Lecture 18 - Protein expression

Question 1

DNA stores information (genes), which is expressed as

Answer 1

RNA and proteins

Question 2

The information (genes) is expressed in 2 steps

Answer 2

1. A copy of RNA is made in a process called transcription
2. The copied information in the form of mRNA is translated to proteins in a process called protein synthesis or translation

Question 3

Transcription begins near

Answer 3

promoter sites

Question 4

Promoter sites are

Answer 4

docking sites of RNA polymerase to initiate transcription

Question 5

Transcription ends near

Answer 5

termination sites

Question 6

RNA polymerase synthesizes a

Answer 6

terminator sequence

Question 7

mRNA in eukaryotes is modified after

Answer 7

transcription

Question 8

In bacteria, polypeptide chains are encoded by a

Answer 8

continuous DNA sequence

Question 9

Introns

Answer 9

intervening base sequences that do not appear in the mRNA of that gene product

Question 10

Exons

Answer 10

DNA sequences that are expressed

Question 11

There is a consensus sequence in higher eukaryotes that signal

Answer 11

splicing

Question 12

Splicing only occurs in the

Answer 12

nucleus and only in eukaryotes

Question 13

The consensus sequence in higher eukaryotes is a _____ at the 5’ end and a _____ at the 3’ end

Answer 13

GU; AG

Question 14

All introns have a ___________ 18 to 40 nucleotides upstream from 3’-splice site (pyrimidine tract)

Answer 14

branch site

Question 15

How does the sequence of mRNA translate into the sequence of a protein?

Answer 15

The ribosomes can “read” the genetic code embedded in the mRNA

Question 16

What is the genetic code?

Answer 16

The relation between the sequence of bases in DNA (or its RNA transcripts) and the sequence of amino acids in proteins

Question 17

Features of the genetic code (4)

Answer 17

1. Three nucleotides (a codon) encode one amino acid
2. The code is non-overlapping
3. The code has no punctuation
4. The code is degenerate

Question 18

What is the Shine-Dalgarno sequence

Answer 18

A ribosomal binding site in bacterial and archaeal messenger RNA, generally located around 8 bases upstream of the start codon AUG

Question 19

Techniques used to control protein expression (3)

Answer 19

1. Can be tagged in vivo with fluorescent proteins to study localization
2. Can be purified to study their structure, interactions, and functions
3. Can be used as medicine

Question 20

General strategy of protein expression consists of

Answer 20

1. Tranfecting/transforming/transducing cells with DNA of choice
2. Transcription, translation (and modification) of protein of interest
3. Purificatino and/or studying protein of interest

Question 21

Mammalian systems can express proteins both

Answer 21

transiently and through stable cell lines

Question 22

Insect cells can be used to produce ____________________ with the correct post-tranlational modifications

Answer 22

complex eukaryotic proteins

Question 23

Two types of insect expression systems:

Answer 23

1. Baculovirus infected
2. Non-lytic insect cells

Question 24

Bacterial cells can produce vast quantities of

Answer 24

proteins rapidly and cheaply

Question 25

Plant expression systems provide a cheap and low-tech means of

Answer 25

mass expression of recombinant proteins

Question 26

Yeast expression systems can generate

Answer 26

large quantities of recombinant eukaryotic proteins

Question 27

Proteins are assembled in vitro using

Answer 27

purified components of the transcription and translation machinery

Question 28

Expression vectors are optimized for the production of

Answer 28

large amounts of proteins

Question 29

The gene of interest in the expression vector often contains fusion tags to

Answer 29

easily purify the expressed protein

Question 30

Promoter sequences are designed to

Answer 30

drive the transcription of large amounts of a protein-coding gene

Question 31

Expression vectors often contain a polylinker region that includes

Answer 31

several restriction sites

Question 32

Expression vectors contain (6)

Answer 32

1. Promoter 2. Fusion tag 3. Polylinker 4. Ribosomal binding site 5. Termination sequence 6. Start and stop codons

Question 33

pET vectors are commonly used to

Answer 33

express proteins using the T7Lac system

Question 34

In E. coli, metabolism of lactose is regulated by the

Answer 34

lac operon

Question 35

In the lac operon, the presence of lactose starts

Answer 35

expression of the β-galactosidase gene

Question 36

An operon is a

Answer 36

functioning unit of DNA, which contains a cluster of genes under the control of a single control site

Question 37

The lac operon encodes genes that are required for

Answer 37

the transport and metabolism of lactose

Question 38

The regulator gene (lacl) encodes

Answer 38

a repressor protein

Question 39

The promoter sites (p) directs the

Answer 39

RNA polymerase to the correct transcription initiation site

Question 40

In the absence of lactose, the lac operon is

Answer 40

repressed

Question 41

Allolactose relieves the

Answer 41

repression of the operator

Question 42

The inducer (allolactose) triggers gene expression by

Answer 42

preventing the lac repressor from binding the operator

Question 43

Allolactose binds to the

Answer 43

lac repressor