the onset of mitosis
- cell synthesis proteins necessary ( lots of microtubules
-shorter than the S phase

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What happens in the Mitotic Phase ( general)

Mitosis
Cytokinesis

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What is Mitosis?

Nuclear division
- daughter chromosomes distributed to 2 daughter nuclei

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What is cytokinesis?

cytoplasm division
- results in two genetically identical daughter cells

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What are the external signals that control the cell cycle?

Growth factors
- received at the plasma membrane
- cause completion of cell cycle
- protein based
- often operate w/ second messenger mechanisms
- regulate cell division

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What are the internal signals that control the cell cycle?

cyclin dependant kinases
stops at G1, G2, or M
allows time for any damage to be repaired
Mitosis Promoting Factor

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What are cyclins?

increase and decrease as the cell cycle continues

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What are the internal factors at G1?

P53 : protein that will stop G1 to allow for corrections
Apoptosis if DNA is damaged beyond repair

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What are the internal signals at G2?

Mitosis will occur if DNA has replicated properly. Apoptosis if DNA is damaged

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What are the internal signals at M?

spindle assembly checkpoint
polo-like and aurora kinases: make sure the chromosomes are properly aligned

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What are the Mitosis Promoting Factors ( MPF)?

-threshold amount
- cyclin + kinase = MPF

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What is chromatin?

loosely coiled: intertangled

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What is a chromosome?

tightly condensed; visible

When is DNA visible?

DNA is visible when it is a duplicated chromosome; getting ready to divide

What are all the cells in our body? diploid or haploid?

Diploid= 2n

What are the only cells in the body that are haploid?

sperm and egg cells - haploid = n

How many different types of chromosomes do humans have?

How many chromosomes do most cells in the human body have?

46 - 23 from father - 23 from mother

what is a karyotype?

the way in which we image chromosomes? - all 23 pairs of chromosomes laid out - 1-22 are autosomes - 23 is the sex chromosomes

What are autosomes?

specify body traits

What are homologous chromosomes?

homologs - two chromosomes that carry the same kind of genetic traits

how do you get a karyotype?

- get a blood sample - take dividing white blood cells and stop them before they divide - photograph chromosomes - match homologs

Do homologs carry the same form of genes?

NO, carry the same genes but not the same forms of that gene

Where does the centrosome start at the beginning of the mitotic phase?

- outside of the nucleus

What is the MTOC?

microtubule organizing center - the job is to organize the mitotic spindle - contains many fibers - each composed of a bundle of microtubules

How do the centrioles move through interphase?

-2 barrel shaped centrioles - oriented at 90* angles - centrosome replicated in S phase - centrosomes in G2 move toward opposite sides of the cell - forming the poles

What occurs in prophase?

make space for movement of genetic material -nuclear envelope disintegrates - nucleolus disappears - spindle begins to take shape - two centrosomes move away from each other -form microtubules asters

What are asters

microtubules in star like arrays

What happens in Prometaphase?

- centromere of each chromosome develops 2 kinetochores - hook up specialized microtubules

what are the kinetochores and how do they work?

specialized protein complex - one over each sister chromatid - physically hook sister chromatids up with specialized microtubules

What are the three specialized microtubules?

- kinetochore - astral - polar

What are the kinetochore fibers?

anchor to kinetochore proteins and hook up with sister chromatids

what are astral fibers?

stabilize position of the pole - run from pole to plasma membrane

what are the polar fibers?

run from the pole toward midline of cell that don't attach to anything

What happens in metaphase?

chromosomes are lined up on the metaphase plate - chromosomes pulled around by the kinetochore - 46 chromosomes all lined up in the middle

What property of microtubules lets it pull the chromosomes?

microtubules have the ability to simultaneously lengthen and shorten.

What happens in anaphase?

- centromere dissolves releasing sister chromatids - sister chromatids separate ( daughter chromosomes) -spindle microtubules attached to kinetochores shorten, while those not attached lengthen to push poles apart

What happens in telophase?

spindle disappears - now two clusters of daughter chromosomes - still 2 of each type with all types represented - clusters are daughter nuclei - nuclear envelopes form around the two incipient daughter nuclei - chromosomes uncoil and become diffused chromatin again - nucleolus reappears in each daughter nucleus

What occurs during cytokinesis?

division of cytoplasm - allocates mother cell's cytoplasm equally to daughter cells - encloses each in its own plasma membrane - often begins in anaphase - cleavage furrow appears between daughter nuclei - formed by contractile ring of actin filaments

How do prokaryotes reproduce?

Asexual reproduction - binary fission

Are mitosis and apoptosis opposing forces? T/F

True

What are caspases?

Apoptosis enzymes - ordinarily held in check by inhibitors - can be unleashed by internal or external signals

What are some diseases that can result from too much apoptosis?

- Alzheimer - Huntington - Parkinsons

What are some diseases that can result from too little apoptosis?

- cancer - autoimmune disease

Why does our body need apoptosis?

- remove abnormal cells - keep a balance within the body

What are the intrinsic pathways that lead to apoptosis?

UV, Chemotherapy, ER stress

What are the extrinsic pathways that lead to apoptosis?

death ligand and receptor activates enzymes to trigger apoptosis