Biology > Cell cycle > Flashcards

Cell cycle Flashcards

Mitosis, meiosis, stem cells (63 cards)

Start Studying
1
Q

What is the cell cycle?

A

It is a highly ordered sequence of events that takes place in a cell, resulting in division of the cell and the formation of two genetically identical daughter cells

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

What are the two stages of cell cycle?

A

Interphase and mitotic phase

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

What is interphase?

A

It is normally referred to as the “resting stage” of the cell as the cell is not actively dividing. however, the cell is performing its function of that particular cell type

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

What are the three stages interphase?

A

G1, S and G2

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

What happens during the G1 phase?

A

The cell grows in size
The organelles replicate
Protein synthesis takes place (translation and transcription happens)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

What happens during the S phase?

A

DNA is replicated and;
Chromosomes are synthesized

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

What happens during the G2 phase?

A

Energy stores are increased
Cell continues to grow in size
Damaged chromosomes are repaired

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

What is the mitotic phase?

A

It is the period of cell division because the cell divides into two

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

What are the 2 stages in the mitotic phase?

A

Mitosis and Cytokinesis

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

What is the G0 phase?

A

It is when the cell leaves the cell cycle either permanently or temporarily

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

What are the 2 reasons why cells enter the G0 phase?

A
  1. Differentiation: It is when a cell becomes specialised to perform a particular function which makes the cell unable to divide so it stays in G0 permanently
  2. DNA has become damaged: Senescent cells are cells that are not able to divide anymore and these cells increase as we age
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

What are checkpoints?

A

Checkpoints are the control mechanism of the cell cycle that monitor and verify whether the processes at each phase of the cell cycle has been accurately completed before the cell is allowed to progress into the next stage

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

Where are the 3 checkpoints in the cell cycle?

A

G1 checkpoint- at the end of G1 phase before entry into the S phase
G2 checkpoint- at the end of G2 phase before entry into the mitotic phase
Metaphase checkpoint

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

What is checked in the G1 checkpoint?

A
  1. Cell has grown in size
  2. DNA damage
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

What is checked in the G2 checkpoint?

A

Energy stores are increased
DNA damage & replication
Cell growth

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

What is checked in the metaphase checkpoint?

A

This checks that the chromosomes are assembled correctly on the mitotic spindle

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

Explain, with reference to the structure and function of proteins, the importance of G2 checkpoint. (3 marks)

A

DNA has been checked for errors(1) change in sequence of bases is a mutation (1) which leads to change in amino acid sequence(1) function of protein is dependent on its tertiary structure(1) which is dependent on the primary structure(1)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

What is mitosis?

A

It is the process of NUCLEAR DIVISION that occurs before a cell physically divides into two daughter cells

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

Importance of Mitosis

A
  1. It is a form of asexual reproduction which is the production of genetically identical offsprings in multicellular organisms including plants, animals and even fungi
  2. It also provides new cells for growth and repair of tissues and replacements of cells with short lifespan
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

What is a centromere?

A

It is a region where two chromatids are joined together

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
21
Q

What are the 4 stages of mitosis?

A

PMAT
Prophase
Metaphase
Anaphase and
Telophase

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
22
Q

What happens in the prophase stage?

A
  1. Chromatin coils up and condenses to become chromosomes, which take up stain to become visible under the light microscope
  2. The nuclear membrane starts to break down
  3. The nucleolus disappears
  4. Centrioles move to opposite poles of the cell and help in the formation of spindle fibres
  5. Spindle fibres then attach to the centromeres of each chromosome and move it to the center of the cell
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
23
Q

What happens in the metaphase stage?

A

The chromosomes are pulled to the center of the cell and are lined up at the equator of the cell

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
24
Q

What happens in anaphase stage?

A

The centromeres divide and the spindle fibres shorten.
This shortening pulls the sister chromatids to opposite poles of the cell

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
25
What happens in the telophase stage?
the chromatids have reached the poles of the cell and are referred to as chromosomes again. 1. the chromosomes uncoil back to their chromatin state 2. the nuclear membrane starts to reform and the nucleolus reappears the cell is ready to under cytokinesis
26
What happens in cytokinesis?
The cell is divided into two **IN ANIMAL CELLS** : the central membrane is pulled inwards by the cytoskeleton creating a groove or furrow 2. the membranes eventually fuse to form two independent cells
27
Describes cytokinesis in plant cells
1. Vesicles from the golgi apparatus form membrane structures down the centre of the cell 2. These then fuses with the central membrane diving the cytoplasm into two 3. A new cellulose cell wall then forms down the centre.
28
What is Meiosis?
Meiosis is a type of cell division that produces gametes (sperm and egg cells) with half the number of chromosomes as the original cell.
29
What are haploid cells?
They are cells that are produced from meiosis that have half the normal number of chromosome
30
How many divisions does meiosis involve?
It involves 2 divisions; Meiosis I and Meiosis II
31
What are homologous chromosomes?
They are a pair of chromosomes that have the same gene, but have different alleles(versions) of that gene, with one of the chromosome in the pair coming from the maternal side and the other coming from the paternal side.
32
What are alleles?
They are different versions of the same gene.
33
Features of homologous chromosomes
1. They have different alleles of the same gene at the same locus (a position on a particular chromosome) 2. They have the same size and length when they are visible in prophase 3. Their centromeres are also in the same positions.
34
What are the 4 stages of Meiosis I?
PMAT Prophase I Metaphase I Anaphase I Telophase I
35
What happens in Prophase I?
1. Chromosomes condense and become visible 2. The nuclear membrane starts to break down 3. The nucleolus disappears 4. Centrioles move to opposite poles of the cell and help in the formation of spindle fibres 5. Crossing over takes place
36
What is crossing over?
1. This is when the two chromosomes in a homologous pair come together and wrap their chromatids around each other. 2. Parts of the chromatids then break up and exchange their alleles between themselves.
37
What is a bivalent?
They refer to a pair of homologous chromosomes that have paired up during prophase I https://en.wikipedia.org/wiki/Bivalent_%28genetics%29
38
What is a chiasmata?
It is the point where the chromatids are joined together.
39
What happens in Metaphase I?
1. The homologous chromosomes align on the equator of the cell 2. Spindle fibres attach to the centromeres 3. Independent assortment happens
40
What is independent assortment?
This is when the position of each bivalent is independent of all other chromosomes and are randomly separated into any daughter cell
41
What happens in Anaphase I?
The spindle fibres shorten and pull the homologous chromosomes to opposite poles of the cell
42
What happens in Telophase I?
1. The chromosomes have reached the poles of the cell 2. The nuclear membrane reforms 3. Chromosomes uncoil back to their chromatin state 4. Cell undergoes cytokinesis and divides into two cells These two cells are haploid cells because they no longer contain pairs of homologous chromosomes (rather they just contain one homologous chromosome)
43
What are the stages in Meiosis II?
Prophase II Metaphase II Anaphase II Telophase II This stage is similar to mitosis
44
What happens in Prophase II?
1. Chromosomes condense and become visible again 2. Nuclear membrane breaks down 3. Spindle fibres begin to reform
45
What happens in Metaphase II?
1. Chromosomes line up on the equator of the cell 2. Independent assortment takes place and more genetic variation is caused
46
What happens in Anaphase II?
1. The centromere divides and the spindle fibre shortens 2. This shortening pulls the sister chromatids to opposite poles of the cell
47
What happens in Telophase II?
1. The chromatids have reached the poles of the cell and are now referred to as chromosomes 2. The nuclear membrane reforms 3. Chromosomes uncoil back to their chromatin state 4. Each new cell undergoes cytokinesis to produce a total of 4 haploid daughter cells Each haploid cell is genetically different from each other.
48
Sources of genetic variation in meiosis
1. Crossing over : This is when the homologous chromosomes come together and wrap their chromatids around each other and swap their alleles. The chromatids now contain different combinations of alleles which means each of the four daughter cells will contain chromatids with different combinations of alleles 2. Independent assortment: This means that the separation of homologous pair of chromosomes is random so the daughter cells produced by meiosis can contain any combination of maternal and paternal chromosomes with different alleles
49
What are stem cells?
They are undifferentiated cells with the potential to differentiate.
50
What happens when stem cells become specialised?
Once they become specialised, they lose their ability to divide and enter the G0 phase of the cell cycle
51
What is differentiation?
It is when a cell becomes specialised for its job
52
What is potency?
It is the ability to differentiate into different cell types
53
Types of cell potency
1. Totipotency 2. Pluripotency and 3. Multipotency
54
What are Totipotent stem cells?
They are stem cells that can differentiate into ANY type of cell depending on what instructions they are given.
55
Example of a Totipotent stem cell
A zygote is a totipotent stem cell as it can develop into a whole organism.
56
What are pluripotent stem cells?
They are stem cells that can form all tissue types but not a whole organism
57
Example of a pluripotent stem cell
Embryonic cells that are found in early embryos
58
What are multipotent stem cells?
They are stem cells that can form a range of cells within a certain type of tissue
59
Where are adult stem cells found?
In the bone marrow
60
Sources of animal stem cells
1. Embryonic stem cells- present at early stage of embryo development 2. Tissue (adult) stem cells- present throughout life from birth in areas such as bone marrow
61
Sources of plant stem cells
The meristematic tissue is found in meristems in plants. The meristem is the part of the plant where growth occurs e.g. at the tip of roots and shoots
62
Uses of stem cells
1. Developmental biology 2. Treatment of certain diseases like type 1 diabetes, parkinson's disease, heart diseases
63
Ethical issues with the use of stem cells
People believe that life begins at conception and the destruction of embryos is murder. Check the kerboodle textbook for more details.

Biology (11 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2025 Bold Learning Solutions. Terms and Conditions