Lecure #2 Meiosis Flashcards
What are the similarities between mitosis and meiosis? What are the differences?
Similar: only 1 interphase, second division results in the splitting of sister chromatids
Differences:(in meiosis)first division results in the separation of homologous chromosomes, 4 genetically uniques daughter cells are created and they are haploid
Mitosis vs. Meiosis
Mitosis: occurs in stems cells, 2 diploid daughter cells created, daughter cells are genetically identical, process is always happening
Meiosis: single event, occurs in sex cells, 4 haploid daughter cells, each daughter cell is genetically unique
What happens in prophase 1 (meiosis 1)
Chromosomes become visible
DNA has replicated
Homologous chromosomes condense and undergo synapsis
Bivalent forms (homologous chromosomes line up together)
What occurs during crossing over
A bivalent is formed between homologous chromosomes and form a chiasma( chromatids [non-sister and sister] cross over an swap DNA) to overall make recombinant chromatids
What happens in prophase 1 (meiosis 1)
Chromosomes continue to shorten/thicken and chiasma(crossing over becomes more apparent)
Nuclear envelope starts to break down
What happens in prometaphase 1?
Spindles attach to kinetochores on chromosomes
What happens during metaphase 1
Homologous pairs line up in the centre of the cell and bivalents are organized randomly with respect to each other
Mitosis metaphase vs meiosis 1 metaphase
Mitosis: 46 chromosomes aligned in one plane, spindles attached to kinetochores on opposite ends of the sister chromatids, no recombinations
Meiosis: 23 pairs of homologous chromosomes are aligned in one plane, spindles attached to kinetochores on the same side of the sister chromatid, recombination between homologous chromosomes
What happens during anaphase 1
Homologous chromosomes separate (sister chromosomes do not)
What happens during telophase 1 and cytokinesis
Daughter cells are ready to move into prophase 2
What is the ploidy level after cytokinesis in meiosis 1
n, cells went from diploid to haploid
What happens in prophase 2
Nuclear envelope breaks down
Chromosomes condense
What happens during prometaphase 2
Spindles attach to kinetochores on chromosomes
What happens during metaphase 2
Chromosomes align in the centre of the cell
What happens during anaphase 2
Sister chromatids separate
What happens during telophase 2 and cytokinesis
Nuclear envelope reforms and cytoplasm divides
What is the differences between mitosis and meiosis in female vs male germ cells
Males: continuous, embryo(mitosis) to adult (meiosis), four sperm cells created
Females: 2 “arrests”, meiosis 1 arrest in 1+ ochres during each menstrual cycle, meiosis 2 arrests in fertilization, mitosis occurs rapidly
Name the proteins that help to regulate the cell cycle and name their functions
Cyclins - appear and disappear in cyclical functions to activate CDKs
Cyclin-dependent kinases (CDK) - controls progression through the cell cycle
Cyclin-CDK complexes - phosphorylation target proteins that promote cell division
What are the different cyclin-CDK complexes and what are their functions?
M cyclin-CDK: prepares cell for mitosis
S cyclin-CDK: helps to initiate DNA synthesis
G1/s cyclin-CDK: prepares cell for DNA replication
