From DNA to Protein

Question 1

Nucleotides are composed of which 3 things?

Answer 1

1. Nitrogen containing ring compound (Nitrogenous base)
2. Five carbon sugar (Deoxyribose)
3. Phosphate molecule

Question 2

The two Pyrimidine nitrogenous bases in DNA are:

Answer 2

Thymine and cytosine

Question 3

The two Purine nitrogenous bases in DNA are:

Answer 3

Adenine and guanine

Question 4

Nucleotides are joined through ________ bonding between _________ of one nucleotide and _____ of the adjacent nucleotide.

Answer 4

1. Covalent
2. Phosphate
3. Sugar

Question 5

How do DNA strands to differ at the ends?

Answer 5

One strand has a phosphate attached at the number 5 carbon of the sugar. (5’ end)

The other strand has a hydroxyl group attached to the number 3 carbon of the sugar. (3’ end)

Question 6

DNA double strands are complementary to each other, due to what?

Answer 6

Specific base pairing of bases (A:T, C:G)

Question 7

DNA strands are held together with what? Elaborate.

Answer 7

Hydrogen Bonds
~ A is bound to T by two hydrogen bonds
~ G is bound to C by three hydrogen bonds

Question 8

DNA molecule is antiparallel. What does that mean?

Answer 8

One strand oriented in the 5’ to 3’ direction.

The other strand is oriented in the 3’ to 5’ direction.

Question 9

In what 4 ways does RNA structure differ from DNA?

Answer 9

1. Thymine is replaced by uracil
2. The sugar is ribose in place of deoxyribose
3. RNA is generally shorter
4. Exists as a single-stranded molecule not double- stranded

Question 10

How many types of rRNA are there? What are their names?

Answer 10

3 types: mRNA, rRNA, tRNA

Question 11

Why is DNA replicated?

Answer 11

To create identical second copy of molecule.

Question 12

Which direction does DNA replication occur in?

Answer 12

DNA replication is bidirectional:

Begins at specific starting point and proceeds in both direction

Question 13

What enzyme aids the unwinding of DNA strands during replication?

Answer 13

DNA Helicase

Question 14

What is the Replication Fork?

Answer 14

The point where 2 DNA strands are separated.

Question 15

Which enzyme adds new nucleotides as they become available?

Answer 15

DNA Polymerase

Question 16

DNA polymerase can only add nucleotides to the free hydroxyl at which end?

Answer 16

The 3’ end.

Question 17

DNA polymerase replicates in which direction?

Answer 17

Replication goes from 5’ to 3’

Question 18

Enzymes READS DNA template in which direction?

Answer 18

Reading goes from 3’ to 5’

Question 19

How is the Leading DNA strand synthesized?

Answer 19

CONTINUOUSLY as the DNA polymerase moves towards the replication fork

Question 20

How is the Lagging strand synthesized?

Answer 20

DISCONTINUOUSLY in pieces as DNA polymerase moves away from the replication fork

Question 21

Which enzyme must bind to an RNA primer to begin synthesis?

Answer 21

DNA polymerase

Question 22

Where is RNA primer required?

Answer 22

A RNA primer is required at each newly synthesized portion of DNA

Question 23

Which enzyme joins the fragments of the lagging strand?

Answer 23

DNA ligase

Question 24

Which enzyme removes any RNA primers?

Answer 24

A second DNA polymerase

Question 25

What is Transcription?

Answer 25

Transcription is the synthesis of a strand of mRNA from a DNA template

Question 26

mRNA carries the coded information from ____ to the ______.

Answer 26

DNA to the ribosome

Question 27

Where is the site of protein synthesis?

Answer 27

The ribosome

Question 28

What are the three steps of Transcription?

Answer 28

Initiation, Elongation, and Termination

Question 29

What occurs during Initiation?

Answer 29

The enzyme, RNA polymerase binds to a region of the DNA called the promoter

Question 30

What occurs during elongation?

Answer 30

RNA polymerase synthesizes a complementary strand of mRNA from a portion of unwound DNA

Question 31

What occurs during Termination?

Answer 31

RNA polymerase continues down strand of DNA until it reaches a site on DNA called the terminator

Question 32

What occurs at the Terminator during Termination?

Answer 32

At the terminator, RNA polymerase and the new strand of mRNA are released from strand of DNA

Question 33

What is Translation?

Answer 33

Translation is the decoding of information held in the mRNA to synthesize proteins

Question 34

Codons contained in mRNA (three nucleotides that specify a particular amino acid) are read into proteins through what process?

Answer 34

Translation

Question 35

What does rRNA do?

Answer 35

rRNA forms part of the ribosomal machinery used in protein synthesis

Question 36

What does tRNA do?

Answer 36

tRNA recognizes specific sequences of mRNA and transports the required amino acids to form a polypeptide chain

Question 37

The first tRNA binds to a start codon, _ _ _

Answer 37

AUG

Question 38

Amino acids form peptide bonds along the way

Translation is terminated when the ribosomes come to what?

Answer 38

A stop or nonsense codon

Question 39

Which two things occur at the stop codon?

Answer 39

1. The ribosomes separate

2. The new polypeptide chain is released

Question 40

Prokaryotic mRNA is often polycistronic, which means what?

Answer 40

1. prokaryotic RNA contains multiple genes

2. They are often all involved in a single biochemical pathway

Question 41

What is the benefit of polycistronic mRNA?

Answer 41

More than one ribosome can be translating at any given moment, before transcription is even finished