All Cells Arise From Other Cells Flashcards
What is the structure of a chromosome like?
Either a single chromosome (looks like a single wotsit)
Or
1 chromosome can be made from 2 sister chromatids joined at a centromere (two wotsits back to back)
What are the different aspects of a chromosome?
Chromatid
Telomere (bottom of chromosome)
Gene in a particular locus
Non coding region
How many pairs of chromosomes and pairs of chromosomes does a human have?
46 chromosomes
23 pairs of chromosomes
1/2 from each parent
What must happen before a cell can divide?
Organelles must replicate
DNA must replicate
The cell must grow
What cell division is used generally?
Mitosis
What is mitosis important for?
Growth of new cells
Repair of damaged tissues
Asexual reproduction
What are the stages of the cell cycle?
Interphase Prophases Metaphase Anaphase Telophase Cytokinesis
Describe the overview of what happens in interphase?
Cell actively synthesises proteins chromosomes are invisible
DNA replicates
The cell membrane, nuclear envelope, nucleolus and cytoplasm is still present
What are the stages of interphase?
G1- first growth phase
S- Synthesis phase
G2- second growth phase
What happens in the growth phases G1 and G2 of interphase?
Organelles are synthesised and biochemicals are produced
In G2- energy stores are increased to supply 2 daughter cells being formed from one parent
What happens in the S phase of interphase?
DNA is replicated
What happens in prophase?
Chromosomes become visible as they become shorter, denser and darker as a result (no longer stringy)
The nuclear envelope disintegrates
Nucleolus disappears
What happens in metaphase?
The chromosomes line up on the equator of the cell with the help from spindle fibres
What happens in anaphase?
The chromatids separate down the middle and move to the opposite pole as the spindle fibres attached contract
The spindle fibres start to become less visible (disappearing)
What happens in telophase?
Chromatids reach the poles and become indistinct
The nuclear envelope and nucleolus starts to reform
Spindle disintegration
The cell start to split in the middle
What happens in cytokinesis?
The cytoplasm divided producing two new cells containing chromosomes in each
What are spindle fibres made of?
Actin and myosin
What are spindle fibres held in place by?
Centrioles (situated at the poles)
What is generally the longest phase of mitosis?
Interphase
How do you calculate the length of cell division?
Work out the percentage of cells in the required phase(s)
Work out the percentage of the time given for the phase(s) from the tine it takes for a full cycle
I.e
(12/150)x 100 =8%
8% of 16.8 hours = 1.34 hour
What is the mitotic index?
The proportion of cells in a tissue sample that are undergoing mitosis
What should the answer for mitotic index be in?
0 to 1
Or
0% to 100%
How to work out the mitotic index?
Number of cells with visible chromosomes
Divided by
Total number of cells observed
What can occur as a result of uncontrolled cell division?
Cancer-tumours
What is the hayflick limit?
A limited time that a cell can under go mitosis
How does the hayflick limit relate to cancer?
Cancer cells (as well as stem cells) don’t have limit of going through mitosis
What are some causes of cancer?
Carcinogens UV Exposure Radiation exposure Genetic disposition Random Age
Who is cancer more common in? Why?
Older people
Their somatic cells (body cells) accumulate mutations
What happens if gametes mutate?
They are passed onto the next generation
How can cancer spread to secondary tumours?
If the tumour cells squeeze into the blood or lymphatic vessels
Via the blood tumour cells can adhere to blood vessel walls to form distant metastases
Via the lymph they can metastasise in the lymph node
What is a benign tumour?
Enclosed in a capsule and doesn’t invade surrounding tissues
Grows in the centre of the capsule
What is a malignant tumour?
Grows at the edges, invading surrounding tissues and organs
Cells may break off and form secondary tumours elsewhere
What happens when a tumour metasises?
Tumours form in other places from the original tumour
What are the treatments for cancer?
Chemotherapy
Radiotherapy
Surgery
What are the advantages and disadvantages of chemotherapy?
Shrink the tumour or slow the growth
Can relieve symptoms
Chemicals can poison healthy cells
Your immune system is wiped out
What are the advantages and disadvantages of radiotherapy?
Large portions of cancer cells are killed
Shrinks the tumour and relieves the mass
Damage to surrounding tisue
Cant kill cancer cells not seen on scan
What are the advantages and disadvantages of surgery?
Most effective at resection
Symptoms relieved
Risk- bleeding, infection, anaesthetic
Recovery time with potential side effects
How does a prokaryotic bacterial cell replicate?
The cell grows organelles and replicates the DNA
The bacteria lengthens and the DNA moves further apart to opposite ends of the cell
The centre of the bacteria contracts starting to separate the cell
A cell membrane and cell wall is formed across the cytoplasm
The cell separates into two daughter bacterial cells
How do viruses replicate?
The virus attaches to a cell
The virus is engulfed by endocytosis
Viral contents are released, RNA enters the nucleus where it is replicated by the viral RNA polymerase
Viral RNA is used to make viral proteins
New virul proteins are released into the extracellular fluid
The cell not killed continues to make a new virus
