module 6-9 Flashcards
-metabolic processes -cell reproduction
how is the cell cycle inhibited?
factors that inhibit the cell cycle:
-some proteins act at the G1 checkpoint.
(it is often these proteins that are mutated and malfunctioning when cancer is seen.)
what are cyclins?
protein growth factors that combine with another protein (Cdk) to form complexes that promote cell division.
how is the cell cycle promoted?
factors that trigger cell division:
-death of nearby cells
-cells size (if too big, must divide because of SA:V)
-release of growth promoting hormones (e.g hGH/human growth hormone)
-cyclins
what is the G0 phase?
-some cells enter this phase due to environmental conditions, and will remain until conditions improve or an external signal triggers the start of G1
-cells aren’t actively preparing to divide.
-some cells that rarely divide will stay in this phase permanently (mature cardiac muscle cells, nerve cells).
what occurs in cytokinesis of the mitotic phase in plant cells?
- during interphase the golgi accumulates enzymes, structural proteins and glucose before being packaged and dispersing.
- during telophase the golgi vesicles are transported on microtubules to form a phragmoplast at the metaphase plate.
- the vesicles fuse from the center toward the cell walls, and a cell plate is formed.
- as more vesicles fuse the plate enlargens until it fuses with the cell walls
- enzymes use the glucose accumulated between the membrane layers to build a new cell wall.
- the golgi membranes become parts of the plasma membrane on either side of the new cell wall.
what occurs in cytokinesis of the mitotic phase in animal cells?
-starts during late anaphase
-ring composed of actin filaments forms inside the plasma membrane at the former metaphase plate.
-the filaments pull the equator of the cell inwards forming a cleavage furrow.
-the furrow deepens as the actin ring contracts, leading to the membrane cleaving in two.
what occurs in telophase of mitosis
-the chromosomes reach opposite poles and unravel, relaxing into their stretched chromatin configuration.
-the mitotic spindles depolymerized into their tubulin monomers
-a nuclear envelope forms around the chromosomes and nucleosomes appear within the nuclear area.
what occurs in anaphase of mitosis
-the cohesion proteins degrade and the sister chromosomes separate at the centromere.
-each singular chromosome is pulled toward the centromere to which its microtubule is attached.
-the cell elongates as the polar microtubules slide against each other at the metaphase plate.
what occurs in metaphase of mitosis
-all chromosomes align themselves along a plane called the metaphase plate/equatorial plate midway between poles.
-the sisters chromatids are still attached to one another by cohesion proteins.
-the chromosomes are maximally condensed.
what occurs in prometaphase of mitosis
-many processes that began in prophase advance.
-each sister chromatid develops a protein structure called a kinetochore in its centromeric region.
-as the microtubules extend they bind with the kinetochores.
-microtubules that don’t engage the chromosomes are called polar microtubules. they overlap one another and contribute to cell elongation.
what occurs in interphase and it’s 3 stages?
-the cell undergoes normal cell growth while preparing for cell division.
3 stages:
-G1 (gap 1). little change can be observed. cell gathers energy and resources required to replicate chromosomes.
-s-phase. nuclear DNA remains in a chromatin configuration. centrosome is replicated, and the centrosomes give rise to mitotic spindles.
-G2 (gap 2). cell replenished energy stores and synthesizes proteins required for chromosomal manipulation and movement. some organelles re duplicated and the cytoskeleton is dismantled to provide resources. additional cell growth may occur.
what occurs in prophase of mitosis?
-the nuclear envelope starts to disassociate into vesicles, and the membrane-bound organelles and nucleolus disperses towards the outer edges
-the centrosomes begin to move to opposite poles of the cell.
-microtubules that will form mitotic spindles extend between the centrosomes extend push them apart.
what are the 5 stages of mitosis?
-prophase
-prometaphase
-metaphase
-anaphase
-telophase
(PPMAT)
what are the two steps involved in the mitotic phase?
-mitosis (division of the nucleus and duplicated chromosomes)
-cytokinesis (division of the cytoplasm)
what are the two steps involved in cell replication?
-interphase (non-dividing growth and replication stage
-mitotic phase (where cell division takes place)
what is non-disjunction?
-the failure of chromosomes to separate during meiosis.
-can occur when both pairs of the chromosome move to the same poles during anaphase 1, or anaphase 2.
what is random fertilization?
-a source of genetic variation.
-due to independent assortment, gametes are very diverse genetically. during fertilization any one of the (8.4mill) chromosomal combinations of gametes may combine
what is independent assortment
-a source of genetic variation
-occurs during prophase 1 when the chromosomes line up in a random orientation along the metaphase plate.
-also occurs during metaphase where homologous chromosomes are randomly assorted into cells, leading to daughter cells with unique combinations.
what are the steps involved in crossing-over
1.after interphase, the sister chromatids are held together by proteins called cohesions. the DNA molecules of two non-sister chromatids are broken a corresponding points, and the chromatin of the chromosomes continue to condensing.
2. a kind of protein complex called a synaptonemal complex begins to form and attaches one homologue to the other. the chromatin continues condensing
3.the synaptonemal complex is fully formed. the two homologues are in synopsis, where the DNA breaks are closed up when each broken end is joined to the corresponding segment of the non-sister chromatid, producing crossovers
4. the synaptonemal complex disassembles, the homologues move apart slightly but remain attached due to sister chromatid cohesion. the points of attachment are called chiasma. the chromosomes continue to condense as the cell moves into metaphase.
what is crossing-over
a source of genetic variation that occurs during prophase 1 of meiosis.
-produces recombinant chromosomes
draw a diagram of what happens in meiosis
