Zaidi Molecular Review

Question 1

MRNA function

Answer 1

Code for proteins

Question 2

rRNA function

Answer 2

Form the basic structure of the ribosome and catalyze protein synthesis

Question 3

tRNA function

Answer 3

Central to protein synthesis as adaptor between mRNA and amino acids

Question 4

SnRNAs

Answer 4

Function in a variety of nuclear processes, including the splicing of pre mRNA

Question 5

SnoRNA function

Answer 5

Help to process and chemically modify rRNA

Question 6

MiRNA funtion

Answer 6

Regulate gene expression by blocking translation of specific mRNAs and cause their degradation

Question 7

SiRNAs

Answer 7

Turn off gene expression by directing the degradation of selective mRNAs and the establishment of compact chromatin structures

Question 8

How does eukaryotic transcription initiation step begin?

Answer 8

The binding of TFIID to the TATA box (causes distortion in DNA)

Question 9

What is the subunit called of TFIID that recognizes TATA?

Answer 9

TATA-box-binding-protein (TBP)

Question 10

What all factors join to form the transcription initiation complex?

Answer 10

TFIIB, TFIIF, RNA Pol II, TFIIE and TFIIH

Question 11

What factor unwinds the DNA double helix and exposes the DNA template strand during initiation?

Answer 11

TFIIH

Question 12

What causes the polymerase to leave the promoter during initiation to begin elongation?

Answer 12

Phosphorylation of CTD by TFIIH

Question 13

RNA processing in eukaryotes

Answer 13

1. Modification of the 5’ end of mRNA - RNA capping (7-methyl guanosine)
2. Removal of non-coding sequences - RNA splicing (intron removal)
3. Modification of the 3’ end of mRNA - polyadenylation (addiction of poly A tail)

Question 14

What is the genetic code

Answer 14

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

Question 15

The sequence of nucleotides in the mRNA molecule is read consecutively in groups of what ?

Answer 15

Three (codons)

Question 16

Each codon specifies either ____________ or ____________

Answer 16

One amino acid or a stop to the translation process

Question 17

A total of _____ triplet codons code for the 20 known amino acids, thus the code is __________.

Answer 17

61 - degenerate

Question 18

The adaptor hypothesis

Answer 18

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

Question 19

What is the general structure of tRNA

Answer 19

Cloverleaf secondary structure of tRNA. It folds up into a defined 3D structure and contains 4 short double-helical segments

Question 20

Two regions of unpaired nucleotides are crucial to the functions of tRNA - what are they?

Answer 20

1. Anticodon loop - a set of 3 consecutive nucleotides that pair w/ a complementary codon in an mRNA molecule
2. 3’ CCA terminal region which binds the amino acid that matches the corresponding codon

Question 21

Genetic code is translated by 2 adaptors , what are they?

Answer 21

1. ACC tRNA

2. Aminoacyl-tRNA