The Eukaryotic cell cycle, mitosis, and meiosis Flashcards
1
Q
cytogenetics
A
- field of genetics involving microscopic examination of chromosomes and cell division
2
Q
karyotype
A
- photographic representation of the chromosomes from an actively dividing cell
- reveals the number, size, and form of chromosomes
3
Q
autosomes
A
- all of the chromosomes that aren’t sex chromosomes
- appear in homologus pairs
- humans have 22 pairs
4
Q
sex chromosomes
A
- distinctive pair of chromosomes that are different in males and females
- determine the sex of an individual
- XX or XY
5
Q
homologs
A
- members of a pair of chromosomes in a diploid organism
- autosomal homologs are nearly identical in size and genetic composition
- ex: both carry the gene for eye color but one may have brown and the other blue
- sex homologs X and Y are very different in size and composition
6
Q
G1 phase
A
- the cell commits to divide
- cell grows
- cell accumulates molecular changes that help it progress through the cell cycle
7
Q
S phase
A
- chromosomes replicated to form a pair of sister chromatids
- human cells will end S phase with a total of 92 chromatids (46 pairs)
8
Q
G2 Phase
A
- cell synthesizes the proteins necessary for chromosome sorting and cell division
9
Q
M phase
A
- consists of mitosis and cytokinesis
10
Q
Mitosis
A
- division of one cell nucleus into two with separation of sister chromatids
- produces two daughter cells that are genetically identical to the original
11
Q
cytokinesis
A
- follows mitosis
- divides the cytoplasm into two daughter cells
12
Q
internal and external factors that make the decision to divide
A
external
- environmental conditions
- signaling molecules
internal
- cell cycle control molecules
- checkpoints
13
Q
cyclin and cyclin-dependent kinases (cdks)
A
- responsible for advancing the cell through phases of the cell cycle
- amount of cyclins varies through the cell cycle
how they work:
1. increase in response to nutrients and growth factors
2. cyclin binds to CDK so it can phosphorylate other proteins necessary to advancing the cell cycle
3. degrade when that phase is complete
14
Q
three checkpoints in the cell cycle
A
- checkpoint proteins act as sensors to determine if the cell is in proper condition to divide
1. Restriction point (G1)
2. G2 checkpoint
3. metaphase checkpoint
15
Q
what must the cell do to prepare for cell division
A
- DNA is replicated
- sister chromatids become highly condensed
- can be easily seen under a microscope
16
Q
centromere
A
- region where two sister chromatids are tightly associated
- attachment site for the kinetochore
17
Q
mitotic spindle apparatus (mitotic spindles)
A
- responsible for organizing and sorting the chromosomes during mitosis
- composed of microtubules
18
Q
three types of microtubules
A
- astral microtubules
- position the spindle in the cell - polar microtubules
- separate two poles - kinetochore microtubules
- attached to kinetochore bound to centromeres
19
Q
interphase
A
- base of the cell cycle during which the chromosomes are decondensed and found in the nucleus
- G1, S, G2
20
Q
5 stages of mitosis (in order)
A
- prophase
- pro metaphase
- metaphase
- anaphase
- telophase
21
Q
prophase
A
- chromosomes are already replicated and joined as pairs of sister chromatids
- nuclear envelope begins to dissociate into small vesicles
- chromatids are condensed and easily visible by light microscopy
- mitotic spindle starts to form
22
Q
prometaphase
A
- mitotic spindle fully formed
- nuclear envelope completely dissolved and spindle fibers interact with sister chromatids
- centromeres move apart to create (demarcate) the poles
- two kinetochores on each pair of sister chromatids are attached to kinetochore microtubules from opposite poles
23
Q
metaphase
A
- pairs of sister chromatids are aligned in a single row along the metaphase plate
- cell is in metaphase when the alignment is complete
24
Q
anaphase
A
- the connections between pairs of sister chromatids are broken
- kinetochore microtubules shorten and pull the sister chromatids towards opposite poles
- polar microtubules lengthen and push against each other, pushing the poles farther apart
25
Q
telophase
A
- chromosomes have reached their respective poles and decondense
- nuclear envelope re-forms to produce two separate nuclei
26
Q
cytokinesis
A
- two nuclei are segregated into separate daughter cells
- animals produce a cleavage furrow that separates the cells
- plants produce a cell plate, which then forms a cell wall between the daughter cells
27
Q
Meiosis
A
- forms four haploid cells from one diploid
- first separates the homologous chromosomes and then the sister chromatids
28
Q
synapsis
A
- the forming of a bivalent (tetrad) to hold homologous pairs of sister chromatids together
- only during meiosis
- allows for crossing over
29
Q
synaptonemal complex
A
- protein structure that connects homologous chromosomes
- if they dont dissolve fully, it produces one gamete with both and one gamete with none
30
Q
crossing over
A
- physical exchange of chromosome pieces of the crossing bivalent
- helps increase genetic variation
- carefully regulated by cells
31
Q
chiasma
A
- crosover site
- arms of the chromosomes tend to separate but remain adhered at a crossover site
32
Q
Meiosis 1
A
- separates homologous chromosomes
- basically same steps as mitosis but the bivalents form during metaphase 1 and homologous pairs are separated in anaphase instead of the sister chromatids
33
Q
meiosis 2
A
- no S phase between meiosis 1 and 2
- basically mitosis but with half the amount of chromosomes
- separates the sister chromatids
34
Q
sexual reproduction
A
- requires fertilization between two haploid gametes to create a zygote
- mitosis creates many more diploid cells to form a multicellular organism
35
Q
variation in chromosome structure and number
A
- can have major effects on organisms, diseases, and evolution of new species
- chromosome composition tends to remain constant in a given species
36
Q
three ways to identify chromosomes
A
- size
- location of centromere
- banding pattern
37
Q
short vs. long arm (associated letters)
A
- short arm is P
- long arm is q
38
Q
locations of the centromere
A
- metacentric - middle
- ubmentacentric - just off the middle
- submetacentric - off center
- Acrocentric - near end
- telocentric - at the end
39
Q
types of chromosomal mutations
A
- deletions - segment of chromosome missing
- duplication - repeated segment of chromosome
- inversions - a segment has a change in direction along a single chromosome
- translocations - one segment becomes attached to another chromosome
- may be reciprocal
40
Q
Euploid
A
normal number of chromosomes
- ex: two sets in a diploid organism
41
Q
polyploid
A
- three or more sets of chromosomes
- triploid (3n)
- tetraploid (4n)
42
Q
aneuploidy
A
- abnormal number of a particular chromosome
ex: trisomy or monosomy
43
Q
what does deviation from diploidy result in
A
- usually lethal
- polyploidy more common in plants
- individuals can have an imbalance in the level of expression of genes, which disrupts cell function
- some abnormalities can survive (trisomy 21)
44
Q
nondisjunction
A
- chromosomes do not sort properly during cell division
- can produce aneuploid gametes in meiosis
