DNA and Biotechnology

Question 1

DNA is ALWAYS written in the _ to _ direction

Answer 1

5 to 3

Question 2

The two purines are:

Answer 2

Adenine and guanine

Question 3

The three pyrimidines are:

Answer 3

Thymine, uracil, and cytosine

Question 4

Adenine and thymine have ___ H bonds while guanine and cystosine have ___

Answer 4

2

3

Question 5

What are the four rules for aromaticity?

Answer 5

1) Planar
2) Cyclic
3) Have to be conjugated, and this includes triple bonds
4) Huckel’s rule- Contains 4n+2 pi electrons

Question 6

What is the difference between heterochromatin and euchromatin?

Answer 6

Heterochromatin is densely packed, shows up dark on a microscope, and is genetically irrelevant (usually just a lot of repeating C and G)

Euchromatin is loosely packed, shows up light on a microscope, and is genetically relevant (the part that’s transcribed)

Question 7

____ form when chromatin wrap around histones. They have a bead like appearance

Answer 7

Nucleosomes

Question 8

What are the basic steps in DNA replication?

Answer 8

Strand separation occurs at the origins of replication, then the daughter strands are synthesized using RNA primer and DNA polymerase, and finally the telomeres are shortened and tied off to prevent the strand from unraveling

Question 9

The mutation from proto-oncogene to oncogene is more potent than the mutation of tumor suppressor genes because ____

Answer 9

Proto-oncogene mutation are dominant when only one copy of the gene is mutated, but tumor suppressor genes are recessive so both copies of the gene have to be mutated for tumors to form

Question 10

These fragments are created by the lagging strand and are filled in with DNA polymerase and ligase

Answer 10

Okazaki fragments

Question 11

The leading strand is created in the ____ direction and the lagging strand in the ___ direction

Answer 11

5 to 3

3 to 5

This is why the lagging strand has fragments, because it has to wait for the fork to open more in order for it to continue replicating

Question 12

This enzyme prevents supercoiling while DNA is unwinding

Answer 12

Topoisomerases

Question 13

This enzyme unwinds DNA for replication

Answer 13

Helicase

Question 14

This protein prevents single stranded DNA from reannealing

Answer 14

Single strand DNA building proteins

Question 15

This primer is used before DNA polymerase. It makes a short sequence of nucleotides that allows DNA polymerase to attach on and is then later replaced with DNA

Answer 15

RNA primer (primase)

Question 16

This enzyme acts like DNA glue and seals the ends together

Answer 16

DNA ligase

Question 17

This enzyme adds nucleotides after RNA primer has created a short sequence during replication

Answer 17

DNA polymerase

Question 18

What is a more detailed explanation of the steps of DNA replication?

Answer 18

DNA helicase begins to unwind the DNA at the origins of replication (many of which exist in eukaryotic DNA). Single strand DNA binding proteins prevent the newly separated strands from annealing, and topoisomerases prevent supercoiling that would result in the breaking of strands.

RNA primers are then used to create a short sequence of RNA that is used as a template for DNA polymerase to attach to and begin to make the Daughter strands. Eventually the RNA sequence is rewritten into DNA (using RNase H that removes the RNA and DNA polymerase that adds DNA in its place). This is also when leading and lagging strands occur

Finally, because it is impossible for DNA polymerase to go all the way to the end of the strand, the telomeres are shortened and tied off to prevent the chromatin from unwinding

Question 19

How can methylation assist in proofreading?

Answer 19

Endonucleases are able to differentiate between the parent and daughter strands when the parent strand is methylated. If there’s a mutation in the daughter strand, it’s easy to tell what needs to be replaced and what is the original strand

Question 20

Mismatch repair is used to detect and remove errors created in the S phase and occurs in the ___ phase

Answer 20

G2

Since DNA is replicated in S phase, G2 is the time before mitosis to make sure mutations won’t be copied

Question 21

Compare and contrast nucleotide excision repair and base excision repair

Answer 21

In both, endonucleases cut out the damaged part of DNA so that it can be corrected by DNA polymerase and ligase

The only difference is that in base excision repair, just the base is repaired and in nucleotide excision repair, the entire nucleotide is replaced

Question 22

Why can’t human DNA polymerase be used in PCR?

Answer 22

Human DNA polymerase can’t withstand the high temperatures needed to separate the DNA. Instead, bacterial DNA polymerase is used

Question 23

cDNA (or complimentary DNA) are ____

Answer 23

the DNA that arise from reverse RNA transcription

Question 24

_____ blots detect the presence and quantity of DNA in a sample

Answer 24

Southern

Question 25

______ therapy is the process of inserting a normal DNA sequence into someone with a mutation with the hope that the healthy gene will become dominant and erase the mutation

Answer 25

Gene therapy