lab 4 Flashcards
what is the order of mitosis?
interphase (G1, S phase, G2), prophase, metaphase, anaphase, telophase, cytokenisis.
what is the order of meiosis?
meiosis 1- prophase1, metaphase 1, anaphase1, telophase1.
interkinesis
meiosis 2- prophase2, metaphase2, anaphase2, telophase2, cytokinesis.
what happens during G1, S phase, and G2?
G1- cell grows, preforms metabolic funcs, duplication of proteins and organelles.
S- DNA replication occurs, creation of duplicated chromosomes.
G2- cell prepares for division, gain energy to divide, and synth proteins and enzymes
what is interphase?
the period between cell formation and cell div
what is mitosis?
the division of the parent nucleus in which replicated DNA is distributed to two new identical daughter cells.
what is Cytokinesis?
the process of dividing the cytoplasm. begins during late anaphase and continues through mitosis. A ring of actin microfilaments contracts to form a cleavage furrow until the two daughter cells are pinched apart
explain early prophase of mitosis
Chromatin condenses, forming visible chromosomes which are held together by centromere.
centrosome synthesizing microtubules (mitotic spindles) push each centrosome to the opposite poles of the cell. the rest of the microtubules are called asters
explain late prophase of mitosis
nuclear envelope breaks up. mitotic spindles attach to kinetochores and pull chromosomes to the centre of the cell. asters push poles farther apart
explain metaphase of mitosis
centromeres align at metaphase plate (centre) by spindle fibres.
explain anaphase of mitosis
centromeres of chromosomes
split simultaneously, each sister chromatid now becomes a separate chromosome. Chromosomes are pulled toward their respective poles by kinetochores.
this is the shortest phase.
explain telophase of mitosis
Each set of chromosomes at opp poles uncoil to form chromatin. New nuclear membranes form, nucleoli reappear and spindle fibers disappear.
what is the function meiosis?
the production of gametes, introduces genetic variability, and reduces the number of chromosomes, resulting in 23 chromosomes in gametes
what is a diploid cell? haploid?
dip- 2n, 46 chrom, most cells
hap- n, 23 chrom, gametes have this so they can combined w someone elses
how many cells at the end of meiosis? how many times does DNA replicate?
ends with 4 genetically diff daughter cells DNA replicates only once
explain prophase 1
starts w diploid cells. duplicated chroms coil, shorten and become visible as individuals. centrosomes move to opp poles of cell, spindal fibers and astral rays appear and nucleoli and nuclear mem disappear.
what 2 ways introduce genetic variability?
crossing over- is the exchange of genetic material between homologous chromatids which the place where it happens is called the chiasmata, this makes them all unique, during prophase 1
independent assortment- how the 23 pairs of chromosomes align and are pulled apart, during metaphase 1
explain anaphase 1
each tetrad is pulled apart towards opp poles of cell (4-2), one chromosome from each homologous pair reaches each end of the poles. chromosomes consist of a pair of chromatids held together at each centromere
explain metaphase 1
tetrads line un at metaphase plate. theres a 50% chance of which way each chromosome will be pulled in either direction.
explain telophase 1
nuclear mem reforms, nucleoli reform, and chromosomes gradually uncoil to become chromatin.
what is the outcome of meiosis 1?
seperation of two chroms of each homologous pair. there is now two daughter cells which contain, one chromosome from homologous pair, a haploid chrom number, and chromosomes that consist of two chromatids joined at centromere.
explain interkinesis
brief rest period between
meiosis I and meiosis II
explain prophase 2
p-chromosomes become visible and centrioles go to opp poles. mitotic spindles attach to kinetochores and pull chromosomes to the centre of the cell. asters push poles farther apart. nuclear mem and nucleoli disappear.
explain metaphase 2
each chromosome is attached at centromere. spindle fibers attached and chromatid pairs line up along metaphase plate
anaphase 2
centromere of each sis chromatid pair splits and chromatids separate and are pulled to opp ends
explain telophase 2
nuclear mem appears, nucleoli reappear, cytokinesis occurs
what is the end result of meiosis?
4 genetically diff daughter cells that are haploid
what are homologous chromosomes?
a pair of chromosomes, one maternal and one paternal that carry genes for the same traits but express them differently
what is a chromosome?
condensed chromatin, composed of DNA, two sis chromatids joined at centromere
what is a centromere?
links sis chromatids together, spindle fibers attach to it vid kinetochore.
what are sister chromatids?
one of the two identical halves of a chromosome that has been replicated in preparation for cell division
