Cell Nuclear Division D2.1 Flashcards
Cell division
cells divide in two by cell division. only produced by pre-existing cells.
Mother cell
the cell that divides
Daughter cell
the cell produced from cell division
What processes require cell division?
- growth
- reproduction
- maintenance
- tissue repair
What is the role of mitosis in eukayotes?
maintain the chromosome number and genome of cells
What is the role of meiosis in eukayotes?
halves he chromosome number and generates genetic diversity
Anucleate
no nucleus
Chromosome
strand of DNA that carries genes
What is the interphase of cell life cycle?
DNA is duplicated, a single chromosome duplicated to form two identical chromatids called sister chromatids
What is the M-phrase of the cell life cycle?
sister chromatids separate and each nucleus requires one, the cohesin loops must be cut. AKA cell division
Centromere
constricted region that joins two sister chromatids
What three things must happen for cell division to occur?
- condensation of chromatin into chromosomes
- microtubule and spindle fiber organization
- movement of chromosomes
Explain the condensation of chromatin by supercoiling
long, thin chromatin strands are condensed into compact short chromosomes by wrapping the DNA double helix around proteins called histones to produce nucleosomes that continue to coil to produce ‘beads on a string’. continued coiling will result in structure of chromosomes
What are needed for movement of chromosomes?
- centrioles
- centrosomes
- microtubule fibres
- kinetochores
Explain the movement of chromosomes
chromosomes are moved to opposite sides of the cell using microtubules which are assembled at the centrosome’s microtubule organizing center.
Centriole
a cylindrical organelle in animal cells composed of microtubules made of tubulin protein
Centrosome
region close to the nucleus for cell division
Microtubule fibers
attach to chromosomes during nuclear division to form a spindle
Different types of microtubule fibers
- pull apart the sister chromatids
- push spindle poles apart to contribute to cell elongation
Kinetochore
a protein complex associated with the centromere, a microtubule motor that shortens microtubule fibers and puts them under tension causing chromatid movement
Mitosis: Prophase
- chromatin condenses and supercoils, DNA becomes shorter and compact
- the chromosomes become visible as sister chromatids
- nuclear membrane begins to break down
- centrosomes move to opposite sides of the. cell and spindle fibers begin to form
Mitosis: Metaphase
- movement of microtubule spindle fibers cause the sister chromatids to line up along the center aka the metaphase plate.
- microtubules continue to grow and attach to the kinetochores n the centromeres of sister chromatids
- sisters within each chromosome become attached to opposite poles
Mitosis: Anaphase
- microtubules link each chromosome to opposite poles of cell
- cohesin loops are cut, chromatids become separated
- kinetochores shorten the microtubules, pulling to the poles
- non-kinetochore microtubules elongate and stretch the cell
Mitosis: Telophase
- chromosomes arrive at opposite poles of cell and the nuclear membrane reforms around
- chromosomes become less condensed to form chromatin
- nucleoli reappear
- microtubule spindle fibers disappear