4.3 Flashcards
DNA helicase (function)
unzips DNA helix
DNA polymerase (function)
moves along separated strands and produces complementary strands
DNA ligase (function)
fills in the gaps between Okazaki fragments on lagging strand
1 parental DNA molecule makes ___ new daughter DNA molecules
this process is called ___
2
semiconservative replication
DNA helicase…
opens the DNA helix, exposing the nitrogenous bases
DNA polymerase…
reads nitrogenous bases and matches them w/ complementary free nucleotides
DNA ligase…
joins the newly synthesized segments of DNA
which molecule usually detects and corrects errors in DNA replication?
DNA polymerase
exposure to chemicals and radiation may lead to changes in DNA structure called ___
mutations
G1 phase (def)
interval b/n cell division and DNA replication
cell synthesizes proteins, grows, and carries out is preordained tasks for the body
cell accumulates the materials needed to replicate its DNA in the next phase
how accurate is DNA replication?
the few errors made by DNA polymerase are usually corrected by DNA polymerase or other repair enzymes
describe events that occur during the synthesis (S) phase of the cell cycle
a cell makes a duplicate copy of its centrioles and all of its nuclear DNA
what occurs during the G2 phase of the cell cycle?
cell synthesizes enzymes that control cell division and also checks and repairs the newly copied DNA
during the cell cycle, G1, S, and G2 collectively make up the phase known as what?
interphase
S phase (def)
period of synthesis during which a cell makes a duplicate copy of its centrioles and all of its nuclear DNA
which phase is the period of time during which cells are in a non-dividing phase outside of the cell cycle? The length of this period is variable and for some cells it may last days, years, or the rest of one’s life
G0
which phase is a short period fo time of growth and preparation for mitosis? During that time, the cell produces enzymes that control cell division, and also checks and repair the newly copied DNA
G2
indicate which events occur during prophase of mitosis
chromosomes condense
spindle fibers grow from the centrioles
nuclear envelope disappears
centrioles are pushed apart (migrate to opposite poles of cell)
during metaphase, the spindle fibers form a lemon-shaped array called the ___ spindle
mitotic
what is true of the G0 phase of the cell cycle?
an inability to stop cycling and enter G0 is characteristic of cancer cells
the duration of this phase is variable (for some cells it may last days, years, or the rest of one’s life
during this phase cells leave the cell cycle for a “rest” and cease to divide
what occurs during anaphase?
daughter chromosomes migrate to opposite ends of cell
the new nuclear envelop forms, new nucleoli appear, and the mitotic spindle vanishes during which phase of mitosis?
telophase
during the mitotic phase called ___, chromosomes condense, the nuclear envelop disappears, spindle fibers grow, and centrioles migrate to the poles of the cell
prophase
G0 phase
period fo time during which cells are in a non-dividing phase outside of the cell cycle
length of this period is variable and for some cells it may last days, years, or the rest of one’s life
cytokinesis is the division of the cell’s ___ to form 2 cells
cytoplasm
statements that describe telophase
chromatids cluster on each side of the cell
nuclear envelop reappears
cells (start/stop) dividing when they snugly contact neighboring cells or when growth factors are withdrawn
stop
what events occur during prophase of mitosis?
chromosomes condense
nuclear envelope disappears
centrioles are pushed apart
spindle fibers grow from the centrioles
cell division is stimulated by ___ and suppressed by ___
growth factors
contact inhibition
what is a cleavage furrow?
an indentation between the future cells that forms as cytokinesis progresses
cyclins and Cdks are families of proteins that help regulate which of the following?
the cell cycle
the division of the cytoplasm to form 2 cells is called ___
cytokinesis
when do cells divide?
1) when neighboring cells die, opening up space in a tissue to be occupied by new cells
2) when they have replicated their DNA, so they can give each daughter cell a duplicate set of genes
3) when they grow large enough to have enough cytoplasm to distribute to their 2 daughter cells
4) when they are stimulated by growth factors
5) when they receive adequate supply of nutrients
contact inhibition
when cells snugly contact neighboring cells –> cell stops dividing
at 3 specific checkpoints during the cell cycle, a cyclin binds to a Cdk and activates a series of reactions that allow the cell to move on to the next phase. When in the cell cycle do these checkpoints occur?
During the G1 phase
between the S and G2 phases
at the end of metaphase
cyclins and Cdks are families of proteins that help regulate ___
the cell cycle
