Lecture 11

Question 1

true/false: Multiple ribosomes
simultaneously translate
same mRNA

Answer 1

true! the advantage to this is that is boosts efficiency!

Question 2

true/false: Many common antibiotics were
first isolated from fungi

Answer 2

true

Question 3

why were many common antibiotics first isolated from fungi?

Answer 3

fungi and humans are both eukaryotes, and fungi naturally produce antibiotics to kill or inhibit the growth of bacteria, because it limits their competition in the natural environment

Question 4

Proteins fold into the correct three-dimensional
shape either spontaneously or with the help of
_________

Answer 4

chaperone proteins

Question 5

true/false: Newly synthesized proteins require post-
translational modifications to become fully functional

Answer 5

true

Question 6

newly synthesized proteins are covalently modified using which two methods?

Answer 6

phosphorylation (adding phosphate group) and glycosylation (adding glucose)

Question 7

Some proteins bind or associate with small molecule ________ or other protein subunits

Answer 7

co-factors

Question 8

________ are enzymes that degrade proteins

Answer 8

Proteases

Question 9

what do proteases do?

Answer 9

They hydrolyze the peptide bonds between amino acids (can repurpose amino acids for making new proteins)

Question 10

why do we need to degrade proteins?

Answer 10

The lifetime of proteins must be kept short.

Damaged or misfolded proteins must be recognized and removed

Question 11

where are proteins broken down in eukaryotic cells?

Answer 11

in proteasomes

Question 12

Why is it good to house proteases inside the proteosome cylinder?

Answer 12

It keeps the protease activity confined to the proteosome

Question 13

what is the central cylinder of a proteosome cylinder made of?

Answer 13

proteases

Question 14

How are proteins directed to the proteasome
for degradation?

Answer 14

Covalent attachment of a small protein
called ubiquitin

Specialized enzymes tag those proteins
with a short chain of ubiquitin molecules

Question 15

is it possible that life began as RNA?

Answer 15

yes, ribosome are ribozymes

the theory means that RNA stored both genetic information and catalyzed the chemical reactions in primitive cells, DNA took over after but never fully took control because RNA is still used for many biological functions

Question 16

How do cells become different from each other?

Answer 16

The proteins produced in each type of cell are different

Question 17

true/false: Every somatic cell nucleus of an organism contains the complete
genome established in the
fertilized egg

Answer 17

true

Question 18

________ level: if and how often a gene is transcribed

Answer 18

Transcription level

Question 19

________ level: different messenger RNAs made from a given gene
(alternative splicing)

Answer 19

Processing level

Question 20

________: selective mRNAs are able to enter the cytoplasm

Answer 20

RNA transport

Question 21

_______ level: how much of the mRNA is made into protein (and mRNA
lifetime)

Answer 21

Translational level

Question 22

____________ level: Protein lifetime and activity

Answer 22

Post-translational level

Question 23

General transcription factors (GTFs) recognize a part
of the promoter and recruit RNA pol II to form a ______________

Answer 23

pre-
initiation complex (PIC)

Question 24

Transcription depends on _________
(enhancer or silencer) on the DNA

Answer 24

regulatory sites

Question 25

true false: enhancer/silencer regulatory sequences work on their own

Answer 25

false, they need to be recognized by proteins called transcription factors

Question 26

true/false: transcription factors can be activators or repressors

Answer 26

true

Question 27

____________ are DNA-binding proteins that regulate transcription

Answer 27

Transcription factors

Question 28

what two domains do Transcription factors have?

Answer 28

they have a DNA-binding domain they have an activation domain (a binding site for other proteins)

Question 29

true/false: Binding a transcription factor to a regulatory DNA sequence acts as the switch to control transcription

Answer 29

true

Question 30

true/false: The DNA between the regulatory sequence and the promoter loops out- brings the transcription factor into close proximity to the promoter

Answer 30

true

Question 31

how do we close the loop between the regulatory sequence/promoter to the transcription factor?

Answer 31

Mediator proteins serve as adaptors to close the loop

Question 32

_________ attracts and positions the general transcription factors and RNA polymerase at the promoter, forming a transcription initiation complex

Answer 32

mediator proteins closing the loop

Question 33

why are general transcription factors(GTFs) and RNA polymerase unable to assemble on a promoter that is packaged in nucleosomes

Answer 33

the DNA is wound tightly around the histone, they can't access the sequence to initiate transcription

Question 34

true/false: transcription factors bound to their regulatory sequences also play a role in remodeling chromatin structure and changing promoter accessibility by attracting chromatin-modifying proteins

Answer 34

true

Question 35

___________ attaches of acetyl groups to selected lysines in the histone tail - enhance the efficiency of transcription initiation

Answer 35

Histone acetyltransferases

Question 36

___________ removes the acetyl groups from histone tail - decreases the efficiency of transcription initiation

Answer 36

Histone deacetylases

Question 37

How does a transcription factor avoid improperly influencing neighboring gene transcription when bound to the control region of one gene?

Answer 37

Chromosomal DNA of plants and animals is arranged in a series of loops- prevents enhancers from affecting neighboring genes

Question 38

___________ – groups of transcription factors work together to determine the expression of a single gene

Answer 38

Combinatorial control

Question 39

in combinatorial control, what are transcription factors involved in assembling?

Answer 39

Mediators Chromatin-remodeling complexes Histone modifying enzymes General transcription factors and RNA polymerase

Question 40

Do combinations of transcription factors switch genes on and off?

Answer 40

Although they work as a committee, a single transcription factor can play a key role in switching a particular gene(or multiple genes) on or off - one of them has the "final" say!