Nucleic acid function

Question 1

Nucleic acids have 2 major functions. These are

Answer 1

the direction of protein synthesis;

transmission of this information from one generation to the next.

Question 2

Proteins, whether structural components, enzymes, carrier molecules, hormones or receptors, are all composed of a series of _____.

Answer 2

amino acids

Question 3

_____ major amino acids are known, and the sequence of these determines the form and function of the resulting protein.

Answer 3

Twenty

Question 4

All proteins are encoded by _____, and the unit of DNA that contains the protein - coding sequence (together w/ the introns and the neighbouring untranslated regulatory sequences) is, by definition, its _____.

Answer 4

DNA; gene

Question 5

A gene is composed of what components?

Answer 5

Protein coding region; introns; and neighboring untranslated regulatory sequences

Question 6

Genes vary greatly in size from small genes like the _____ and medium - sized genes of _____ to enormous genes such as _____.

Answer 6

globins; 15 – 45 kb; dystrophin

Question 7

Each set of three DNA base pairs, called a _____, codes for an amino acid.

Answer 7

triplet or codon

Question 8

Each codon is shown in terms of the ______.

Answer 8

messenger RNA (mRNA)

Question 9

As each base in the triplet may be any of the four types of nucleotide (A, G, C or T), this results in _____ combinations or codons.

Answer 9

4^3 or 64 possible

Question 10

The corresponding DNA sequence from w/c the mRNA is actually transcribed will be ____.

Answer 10

complementary

Question 11

The corresponding DNA sequence from w/c the mRNA is actually transcribed is called what strand?

Answer 11

antisense strand

Question 12

It is the sequence of the ____ strand that is usually published or used as a reference.

Answer 12

Sense strand

Question 13

This strand contains the AUG or ATG in the mRNA and DNA, respectively.

Answer 13

Sense strand

Question 14

What are the only amino acids that are not encoded by more than one codon?

Answer 14

methionine and tryptophan

Question 15

Because most of the amino acids are encoded by more than one codon. The genetic code is said to be _____.

Answer 15

degenerate

Question 16

Three of the 64 codons designate the termination of a message and these are called _____ and one codon acts as a ____ signal for protein synthesis.

Answer 16

stop codons; start

Question 17

What are/is the stop codons? Start codon?

Answer 17

stop: UAA, UGA and UAG
start: AUG - methionine

Question 18

T/F. With a few possible exceptions, this code is identical in all species. The genetic code used for the synthesis of proteins that are encoded by the mitochondrial genome is also the same.

Answer 18

False. Mitochondrial protein synthesis has its own genetic code.

Question 19

The first stage in protein synthesis is _____.

Answer 19

transcription

Question 20

During transcription, the _____ functions as a template and is read in the 3 ′ to 5 ′ direction by the enzyme RNA polymerase II, with the mRNA being synthesized in the 5 ′ to 3 ′ direction.

Answer 20

template strand

Question 21

During transcription, the template strand functions as a template and is read in the _____ direction by the enzyme RNA polymerase II, with the mRNA being synthesized in the 5 ′ to 3 ′ direction.

Answer 21

3 ′ to 5 ′

Question 22

During transcription, the template strand functions as a template and is read in the 3’ to 5’ direction by the enzyme _____, with the mRNA being synthesized in the 5 ′ to 3 ′ direction.

Answer 22

RNA polymerase II

Question 23

During transcription, the template strand functions as a template and is read in the 3’ to 5’ direction by the enzyme RNA polymerase II, with the mRNA being synthesized in the _____ direction.

Answer 23

5 ′ to 3 ′

Question 24

Transcription proceeds at about ____ nucleotides per second until the _____ is reached.

Answer 24

30; transcription terminator

Question 25

The next stage of protein synthesis occurs in the cytoplasm & is called _____.

Answer 25

translation

Question 26

During translation, as the ribosome moves along the mRNA from the _____ end, each codon is recognized by a matching _____, which contributes its amino acid to the end of a new growing protein chain until a _____ is reached.

Answer 26

5 ′ to the 3 ′; complementary tRNA; stop codon

Question 27

Proteins are encoded by genes containing, on average, approximately ____ exons, each around _____ bp in size.

Answer 27

10; 300

Question 28

Human genes, however, tend to be much larger than would be expected from the encoded protein ’ s amino acid sequence alone. This excess is mainly due to the presence of _____, but also to the 5 ′ and 3 ′ _____.

Answer 28

intervening sequences;
flanking sequences

Question 29

The vast majority of genes consist of alternating coding segments for mature mRNA, _____, and non - coding segments of < 30 bp to over 1 Mbp, called _____, whose function is largely unknown.

Answer 29

exons; intervening sequences or introns

Question 30

Average length of intervening/intron sequences

Answer 30

less than 30 bp to over 1 Mbp

Question 31

The initial mRNA, _____, is a transcript of the gene that includes not only the exons, but also the intervening sequences and some flanking sequences.

Answer 31

heterogeneous RNA or hnRNA

Question 32

Prior to its entry into the cytoplasm, however, the segments corresponding to the intervening sequences are removed by _____.

Answer 32

splicing

Question 33

The sequences around the _____ serve as recognition sites for splicing proteins, and characteristically an intron begins with _____, the 5′ donor site, and ends with _____, the 3 ′ acceptor site.

Answer 33

intron/exon junctions; GT; AG

Question 34

The sequences around the intron/exon junctions serve as recognition sites for splicing proteins, and characteristically an intron begins with GT, the _____ and ends with AG the _____.

Answer 34

5 ′ donor site; 3 ′ acceptor site

Question 35

T/F. Mutations in the bases adjacent to the exon/intron boundaries interfere with mRNA splicing and can cause genetic disease.

Answer 35

True

Question 36

The mRNA 5 ′ end is protected or ‘ capped ’ with a _____ residue, and the _____ extends downstream from this cap site to the beginning of the protein – coding sequence.

Answer 36

methyl guanylate; 5′ untranslated region (5 ′ UTR)

Question 37

In the initial mRNA transcript, _____ extends from the protein translation stop codon to the poly(A) tail.

Answer 37

3 ′ untranslated region (3 ′ UTR)

Question 38

This tail of 100 – 200 adenylate (i.e. AMP) residues is not encoded in the DNA but is added enzymatically to aid cytoplasmic transport and, possibly, mRNA stability.

Answer 38

poly-A tail

Question 39

The poly-A tail is consist of _____ adenylate residues.

Answer 39

100-200

Question 40

Many proteins are not in their final form after ribosomal translation. The subsequent post - translational alterations include:

Answer 40

the formation of disulphide bonds;
hydroxylation;
glycosylation;
proteolytic cleavage;
phosphorylation

Question 41

Each step in the production of the final protein is important, as many proteins are highly dependent for function upon their exact _____, w/c in turn is determined by their _____ and _____.

Answer 41

three - dimensional shape or tertiary structure;
amino acid sequence;
post - translational modifications

Question 42

In general, acidic (e.g. Asp, Glu) and basic (e.g. Lys, Arg, His) amino acids are found on the _____ of a folded protein, with hydrophobic amino acids (e.g. Ala, Val, Leu) _____ orientated.

Answer 42

surface; internally

Question 43

Examples of acidic amino acid; basic.

Answer 43

acidic: Asp, Glu
basic: Lys, Arg, His

Question 44

The effect of an amino acid substitution thus not only depends upon its relationship to the ____ of the protein but also upon the change in ____ and hence the degree of consequent disruption to the protein ’ s _____.

Answer 44

active site; charge or hydrophobicity; tertiary structure.

Question 45

The DNA sequence of a gene allows prediction of the _____ and _____ sequence and often the general function and intracellular location of the protein.

Answer 45

mRNA; protein amino acid

Question 46

True/False. DNA sequences reliably predict the patterns of alternative splicing, the post - translational modifications, the three – dimensional (i.e. tertiary) structure of the protein, its precise functions or its expression patterns.

Answer 46

False

Question 47

To investigate gene expression, RNA analysis may be carried out by what methods?

Answer 47

reverse transcription PCR
microarray analysis
Northern blotting.

Question 48

Protein size and abundance can be determined by the antibody - based technique known as _____.

Answer 48

Western blotting

Question 49

To visualize the intracellular location of a protein, _____ can be undertaken using a fluorescent antibody that binds specifically to that protein.

Answer 49

immunofluorescence microscopy

Question 50

To determine the protein ’ s three – dimensional structure, these methods may be used.

Answer 50

X - ray crystallography
nuclear magnetic resonance spectroscopy may be used.