Bio exam 3 chapter 16

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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?


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