Ch. 3 from genes to proteins

Question 1

Nucleic Acids

Answer 1

• are polymers of nucleotide residues.
• The major nucleic acids are deoxyribonucleic acid (DNA) and ribonucleic acid (RNA)

Question 2

Nucleotide

Answer 2

-A compound consisting of nucleosides in which one or more phosphates are linked to the sugar to form a nucleotide

Question 3

Nucleosides

Answer 3

• is composed of a nitrogen-containing base and a sugar

Question 4

Purines

Answer 4

• Adenine
  -Guanine
  -Purine

Question 5

Pyrimidines

Answer 5

-Cytosine
-Thymine
-Pyrimidine

Question 6

Difference between RNA and DNA

Answer 6

RNA: contains adenine, cytosine, guanine, and uracil
DNA: contains adenine,cytosine,guanine, and thymine
The sugars:
In RNA: its ribose
In DNA: its 2’-deoxyribose

Question 7

The numbering system of cyclic sugars

Answer 7

• The sugar atoms in DNA and RNA are numbered with primes to distinguish them from atoms of the attached bases.

Question 8

The naming of nucleotides with one phosphate, two or three phosphate groups

Answer 8

• The nucleotide with one phosphate is known as nucleoside monophosphate (ex. adenosine monophosphate)
  -The nucleotide with two phosphates is known as nucleoside diphosphate (ex. guanosine diphosphate)
• The nucleotide with three phosphates is known as nucleoside triphosphate (ex. cytidine triphosphate)
• Each are represented by three-letter abbreviations (ex. AMP,GDP, CTP)

Question 9

Structural features of Coenzyme A

Answer 9

• Contains adenosine, a residue called pantothenic acid ( also known as vitamin B5) which is used to make adenosine.
• It also contains a sulfhydryl group that is the site of attachment of other groups and is very reactive ( draw Coenzyme A)

Question 10

Structural features of NAD+

Answer 10

• NAD+ is an important electron acceptor in metabolism and is a derivative of the vitamin niacin
  -NAD+ contains nicotinamide which is a base, Ribose which is a sugar, and adenosine.
• The related compound NADP contains a phosphoryl group at the adenosine C2 position.

Question 11

Structural features of FAD

Answer 11

• FAD also contains adenosine
• Oxidation and reduction of FAD occurs at the riboflavin group which is also known as vitamin B2

Question 12

How are nucleotides linked to nucleic acids?

Answer 12

• Nucleotides are connected by phosphodiester bonds when a single phosphate group forms ester bonds to both C5’ and C3’.
• Backbone consists of the sugar-phosphate groups.
  -The sequence of bases is read from 5’ to 3’ ( 5’ end is a phosphate group attached to the C5’ and the 3’ end bears a free OH group)

Question 13

Specific interaction of bases

Answer 13

• Bases are linked by hydrogen bonds
  -Adenine and thymine are always complimentary and are linked by two hydrogen bonds
• Guanine and Cytosine are complementary and form three hydrogen bonds.

Question 14

Composition of the backbone of nucleic acids

Answer 14

• The backbone of nucleic acids consists of sugar-phosphate backbones of the two DNA strands which are separated by a constant distance regardless of the base pairs.

Question 15

DNA double helix

Answer 15

• DNA is antiparallel and the two strands of DNA twist around each other to generate the double helix.
• The double helix is super stable and is twisted in a right-handed fashion and creates two grooves major and minor.
• The diameter of the helix is 20A and it completes a turn every 10 base pairs which correlate to the axial distance of about 34A.
• The sugar-phosphate backbones define the exterior of the helix
• The base pairs are located in the center of the helix and are perpendicular to the helix axis.
• The edges of the base pairs are exposed in the major and minor grooves to allow certain DNA binding proteins to recognize specific bases.

Question 16

Central Dogma (refer to Anki for photo)

Answer 16

-a portion of DNA(gene) is transcribed to produce a complementary strand of RNA, then RNA is translated into protein.

Question 17

DNA replication

Answer 17

• is when the double helix unwinds so that each parental strand can serve as a template for the syntheses of a new complementary strand. This results in two identical double-helical DNA molecules.

Question 18

RNA synthesis

Answer 18

• is known as transcription in which RNA is synthesized using a DNA template, transferring genetic information of DNA to RNA
• The non-template strand is called the coding strand and the template strand is called the non-coding strand

Question 19

Protein Synthesis aka translation

Answer 19

-After transcription, the mRNA is translated by a ribosome, at the ribosome small molecules known as tRNA which carry amino acids recognize sequential sets of three bases known as codons in the mRNA through complementary base pairing.

Question 20

Genetic code

Answer 20

• is the correspondence between amino acids and mRNA codons.
• There are a total of 64 codons, 3 of the codons are stop signals that terminate translation, and the 61 leftover codons represent the 20 amino acids found in proteins

Question 21

Noncoding strand

Answer 21

• is the template strand and is the DNA strand that has a complementary sequence to the transcribed RNA ( except T is replaced with U due to the strand being RNA)

Question 22

Coding strand

Answer 22

-is considered the nontemplate strand
- It is the DNA strand that has the same sequence as the transcribed RNA ( except T is replaced with U due to the strand being RNA)

Question 23

Mutated genes and its consequences

Answer 23

• Mutated genes can cause disease due to an error
  -Researchers use the defective protein associated with a certain disease to track down its relevant genetic defect.
• An example of a mutation in a gene is in the variant hemoglobin protein that causes sickle cell anemia which results from the substitution of the amino acid glutamate by valine. In the protein chain, the normal code GAG has been altered to GTG.
• While most human diseases are polygenic, sickle cell is considered to be a monogenic disease.