Mitosis Flashcards
What is mitosis?
Cell division of somatic cells
Why is mitosis necessary?
For growth
To replace dead cells
What is a histone?
The protein around which DNA folds
How many chromosomes does a human cell have?
46
23 pairs
What do chromosomes look like when replicated?
Like an x
What does an unreplicated chromosome look like?
Like a vague S
What is the first phase of the cell cycle?
Interphase
What happens during interphase?
Three phases occur
What are the phases within interphase?
G1
S
G2
What happens during the G1 phase?
The cell grows
The cellular content replicates
What happens during the S phase?
Synthesis
DNA replication
What happens during the G2 phase?
The cell checks that replication happened correctly
How many phases of karyokinesis are there?
Four
What are the four phases of mitosis?
Prophase
Metaphase
Anaphase
Telophase
What is a chromatid?
The one half of the ‘x’ of a replicated chromosome
What connects the two chromatids of a chromosome?
The centromere
How do you remember the four phases of mitosis?
PMAT
What happens during prophase?
The nuclear membrane, nucleus and nucleolus disintegrate
Chromosomes condense
In an animal cell, the centrioli move to opposite poles
They form spindle fibres
What happens during metaphase?
The chromosomes line up down the equatorial line (in the middle of the cell)
Spindle fibres attach to the centromeres
What happens during anaphase?
The spindle fibres of the centrioles shorten and pull the chromosomes apart
Chromatids separate and move to opposite poles
Cytokinesis begins
What happens during telophase?
The nuclear and plasma membrane form in the different daughter cells
Nucleolus forms
Spindle fibres disappear
What happens during cytokinesis?
The cells separate
Animal: cytoplasm invaginate
Plant: transverse wall /cell plate forms
What is the main purpose of mitosis?
A mother cell divides to form two daughter cells
Do the daughter cells differ, either from the mother cell or from each other?
No, they are all identical and have the same genetic material
What are chromosomes?
Thread-like structures found in the cell nucleus in all cells
What do chromosomes do?
Transfer hereditary characteristics from generation to generation
How do chromosomes appear when not dividing?
As a mass of threads in the nucleus called the chromatin network
What happens to the chromatin network when the cells divide?
The chromatin network condenses
The threads become thicker and shorter
They become single stranded chromosomes
What is the structure of a chromosome like?
The nucleic acid DNA that is wrapped helically around histones
What is a gene?
A DNA segment along the length of each chromosome
What does a gene do?
Controls a specific hereditary characteristic
What is replication?
When all genetic material in the nucleus duplicates itself
How does the chromosome appear after replication?
Two identical units called chromatids
How are chromatids joined?
By a centromere
What happens when a cell gets cancer?
Its mitosis is no longer controlled
What causes cancer?
A mutation in a particular part of the DNA
What does your body do to try and prevent cancer?
The checks before prophase
The cell will “commit suicide”
What can cause cancer?
Carcinogens (cancer causing agents)
What is a tumour?
A mass of cells
What are the two types of tumours?
Benign
Malignant
What is a benign tumour?
A tumour that doesn’t grow
Does not penetrate tissues
Usually enclosed in a capsule
What is a malignant tumour?
A tumour that grows
What does a malignant tumour do?
Squashes healthy cells
Steals nutrients from other cells
How are cancer cells different?
They do not listen to signals to stop growing
Spread around the body
How do cancer cells spread to the rest of the body?
Through the blood stream
How do cancer cells steal nutrients?
They produce proteins to grow blood vessels
What is metastasis?
It refers to the spread of malignant cancer cells
How is cancer identified?
Sometimes physical lumps are visible
Sometimes symptoms can indicate it
Blood tests can reveal whether you truly do have cancer
What does a carcinogen do?
Causes a change or mutation in the DNA
What are examples of carcinogens?
Cigarette smoke Radiation X rays UV light Food additives Dangerous chemicals A virus can cause cancer as well
How can a virus cause cancer?
Viruses mutate cells’ DNA
This can cause the cell to become cancerous
What kind of viruses can cause cancer?
HPV virus (cervical cancer) Hepatitis B or C
Is cancer contagious?
No, but the causes (like the viruses) are sometimes contagious
Is it true that only females can get breast cancer?
No, males can get it too
What is a doctor that treats and deals with cancer?
Oncologist
What kind of tests are used to identify cancer?
X-rays: to look for a tumour
Blood tests
Biopsy- to test the actual tumour cells
What are some of the cancer treatments?
Chemotherapy
Removal
Radiotherapy
Cryotherapy
What is chemotherapy?
The patient is given a mixture of chemicals to destroy the cancer cells
What is radiotherapy?
When radiation is used to focus on the particular spot where the cancer is
What is cryotherapy?
The cancer cells are frozen with liquid nitrogen
What ability do cells in multicellular organisms have?
To divide continuously
What two types of cells exist in the human body?
Somatic cells
Gametes
What are somatic cells?
Body cells
What are gametes?
Sex cells
Female eggs or male sperm
What kind of cell division is when gametes are formed?
Meiosis
What is the cell cycle?
The period during which a cell grows, replicates and divides
How is the cell cycle divided?
Interphase
Mitosis
What is the longest part of the cell cycle?
Interphase
What is interphase?
The period between two consecutive cell divisions
What are the two phases of mitosis?
Karyokinesis
Cytokinesis
What is karyokinesis?
Division of the nucleus and chromosomes
What is cytokinesis?
Division of the cytoplasm, organelles and cell membrane
Why is mitosis important?
Growth
Repairs
Worn out cells are replaced
In some plants: asexual reproduction
What happens to a cancer cell?
It loses its original function
