12. Cell Division Flashcards
Cell continuity def
Means all cells develop from pre existing cells.
3 steps to form a new cell
- Produce new materials.
- Grows larger
- Reproducing to form a new cell
When (not) dividing what shape is the chromosomes in?
When not dividing chromosomes are long thin threads called chromatin.
When dividing the chromatin forms a number of clearly distinguishable chromosomes.
Chromosome def. and how many in each cell
A coiled thread of DNA and protein found in the nucleus.
23 pairs in each cell, 46 single chromosomes
Role of genes and what they are
Responsible for inheritance and characteristics.
Sections of DNA on the chromosome.
This DNA has the info for forming proteins
Difference between haploid and diploid
Haploid: has one of each set of chromosomes. Symbolised by ‘n’. No. of chromosomes = 23. Eg. Egg and Sperm
Diploid: has two of each set of chromosomes. Symbolised by ‘2n’. No. of chromosomes= 46. Eg. Every cell in the body.
Cell cycle def.
Changes that occur in a cell between one cell division and the next.
Parts of the cell cycle
Interphase: The phase when the cell is not dividing.
Mitosis/Meiosis: when cell is dividing.
What happens during interphase
Is an active stage. Cell is not dividing. Chromosomes appear as chromatin. 1. New cell organelles formed. 2. Forms enzymes needed for growth and division. 3. Chromosomes become visible as single strands. 4. They replicate 5. They then duplicate.
Replication
When chromosomes make identical copies.
Duplication
When cells pair up
Stages of mitosis
Prophase, Metaphase, Anaphase, Telophase.
Party Monday and Tuesday
Prophase
Nuclear membrane disassembles.
Nucleolus disappears.
Spindle fibres form in the cell
Metaphase
Chromosomes line up in the equator of the cell.
Spindle fibres go to poles.
Spindle fibres attach to the chromosomes at the centromere.
(Metaphase:Middle)
Anaphase
Spindle fibres contract and pulls the chromosome to the pole.
(Anas dad the builder pulls apart, he’s a contractor)
Telophase
Chromosomes form chromatin
Spindle fibres disappear.
Nuclear membrane surrounds the chromatin at each pole.
Resulting in two new nuclei.
Cell division in animals
A groove called a cleavage furrow forms in the equator between two nuclei.
This furrow deepens until the cell splits.
Eventually the cell forms 2 new cells
Cell division in plants
Rigid cell wall prevents cleavage.
Vesicles form in the equator.
They join together to form a cell plate, which attaches to cell membrane.
Two new cells form.
Function of mitosis in unicellular organisms
Asexual reproduction
Function of mitosis in multicellular organisms.
New cells, not new individuals.
Responsible for growth and renewal and repair of cells.
Meiosis
Parent cell divides into 4 haploid daughter cells.
Occurs in ovaries and testes to produce an egg and sperm.
Autosome
Is a non sex chromosomes. 22 pairs in every human cell
Sex chromosome
Determines the gender. One pair in each human cell. Either XX(female) or XY ( male)
Function of Meiosis
Multicellular organisms:
Responsible for sexual reproduction.
Give rise to variation in species in organisms
What is Cancer.
When a cell/ group of cells lose the ability to control the rate of cell division.
What is it celled when a cell loses the ability to control the rate of cell division
Tumour- can be malignant or benign.
Benign tumours
Means kind, not life threatening. Do not invade other tissues.
Eg. Warts, skin tags
Cells stop dividing after some time
Malignant tumour
Invades other cells
Move around the body
Cancer cells divide infinitely.
Cause of cancer
When normal genes are altered to form cancer causing genes called oncogenes.
Caused by agents called carcinogens.
Eg. Cigarette smoke, uv radiation, some viruses, asbestos fibres
Treatment of cancer
With radiation ( burn out cancer) Chemotherapy ( chemicals slow down mitosis) Surgery
