What is the function of meiosis?
Creation of gametes
How do cells form?
- When existing cells divide
2. 1 parent cell= 2 daughter cells (identical to parent)
What is the cell cycle?
• series of processes that takes place between one cell division and the next
- Karyokinesis ( nuclear division)
- Cytokinesis ( cytoplasmic cleavage)
• cells prepare for mitosis
1. Phase between division
2. Cell spends most time in interphase:
- growth and production of new materials ( synthesizing protein + new organelles)
- replication of DNA
Duplication of chromosomes ( 2 identical chromatids)
- final growth for cell division
Describe early prophase
• part of karyokinesis
- chromosomes become visible
—threads of chromatin become thicker and shorter
Describe late prophase
- Centrioles separate, move to poles and spindle fibers from between them
- Nuclear membrane and nucleus break down
- Chromatids become visible
- Chromatin network becomes visible as chromosomes: 2 chromatids attached by a centromere
What is the function of mitosis?
Create somatic cells
- Chromosomes align at equator
2. Spindle fibers attach to their centromeres
- Spindle fibers contract, pulling apart chromosomes
- Chromatids move to polar regions of spindle [group at poles]
- One chromatid of each chromosome moves to opposite poles
- Now called ‘daughter chromosomes’
- Identical daughter cells
- Nuclear membrane reforms
- Nucleus reforms
- Cytokinesis occurs
( cytoplasmic cleavage)
- Division of cytoplasm
- Occurs at the end of telophase
- (Animal cell) - constriction of cell membrane around equator
- constriction continues into parent cell
- this divides cytoplasm between the 2 nuclei
What is the role of mitosis?
- zygote can grow into multicellular organism
- body cells have same no. of chromosomes + genetic make-up
- REPLACE dead cells + REPAIR damaged cells
- Asexual reproduction- produces new individuals
Important in biotechnology + genetic engineering: able to generate whole organisms from limited cells
What is a centriole?
- Small organelle
- 0,4 micrometers long
- Hollow cylinder —9 long fibrils—each fibril= 3 micro tubules
- Animal cells= 2 centrioles found in centromere
What is the function of the centriole?
- Grow spindle fibers
- align chromosomes during cell division
What are the structures that make up a chromosome?
Describe them in detail
1. CHROMATIDS •formed by a series of genes •2 identical strands that from the chromosome —key to precise nuclear division 2. CENTROMERE •region holding chromatids together 3. GENES •block of DNA carrying 1 characteristic of Organism
What are homologous chromosomes and what do they do?
- Pair of chromosomes that carry corresponding genes
•a body cell 2 chromosomes of genes for a
What are the common cancers?
(LOB Purple BuCks)