Nucleic Acid, Replication, Transcription and mRNA processing Part 2 - (Week 5)

Question 1

If Avery, Macleod and McCarty found that samples of heat killed bacteria treated with RNase and DNase transformed bacteria, but samples treated with protease did not, what conclusion would they have made?

Answer 1

Protein is the genetic material

Question 2

How did the building of a structural model of DNA come about?

Answer 2

• Maurice Wilkins and Rosalind Franklin produced a picture of the DNA molecule
• using X-ray crystallography
• diffraction pattern gives info on molecular structure

Question 3

What did Watson and Crick developed?

Answer 3

• molecular structure of nucleic acid
• 3 dimensional structure of DNA (double helix)
• built a model where backbones were antiparallel (their subunits run in opposite directions)

Question 4

What is the chemical structure of DNA?

Answer 4

• a polymer made of nucleotides
• sugar group, phosphate group and a base
• bases: adenine, thymine, guanine, cytosine

Question 5

What holds the strands of DNA together?

Answer 5

• hydrogen bonds between bases on adjacent strands

- A&T and G&C

Question 6

How is DNA transformed to proteins?

Answer 6

• bases on a single strand of DNA act as a code
• letters from 3 letter codons
• codes for amino acids (building blocks of proteins

Question 7

What is the cycle of DNA to proteins?

Answer 7

• DNA to RNA, transcription

- RNA to Proteins, translation

Question 8

Whats is base pairing?

Answer 8

• discovered by Watson and Crick
• Purine & Pyrimidine, width = consistent with X-ray data
• pairing = specific dictated by base structures
• A paired with T
• G with C
• Chargaff’s rules

Question 9

In humans, 20% of bases in DNA = cytosine. What % of the bases are expected to be thymine?

Answer 9

30% - (20 + 30) = 50%, half of base pairs

Question 10

What are nucleotides?

Answer 10

• building blocks of nucleic acids
• organic molecules that serve as the monomer units for forming nucleic acid polymers deoxyribose acid (DNA) + ribonucleic acid (RNA)
• composed of 3 subunit molecules:
  + nitrogenous base
  + 5-carbon sugar
  + phosphate group

Question 11

What are nucleic acids?

Answer 11

• polymeric macromolecules assembled from nucleotides

Question 12

What are nucleosides?

Answer 12

• 5-carbon sugar molecule attached to a nitrogenous base

Question 13

What are the structural elements of nucleotides?

Answer 13

• the nitrogenous base (nucleobase) + indicated by “base” and “glycosidic bond” (sugar bond).

Question 14

Uracil is used in DNA. True or False?

Answer 14

False - it is used in RNA as a pyrimidines

Question 15

What are the two types of nucleic acids?

Answer 15

RNA and DNA

Question 16

Information about ribonucleic acid (RNA):

Answer 16

• converts the genetic info contained within DNA to a format used to build proteins
• RNA has only one strand, and is made up of nucleotides
• molecules = variable in length, but = much shorter than DNA polymers
• contains ribose sugar molecules
• A,G,C,U

Question 17

Information about deoxyribonucleic acid (DNA):

Answer 17

• replicates + stores genetic info
• consists 2 strands arranged in a double helix, made up of nucleotide subunits
• DNA = much longer polymer than RNA
• sugar in DNA = deoxyribose, containing one less hydroxyl group
• A,T,G,C

Question 18

What are some differences between DNA and RNA?

Answer 18

• RNA has a hydroxyl group on the 2’ carbon of its sugar
• contains uracil instead of thymine, + is usually single stranded
• hydrogen bonds between base pairs

Question 19

Both DNA and RNA consist of repeating units of nucleotides. Which is NOT a component of a nucleotide found in RNA?

Answer 19

Thymine

Question 20

What is the structure of a DNA strand?

Answer 20

• polynucleotide chains have nitrogenous bases linked to a sugar-phosphate backbone
• nucleotides = linked by phosphodiester (C-O-P-O) to form a DNA strand
• phosphodiester bonds of the DNA give the polarity of the DNA strand (5’ phosphate & 3’ hydroxyl end)

Question 21

What are phosphodiester bonds?

Answer 21

• when exactly 2 of the hydroxyl groups in phosphoric acid react with hydroxyl groups on tother molecules to form 2 ester bonds

Question 22

What are esters?

Answer 22

• function group in organic chemistry

- carbon bound to 3 other atoms

Question 23

What are hydrogen bonds?

Answer 23

• weak force that forms a special type of dipole-dipole attraction which occurs when a hydrogen atom = bonded to a strongly electronegative atom
• weaker than an ionic bond/ covalent bond but stronger than van der waals forces