Unit 4 - Cell Cycle, Mitosis, Meiosis Flashcards
(55 cards)
1
Q
Gametes
A
- 23 different chromosomes (no pairs)
- haploid
-ova (eggs) and sperm
2
Q
Zygotes
A
Fertilized egg
- Egg + sperm
3
Q
Somatic cells
A
- all body cells except for ones undergoing/resulting from meiosis
- muscle, nerve
4
Q
How many chromosomes are in somatic cells
A
- 46 = diploid
- 23 homologous pairs (one form each parent)
5
Q
Homologous chromosomes
A
- found in somatic cells
- a chromosome pair (one from each parent) that are highly similar in length, centromere position, and have genes for the same trait (eye colour0 in the same location (locus)
- may have alleles that code for proteins that produce alternate versions of that trait
6
Q
Gene
A
- unit of heredity
- region of DNA which contains information for synthesis of a protein
7
Q
Alleles
A
- different versions of a gene
- ex. Blue eyes (chromosome from one parent), brown eyes (chromosome from second parent)
8
Q
Diploid cells
A
Contain 23 chromosomes from an ovum paired with 23 chromosomes from a sperm = 46 chromosomes
9
Q
How are chromosomes numbered
A
- 1 to 23
- 1 to 22 = autosomal chromosomes (autosomes)
- 23 = sex chromosome
10
Q
Autosomal chromosomes
A
- contain genes for somatic characteristics
- ex. Hair colour, eye colour, height
- each autosomal chromosome pair is not identical, but equivalent = homologous chromosomes
11
Q
Sex chromosomes
A
- contain genes that determine biological sex
- XX = female
- XY = male
- X or Y from sperm
- X from ovum
12
Q
Mitosis
A
- cell cycle for growth and repair of tissues
- diploid somatic cell to 2 genetically indentical somatic diploid cells
- 2 stages
1. Interphase
2. Mitotic/cell division phase
13
Q
Interphase (mitosis)
A
- G1, S and G2
- cells spend most of their lives here
- chromosomes are present as long thread-like chromatin strands
- normal cellular metabolic activities occurring (ex. protein synthesis)
- must have 2 of everything in order to divide (everything must duplicate)
14
Q
G1 of interphase
A
- growth and metabolism
- Centrosome replication begins
15
Q
G0 of interphase
A
- cells that do not divide again once mature (stay in G1)
- nerve and some muscle cells
16
Q
S phase of interphase
A
- chromosomes replicate, but are still present as long thread-like chromatin strands ( not individually visible)
- ALWAYS occurs before cell division
- Replicates are called sister chromatids
17
Q
Sister chromatids during S phase
A
- attached rot each other at an area of DNA called the centromere
- Kinetochore form on each centromere
18
Q
Kinetochore
A
- site of attachment of spindle microtubules
19
Q
G2 phase
A
- Growth and metabolism
- production of enzymes and other proteins needed for cell division
- Centrosomes replication is completed
20
Q
What does the mitotic phase involve
A
- Mitosis
- Cytokinesis
21
Q
Mitosis
A
Is the division of nuclear material (chromosomes)
22
Q
4 phases of mitosis
A
- Prophase
- Metaphase
- Anaphase
- Telophase
23
Q
Cytokinesis
A
Is the division of cytoplasm
24
Q
What happens when the mitotic phase ends
A
- mitosis and cytokinesis are complete
- resulting diploid cells to into interphase (G1)
- cycle starts over
25
What happens to chromosomes during mitosis
- condense (thicken and coil)
- become individually visible
26
What happens to the nucleoli during prophase (mitosis)
They disappear
27
What happens to the nuclear envelope during prophase (mitosis)
It breaks up
28
Centrosomes during prophase (mitosis)
Move to opposite ends (poles) of the cell
29
Spindle microtubules during prophase (mitosis)
Grow out of Centrosomes and attach to Kinetochore proteins of each sister chromatid, forming the spindle apparatus
- spindle begins to move chromosomes towards cell equator
30
Metaphase (mitosis)
46 replicated chromosomes line up on cell equator
31
What happens during anaphase (mitosis)
- spindle microtubules shorten and pull the Kinetochores away from each other
- causes separation of centromeres
- results in separation of the sister chromatids into 92 individual chromosomes
32
How many chromosomes migrate to each pole during anaphase (mitosis)
46
33
When does cytokinesis being in mitosis
At the end of anaphase
34
What happens to chromosomes during telophase (mitosis)
They uncoil into long thread-like strands of chromatin
35
What reappears during telophase (mitosis)
- nucleoli
- nuclear envelope
36
During what phase of mitosis do the spindles disassemble
Telophase
37
During what phase of mitosis does cytokinesis end
At the end of telophase (after telophase is complete)
38
What does meiosis produce
Gametes (ovum and sperm)
- 1 cell (diploid) produces 4 genetically unique gametes (each haploid)
39
Stages of meiosis
1. Interphase
2. Meiosis I
3. Meiosis II
40
Interphase of meiosis
Is the same as interphase of mitosis
41
Meiosis I
- reduction division in which chromosome number changes from diploid to haploid)
- stages:
1. Prophase I
2. Metaphase I
3. Anaphase I
4. Telophase I
5. Cytokinesis
42
Prophase I
- homologous chromosomes attach together to form tetrads (4 chromatids in a row)
43
Metaphase I
- 23 tetrads line up along cell equator
44
What happens to tetrads during anaphase I
They separate and migrate to opposite poles
- one homologous chromosome (with 2 sister chromatids) goes to each pole
45
Do sister chromatids separate during anaphase I
NO!!!
46
Telophase I
- identical steps to telophase of mitosis but with 23 replicated chromosomes instead of 46
47
After meiosis I and cytokinesis
- each new cell has 23 different chromosomes (1/2 the number of- haploid)
48
After meiosis I and cytokinesis do the cells have homologous chromosomes?
NO!!!
49
What does each cell have after meiosis I and cytokinesis
A single copy of each autosomal chromosome and a single sex chromosome
50
Meiosis II
Is the same as mitosis except it starts with 23 chromosomes instead of 46
51
metaphase II
23 replicated chromosomes line up at equator
52
Anaphase II
Sister chromatids split up and 23 chromosomes migrate to each pole
53
Cytokinesis after meiosis II
Is the same as for mitosis/meiosis I
- begins in anaphase/anaphase I/anaphase II
- continues through telophase/telophase I/telophase II
54
Why does meiosis occur
- we need to turn diploid germ cells into haploid gametes (ova/sperm)
- create zygotes
55
Zygote
46 chromosome cell formed from a 23 chromosome haploid sperm cell combined with a 23 chromosome haploid ovum
