Cell division Flashcards
What is mitosis and what are its uses?
A type of cell division where cells produce identical copies of themselves
Used for growth and repair and asexual reproduction
Explain interphase
Gap phase 1 (G1) - cell grows and replicates its organelles
- high protein synthesis
Synthesis phase (S) - cell replicates DNA
Gap Phase 2 (G2) - cells keeps growing until all organelles duplicated
When do cells check it DNA for errors?
Before S phase and one straight after S phase
Describe the process of mitosis
Prophase - chromosomes condense and nuclear envelope breaks down. Centrioles move to opposite ends of cell and form spindle fibres
Metaphase - chromosome line up along middle of cell and spindle fibres attach to centromere
Anaphase - Spindle fibres contrat and pull chromatids to opposite poles of the cell
Telophase - Chromosomes decondense and nuclear envelope reforms which forms 2 new nuclei
Cytoplasm divides and 2 genetically identical cells form
What are gametes?
Gametes are sex cells
Gametes are haploid
Gametes fuse during sexual reproduction to form a zygote which contains full number of chromosomes - diploid
What is meiosis?
Type of cell division which produces gametes for sexual reproduction
Produces 4 genetically different daughter cells - haploid cells
Haploid cells fuse to form diploid cell called zygote
Describe meiosis 1
Interphase: DNA replicates so there are 2 identical copies of each chromosomes (chromatids)
Prophase 1: chromatids condense and are arranged into homologous pairs. Crossing over occurs between pairs and nuclear envelope breaks down
Metaphase 1: Homologous pairs randomly line up along middle of cell and attach randomly to spindle fibres by centromere
Anaphase 1: Spindle fibres contract and pull homologous pairs to either poles of the cell
Telophase 1: Nuclear envelope forms around homologous pairs of chromosomes. Cytokinesis results in formantion in daughter cells
Describe meiosis 2
Prophase 2: chromosomes condense, nuclear envelope breaks down and spindle fibres form
Metaphase 2: Chromosomes line up in middle of cell and attach to the spindle fibres by centromere
Anaphase 2: Spindle fibres contract and pull sister chromatids to either poles of cell
Telophase 2: Nuclear envelope reforms around chromatids and cytokenesis takes place. 4 genetically different daughter cells produced
How does meiosis increase genetic variation?
Crossing over:
- happens during prophase 1
- Homologous pairs exchange genetic material which forms chromosomes with different allele combinations
Independent assortment:
- Chromosomes line up along the middle of the cell in a random order
- Different combinations of chromosomes will end up in each gamete
what are stem cells?
Unspecialised cells which have the ability to become specialised cells
This process is called cell differentiation
Divide by mitiosis
What are the different levels of potency?
Totipotent - divide into any type of cell
Pluripotent - divide into any type of cell except embryonic cells
Multipotent - can divide into handful of cells
Unipotent - can divide into one type of cell
How are stem cells used in medicine?
Stem cell transplants - given to patients with leukemia
Research - develop ways of growing whole organs from stem cells which can be transplanted into patients to replaced damaged organisms
