Bio exam 3 chapter 16
postpone the erosion of genes near the ends of DNA molecules
Telomeres do not prevent the shortening of DNA molecules, they do, however, _____
germ cells
Telomeric shortening cannot be tolerated in__
Because it contains more information than RNA or Protein, and because it is the only biological molecule that can copy itself.
Why must a cell copy its DNA?
Neither strand would form because new DNA cannot be synthesized without a primer
Without the activity of the primase enzyme what would happen during DNA replication?
chromatin
a complex of DNA and protein
Unwinds DNA to create two single strands
helicase
Can remove RNA nucleotides as it adds new DNA in a 5' - 3' direction
polymerase I
Assembles new DNA strand in the 5' - 3' direction
polymerase III
Provides an RNA primer to start new DNA strand synthesis
primase
Binds to and stabilizes the single stranded DNA
single strand binding proteins
continuous in the 5 to 3 direction
synthesis of leading strands is
Maintains telomere length in germline cells to protect the health of gametes
telomerase
generally shorter in older individuals.
telomeres in somatic cells are__
may be protective against cancer by limiting continuous cell division; research suggests that telomerase activity within tumor cells can be oncogenic
telomeric shortening
DNA polymerase
to elongate the lagging strand, ____ must work in the direction away from its replication fork
Travels ahead of helicase "nicking" and swiveling the DNA to relieve torsional strain on the molecule
topoiosomerase
2 copies of each chromosome
what are diploid cells?
euchromatin
what are loosely packed chromatin called?
they have a circular genome, a single DNA molecule, and one origin of replication
what are the different genomes and the different replication of bacteria? (prokaryotic)
they have a linear genome, they have multiple linear chromosomes, and they have multiple origins of replication on each chromosome
what are the different genomes and the different replication of humans? (eukaryotic)
Helicase, single strand binding protein, primes, topoisomerase, polymerase, ligase
what are the proteins that are recruited?
DNA ligase
what can join the 5 end of one DNA molecule with the 3 end of another
DNA polymerase 1
what can remove RNA nucleotides and fill in the gap with DNA nucleotides?
a primer and a DNA template strand
what do most DNA polymerases require?
they recruit proteins necessary for replication
what do specific DNA sequences (A and T rich repeats) do?
telomerase
what is expressed in germ cells to maintain telomeres at their original length?
DNA polymerase III; Okazaki fragments
what is the lagging strand synthesized by? what are these series of segments called? (LOOK AT ANIMATION
primase
what must assemble new primers in lagging strand synthesis?
they only add nucleotides to the free 3 end of a growing strand, therefore a new DNA strand can elongate only in the 5 to 3 direction
where do DNA polymerases add nucleotides?
in the nucleus of eukaryotic cells
where is chromatin found?
eukaryotic chromosomes
which type of chromosomes do not appear to have termination sequences like prokaryotes?
human polymerase
50 nucleotides/sec
bacterial polymerase
500 nucleotides/sec
DNA polymerase will mistakenly add the wrong nucleotide
About once ever 100,000 nucleotides (1500 times per average human chromosome)..
exonuclease
Both DNA Pol I and DNA Pol III have 3' to 5' ______ activity which allows them to remove the mistaken nucleotide as soon as it is added
cell division
Cells must only replicate their DNA in preparation for what?
express genetic information coded in these regions
Dense packing of the heterochromatin makes it difficult for the cell to...
heterochromatin
During interphase a few regions of chromatin (centromeres and telomeres) are highly condensed into
They have less total DNA to copy.
Eukaryotic cells have multiple origins of replication on their chromosomes. Why do you think that prokaryotic cells have only one origin of replication on their chromosomes?
telomeres
Eukaryotic chromosomal DNA molecules have special repetitive, non-coding nucleotide sequences at their ends called
They contain ter sites (23bp sequences); they cause termination in vitro; a protein bound to the ter site stops the replication fork from proceeding
Explain the termination sequences in prokaryotes.
The leading strand is synthesized in the same direction as the movement of the replication fork, whereas the lagging strand is synthesized in the opposite direction.
How do the leading and the lagging strands differ?
The leading strand would not be able to connect to the lagging strand approaching it from the next origin of replication
If DNA pol I was non-functional, how would that affect the leading strand during DNA synthesis in a eukaryotic cell? (check this one slide 40)
5'TGCAAT3'
If one strand of a DNA molecule has the sequence of bases 5'ATTGCA3', the other complementary, antiparallel strand of DNA would have the sequence:
nucleoid
In a bacterium, the DNA is "supercoiled" and found in a region of the cell called the
DNA polymerase
Which enzymes catalyze the elongation of new DNA at a replication fork?
interphase
at what stage is some chromatin organized into a 10 nm fiber, but much is compacted into a 30nm fiber through folding and looping?
histone proteins
eukaryotic chromosomes have linear DNA molecules associated with a large amount of
histones
found in eukaryotic cell nuclei that package and order the DNA into structural units called nucleosomes. They are the chief protein components of chromatin, acting as spools around which DNA winds, and playing a role in gene regulation.
Lagging strands must be made
if synthesis of the leading strand is continuous in the 5 to 3 direction, how is the other strand copied in each direction?
must pack much more tightly into pairs of chromatids
in preparation of cell division, chromatin...
Joins two DNA strands together at their ends
ligase
the nucleus
most chromatin is loosely packed where during interphase?