Cell division Flashcards
What are the two classes of cell division?
Meiosis and mitosis
What are the products of meiosis?
Gametes (haploid cells)
What are the products of mitosis?
Two diploid daughter cells that are identical to the mother cell
What are sister chromatids bound together by?
Cohesin complexes bind the two sister chromatids tightly together along their entire length
In what stage of meiosis does **pairing **occur?
Prophase I
How does pairing occur between homologs?
Through interactions between complementary DNA sequences called pairing sites
What is a bivalent?
A four-chromatid structure formed during prophase I
What is synapisis?
A process in which the axial core of a homolog becomes tightly linked to the axial core of its partner by a closely packed array of transverse filaments
What complex is formed as a result of synapsis?
Synaptonemal complex
What are the stages in prophase I?
- leptotene
- zygotene
- pachytene
- diplotene
- diakinesis
What are the stages in mitosis? Give an outline of what happens in each.
- interphase
- prophase
- metaphase
- anaphase
- telophase
- cytokinesis
What happens during zygotene during prophase I of meiosis?
Maternal and paternal homologs pair together to form bivalents
What happens during pachytene during prophase I of meiosis?
Chromosomes thicken and “crossing over” occurs
What happens during diplotene during prophase I of meiosis?
Homologs seperate, but are held together by chiasmata
- Lazy
- Zebras
- Party
- Down
- Ditches
- Leptotene
- Zygotene
- Pachytene
- Diplotene
- Diakinesis
What is kinetochore synonymous with?
Centromere
What is nondisjunction?
- the failure of paired chromosomes to seperate during meiosis I
- failure of sister chromatids to seperate dring meiosis II
Define euploid
A cell with 46 chromosomes
Define aneuploidy
A non-euploid cell, a cell that contains an abnormal number of chromosomes
What is an example of trisomy?
- Trisomy 21/ Down syndrome
- Klinefelter syndrome (XXY)
What is an example of monosomy?
Turner syndrome (XO)
What is “crossing over”?
A process where DNA segments of homologous chromosomes are exchanged during prophase I (pachytene)
What protein initiates crossing over? How does it do this?
*Spo11, *it creates a double-stranded break in the DNA of the chromatid
What multienzyme catalyses homologous recombination in crossing over?
Recombination complex
