LO10 Flashcards
Carry genetic information
chromosomes
each chromosome contains ______ of genes
1000’s
definition: a segment of DNA that codes for a protein
gene
DNA is a ______________ gene
protein-coding
RNA is a ______________ gene
non-coding
regulate the expression of protein-coding genes
non coding genes
has multiple linear chromosomes
eukaryotes
has single circular chromosomes that is supercoiled in the nucleoid region
prokaryotes
are highly organized
chromosomes
DNA double helix would around histone proteins
chromatin
Definition: prevent the DNA from getting tangled and help regulate gene expression
histones
basic unit of chromatin structure is the ____________
nucleosome
nucleosome includes _____ bp of DNA wrapped around ___ histones
146; 8
nucleosomes are packed together to form compacted _______
chromatin
most cells ____ when mature
divide
definition: the longest part of the cell cycle
interphase
there is not division during this phase of the cell cycle
Interphase
during interphase a cell is (doing what?)
growing and carrying out normal activities while preparing to divide
includes mitosis + cytokinesis
M phase
definition: division of the nucleus in five stages
M phase
this phase result in two genetically identical daughter nuclei
M phase
division of the cytoplasm
cytokinesis
this phase splits the cell and results in two identical daughter cells
cytokinesis
Interphase includes three parts
G1, S, G2
the first gap phase and longest part of interphase
G1
during G1 the cell does what?
grows and prepares for S phase
what happens when some cells don’t divide once their mature
they remain in a modified G1 (called G0) permanently
what cells remain in G0
animal blood cells, neurons and muscle cells
S in interphase is what?
synthesis
what happens during the S phase of Interphase
- DNA replication occurs and additional histone proteins are synthesized to help organize the new DNA
- centrioles are duplicated
G2 is what in interphase
The second gap phase
during G2 what happens
- the cell makes final preparation for M phase
what is the first stage of mitosis
prophase
how does prophase begin
as chromatin condenses to form mitotic chromosomes
definition: a chromosomes that is temporarily attached to an identical during cell division
chromatid
during prophase each chromosome temporarily consists of ______________ joined at their ________
two identical sister chromatids; centromeres
during prophase the ____ begins to form
mitotic spindle
the mitotic spindle is made from
microtubules
spindle microtubules eventually do what?
attatch to proteins called kinetochores at the centromere of each sister chromatid
in prophase the nuclear envelope begins to what?
fragment and the cytoskeleton is disassembled
during _______ spindle microtubules attach to sister chromatids and gradually move chromosomes towards the equator
prometaphase
prometaphase begins when?
the nuclear envelope is complete
during prometaphase sister chromatids end up attached to spindle microtubules from _______ poles
opposite
this phase in M phase occurs when the chromosomes are aligned along the metaphase plate in the middle of the cell
metaphase
this phase in M phase begins when the sister chromatids start to separate
anaphase
during anaphase what happens to sister chromatids
they are pulled to opposite poles of the cell by shortening microtubules as the cohesin proteins that holding the chromatids together dissociate
M Phase: the last phase of mitosis and results in a return to interphase conditions
telophase
what happens during telophase
- the nuclear envelope re-forms
- chromosomes decondense
- spindle microtubules are disassembled
cytokinesis begins when?
late anaphase or telophase
in cytokinesis animal and fungal cells do what?
form a contractile ring or microfilaments and myosin to physically separate the daughter cells
in cytokinesis plant cells do what?
form a cell plate along their equator
the cell plate plant cells from is made from
membranous vesicles that form plasma membrane between the daughter cells
how do prokaryotes divide
by binary fission
definition: binary fission
method of asexual reproduction in that it produces daughter cells that are genetically identical to the parent cells
steps of binary fission
- begins with a cell’s circular chromosome
- duplicated chromosomes move to opposite ends of the cell
- cell divides as the plasma membrane grown inward
- a new cell wall forms between the daughter cells
in eukaryotes mitochondria and chloroplast divide how?
by binary fission in interphase
definition: ensure tha tthe events of a particular stage are properly completed before the next stage begins
cell-cycle checkpoints
what are the checkpoints that eukaryotes have
- G1-S checkpoint
- G2 - M checkpoint
- metaphase - anaphase
this checkpoint ensures that the cell has the needed nutrients and enzymes to synthesize DNA
G1-S checkpoint
this checkpoint ensure that DNA replication is finished before the ce;l begin mitosis
G2-M checkpoint
if a cell is damaged or unreplicated DNA this checkpoint will prevent it from entering M phase
G2-M checkpoint
this checkpoint ensures that kinetochores are properly attached to spindle fibers along the metaphase plate
metaphase - anaphase checkpoint
if this checkpoint is defective what will happen?
chromosomes may not be properly separated during anaphase
definition: individuals have 3 copies of chromosomes 21 because chromosomes were not properly separated
trisomy-21
definition: kinases that bind with cyclin proteins to form cyclin-Cdk complexes that regulate the cell cycle by phosphorylating needed enzymes
Cyclin-dependent kinases (Cdk’s)
in animals somatic cells are _____
diploid 2n
definition: contain two copies of each chromosome
diploid
homologous pairs are what?
two copies of chromosomes
definition: contain the same genes in the same order but they may have dif variant of those genes
homologs
somatic cells
non-reproductive cells
gametes
reproductive cells
definition: typically haploid n
reproductive cells
definition: union of two haploid gametes to form a diploid zygote
fertilization
sexual reproduction requires what?
a reduction division in the reproductive cells prior to fertilization to offset the combining of chromosomes during fertilization
during meiosis a diploid cell undergoes what?
two division meiosis I and II
at the end of meiosis what is produced
four haploid cells
what is apart of the meiotic cell cycle
interphase + M Phase
definition: an abbreviated interphase without an S phase
interkinesis
during interphase of meiosis chromosomes are duplicated
during S phase and producing sister chromatids
at the beginning of prophase I homologous chromosomes under go what?
synapsis
during synapsis what happens?
homologs join to form tetrads of four chromatids
homologs are held together by what
synaptonemal complex which facilitates crossing over
what happens during crossing over in prophase 1
equivalent segments of DNA are exchanged between nonsister chromatids
- this allows for genetic recombination
definition: where crossing over occurs
chiasmata
things that happen during prophase I include
- chromatin condenses
- meiotic spindle forms and centrioles duplicated
- nucleus fragments
during metaphase 1 where are tetrads?
lined up along the equator
during anaphase I what happens?
- homologs are pulled to opposite poles
- sister chromatids remain attached
- each pole receives a random combination of maternal and paternal homolgs
During telophase I what happens
- nuclei reform and chromosome decondense
- each nucleus is haploid
meiosis 1 cytokinesis produces what?
two genetically different haploid daughter cells
in meiosis II each haploid daughter cell
proceed through interkinesis and then enters meiosis II
in prophase II there is no crossing over
homologs are in different daughter cells
during metaphase II chromosomes line up where?
along the metaphase plate
- sister chromatids are attatched to microtubules from opposite poles
during anaphase II sister chromatids are pulled where?
to opposite poles
during telophase II there is?
one chromatid from each homolog at each pole
