Chapter 6: Cell Division Flashcards
1
Q
cell division
A
- functions in reproduction, repair, and growth
- mitosis produces two genetically identical daughter cells known as clones with 2n
- meiosis results in haploid cells (n)
2
Q
chromosome
A
highly coiled and condensed strand of DNA
3
Q
structure of chromosome
A
-two SISTER chromatids (copies) joined by a centromere
4
Q
kinetochore
A
protein on centromere that attaches the chromatid to the mitotic spindle during cell division
5
Q
cell cycle
A
regular sequence of growth and division
6
Q
timing and rate of cell division
A
- affects the normal development, depending on the cell
- if not controlled by kinases allosteric interactions, can lead to cancer
7
Q
ratio of surface area to volume
A
- as cell grows, the volume grows faster than the surface area of cell membrane, which affects the exchange of nutrients and waste products
- determinant of when cell divides
8
Q
capacity of the nucleus
A
- need enough genetic information to provide nutrients for the cell
- determines when cell divides
9
Q
phases of the cell cycle
A
- interphase
- mitosis
- cytokinesis
10
Q
interphase
A
- chromatin is not condensed
- nucleus contains one or more nucleoli
- centrosome with 2 centrioles in cytoplamsm of animal cells
- plants lack centrosomes, but have MTOC (microtubule organizing centers)
1. G1 phase: intense growth and biochemical activity
2. G1 checkpoint (restriction point in animals): cell checks to ensure that enough DNA, nutrients, etc. are present in order to commit to division
3. S phase: synthesis (replication) of DNA, duplication of centrosome
4. G2 phase: cell continues to prepare for cell division
5. G2 checkpoint: is DNA replicated properly?
6. G2-M transition: centrosomes separate from each other
11
Q
mitosis
A
- actual dividing of the nucleus
1. prophase
2. metaphase
3. anaphase
4. telophase
12
Q
prophase
A
- nuclear membrane disintegrates
- strands of chromosomes condense
- nucleolus disappears
- mitotic spindle begins to form in the cytoplasm, extending from one centrosome to the other
13
Q
metaphase
A
- chromosomes line up in single file on the metaphase plate
- centrosomes are already on the opposite poles of the cell
- spindle fibers run from centrosomes to kinetochores in the centromere
- M-spindle checkpoint: chromosomes are attached to kinetochores and are lined up on the metaphase plate
14
Q
anaphase
A
-centromeres of each chromosome separate because spindle fibers pull apart sister chromatids
15
Q
telophase
A
- chromosomes cluster at the opposite ends of the cell
- nuclear membrane begins reforming
- supercoiled chromosomes begin to uncondense
- once 2 individual nuclei form, mitosis is completed
16
Q
cytokinesis
A
- dividing of the cytoplasm
- animal: cleavage furrow due to actin and myosin m microfilaments pinching the cytoplasm
- plant: cell plate forms so that daughter cells don’t separate from each other, but rather form a new cell wall and middle lamella (sticks cells together)
17
Q
characteristics of normal cells
A
- contact inhibition (density dependent inhibition): cells grow and divide until they become to crowded and enter G0 phase
- anchorage dependence: division will only occur if cell is attached to surface
18
Q
cancer cells
A
-uncontrollable cell growth
19
Q
meiosis
A
- generates genetic diversity that natural selection and evolution act upon
- produces haploid gametes by dividing the nucleus 2x
- genetic material is randomly separated and recombined
20
Q
sexual reproduction
A
joining of 2 haploid cells
21
Q
meiosis I (AKA reduction division)
A
process by which homologous chromosomes separate
- interphase (copying DNA)
- prophase I
- metaphse I
- anaphase I
- telophase I
- cytokinesis I
22
Q
prophase I
A
- chromosomes pair up with homologue into a tetrad by synapsis
- crossing over: exchange genetic material
- chiasmata: visible result of crossing over
23
Q
metaphase I
A
- double file: homologous chromosomes lined up along metaphase plate
- spindle fibers are attached to centromere of each pair of homologues
24
Q
anaphase I
A
-separation of homologous chromosomes by spindle fibers
25
telophase I
-homologous pairs continue to separate until each pole has halpoid number of chromosomes, but the same number of chromatids
26
cytokinesis I
-usually occurs with telophase
27
meiosis II
- functionally the same as mitosis, including the same steps
- chromosome number remains haploid (no duplication before separation)
- anaphase II: separate chromosomes into chromatids, leading to each cell gaining haploid cells
28
independent assortment of chromosomes
homologous chromosomes separate depending on the random way they align on the metaphase plate
29
crossing over
produces recombinant chromsomes that combine genes from both parents in an individual
30
random fertilization
sperm fertilizes egg randomly
31
protein kinases
- common in cell signal transduction
- controls cell cycle timing
- catalyze phosphorylation of target proteins that regulate the cell cycle
32
cyclin-dependent kinases
-activated by binding with cyclin, which exposes the active site of the CDK and activates the molecule
-example of allosteric inhibition
-regulate cell cycle at specific checkpoints
-cyclins synthesized in response to molecular signals, including growth factors
growth factor --> cyclin synthesis --> CDK activation --> cell cycle
33
apoptosis
- programmed cell death of infected, damaged, or old cells
- cell components are chopped up and packaged in vesicles where they are engulfed by scavenger cells
- embryonic development, prevent cancerous cells
- plant cells: defense mechanism in fungus and bacteria by leaving no tissue that can spread infection
- mammals: signals from different sources (inside or outside cell) trigger pathways involving caspases (enzymes) to carry out apoptosis
- evolved early in the evolution of eukaryotic cells
