Module 1.4 RNA and Gene Expression

Question 1

Central Dogma

Answer 1

DNA transcribed into RNA
RNA translated in amino acid chain
Amino acid chain folded in protein

Question 2

Chemical Nature of RNA

Structural components

Answer 2

• RNA contains the sugar ribose with an –OH group at 3’ AND 2’ carbons (ribose vs deoxyribose)
• RNA contains the base uracil instead of thymine. Uracil as -H instead of -CH₃ (methyl group)
• Uracil base-pairs with adenine (2 hydrogen bonds)

Mostly single-stranded

Question 3

Types of RNA

Messenger RNA (mRNA)

function

Answer 3

RNA that encodes proteins
transcribed from protein-coding genes

all other RNA types are transcribed from non-protein coding genes

Question 4

Types of RNA

Transfer RNA (tRNA)

Answer 4

RNA that acts as an adapter between mRNA and amino acids
selects amino acids and hold them in place on a ribosome

Question 5

Types of RNA

Ribosomal RNA (rRNA)

function

Answer 5

RNA that forms the ribosome, the main machinery for protein synthesis

Question 6

Types of RNA

Small nucleolar RNA (snoRNA)

function

Answer 6

RNA that facilitates chemical modification of RNAs

Question 7

Types of RNA

MicroRNA (miRNA)

function

Answer 7

RNA (smaller transcript) that regulates gene expression

Question 8

Types of RNA

Small interfering RNA (siRNA)

function

Answer 8

RNA that silences gene expression

Question 9

Types of RNA

Long non-coding RNAs (lncRNA)

function

Answer 9

RNA (longer transcript) that regulates gene expression

Question 10

Genetic Codon

Stop Codons

3

Answer 10

UAA
UAG
UGA

Question 11

transcription

Answer 11

copy portion of DNA to RNA

Question 12

gene

Answer 12

sequence of DNA nucleotides transcribed to produce a functional RNA

Question 13

protein functions

Answer 13

cellular structure
enzymatic activities
hormonal regulation
signaling molecules
transportation
etc…

Question 14

protein-coding genes

Answer 14

Genes that encode information used to specify the linear order of amino acids for every protein the organism makes

Question 15

non protein-coding genes

Answer 15

Genes that encode RNAs that have structural and catalytical roles in the cell

can fold into 3D structures like proteins

Question 16

RNA polymerase

Answer 16

enzyme that mediates transcription
catalyzes formation of phosphodiester bonds of RNA chain stepwise along one of strand of DNA

Question 17

RNA polymerase

active site

Answer 17

Location in RNA Polymerase that unwinds DNA helix

Question 18

Transcription

ribonuclesoide triphosphates

Answer 18

Added to RNA strand by RNA polymerase as nucleoside monophosphates (eg. AMP) through high-energy hydrolysis. Ribose instead of deoxyribose (dAMP)
ATP
GTP
CTP
UTP

Question 19

DNA replication vs Transcription

3 differences

Answer 19

1. RNA doesn’t stay hydrogen-bound to DNA (RNA exit channel)
2. RNA molecules shorter (< few thousand) than DNA (250 million)
3. RNA polymerase can start chain without a primer

Question 20

small nuclear RNA (snRNA)

Answer 20

Functions in various nuclear processes (eg. splicing)
directs splicing of pre-mRNA as part of maturation process

Question 21

Genetic Codon

Answer 21

Rules for translating mRNA to amino acids based on 3-nucleotide sequences

Question 22

start codon

code and amino acid

Answer 22

AUG
Methionine
M

Question 23

tRNA structure

size, components

Answer 23

~80 nucleotides in clover leaf secondary structure
Loops: T, D, Anticodon with 3 base pairs
Amino acid matching anticodon bp attached at 3’ end of tRNA

tRNA + amino acid = charged tRNA

Question 24

amino acid tRNA synthetase

Answer 24

enzyme that couples an amino acid to a tRNA molecule with its corresponding anticodon

Question 25

Ribosome structure

Answer 25

large and small subunit each composed of one or more rRNA + ribosomal proteins

Question 26

N-terminal

protein structure

Answer 26

end of a protein synthesized first

Question 27

initiator tRNA

Answer 27

tRNA that codes for methioninie (AUG) but has a different sequence than a regular methionine tRNA
this methionine usually removed later by a specific protease

Question 28

Translation

process

Answer 28

1. Initiator tRNA binds to mRNA
2. Small ribosomal unit binds at start codon site
3. Large ribosomal subunit binds and begins elongation
4. Charged tRNA sequentially binds to A, P, and E ribosomal sites

Question 29

Ribosomal binding sites

Answer 29

1. A (aminoacyl): tRNA binding
2. P (peptidyl): peptide bond formation (connect amino acids)
3. E (exit) tRNA ejection when ribosome moves along mRNA

Question 30

Codon

Answer 30

3 mRNA nucleotide code that translates to specific amino acid
Amino acids tend to have the same 1st and 2nd nucleotide for their codons

Question 31

C-terminal

Answer 31

end of a protein synthesized last