Transcription and Translation (Lec 7 & 8)

Question 1

True or False?

Genomic DNA controls protein synthesis directly

Answer 1

false

Question 2

Transcription, simply, is….

Answer 2

DNA -> RNA

Question 3

Translation, simply, is…

Answer 3

RNA -> Protein

Question 4

What is mRNA?

Answer 4

messenger RNA - codes for proteins

Question 5

what is rRNA?

Answer 5

ribosomal RNA, forms the basic structure of the ribosome and catalyzes protein synthesis

Question 6

What is tRNA?

Answer 6

Transfer RNA, central to protein synthesis as adaptors between mRNA and amino acids

Question 7

What is snRNA?

Answer 7

small nuclear RNA, function in a variety of nuclear processes, including the splicing of pre-mRNA

Question 8

What is snoRNA?

Answer 8

small nucleolar RNA, help to process and chemically modify rRNA

Question 9

What is miRNA?

Answer 9

MicroRNA, regulate gene expression by blocking translation of specific mRNA and cause degradation

Question 10

What is siRNA?

Answer 10

small interfering RNA, turn off gene expression by directing the degradation of selective mRNA and the establishment of compact chromatin structure

Question 11

What are the stages of prokaryotic transcription?

Answer 11

sigma factor attaches, sliding, closed complex forms, open compile, abortive initiation, promoter clearance and sigma factor release, elongation, termination hairpin, termination

Question 12

Describe Eukaryotic Transcription initiation

Answer 12

begins with the binding of TFIID to the tata box via TBP, TFIIB is recruited, followed by TFIIF, RNA pol I, TFIIE, and TFIIH; all these factors join to form the transcription initiation complex; DNA unwinds and exposes template strand; RNA pol II makes short lengths of RNA; phosphyorylation of CTD by TFIIH causes the pol to leave the promoter and begin elongation

Question 13

How does transcription initiation in vivo begin?

Answer 13

binding of general transcription factors, RNA pol, mediator, and chromatin remodeling complexes, and histone-modifying enzymes

Question 14

Describe RNA processing in Eukaryotes

Answer 14

modification of the 5’ end of mRNA - RNA capping (7-methyl guanosine)

removal of non-coding sequences - RNA splicing (intron removal)

modification of the 3’ end of mRNA - Polyadenylation (addition of poly A tail)

Question 15

What is the genetic code?

Answer 15

set of rules that convert the nucleotide sequence of a gene into the amino acid sequence of protein using mRNA as an intermediary

Question 16

How many total codons are there and how many known amino acids are there?

Answer 16

61 triplet codons; 20 known amino acids

Question 17

What does the adaptor hypothesis state?

Answer 17

the genetic code is read by molecules that can recognize a codon and carry the corresponding amino acid

Question 18

What role does tRNA play as the adaptor?

Answer 18

binds specific codons and brings with it an AA

Question 19

What is the general structure of tRNA?

Answer 19

cloverleaf: secondary structure of tRNA

two regions of unpaired nucleotides are crucial to the functions of tRNA

Question 20

What is the anticodon loop?

Answer 20

one of the two regions of unpaired nucleotides: a set of 3 consecutive nucleotides that pair with a complementary codon in an mRNA molecule

Question 21

What is the other region of unpaired nucleotides in tRNA that is not the anticodon loop?

Answer 21

3’ CCA terminal region which binds the amino acid that matches the corresponding codon

Question 22

Genetic code is translated by two adaptors. What are they?

Answer 22

tRNA synthetase, and aminoacyl-tRNA

Question 23

What is step 2 of translating mRNA?

Answer 23

peptidyl transferase

Question 24

What are the three stop codons?

Answer 24

UAA, UAG and UGA

Question 25

What recognizes the stop codons?

Answer 25

release factors

Question 26

What do release factors bind to?

Answer 26

A site of ribosome containing the stop codon - catalyzes the addition of a water molecule instead of an amino acid

Question 27

Where does the protein fold into its 3D structure?

Answer 27

cytoplasm, after it has been released from ribosome