MITOSIS Flashcards
Outline role of microtubules in mitosis (4)
- Forms part of spindle fibres
- Attachment to centromeres
- Movement of sister chromatids to opposite poles
- Spindle fibres shortening at anaphase
Explain how terms monomer + macromolecule can be applied to tubulin
- MONOMER = protein/tubulin composed of AA joined together by peptide bonds
- MACROMOL= Large molecule composed of amino acids/ polypeptide chains like protein
Explain why it’s important that daughter cells produced during mitotic cycle in humans are genetically identical
- Same number of chromosome as parent cell
- cell would be rejected if genetically diff
- role of immune system in removing genetically different cells
Name 2 factors that increase chance cancer cells will develop
- UV/X rays
- ionizing radiation + gamma rays
- Radon
- Viruses;HPV + HIV
- Genetic/hereditary factors
Describe what’s is occur in in telophase
- Chromosomes uncoil/decondense
- Chromes become chromatin + enters interphase
- Spindle fibres break down/ microtubule disassemble
- Nuclear envelope reforms
- Nucleolus/ forms
- Cell membrane furrows
- Cleavage furrow develops = fusion and divides cell into 2
Describe events that occur during prophase
- Chromatin/chormomes condense + become visible
- Supercooling = two sister chromatids joined together at centromere
- Nucleolus diseapers
- Nucleur enevlope disables/breaks down
- Centrioles move to poles
- Spindle fibres start to form
Suggest why some cells appear empty w no nucleus or chromomes under miscroscope
- not sectioned to include nucleus
- did not take up stain/not stained
- cells dead
Describe what occurs in cytokinesis in plant cell
- Cell plate forms across equator of cell = made from vesicles
- Cell wall/cellulose laid down - Cytoplasm divided into two = 2 genetically identical Daughter cells
- organelles shared out e.g vesicles transported to equator
Suggest role of meristaimatic cell + explain features that aid it to carry out its role
- Form cells that can differentiate/totipotent
- Cell replacement/repair/growth
- Divides to give more/continuous supply of stem cells
- Stem cells are undifferentiated = not specialized
- Able to divide/undergo mitosis = can replicate
In cell cycle, more mRNA produced in G1 phase than during mitosis,m suggest why
- More proteins/polypeptides made
- Proteins required for growth/to provide protein for DNA synthesis
- During mitosis DNA highly condensed
State substances used to synthesizes DNA during S phase
- ATP
- Activated free nucleotides
- DNA polymerase
- DNA ligase
- DNA helicase
Describe behaviour of nuclear envelope during mitosis
- Breaks down in prophase
- Reforms after anaphase IN telophase
- Reforms vesicles/vesicles fuse to form new membrane
- Reforms around both sets of daughter chromosomes
FUnction of telomerase
- permit continued replication = adds bases to ends of chromosomes = continued cell division = get around haeflick limit
- Acts as buffer so genes aren’t lost from ends of chromosomes during DNA replication/ no fusion
- Made of non coding DNA
- Prevents loss of genes + Caps ends of chromosomes
Why is continued replication bad +s shortening of telomeres
- Telomeres regulate Cell division+ protect genes
- get shorter + gene exposure + damages chromosome = cannot replicate
- Uncontrollable division + mitosis = mutation —> cancer
Two cells containing telomerase
Stem cells and lymphocytes
Totipotent STEM cells
TOTI= can differentiate into any type of cell e.g zygote
- all genes active
- exposed to chemicals + gene switched off
Haematopioetic stem cells + tissue replacement
- Multipotent stem cells and differentiate into ANY other type of blood cells (found in bone marrow)
Stem cell therapy = introduction of new adult stem cells into damaged tissue to treat disease/injury
Tissue replacement = used fro transplants + used embryonic stem cells but have to destroy embryo (unethical)
role of centrioles during mitosis
1) act as MTOCs
2) assemble/form spindle fibres during prophase
3) contraction of spindle fibres during anaphase separates sister chromatids
Describe how the spindle is involved during mitosis.
- Prophase: attach to centromere of each chromosome
- Metaphase: arrange chromosomes at equator/metaphase plate of cell
- Anaphase: spindle fibres contract and pull apart sister chromatids to poles of cell
- Telophase: elongate to push nuclei apart
Differences in plant and animal cells mitosis
1) plant cells don’t have any visible centriole or aster
2) daughter cells get separated by cell plate in plants
metaphase
- Spindle fibers extend fully from centrosomes
- Spindle fibres reach chromosomes + attach to centromeres
- chromosomes line up across equatot/metaphse plate
Anaphase
- centromeres have divided
- Sister chromatids move to opp poles by spindle fibres
- sister chromatids at the centromere + shorten
- NO NUCLEAR ENVELOPE
Chromatin
Combination of DNA and proteins
G1 phase
- growth
- transcription + translsation = proteins synthesised/RNA
- increase in vol of cytoplasm
S phase
- doubles number of strands
- Semi conservative replication
- chromosome becomes two chromatids
M phase (mitosis)
Production of genetically identical cells
- growth
- cell replacement
- repair of tissues
- asexual reproduction
CentroMERE
- Site of attachment of spindle microtubules
- Each metaphase chromosome has two kinetochores at its centromere
CentroSOME
- Present at the poles of the spindle
- An organelle found in animal cells that acts as an MTOC for construction of the spindle
Chemotherapy
-cancer treatment preventing DNA replication/inhibits METAPHASE–> damaging spindle fibres
- chromosomes CANNOT travel to the poles of the cell
G2
Proof checking + cell continues growing
- if CBP doenst occur = enzymes will remove bases + complimentry bases pairs will form
- DNA normal aagin
Pluripotent STEM cell
- undiffrentiated cells
- some genes switched off/deactivated
- can differentiate into specialised cells BUT NOT TOTIPOTENT/embryonic
Describe how fertleised egg is source of Pluripotent STEM cell
- fertelised egg allowes to divide 7erval times = blastocyst
- cells in inner cell mass = pluripotent
- IVF
explain importance of DNA replication during development of zygote into blastocyst
- zygote divides by mitosis = blastocyst
- identical copies of DNA
- all cells in blastocyst diploid
- so when mitochondra divide will have copy of DNA
Describe root tip squash so chromosomes can be seen
- ## cut root tip + add HCL +orcein stain
