Exam 3- Mitosis and Chromosomes Flashcards
What is the cell cycle?
Orderly set of stages and substages between one division and the next
What happens prior to the next division?
- cell performs normal activities
- cell grows larger
- The number of organelles doubles
- DNA is replicated
What are the two major stages of the cell cycle?
- Interphase ( 90%)
- mitotic phase
What is the order of interphase?
G1 —> S—> G2
Do all cells turn over/ go through mitosis at the same rate?
No
Why do cells go through the cell cycle?
growth, cell replacement, Asexual reproduction
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
what is an example of non-cycling cells?
skeletal and neurons
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
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
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
What happens in the Mitotic Phase ( general)
- Mitosis
- Cytokinesis
What is Mitosis?
Nuclear division
- daughter chromosomes distributed to 2 daughter nuclei
What is cytokinesis?
cytoplasm division
- results in two genetically identical daughter cells
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
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
What are cyclins?
increase and decrease as the cell cycle continues
What are the internal factors at G1?
- P53 : protein that will stop G1 to allow for corrections
- Apoptosis if DNA is damaged beyond repair
What are the internal signals at G2?
Mitosis will occur if DNA has replicated properly. Apoptosis if DNA is damaged
What are the internal signals at M?
- spindle assembly checkpoint
- polo-like and aurora kinases: make sure the chromosomes are properly aligned
What are the Mitosis Promoting Factors ( MPF)?
-threshold amount
- cyclin + kinase = MPF
What is chromatin?
loosely coiled: intertangled
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?
23
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
