New Deck for Exam 4: Chandra Flashcards
What is the centromere?
-point of constriction
kinetochore?
-attachment site for microtubules
how to chromatids stay attached at centromere?
cohesin
interphase includes what?
G1, S, G2
what are the check points in the cell cycle?
G1/ S checkpoint: Cell decides to divide, primary point for external cell influence
G2/S checkpoint: cell makes comiment to mitosis, make sure DNA replicated properly
Late metaphase: cell makes sure all chromosomes are attached to spindle
What are the irreversible points in the cell cycle?
- after synthesis or DNA replication
- separation of sister chromatids
How do bacteria divide and what are the three facts associated with bacterial division?
- bacteria cells divide by binary fission
1. Singular circular chromosome
2. replication is clonal
3. there is no sexual life cycle
chromosomes are made up of?
- 60 precent protein, 40 precent chromatin
What is the process of binary fission
- starts at orgin of replication
- procceeds biodirectionally to site of termination
- septum forms to divide cell into two, FTZ protein makes the rings that seperates the bacteria
In the NONDIVIDING NUCLEUS
compare heterochromatin and euchromatin
heterochromatin: chromatin packed tightly, not expressed
euchromatin: expressed, not packed tight, when work happens
what is the best way to store DNA
nucelosome
what is the nucelosome and histone?
- complex of DNA and histone proteins, promote and guide coiling of DNA
- histone is + charged , attracted to - phosphate group in dna
-DNA duplex coiledaround 8 histone proteins every 147 base pairs
solenoids?
nucelosomes wrapped into higer ordered coils, usual state of nondividing chromatin
how is chromatin in solenoid arranged?
arranged around scaffold of protein for maximum compaction in mitosis, looping is aided by CONDENSIN PROTEIN
What are the levels of chromosome organization?
- starts as DNA double helix, then solenoid
- chromatin loop, looks like magnet C shape
- chromatin loop, looks like flowers coiled around scaffold
- chromosomes in the form of idenical sis chromatin, only occurs when cells are about to divide
prior and after replication:
prior: each chromosome is composed of a single dna molecule
after: each chromsomes is comp[osed of two idenical DNA molecules
visable as to chromosome as they become more condensed
-held together by cohesion pro.
Order of mitosis?
- prophase
- prometaphase
- metaphase
- anaphase
- telophase
order of cell cycle?
- G1
- S
- G2
- M
- Cytokenesis
What happens in G1
primary growth phase, longest phase
what happens in S
Dna replication
what happens in G2
organelles replicate, microtubles organise, use motor pro. to coil tightly, chromatids stay attached at centromere by cohesin pro., centromeres replicate
cytokensis
seperation of 2 new cells
kinetochore:
attachement site for microtubles
cytokenesis vs kinetochore
congression?
chromosomes move to center of cell
aster?
array of microtubles
sexual life cycle
made up of meiosis and fertilization
diploid cell
humans are diploids, somatic cells of adults have 2 sets of chromosomes
haploid cell
gametes only have one set of chromosomes untill fertlized with sperm
crossing over?
allows homologous to exchange coromosomal material
chiasmata?
site of homologous crossing over, 2-3 crossing over per chromosome
1st meiotic division is called what
reduction division
is there DNA replication BETWEEN MEIOTIC DIVISIONS
NO
2nd meiotic division does not…?
further reduce the number of chromosomes
meiosis 1 and 2 phases:
- prophase 1
2.metaphase 1 - anaphase 1
- telophase 1
- prophase 2
- metaphase 2
- anaphase 2
- telophase 2
what are the final products of meiosis 2?
- 4 cells containing haploid sets
- in animals, gamete is develped
synapsis?
during early prophase 1..
- homologous become closely associated
- includes formation of synaptonemay complexes
what happens in prophase 1 of MEIOSIS
- spindle forms
- chromosomes coil tighter
-crossing over occurs - each chromosome made up of 2 sis chromatids
- remain attached to chisamata
what happens in metaphase 1 of MEIOSIS
- chiasmata holds homologous together after crossing over
-microtubules from each pole attach to each homologue
-homologues are lined in the middle
what happens in anaphase 1 of MEIOSIS
- microtubles of spindle shorten
- chiasmata breaks
homolouges are seperated from each other and moved to opposite ends of poles - each pole has a complete hapolid (23) set of chromosomes
what happens in telophase 1 of MEIOSIS
- nuclear envelope reforms
- sister chromatids are no longer identical
- cytokinesis may/may not occur after telophase 1
what are the steps of meiosis 2?
nondisjunction?
faliure of chromosomes to move to oppositve poles nuring meiotic division
aneuploid gametes
gametes with missing or extra chromosomes, causeif miscarrage
cyclin dependent kinase
- enzyme that phosphlorates protiens.
-primary mechinism of cell cycle control
-partner with different cyclins during different parts of cell cycle
-CDK controlled by phosphloration
what do growth factors do?
override cellular control that can inhibit cell division
trigger intercellular signaling systems
genes that commonly cause cancer
- proto-oncogene
- normal cell gene that becomes mutated - tumor supressor genes
- messes up with P53 that moniters if DNA is made how it should be
-generally haults cell division and repairs enzymes if damage to dna
- absent in cancer genes
what is the product of meiosis 1
2 daughter cells with one homologue from each chromosome pair
what is the product of meiosis 2
does not farther reduce the number of chromosomes, but separates daughter cells to create 4?
what is special to prophase 1 in meiosis 1
homologous chromosomes pair snypasus and crossing over occur
meiosis vs mitosis in metaphase 1:
meiosis: paired homologous chromosomes align on metaphase plate
mitosis: individual homologues allign on metaphase plate
