Lecture 3 - Introduction to Nucleic Acids

Question 1

What is the central dogma of molecular biology

Answer 1

DNA Replication > Transcription (to RNA) > Translation (to protein)

Question 2

What is the general structure of a nucleic acid in DNA?

Answer 2

Sugar with base attached at 1’ and phosphate on 5’, no 2’ OH

Question 3

What is the difference between DNA and RNA?

Answer 3

RNA has 2’ OH

Question 4

What is the difference between a nucleotide and nucleoside?

Answer 4

Nucleotide has a 5’ phosphate, nucleoside has 5’ OH

Question 5

What is the direction of phosphodiester bonds?

Answer 5

5’ to 3’

Question 6

What charge does this create for the backbone of the DNA molecule?

Answer 6

Negatively charged

Question 7

What is the general structure of a pyrimidine?

Answer 7

6 member ring with N at 1st and 3rd carbons

Question 8

What bases are pyrimidines?

Answer 8

Cytosine, thymine, and uracil

Question 9

What is the different between thymine and uracil?

Answer 9

Thymine demethylated at the 5th carbon = Uracil

Question 10

What is the general structure of a purine?

Answer 10

6 member ring attached to 5 member ring

Question 11

What bases are purines?

Answer 11

Adenine and guanine

Question 12

What are some functions for nucleotides?

Answer 12

Building blocks for nucleic acid polymers (DNA, RNA), energy carriers (ATP, GTP), coenzymes (FAD, NADP), precursors for secondary messangers (cAMP)

Question 13

How are strands of DNA arranged?

Answer 13

In antiparallel strands with complementary base pairing

Question 14

Which bases pair with which and with how many hydrogen bonds?

Answer 14

G-C (3 H bonds), A-T (A-U) (2 H bonds)

Question 15

What are the structural features of B DNA?

Answer 15

Right handed helix, 90 degrees from bp to backbone, 1 turn of helix = 10.5 bp, 34 angstroms, major and minor grooves

Question 16

What are the two other forms or DNA?

Answer 16

A DNA and Z DNA

Question 17

Important facts about A DNA?

Answer 17

Right handed, 11 bp/turn, essentially shorter, squater version of B DNA

Question 18

Important facts about Z DNA?

Answer 18

Left handed, 12 bp/turn, elongated

Question 19

DNA bending facilitates what…

Answer 19

Protein DNA interactions!

Question 20

What are some factors in DNA’s denaturation?

Answer 20

Size, GC content, [salt], pH

Question 21

How is DNA packaged into cells?

Answer 21

Wound around nucleosome (comprised of 8 histone proteins), fold into 30 nm fiber, form loops, and ultimately coil into chromosome.

Question 22

What is the difference between euchromatin and heterochromatin?

Answer 22

Euchromatin is loosely packed (being transcribed) and heterchromatin is tightly packed.

Question 23

What causes negative supercoiling? What about positive?

Answer 23

Underwound DNA = negative

Overwound DNA = positive

Question 24

What enzymes exist to relieve supercoiling?

Answer 24

Topoisomerases

Question 25

What is the difference between type 1 and type 2 topoisomerase?

Answer 25

Type 1: cuts one strand to relieve supercoiling

Type 2: cuts both strands

Question 26

In what ways is RNA different than DNA?

Answer 26

1. Single stranded 2. Shorter in length 3. Complex tertiary structure 4. Unstable

Question 27

What are the types of RNA?

Answer 27

mRNA - contains info from DNA and is template for protein synth

NON-Coding RNAs; rRNA, tRNA, miRNA, ribozymes