Chapter 12, 13 Flashcards
1
Q
Cell division functions in
A
Renewal and repair, replacing cells that die from normal wear amd tear
2
Q
DNA
A
Deoxyribonucleic acid, a long thin molecule that stores genetic information
3
Q
Genome
A
an organism’s complete set of DNA
4
Q
Double helix of dna wraps tightly around ____
A
Histones
5
Q
Histones
A
Help maintain structure and activity of the genes
6
Q
When a cell is not dividing, and even as it replicates it’s DNA, the genetic material is in the form of
A
A long thin chromatin fiber
7
Q
After DNA replication, chromatin does what
A
Becomes densely coiled and folded until it becomes a chromosome
8
Q
Each duplicated chromosome is made up of
A
Two identical have called chromatids
9
Q
Chromatids
A
Each half of a chromosome that forms as the DNA makes a copy of itself before cell division (sister chromatids)
10
Q
Centromere
A
Hold together chromatids
11
Q
Sex chromosomes
A
Chromosomes that determine the sex of an organism
12
Q
Autosomes
A
Non-sex chromosomes which help determine all of your traits
13
Q
An organism has pairs of autosomed bc
A
They receive on copy if each autosome from each parent (these pairs are homologous cheomosomes)
14
Q
Homologous chromosomes
A
Pairs of chromosomes that are made the same size and shape and carry genes for the same traits
15
Q
Somatic cells
A
Any cell in multicellular organisms except a sperm or egg
16
Q
Example of somatic cells
A
All body cells such as skin heart liver and blood cells
17
Q
Human somatic cells have a total of how many chromosomes
A
46
18
Q
Gametes
A
Haploid reproductive cell
19
Q
Inhumans, gametes are
A
Sperm or egg
20
Q
Human gametes have a total of how many chromosomes
A
23
21
Q
Diploid cells
A
Have 2 sets of chromosomes, all cells except sperm and egg
22
Q
Abbreviation for diploid cells
A
2n
23
Q
Diploid number for humans
A
46
24
Q
Haploid cells
A
Only contain 1 set of chromosomes (sperm and egg)
25
Abbreviation for haploid cells
1n
26
Haploid number for humans
23
27
Cell cycle
A repeating set of events that make up the life of a cell
28
Cell cycle is a mechanism in which each _______ receives what
each daughter cell receives an identical and a complete complement of chromosomes (a complete genome passed from parent cell to daighter cells)
29
Cell cycle produces
2 genticslly identical daighter cells allowing orgs to grow, replace cells, and reproduce asexually
30
Interphase
Period in cell cycle when the cell is not dividing (90% of cell cycle)
31
Steps of interphase
```
G1 phase (first gap)
S phase (synthesis)
G2 phase (second gap)
G0 phase
```
32
G1 phase
During g1 phase the cell grows, if a cell does not receive a signal to go to the S phase it enters g0 phase
33
S phase
The cell's DNA is copied
34
G2 phase
The cell continues to grow and prepares for cell division- a single centrosome duplicates, forming two centrosomes
35
Centrosome
A region in animal cells that organize the microtubules of the mitotic spindle- each centrosome contains two centrioles
36
G0 phase
In this phase the cell does not prepare for cell division, it is a mature cell that will never divide again
37
Ex of g0 phase
Nerve and muscle cells are in g0 phase
38
Steps of cell cycle
Interphase and mitosis
39
Mitosis: when does it occur? What does it play a role in?
During mitosis the cell divides- occurs after DNA replication- plays role in growth, repair, and asexual reproduction
40
Mitosis follwed by cytokinesis produces
Two gentically identical daughter cells
41
Mitosis allows for asexual reproduction of orgs in which
Daughter cells are genetically identical to the parental cell, allowing for genetic info transfer to subsequent generations
42
Steps of mitosis
Prophase
Metaphase
Anaphase
Telophase
43
Prophase
Chromatin fibers become more tightly coiled forming chromosomes
Nucleus begins to disappear
Centrosomes begin to move to opposite ends of the cell
Microtubules called spindle fibers radiate from the centrosomes creating a mitotic spindle
Kinetochored form on the centromere of the chromosome
Spindle fibers attach to the kinetochores
44
Mitotic spindle
Combo of centrosomes and the spindle fibers
| Radial arrays of shorter microtubules that extend from the centrosomes look like stars and are called asters
45
Kinetochores
Regions on the chromosomes where the spindle fibers attach
46
Metaphase
Spindle fibers put all the cheomosomes so that they line up in the middle of the cell along the metaphase plate
47
Metaphase plate
Imaginary plate that is in the middle of the two centrosomes
48
Anaphase
Spindle fibers shorten, pulling apart chromosomes into individual chromatids, which then migrate to opposite poles
Cell begins to elongate
49
Once the chromatids are pulled apart in anaphase they are considered to be their own chromosome
.
50
Telophase
Chromosomes reach opposite ends of the cell and being to uncoil forming chromatin
Spindle microtubules (spindle fibers) disappear
Nuclear envelope forms around each set of chromosomes
Cytokinesis begins
51
Cytokinesis
Division of the cytoplasm of the cell
52
Cytokinesis in animals
The cleavage furrow pinches inward eventually sitting the cell into two offspring cells
53
Cytokinesis in plants
A cell plate forms across the middle of the cell splitting the cell into two offspring cells
54
Binary fission
Division of a prokaryotic cell into two identical offspring cells
55
Binary fission....
Form of asexual reproduction
Occurs in prokaryotes (bacteria)
Occurs in single celled eukaryotic cells
56
Steps of binary fission
1. DNA is replicated
2. Cell grows and elongates until it is 2x the size of the orginal cell
3. Cell wall forms between the 2 cheomosomes and cell splits into 2 new identical cells
57
Cell cycle control system
A cyclically operating set of molecules in the eukaryotic cell that both triggers and coordinates key events in the cell cycle
58
A checkpoint in the cell cycle...
Is the control point where stop and go ahead signals can regulate the cycle
59
Three major checkpoints
Are found in the G1 G2 and M phases
60
G1 checkpoint
If a cell receives a go ahead signal at the G1 checkpoint it will usually complete G1, S, G2, and M phases and divide; if it does not receive a go ahead signal at that point the cell will enter the G0 phase
61
Not dividing cells may exit the cell cycle or hold at a particular stage of the cell cycle
.
62
Cell cycle checkpoints are controlled by
Cyclins and protein kinases
63
Cyclin
Cellular protein that plays an important role in regulating the cell cycle
64
Protein kinases
Enzymes that activate or inactivate other proteins by phosphorylating them
65
Certain protein kinases give the go ahead at what checkpoints
G1 and G2
66
To be active, protein kinases must be attached to
A cyclin. Because of this requirement, these kinases are called cyclin dependent kinases (Cdks)
67
Mitosis-promoting factor
When cyclins that accumulate during G2 associate with Cdk molecules, the resulting MPF complex phosphorylates a variety of proteins
68
The MPF complex phosphorylates a variety of proteins, initiating mitosis
Cyclins must be present in large concentration to create the MPF
69
Growth factor
Approaching released by certain cells that stimulate other cells to divide
70
A growth factor made by platelets that stimulates division of fibroblasts, a type of connective tissue that helps heal wounds
Platelet-derived growth factor (PDGF)
71
Loss of cell cycle control
Cancer cells do not heed the normal signals that regulate the cell cycle. They divide excessively and invade other tissues. Stop dividong at random points rather thancheckpoints
72
Cancer cells evade the normal controls that trigger a cell to undergo
Apoptosis when something is wrong
73
Meiosis
Process of cell divisoon that produces haploid reproductive cells called gametes
74
Fertilization
The union of haploid reproductive cells creating a zygote
75
Zygote
Combo of two gametes to give a diploid cell
76
How many divisions in meiosis
2
77
What happens to number of chromosomes in meiosis
Reduced from diploid 2n to haploid 1n
78
Meiosis results in
4 different haploid eggs or sperm
79
Prophase 1 of meiosis
Homologous chromosomes pair up in a process called synapsis
80
Tetrad
Each pair of homologous chromosomes
81
Crossing over
During synapsis, chromatids may twist around each other and trade places during prophase 1
82
Metaphase 1 in meiosis
Tetrads line up randomly along the metaphase plate
83
Anaphase 1
Homologous chromosomes are separated and each one moves to an opposite pole
84
Telophase 1
Homologous chromosomes reach opposite ends and cytokinesis begins
Cell is now haploid but still has 2 sister chromatids
85
Reproduction processes that increase gentic variation are evolutionary conserved and are shared by various orgs
Crossing over, random orientation of chromosomes, random fertilization, and mutations all lead to genetic variation
