9 - Mitosis and Meiosis Flashcards
what is ploidy?
number of chromosomes in a cell
What is G0?
non-replication / dividing cell s
that is the role of condensin?
- protein complex
- condenses chromosomes
- binds to two points on the DNA and folds the chromatin
- takes a helical shape
What is a karyotype?
- photo of full set of chromosomes in homologous pairs in decreasing size
- specific to different organisms
what are the male sex chromosomes?
XY or ZZ
What are the female sex chromosomes?
XX or ZW
What is the name of the chromosomes that are not sex chromosomes?
autosomes
Which chromosome is number 1?
- the largest one
- number goes up as chromosomes get smaller
What are centromeres?
- constitutive heterochromatin repetitive DNA
- bind to kinetichore in mitosis
What are telomeres?
- constitutive heterochromatin
- repetitive DNA
- protects ends of DNA from degradation
describe the structure of the kinetochores
- nucleosome
- CENP-A-containing nucleosome (histone variant)
- inner kinetochore
- outer kinetochores
- spindle microtubules
How is the kinetochore recruited to the correct region?
- nucleosome at the centromere contain CENP-A (a histone variant)
- this recruits the kinetochore
Explain the stages of mitosis
Prophase
- condensin is recruited and chromosomes condense
Metaphase
- kinetochores attach to the centromeres of each sister chromatids
- line them up at the centre
Anaphase
- spindle microtubules pull sister chromatids apart ad towards opposite poles of the cell
Telophase
- nuclear membranes form around the two groups of chromosomes
Cytokenesis
- cytoplasm splits
What holds sister chromatids together
cohesin
explain sister chromatid adhesion across mitosis
prophase
- arms are attached by cohesin
metaphase
- connected at the centromere y cohesion
- arms are separated
anaphase
- cohesin at centromere degraded
- chromatids separated
What are the two models cohesin function?
- ring model - wraps around two strands
- handcuff model - wraps around one strand and interlinked with another cohesin
Explain bacterial mitosis (binary fission)
- DNA is replicated
- cell elongates and cross wall is formed (separating cells)
- cells divide
What is the differences between bacterial and eukaryotic mitosis?
- no nuclear envelope
- no spindles needed as only one chromosome
- plasmids are also replicated
- axsexual reproduction
explain organelles in cell division
- mitochondria and chloroplasts carry out binary fission due to bacterial origin
- organells partitioned in mitosis
- in meiosis only maternally inherited
when is the germ line set aside in development?
week 7
explain the stages of meiosis
Prophase I
- chromosomes condende
- nuclear membrane breaks
Metaphase I
- pairs of homologous chromosomes go to centre of cell
Anaphase I
- homologous chromosomes move to opposite poles of the cell
Telophase and Cytokenesis I
- cytoplasm divides
Prophase II
- new spindle forms around chromosomes
Metaphase II
- chromosomes line up at the equator
Anaphase II
- centromeres divide
- chromatids move to opposite poles of the cell
Telophase and Cytokenesis II
- nuclear envelope forms around chromosomes
- cytoplasm divides
What is thought to be a way that homologous chromosomes pair up in meiosis?
- Programmed double stranded breaks
- reaches out for homologous chromosome
- brings them closer together
- forms synaptoemal complex
- when strand is repaired SC disassembles
What are chiasmata?
sites where cross overs happen
What is a tetrad or bivalent arrangement?
- arrangement of chromosomes during crossing over
