Bio Lesson 19 - Exam 4

DNA replication

DNA makes a copy of itself for cell division (nucleus)

DNA transcription

DNA creates messenger RNA (nucleus)

RNA translation

RNA is translated to produce a protein (cytoplasm)

replication

The structure of DNA suggests a method for _____

hydrogen, complementary

the structure of DNA —> two strands are held together by _____ bonds via _____ base pairing

weak (can break and reform)

hydrogen bonds are ____

template

a strand of DNA can be used as a _____ to make the complementary strand

conservative model

two old strands stay together, two new strands pair

semi conservative model

each daughter molecule has one old strand (“conserved” from the parent molecule) and one newly made strand

dispersive model

all strands could be a mix of old and new DNA

Matthew Meselson and Frank Stahl

who devised an experiment to test the various models of DNA replication

heavy (¹⁵N), lighter (¹⁴N)

In the Meselson and Stahl’s Experiment, they grew bacteria in a culture with a ____ isotope of nitrogen (___), moved the bacteria into media with a _____ isotope of nitrogen (_____), and separated the DNA based on density

¹⁵N to ¹⁴N, ¹⁴N, semi-conservative

In the Meselson and Stahl experiment, bacteria were switched from _______, and over time more new _____ DNA appeared while the original mixed (¹⁵N + ¹⁴N) DNA stayed the same, proving DNA replication is ______.

semi conservative

DNA replication is _____

proteins

While conceptually simple, the actual process of DNA replication requires many interacting _____

fast

DNA replication is amazingly ____

errors

DNA replication occurs without many _____

1000

50

in bacteria, DNA replication is about _____ nucleotides/second

in humans, DNA replication is about ____ nucleotides/second

replication, template

Enzymes and proteins DO _____. DNA is just a _____.

No, DNA is just a template

does DNA perform replication?

Enzymes and proteins

what does replication by copying the DNA template

nucleus, entire strand

DNA occurs in the _____ and copies _____ of DNA

original DNA, new

in semi conservative process each new double helix contains one strand from the ______ double helix and one _____ strand

unwinds, separates

Before a cell divides, the DNA double helix _____ and ______

base-pairing

during cell division, each original DNA strand acts as a template for _____

double helices, daughter

DNA replication (carried out by enzymes and proteins) creates the two new _____, which are then passed on to the _____ cells.

prokaryotes

eukaryotes

______ → one origin, circular DNA, single chromosome

______ → many origins, linear DNA, multiple chromosomes

origin of replication

a specific site (DNA sequence) where DNA replication begins

replication fork

the site at each side of the replication bubble where DNA strands are unwound and separated

origin of replication, bubble, directions, copied

DNA replication begins when proteins attach to the ______, separate the DNA strands to form a replication _____, and replication proceeds in both ____ until the chromosome is fully _____

helicase, single-stranded binding

Replication begins when _____ recognizes the origin of replication and unzips the DNA into two strands, while _____ proteins stabilize the separated strands

helicase

protein that untwists the double helix at the replication fork

single-strand binding proteins

bind to the newly separated DNA strands and prevent them from re-pairing

topoisomerase

protein that breaks, swivels, and rejoins the parental DNA ahead of the replication fork, relieving the strain caused by unwinding

helicase, single-stranded binding proteins, topoisomerase, primase, DNA polymerase III, DNA polymerase I, DNA ligase

what are the important proteins that do replication (7)

helicase

unzips the DNA double helix

Single-stranded binding proteins (SSB)

keep strands from re-pairing

topoisomerase

relieves strain ahead of the replication fork

primase

adds RNA primers to start replication

DNA polymerase III

builds the new DNA strand (adds nucleotides)

DNA polymerase I

replaces RNA primers with DNA

DNA ligase

joins DNA fragments (Okazaki fragments) together

RNA primer, 3’

to start the new strand, primase makes an _____ that provides a starting ____ end so DNA polymerase can begin adding nucleotides, since DNA cannot start from scratch.

parental, new

once the DNA is unwound at an origin of replication, the two _____ stands serve as templates for the ____ strands that will be made

primer

DNA nucleotides can’t start from scratch, they need something to start the process → _____

primer

a short RNA sequence made by primase that provides a starting 3’ end for DNA nucleotides to begin building a new DNA strand

3’, 3’

DNA polymerase can only add new nucleotides to the ____ end of an existing strand, so the new DNA grows by extending from that _____ end (provided by the primer)

primase (enzyme)

creates an RNA polymer (primer) that is complementary to the template DNA strand

RNA primer

Primase creates an _____

RNA, DNA

_____ can start a new nucleic acid chain (the primer) from scratch, but ____ can not

primer

a very short RNA piece (only 5 to 10 nucleotides long) that starts DNA replication

elongation

building the new DNA strand from the template strand

DNA polymerases

enzymes which build a new DNA strand by adding nucleotides to a preexisting chain

two (polymerase III & polymerase I)

bacteria have _____ polymerases involved in DNA replication

three (polymerases a, weird s, and weird e)

eukaryotes have a family of _____ polymerases

eukaryotes

prokaryotes (bacteria)

3 polymerases = _____

2 polymerases = _____

DNA Polymerase III

catalyzes the formation of a covalent bond between the 3’ carbon of the growing DNA strand and the 5’ phosphate of the incoming nucleotide, adding nucleotides during DNA replication

TRIphosphate

DNA Polymerase III begins as a nucleotide _____

nucleotides

DNA Polymerase III forms covalent bonds between _____

5’ → 3’ (by adding to the 3’ end)

3’ → 5’

DNA Polymerase III BUILDS DNA in the ______ direction

It READS the template strand in the ______ direction

reads

builds

DNA Polymerase III _____ the template strand in the 3’ → 5’ direction

DNA Polymerase III _____ DNA in the 5’ → 3’ direction

energy

each incoming nucleotide already contains the _____ needed to be added to the growing DNA strand

leading strand

the new DNA strand that is synthesized continuously in the 5’ → 3’ direction from a single RNA primer, following the replication fork

5’ → 3’

the leading strand is built continuously in the _____ direction

helicase

opposite direction, helicase

To build the leading strand, DNA polymerase III follows ____

To build the lagging strand, DNA polymerase III needs to build in the _____ to the _____

leading

To build the _____ strand, DNA polymerase III follows helicase

lagging

To build the _____ strand, DNA polymerase III needs to build in the opposite direction to helicase

lagging strand

the new DNA strand that is synthesized discontinuously in short segments called Okazaki fragments (each made 5’ → 3’ away from the replication fork) and requires multiple RNA primers

away, 5’ to 3’

To make the lagging strand, DNA polymerase III must move _____ from the replication fork to work in the _____ direction

Okazaki fragments

short segments of DNA synthesized on the lagging strand (each built 5’ → 3’) that are later joined together by DNA ligase

RNA primer

On the lagging strand, each Okazaki fragment requires a new _____ to begin synthesis

primase

For each Okazaki fragment, _____ makes an RNA primer

leading

lagging

_____ strand → happens once (continuous)

_____ strand → repeats this process many times because it’s built in fragments (Okazaki fragments)

polymerase III, polymerase I, ligase

DNA _____ builds an Okazaki fragment from an RNA primer until it reaches the next fragment, then DNA _____ replaces the RNA primer with DNA and DNA ____ joins the fragments into a continuous strand.

replication machine

DNA replication proteins work together to form a _____

replication fork

one complex of proteins at each _____ works to synthesize

nuclear matrix

the replication machine is attached to the _____

through, along

in the DNA replication machine, the DNA moves ____ the machine, the machine does not move ____ the DNA

lagging, Okazaki fragments

in the DNA replication machine, the _____ strand loops back through the replication machine to generate the ______

primase, replication

_____, which is associated with the replication machine, controls the rate of _____

replication fork, synthesizes

At each _____, DNA replication proteins form a replication machine that ____ the leading and lagging strands as DNA moves through it, with primase helping control the rate of replication.

mismatch repair

a process where enzymes detect incorrectly paired bases in newly synthesized DNA, remove the mismatched section, and replace it with the correct nucleotides

mechanisms

Cells have _____ to fix mistakes in DNA

proofreading mechanism

DNA polymerases at the replication fork can “back up” and remove a nucleotide that is incorrectly paired – a ______

mismatched

Cells can repair _____ DNA

DNA polymerase, mismatch repair

Cells fix DNA replication errors using proofreading by ______ and ______, which removes and replaces incorrect bases to keep DNA accurate.

origins, helicase, topoisomerase

Replication starts at _____: _____ unzips DNA, SSB proteins stabilize strands, ______ relieves strain

hydrogen, each strand

DNA strands separate due to weak _____ bonds, allowing copying of _____

continuous, ligase, primers

The leading strand is _____; the lagging strand is built in Okazaki fragments and joined by _____ after _____ are replaced.

DNA, primers, strands, DNA molecules

DNA replication is semi-conservative, where each original strand serves as a template to build a new strand, and important enzymes unzip _____, add _____, build ____, and join them to form two identical ______ with one old and one new strand.