BGM1004/L09 Mitosis & Meiosis Flashcards
What are the products of mitosis?
2 genetically identical daughter cells
What is mitosis necessary for? (4)
Embryonic development
Replacement of skin cells
Wound healing
Production of reticulocytes
What is the result of uncontrolled rounds of mitosis?
Tumour formation
Name the 3 phases of interphase.
G1, S & G2
What occurs during G1?
Growth phase in which biosynthesis activities increase in preparation for DNA synthesis
What occurs during S phase?
DNA replication
When does G2 occur?
Lasts until mitosis begins
What is a kinetochore? (2)
Protein structure located at centromere
Attachment point for mitotic spindle
What are spindle fibres? (2)
Formed from microtubules that run between poles of a cell
Create axis for separation of chromosomes
What is a centriole?
Cytoplasmic organelle composed of 9 groups of microtubules serving as foci for mitotic spindle fibre gneration
What is a centrosome?
Region of cytoplasm containing pair of centrioles
What occurs during G2?
Chromosomes are extended
What occurs during Prophase of mitosis?
Chromosomes condense
Centrioles divide and move apart
When do chromosomes become recognisable as double structures?
Prometaphase
What occurs during prometaphase of mitosis? (2)
Centrioles reach opposite poles
Spindle fibres form and attach to kinetochore
What occurs during metaphase of mitosis?
Centromeres align on metaphase plate
What occurs during anaphase of mitosis?
Centromeres split
Daughter chromosomes migrate to opposite poles
What occurs during telophase of mitosis? (3)
Daughter chromosomes arrive at poles
Chromosomes decondense
Nuclear envelope forms
What are the products of meiosis?
4 genetically different gametes
Give the 5 stages of Prophase I in meiosis.
Leptonema
Zygonema
Pachenema
Diplonema
Diakinesis
What occurs during Leptotene of meiosis?
Duplicated chromosomes start to condense
What occurs during Zygotene of meiosis?
Synapsis begins
What occurs during Pachytene of meiosis?
Synapsis complete
Crossing over
What occurs during Diplotene of meiosis? (2)
Synaptonemal complex disappears
Chiasma visible
What occurs during Diakinesis of meiosis?
Bivalent ready for metaphase
What is the frequency of crossing over in humans?
Occurs at least once in each chromosome arm
What forms between paired homologous chromosomes in meiosis?
Synaptonemal complex (nucleoprotein ‘zipper’)
What occurs during Metaphase I of meiosis?
Alignment of tetrads on metaphase plate
What occurs during Anaphase I of meiosis?
Half of tetrad (dyad) migrates to one pole, the other half to opposite pole (disjunction)
What occurs during Telophase I of meiosis?
Nuclear membranes form around dyads
Cell division
What does Meiosis II follow?
Telophase I or short interphase
What form do chromosomes take during Prophase II of meiosis?
Each dyad composed of sister chromatids
What occurs during Metaphase II of meiosis?
Alignment of dyads on metaphase plate
What occurs during Anaphase II of meiosis?
Half of dyad (monads) migrate to opposite poles
What occurs during Telophase II of meiosis?
Cytokinesis
What is the difference in meiotic divisions between sperm and egg cells?
In oogenesis, meiotic divisions may not be continuous
Where does the first division in oogenesis arrest?
Prophase I
What is aneuploidy?
Chromosome number is not an exact multiple of haploid number
What is trisomy?
When 3 copies of a chromosome are present rather than 2
What is trisomy 8?
Warkany syndrome
What is trisomy 12?
Chronic Lymphocytic Leukemia
What is Trisomy 13?
Patau Syndrome
What is trisomy 18?
Edwards Syndrome
