Cell Division

?
  • Created by: Lotto65
  • Created on: 14-01-17 15:03
In eukaryotes, nearly all the DNA of a cell is stored in the...
Nucleus
1 of 85
True/false: DNA can be seen with a light microscope
False
2 of 85
How much DNA is in the human nucleus?
2m
3 of 85
Why does the DNA fit in the 5 micrometer nucleus?
Because it is so narrow
4 of 85
Structurally, what are chromosomes?
DNA with proteins attached to them
5 of 85
What is condensation?
During mitosis, the chromosomes become shorter and fatter
6 of 85
What causes condensation?
Supercoiling
7 of 85
When can chromosomes be seen with a light microscope?
When they are condensed enough in the early stages of mitosis
8 of 85
What are sister chromatids?
The two parts of a chromosome
9 of 85
What is a centromere?
The point where the sister chromatids are held together
10 of 85
What does the 'sister' part of sister chromatid say about the chromatids?
They have an identical DNA molecule
11 of 85
What is the name of a chromatid once the centromere has divided?
Chromosomes
12 of 85
What happens in early prophase?
Spindle microtubules are growing and the chromosomes are getting shorter and fatter due to supercoiling - nucleolus breaks down
13 of 85
What is happening in late prophase?
The spindle microtubules extend from each pole to the equator. Each chromosome is still two sister chromatids and a centromere
14 of 85
What is happening in metaphase?
Spindle microtubules attach to each centromere from opposite sides and put under tension to check attachment. Nuclear membrane has broken down so they are free to line up along the equator
15 of 85
What is happening in anaphase?
The centromere divides and chromatids become chromosomes. Spindle microtubules gently pull the genetically identical chromosomes to opposite poles
16 of 85
What is happening in early telophase?
Spindle microtubules break down. All chromosomes have reached poles and nuclear membranes and nucleolus form around them
17 of 85
What is happening in late telophase?
Chromosomes uncoil and are no longer individually visible. The cell divides to form two cells with genetically identical nuclei
18 of 85
What is the process called where the cell splits?
Cytokinesis
19 of 85
What is the mitotic index?
The ratio between the number of cells in mitosis in a tissue and the number of observed cells
20 of 85
How is mitotic index used by doctors?
To predict how rapidly a tumour will grow and what treatment is needed
21 of 85
What sort of tumour does a high mitotic index show?
Fast growing
22 of 85
What is the official definition of cytokinesis?
The splitting of the cytoplasm to form two cells
23 of 85
Is cytokinesis the same in animal and plant cells?
No
24 of 85
How does cytokinesis take place in plant cells?
A new cell wall is formed across the equator that divides the cell in two
25 of 85
How does cytokinesis take place in animal cells?
The plasma membrane at the equator is pulled inwards until it meets the centre of the cell, dividing it in two
26 of 85
Give examples of when mitosis is used
Growth, tissue repair, embryonic development, asexual reproduction
27 of 85
Why does condensation occur?
To package the chromosomes and DNA into shorter structures to fit in the nucleus
28 of 85
What aids the supercoiling process?
Histones and enzymes
29 of 85
Where do microtubules grow out of?
Microtubule organising centres
30 of 85
How is the plasma membrane pulled inwards in cytokinesis in animal cells?
A ring of contractile protein (actin and myosin) inside the plasma membrane
31 of 85
How is the membrane formed in plant cells for cytokinesis?
Vesicles move to the equator and fuse to create tubular structures. More vesicles fuse to form two layers
32 of 85
What happens in plants after cytokinesis?
Pectins and other substances in vesicles are deposited into the cytoplasm by exocytosis. The daughter cells bring cellulose to the equator and deposit it by exocytosis adjacent to the middle lamella. Each cell builds its own cell wall
33 of 85
What do the pectins form?
The middle lamella
34 of 85
What does the middle lamella do?
Links the new cell walls
35 of 85
What is the cell cycle?
The sequence of events between one cell division and the next
36 of 85
Name the two phases of the cell cycle
Interphase and cell division
37 of 85
What happens during interphase?
Many metabolic reactions occur in the cell and it is a very active stage
38 of 85
Name a metabolic reaction that happens in the cell division stage and interphase
Cell respiration
39 of 85
Name two metabolic reactions that only occurs in interphase
DNA replication and protein synthesis
40 of 85
Name two organelles that increase in number during interphase
Mitochondria and chloroplasts
41 of 85
Name the three stages of interphase
G1, S and G2
42 of 85
What happens in the S stage of interphase?
The cell replicates all its genetic material in the nucleus
43 of 85
Why do cells need to replicate their genetic material?
So after mitosis, both daughter cells have a complete set of genes
44 of 85
Why do some cells not go past G1 stage of interphase?
They are never going to divide so do not need to prepare for mitosis
45 of 85
What is the smaller stage after mitosis in the cell cycle called?
Cytokinesis
46 of 85
What is a cyclin structurally?
A protein
47 of 85
What do cyclins do?
They ensure tasks are performed at the right time in the cell cycle and that each task has been fully completed before the cell goes onto the next stage
48 of 85
What can cyclins bind to?
Cyclin-dependant kinases
49 of 85
What is a cyclin-dependant kinase?
An enzyme
50 of 85
How do kinases work?
They become active when cyclins bind to them. This causes them to attach a phosphate group to other proteins in the cell which triggers them to become active and carry out tasks specific to the stage of the cell cycle
51 of 85
How many different types of cyclins are there in the cell?
4
52 of 85
At what point does a cell move onto the next stage of the cell cycle?
When the cyclins reach a threshold concentration
53 of 85
True/false: Cells only divide when new cells are needed
True
54 of 85
What is serendipity?
Making a discovery by accident
55 of 85
Was discovering cyclins an example of serendipity?
Yes
56 of 85
How did Tim Hunt discover cyclins?
Examining protein synthesis in sea urchin eggs, he found there were some proteins that increased and decreased in concentration repeatedly and these levels matched certain stages of the cell cycle
57 of 85
What is oncogenesis?
The formation of tumours
58 of 85
What are oncogenes?
Genes involved in the control of the cell cycle
59 of 85
How does oncogenesis start?
A genetic mutation in oncogenes
60 of 85
Can you get a tumour if one oncogene in one cell mutates?
No - several in the same cell need to mutate for control to be lost
61 of 85
What is a mutagen?
Chemicals that causes mutations
62 of 85
What else causes mutations other than chemicals?
Ionising radiation
63 of 85
What happens when the cell cycle of a cell is lost?
The cell undergoes many uncontrolled divisions to form a mass of cells (primary tumour)
64 of 85
What are the properties of benign tumours?
Do not grow rapidly and do not spread - cells adhere to each other
65 of 85
What is the risk of benign tumours?
Press on organs and damage them
66 of 85
What are the properties of malignant tumours?
Aggressive and can detach cells to be carried elsewhere in the body to form secondary tumours
67 of 85
What is metastasis?
The spreading of cells to form tumours elsewhere in the body
68 of 85
There is a positive correlation between ... and death rate due to cancer
Cigarette smoking
69 of 85
The more cigarettes smoked per day...
The higher the chance of developing cancer in the lungs or other organs
70 of 85
What does carcinogenic mean?
Cancer causing
71 of 85
Is there evidence that chemicals in tobacco smoke are mutagenic?
Yes
72 of 85
What is another word for a malignant tumour?
Carcinoma
73 of 85
Give examples of ionising radiation that causes cancer
X-ray and short wave UV light
74 of 85
What are mutations?
Random changes in the base sequence of genes
75 of 85
Can genes become cancer-causing if they mutate?
Only oncogenes
76 of 85
Give examples of where cancer occurs in those that have smoked
Mouth, larynx, pharynx, lungs, bladder, kidneys, pancreas, cervix, stomach and oesophagus
77 of 85
There is a correlation between amount of cigarettes smoked and death rate by cancer but what other pattern was found?
A higher death rate amongst those who smoked once but don't anymore
78 of 85
Mitochondria always come from...
The mother
79 of 85
What is a somatic cell?
A body cell
80 of 85
What happens in stage G1 of the cell cycle?
All cellular contents apart from the chromosomes are duplicated
81 of 85
What happens in stage G2 of the cell cycle?
Cell double checks for errors and repairs
82 of 85
What does phosphorylate mean?
Attach a phosphate group
83 of 85
How do metastatic cells get to other parts of the body?
In the bloodstream
84 of 85
What has the tobacco industry been doing with their results?
Suppressing them into the health effects of smoking which is unethical, causes social harm but has not been made illegal
85 of 85

Other cards in this set

Card 2

Front

True/false: DNA can be seen with a light microscope

Back

False

Card 3

Front

How much DNA is in the human nucleus?

Back

Preview of the front of card 3

Card 4

Front

Why does the DNA fit in the 5 micrometer nucleus?

Back

Preview of the front of card 4

Card 5

Front

Structurally, what are chromosomes?

Back

Preview of the front of card 5
View more cards

Comments

No comments have yet been made

Similar Biology resources:

See all Biology resources »See all Cellular processes and structure resources »