Cell Cycle Mitosis Flashcards
functions of cell division
Growth (usually multicellular organism), Asexual reproduction,Repair
Chromosome-
eukaryotic DNA molecule with proteins attached to it
Histones
chromosomal proteins that act as a spool for the DNA (DNA wounds twice around each histone)
Nucleosome
one unit of histone–DNA spool
pros and cons of tightly compact
benefit of tightly compact–no tangled, organized drawback–sometimes we need enzymes to access the DNA to copy it
Genome
cell’s total amount of DNA
gene
section of DNA codes for a protein that governs or controls a specific trait
how long is the DNA in a typical human cell?
3 meters DNA
how many genes do humans have
20k
Somatic cells amount of chromosomes
46
Gametes amount of chromosomes
23
chromatin
When not in cell division, chromosomes takes a granular appearance-contains one long linear DNA molecule associated with proteins
granular
grainy
each chromosome after duplication
consists of 2 sister chromatids-which are identical copies of one another
centromere
found in the middle of each chromatid and holds the chromatid together
mitosis (technical definition)
division of the nucleus
during process of mitosis-what happens to sister chromatids?
Sister chromatids are pulled apart and function as chromosomes
cytokinesis
division of the cell
what is mitosis followed by?
cytokinesis
fertilization–chromosomes
23 chromosomes from mother’s egg join with23 chromosomes from a father’s sperm to form 46 in a fertilized egg
karyotype
chromosomal constitution of 46 chromosomes that humans have. 2 copies of 23 (1-22 and xx or xy)
xx
female
xy
male
down syndrome
3 copies of chromosome 21
meiosis
Gametes in person are produced by meiosis (takes place in germ cells), which halves # of chromosomes and only occurs in gonads
M phase
Mitosis and cytokinesis. When cell divides. Stages—prophase, prometaphase, metaphase, anaphase, telophase
Interphase
Rest of cell cycle. Living its life. Phases—G1, S, G2
G1 phase
First gap/growth. Growth of cell.
G0
Permanent G1–many cells. Include neurons after certain age.
S phase
Synthesizing/copying DNA. Only cells destined to divide get here.
G2 phase
gap growth 2Completes prep for cell division
Mitotic spindle
Fibers made of microtubules and proteins, forms during prophase, Assembly begins at the microtubule organizing center, or MTOC
centrioles number
(2 centrioles copy to 4 precell division)
microtubule organizing center, orMTOC
centrosome
Colchicine
poison produced by plants that blocks microtubule assembly
Animals v plants–centrioles
animals have a pair of centrioles at the centrosome + plants lack centrioles
Interphase
Nucleus is defined; Two centrosomes (centrosome has replicated) are located outside of the nucleus; (4 centrioles) Microtubules extend from centrosomes, in asters- very short–radial shape like wheel spokes; Chromosomes are duplicated, inchromatin form
Prophase
Chromatin condenses intochromosomes; Nuclear envelope breaks intosmall vesicles; nucleolus disappears; Mitotic spindle starts to form, radiates out from the centrosome; Centrosome moves away from each other, (pair of centrioles ineach centrosome that has earlier duplicated)
Prometaphase
Microtubules extend toward middle of cell and attach tokinetochores, Chromosome pulls back and forth until itsettles halfway between the poles (opposite ends of the cell), Microtubules that do not attach to kinetochores attach to other microtubules,
kinetochores
structures of proteins and DNA found on either side of the centromere
- Metaphase
Centrosomes are atopposite poles; Chromosomes line up at metaphase plate-the middle of the cell, or the equator of the cell; Kinetochores are attached tomicrotubules; Spindle–entire apparatus of microtubules– is present
Anaphase
Centromeres of chromosomes separate, thus separating the sister chromatids; Each chromatid is now called a chromosome; Kinetochore microtubules shorten so chromosome move toward the poles; By end of anaphase, duplicate sets of chromosomes areon opposite ends
Telophase
Daughter nuclei form at two poles, nuclear envelopesstart to reform; Chromosome becomeschromatin; Cytokinesis begins
Cytokinesis in animal cells
Involves cleavage- appearance of cleavage furrow, which begins as a shallow groove near the metaphase plate–equator of cell. Microfilaments pull like drawstrings until two new cells are formed
Cytokinesis in plant cells
During telophase, cell plate forms-vesicles join in the middle of the cell. Cell wall materials (cellulose) collect in cell plate as it grows. Cell plate enlarges untilthe membrane fuses with the plasma membrane
binary fission
reproduction of prokaryotes. Bacteria contain single chromosome consisting of DNA arranged in a double helix circle. Chromosome attaches to plasma membrane and replicates. Plasma membrane grows in between the replicated DNA and splits the cell
Molecular control system
Regulated at certain checkpoints by internal and external controls
Cell-Cycle Checkpoints:
internal control. cell cycle in animal cells will stop at certain points, and will only continue if important events in that stage havebeen completed correctly
G1–checkpoint
system will stop and cell can grow further if necessary before a new round of DNA replication. Cell can check that the environment is favorable for cell division before the S phase
G2–checkpoint
Another Size checkpoint. also checks that DNA replication iscomplete before mitosis
metastasis
spread of cancer cells beyond original site
third checkpoint in mitosis
in metaphase checks that each chromatid has a spindle fiber that’s attached to it before anaphase
Cyclins and Cyclin-Dependent Kinases function
help at checkpoints; All eukaryotic cells essentially use the same molecules to control the events of their cell cycle
Protein kinases
enzymes that catalyze the transfer of a phosphate group to a target protein. Since they depend on the activity of the cyclins, they are called cyclin-dependent kinases.
Cyclins-
Their concentrations vary in a cyclical fashion during mitosis. Must bind to the kinases for the kinases to become active
M-Phase promoting factor (MPF)-
protein kinase that increases rapidly right before mitosis and falls rapidly toward end of mitosis; Kinase must be bound to a specific cyclin in order to work.
What triggers different steps of cell cycle?
Different cyclin-Cdk complexes trigger different steps of the cell cycle
Cancer cells
Divide excessively, invade other tissues, do not respond to internal orexternal control signals, such as density-dependent inhibition oranchorage dependence (perhaps make growth factors themselves)- Either have mutations in proliferation genes or antiproliferation genes.
oncogene
mutation in proliferation gene causesthe protein produced by the gene to be overexpressed leading to excessive cell multiplication
a mutation in a tumor-suppressor gene
mutation in anti-proliferation gene can release a cell from the normal restraints on cell multiplication, leading to excess cell division
Malignant cells
Cancer. can have an abnormal number of chromosomes, an abnormal metabolism. Loses attachments and can spread to other tissues, such as blood, lymph vessels, other organs- can form new tumors.
benign tumor
If abnormal cells remain at original site –can be easily removed
cancer formation
Single cell undergoes transformation. If cell does not get destroyed by body, can proliferate to form tumor- mass of abnormal cells within otherwise normal tissue If cells invade one or more other organs–>cancer.
transformation of single cell
conversion of normal cell into cancer cell
Cdk inhibitor proteins
block assembly or activity of one or morecyclin-Cdk complexes.
p21
cdk(inhibits MPF) inhibitor protein. p21 will stop the cell cycle when DNA is damaged, allowing the cell time to repair the damaged DNA.
External Signals (cell division)
Growth factor, Density-dependent inhibition, Anchorage dependence, Survival factors
Growth factor
type of protein released by body cells that stimulate other cells to divide
platelet derived growth factor
released by platelets in a wound that causes the surviving cells to replicate, healing the wound
Density-dependent inhibition
crowded cells stop dividing at certain population densities.
Anchorage dependence
cells must be attached to somethingunderneath in order to divide
Survival factors
are necessary for cells to live- if not, they undergo apoptosis
apoptosis
programmed cell death. Helps form fingers during development; helps tissues remain the appropriate size.
activation of Protein kinases
Activated only at certain times throughout the cell cycle, after which they quickly become deactivated. Switched on and off through proteins called cyclins.
MPF effects
Causes the chromosome to condense, nuclear membrane to break down, and microtubules to form into spindle fibers;
p21 production
produced when the RNA is stimulated by a protein called p53. Mutations in p53 gene lead to higher rates of cancer.
