Biology test chapter 8

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what is chromatin?
DNA/protein complex which is loosely packed between cell divisions
what are chromosomes?
tightly packed and coiled DNA with proteins called histones
What are histones?
proteins which help maintain the shape of the chromosomes and aid in the packing of DNA
what are chromatids?
what the chromosome is made up of (two)
what forms when the DNA replicates itself before cell division?
chromatids
what happens when somatic cells divide?
each daughter cell receives one chromatid
what holds the two chromatids together?
a centromere
how many chromosomes do humans have per somatic cell?
46
how many chromosomes do humans have per gamete?
23
What are sex chromosomes?
determine the gender of an organism
what are sex chromosomes labelled in humans?
female= xx
male= xy
what are autosomes?
the remaining 44 chromosomes in each cell (22 pair)
what are homologues?
two copies of each autosome
What are diploid cells?
2n- cells having 2 homologous chromosomes
all human cells except reproductive cells are what?
diploid cells
What are haploid cells?
1n- reproductive cells (such as eggs and sperm cells) containing only one set of unpaired chromosones. each only have one chromatidof each homologous pair
be able to label the parts of the cell cycle
what is interphase?
the time between cell divisions immediately after cell division
what are the 4 phases of interphase?
G1, G0, S, G2
What happens during the G1 phase?
offspring grows to full size
What happens during the G0 phase?
some cells once mature do not divide. nerve cells mature and live as long as the body and red blood cells do not replicate but die at 120 days
What happens during the S phase?
DNA is copied and chromosomes are formed
What happens during the G2 phase?
cell prepares for cell division
What are the parts of cell division?
mitosis and cytokinesis
what is mitosis?
division of the nucleus
what are the 4 phases of mitosis?
prophase, metaphase, anaphase, telophase
What happens during prophase?
1. DNA is coiled into chromosomes
2. chromatids are connected by a centromere
3. nucleolar and nuclear membranes disintegrate
4. centrioles produce spindle fibers which attach to the centromere
what happens during metaphase?
chromosomes are moved to the center of the cell and held in place by the spindle fibers
What happens during anaphase?
chromatids separate at the centromere
what happens during telophase?
1. spindle fibers break down
2. chromosomes return to less densely coiled chromatin
What is cytokinesis?
begins with the pinching in of the cell membrane between two poles
What is prokaryotic cell division?
binary fission
what is the cleavage furrow?
pinches the cell into two using microtubuals
What is binary fission?
asexual reproduction
what is eukaryotic cell division?
meiosis
what is meiosis?
process of cell division that reduces the number of chromosomes in the new cell to half the original cell; the cell divides twice resulting in 4 haploid cells
what are gametes?
eggs and sperm cells in humans
how many chromosomes does each gamete contain?
23
what does the fusion of two gametes results in?
a diploid cell
What are the phases of meiosis?
interphase, meiosis I, Meiosis II
what happens during interphase of meiosis?
goes through G1, S, and G2, matures and grows and copies DNA just like autosome
What are the parts of meiosis I?
prophase I , metaphase I, anaphase I, telaphase I, cytokinesis I,
describe prophase I
1. DNA coils into chromosomes
2. spindle fibers appear
3. nuclear and nucleolar membranes disassemble
synopsis- every chromosome lines up next to its homologue
describe synopsis
crossing over occurs between homologues and each pair of homologous chromosomes is called a tetrad
describe metaphase I
tetrads line up at midline,
spindle fibers from one pole attach to the centromeres
describe anaphase I
homologous chromosomes move to opposite poles of the cell
describe telaphase I
1. chromosomes reach opposite poles of cell
2. chromosomes do NOT uncoil into chromatin
3. nuclear and nucleolur envelopes reform
describe cytokinesis I
2 new haploid cells are formed
What is meiosis II?
occurs in each cell that went through meiosis I
what are the parts of meiosis II?
prophase II, metaphase II, anaphase II, telaphase II, cytokinesis II
describe prophase II
spindle fibers form and begin to move chromosomes toward midline
describe metaphase II
chromatids face opposite poles of cell
describe anaphase II
individual chromatids separate and move toward opposites poles of cells
describe telaphase II
nuclear membrane forms around chromosomes and the nucleolus appears
describe cytokinesis II
complete cell division resulting in 4 new haploid cells
what happens in the reproductive organs of the organisms?
gametes are formed meiosis is completed
what spermatogonius?
production of sperm cells
what is spermatogonium?
immature sperm cells are produced in the testes
what is spermatocytes?
mature sperm cells
what is oogenesis?
production of one ova and 3 polar bodies
what is an oogonium?
immature egg cell
what is an oocyte?
mature egg cell
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