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Biol 1441: Chapter 12
Meisosis |
sex cells (gametes)
Produce nonidentical daughter cells |
Gametes |
egg, sperm (23 chromosomes)
|
Mitosis |
somatic cells
Body cells (46 chromosomes)
Every single cell in your body (except sex cells!)
Produces identical daughter cells
Division for growth and repair |
Chromosomes |
supercoiled DNA
Only present when cell is getting ready to divide
(after the DNA is replicated)
Visible with a light microscope |
All other times DNA is...
|
Chromatin |
Gametes |
23 total chromosomes
|
Somatic Cells
|
46 total chromosomes
|
Sister Chromatids
|
Identical DNA molecules
|
Sister chromatids attached at...
|
Centromere |
One chromosome that duplicates into...
|
TWO sister chromatids
|
Two main phases of the cell cycle
|
1. Mitotic (M) Phase
2. Interphase |
Mitotic (M) phase
|
mitosis and cytokinesis
|
Mitosis
|
the division of the nucleus
|
Cytokinesis |
the division of the cytoplasm
|
Interphase
|
cell growth & copying of DNA
~90% of the cell cycle |
Sub-phases of Interphase
|
G1 phase
S phase
G2 phase |
G1 |
Cell growth and work
|
S1 (DNA Synthesis)
|
Copy DNA
|
G2
|
Preparing for mitosis, organelle replication
|
5 Phases of Mitosis
|
Prophase
Prometaphase
Metaphase
Anaphase
Telophase |
Prophase |
Chromatin condenses into chromosomes (now visible)
Mitotic spindle begins to form
Centrosomes begin to move apart |
Mitotic Spindle
|
Controls movement of chromosomes using microtubules
|
Kinetochores |
protein associated with the centromere (each sister chromatid has one)
|
Cytokinesis
|
formation of cleavage furrow
|
Cleavage Furrow
|
groove in the cell surface near the metaphase plate
|
Binary Fission
|
"Division in half" |
Specific checkpoints |
where cell cycle stops until a go-ahead signal is received |
3 Major Checkpoints
|
G1 Checkpoint
G2 Checkpoint
M Checkpoint |
G1 Checkpoint
|
cell is large enough to divide, enough nutrients are available to support the resulting daughter cells |
G2 Checkpoint
|
DNA replication in S phase has been completed successfully
|
M Checkpoint
|
all of the chromosomes
are attached to the mitotic spindle by a kinetochore |
Cyclins |
Regulatory proteins involved in cell cycle control-concentration varies (cyclically)
|
Cyclin-dependent kinases (Cdks)
|
Regulatory proteins involved in cell cycle control- concentration constant
|
Oncogenes
|
Mutated or amplified genes involved in cell growth and differentiation
|
Proto-oncogene
|
normal non-mutated oncogene
|
Tumor Suppressors
|
Function to inhibit cell growth- cell cycle check points, DNA damage repair
Recessive - Loss of function |
Internal Signal
|
kinetochores not attached to spindle microtubules, send a molecular signal that delays anaphase
|
External Signal
|
growth factors, proteins released by certain cells that stimulate other cells to divide
|
{External Signals}
Density-dependent inhibition |
crowded cells stop dividing
|
{External Signals}
Anchorage dependence |
cells must be attached to a substratum in order to divide
|
Benign Tumor
|
If abnormal cells remain at the original site
|
Malignant Tumor
|
invade surrounding tissues & metastasize
Moves to other parts of the body
May form secondary tumors |