Cell Division Flashcards
Define the cell cycle:
What a cell is doing in it’s lifetime.
*consists of 2 stages which alternate with each other
- Interphase:
- Normal metabolic functions of cell : Metabolism
- (skin –> sweating, shivering etc)
- Cell division:
- MITOSIS (most cells)
- MEIOSIS (ovary & testes cell)
Cell structure : Interphase
- chromosomes not visible as separate (entangled : CHROMATIN network (DNA)
- Chromatin Network: UNREPLICATED chromosomes
- Each UNREPLICATED chromosome =
(carries) 1 set DNA
End of Interphase:
DNA replication occurs
(process where DNA of chromosome makes an exact copy of itself to form:
2 identical DNA molecules
End of DNA replication:
- Replicated chromosome is formed.
(carries 2 sets DNA) - 1 set DNA per Chromatid
- two chromatids joined by: CENTROMERE
Why is DNA replication a significant process?
Ensures that each new daughter cell formed will receive the correct amount of DNA at the end of mitosis
1.2 Cell Division (structure)
Mitosis / Meiosis (NEVER BOTH)
why do somatic cells divide by Mitosis?
To form identical daughter cells in body for:
- Growth
- Repair & Replacement
- Reproduction (asexual & vegetative)
why do somatic cells divide by meiosis?
To form GAMETES (sex cells) for sexual reproduction
Define: Chromosome
The DNA- containing structure that is made up of genes
(found in cells during cell division)
Gene:
segment of DNA
Define:
Centrosome
Structure that is responsible for the formation of spindle fibres during cell division in animal cells
(made up of 2 centrioles)
Define:
Centromere
Structure that holds two Chromatids together in a replicated chromosome and which also attaches the chromosome to the spindle fibres during cell division.
Define:
Centriole
Two structures arranged at right angles to each other and together make up the centrosome.
Define:
Chromatin Network
The DNA-containing network found in cells in interphase (non-dividing)
Define:
Chromatid
A replicated chromosome is made up of two chromatids held together by a centromere
Cell division occurs in 2 parts:
- KARYOKINESIS
Division of Nucleus
(making new nucleus for each
daughter cell) - CYTOKINESIS
Division of cytoplasm (cytosol &
organelles)
Sharing btw daughter cells.
similarities :
PROCESS: mitosis / meiosis
SOMATIC Cell = Mother cell
Mother Cell is DIPLOID:
full set chromosomes in pairs
Diploid = 2n
Mitosis (properties) / stats
- 2 daughter cells formed
- Both: identical to mother cell
- Diploids
- Same chromosome no. (as mother)
Meiosis / stats
- 4 gametes (sex cells) formed
- each: different to mother cell
- Haploids
- 1 set chromosomes
*each chromosome number in the cell carries ONE INDIVIDUAL chromosome (not a pair)
Haploid:
single set of chromosomes in cell (n)
Diploid:
contains 2 sets of chromosomes (2n)
Karyokinesis (division of nucleus)
- Prophase
- Metaphase
- Anaphase
- Telophase
- Prophase
- DNA instructs nucleolus & nuclear membrane (structures in nucleus) to DISAPPEAR
- Chromosomes in Chromatin network Condense (shorten) and become visible as replicated chromosomes.
- The spindle is formed. centrioles start to move apart and towards poles - making microtubule threads btw centrioles as they move
centrioles = poles
microtubule threads = spindle threads - Each replicated chromosome attached to spindle threads @ centromere
- Metaphase
- Chromosomes line up singly / individually on equator (equatorial phase)
- Centromere of the chromosome is on the equator.
- Anaphase
replicated –> unreplicated chromosomes
- Centromere of each replicated chromosome SPLITS & chromatids separate =
Daughter Cells : full DNA set
(unreplicated) - Spindle threads contract and pull the daughter chromosomes to opposite poles.
- The daughter chromosomes move to the poles in v-shape
- The unreplicated chromosomes group at each pole.
- Telophase
- Nuclear membrane, Nucleolus, Chromatin Network REAPPEARS
- Spindle threads disappear
- Centrioles group at each nucleus
- A separate nucleus is present at each pole.
Cytokinesis:
Animal Cells
INVAGINATION
- An invagination in Cell Membrane occurs at cell equator.
- The invagination gets larger, moving towards middle of the cell at equator.
- Eventually separates the 2 cells from each other by pinching them off - separates cytoplasm btw 2 cells.
Cytokinesis:
Plant Cells
- Cell plate forms at equator of cell
(create inner pectin wall/ membrane for 2) - Cell wall & membrane build up and form on either side of cell plate on equator.
- Cytoplasm & organelles are separated equally into 2 new cells
Once mitosis is complete…
interphase occurs
What is Cancer?
- Uncontrolled Cell Division & Growth
(interphase eliminated) - Cells behave abnormally
Tumors are formed:
Cells divide more rapidly
- Cells of tumors Break off & carried in blood around body =
NEW GROWTH - structure of abnormal cells : mutates over time
BENIGN tumors
Tumors stay on one place in the body often within a capsule.
MALIGNANT tumors
- Cells break off and metastasis occurs
(spread in blood to other areas of body and forms more tumors)
Causes of cancer:
- Increasing Age
- Enviro Causes
- Viruses (trigger)
- Inherited genes
Environmental causes:
- Carcinogenic chemicals
- industrial chemicals
- pesticides
- insecticides
- colourants
- preservatives
- cigarettes - Radiation
- UV rays
- X rays
- Nuclear power
Viruses can trigger cancers:
- HPV: cervical cancer
- Hepatitis B & C: liver cancer
-Herpsvirus : Kaposi Sarcoma
Inherited genes:
Mutated genes can be passed on from generation to generation.
(breast cancer, colon, prostate)
Treatments of Cancer:
- Surgery
- Chemotherapy
- Radiotherapy
*homeopathic
Surgery:
The removal of the affected tissue or part is done in order to remove the cancer and its possible spread throughout the body.
Chemotherapy:
Specific drugs are taken at intervals to treat the existing cancer and to prevent the spread of it to other parts of the body.
Radiotherapy:
X rays and gamma rays are used in medical biotechnology in order to kill cancer cells.
*alternative (homeopathic)
- traditional healers, homeopaths and other alternative medical healers.
Many alternative therapies can be used alongside allopathic medical treatments for cancer
Radiotherapy & chemotherapy:
Medical biotechnology
Biotechnology:
(changes DNA)
- Manipulates genetic composition of living cells using tech in a laboratory to develop products for specific purposes.
- used to satisfy human desires (insulin)
- Cells used are genetically changed forever and their genome cannot be restored as DNA is self replicating.
Define : Stem cells
Cells that are undifferentiated and unspecialised and can develop into any type of body (somatic) cell.
Where can stem cells be found?
- Placenta
- Embryo
- Foetal tissues
- Adult stem cells (difficult to reprogram)
- Found in various organs, specifically to repair the cells in these organs.
Advantages to organism to use stem cells rather than donated cells to repair or replace damaged cells or organs?
- Stem cells unlikely to be rejected by body as they originate from the person’s own body.
- Don’t need to live on meds :
anti-rejection drugs / cortisone
Define: Cloning
A process where an identical copy of a whole organism or tissue or organ is made from an existing somatic cell.
The cloning process:
- A somatic cell is removed from a donor organism A who needs to be cloned
- An ovum is removed from another organism B and the ovum’s nucleus is removed and discarded so the ovum no longer contains any genetic material of organism B
- The nucleus of somatic cell from Organism A is removed and placed into ovum of organism B. The ovum contains full set of genetic material of organism A only.
- An electric shock is given to the ovum to stimulate normal cell division (mitosis) to produce an embryo.
- (can also use B as surrogate)
The embryo is placed into surrogate organism c’s uterus, where it develops into the clone of organism A - There is no genetic material present in the clone of either organism B or C, only that of organism A
