Biology -- Chapter 20

Front 1

So, how do you go about replicating such complex genetic material?

Back 1

Compliementarity! Due to the double helix, you can simply read one strand, and immediately know what the next one is (because they have to run anti-parallel to each other).

Front 2

How are the two strands bound to each other? And what's the significance of a bond like this?

Back 2

Hydrogen bonds.
Not very strong, but when you have millions of them, it becomes very strong. But, of course, when applied to great heat or pressure, they can break apart.

Front 3

What does anti-parallel mean?

Back 3

Running 5' to 3' one way, 3' to 5' prime the other way. And also, each nucleotide (A, T, G, C) has to complement the one on the other.

Front 4

In what way are the complementary strand made?

Back 4

Added in the 5' to 3' direction, complementing the template strands which is in the 3' to 5' direction.

Front 5

What is the origin of replication?

Back 5

Nucleotide motif that tells the replication enzymes to start replication from this point. Shorthand for this is “Ori”.

Front 6

Helicases?

Back 6

Enyzmes that unwinds the double helix and prevents them from forming double strands again (done by single stranded DNA binding proteins

Front 7

What does primase do?

Back 7

It's an RNA primer. Lays down the primer that polymerase will start replicating from -- Adds a few nucleotides of ribonucleic acids(RNA) across from the template strand – acts as a starting point for synthesizing new DNA. It's little strand will later be replaced with DNA.

Front 8

What does topoisomerase do? Why does it need to do this?

Back 8

Nicks the unwinding helix allowing the tension to be released.
Needs to do this because as the helicase is unwinding the DNA, tension is being built up. IT needs to be released.

Front 9

Okazaki Fragments? Does polymerase join them together?

Back 9

Small segments of replicated DNA betwee RNA primers. Polymerase DOES NOT join these together.

Front 10

What is POL III? What's important to know about it?

Back 10

DNA dependent DNA polymerase III �-- Requires DNA as its template, and synthesizes the new strand of DNA.

**It is the basic one that does the bulk of the work

Front 11

DNA Polymerase I? Ligase?

Back 11

Replaces the RNA primer with DNA. Cleans up the loose ends.

Ligase joins the Okazaki fragments together.

Front 12

Two requirements for both Pol I and Pol III?

Back 12

(1) Require a template strand of DNA --replicates a complimentary DNA strand based on the sequence of the DNA template.

(2) Require a primer from which to add on dNTPs in 5' to 3' direction -- the primer can be either DNA or RNA, but only RNA primers are put down by the Primase enzyme during replication

Front 13

Differences in origins of replication between pro and euka?

Back 13

Euka have many, pro only have one.

Front 14

bacterial DNA shape? Chloroplast/ Mitochondria DNA shape?

Back 14

All circular, not linear like euka DNA.

Front 15

Gyrase in circular DNA?

Back 15

Prevents knots

Front 16

Two steps in "proof reading" the transcribed DNA?

Back 16

(1) Checks to see if there are any bulges due to non-compliemntary nucleotides being placed in the wrong place (i.e., an T with G, not a C with G). since they're both of the same charge, they will repel each other, creating a bulge which can be detected, and fixed.

(2) after that, there are still patrollers that check to see if is anything is wrong. If there is, they can easily swap it out and fix the problem.

But, inevitably, mutations do happen!

Front 17

Excision repair?

Back 17

DNA can also be damaged by UV or radioactivity. There is a way to repair this. A nuclease enzyme cuts the damged DNA out at two points, then polymerase goes in a fill it in, and ligase fills in the gaps.

IF your body can't do this, it can be devastating if you live in warmer climates.

Front 18

Kary Mullis? PCR?

Back 18

Nobel prize winner, discovered a way to test and check if someone's DNA is the same we found on a knife, or something.

Took enzymes from Archea (since they're very resistant to heat), and used them for his process (which required intensive heating).
The PCR (polymerase chain reaction) generates a large amount of DNA (that can be analyzed) from a very small amount. Within an hour, there is enough DNA to check.

Front 19

What is taq?

Back 19

Needed for the process: Thermus AQuaticus polymerase.