DNA & RNA

Question 1

What type of organic molecule are DNA & RNA?

Answer 1

Nucleic acids (polynucleotides)

Question 2

Funciton of DNA?

Answer 2

To carry and pass on instrucitons for protein synthesis

Question 3

What is a nucleotide made of?

Answer 3

Phosphate group, ribose sugar & organic/nitrogenous base

Question 4

Types of organic bases with examples and how they bond

Answer 4

Purines (2 rings): Adenine, guanine
Pyrimidines (1 ring): Uracil, thymine, cytosine
Purines bond to pyrimidines (A-G 2 bonds, G-C 3 bonds)

Question 5

Differences b/w DNA & RNA?

Answer 5

DNA: Double stranded, Thymine, Deoxyribose, in nucleus
RNA: Single strand, Uracil, Ribose, in cytoplasm/RER

Question 6

Structure of DNA?

Answer 6

Anti-parallel double helix

Question 7

What are non-bonded (free) nucleotides called?

Answer 7

Nucleosides (they have 3 phosphate groups)

Question 8

Enzymes used in DNA replication (in order)

Answer 8

Helicase, RNA primase, DNA polymerase (III), DNA polymerase (I), Ligase

Question 9

Functions of enzymes in DNA replication

Answer 9

Helicase: Unwinds DNA by breaking hydrogen bonds
RNA primase: Adds RNA primer for enzyme to lock on
DNA polymerase (III): Adds complementary bases
DNA polymerase (I): Replaces RNA primer with DNA
Ligase: Sticks Okazaki fragments together

Question 10

Theories of replication + explanation

Answer 10

Conservative: One new double helix, original stays same
Semi-conservative: Double helices have new + old strand
Dispersive: All strands has new and old bits

Question 11

What are strands of DNA called during replication?

Answer 11

Leading and lagging strand

Question 12

Which direction does DNA polymerase (III) synthesize bases?

Answer 12

5’ —-> 3’

Question 13

Types of RNA + explanation

Answer 13

mRNA: Carries protein synthesis info to ribosomes
tRNA: Forms polypeptide chains
rRNA: Makes up ribosomes

Question 14

What is the start codon?

Answer 14

AUG (also codes for methianine)

Question 15

Introns vs. Exons

Answer 15

Introns: Highly repetitive, do not code for anything, short
Exons: May be genes (code for proteins), unique, long

Question 16

What is a gene?

Answer 16

A base sequence of DNA that codes for a protein

Question 17

What is a nucleosome?

Answer 17

A section of DNA wrapped around 8 histone proteins

Question 18

Function of histones?

Answer 18

To assist replication and wrap DNA to save space

Question 19

Phases of transcription

Answer 19

Initiation
Elongation
Termination

Question 20

What is an operon made of (parts + functions)?

Answer 20

Promoter: RNA polymerase locks on here
Gene: Is transcribed into mRNA
Terminator: RNA polymerase stops transcribing here

Question 21

Parts of the lac operon?

Answer 21

Regulator, Promoter, Operator, Lac Z Lac Y Lac A, Terminator

Question 22

Parts of a ribosome?

Answer 22

Large & small subunits
A slot (Aminoacyl), P slot (Peptidyl), E slot (Exit)

Question 23

Where do replication, transcription and translation occur (+ function)

Answer 23

Replication: nucleus, makes copy of DNA before mitosis
Transcription: Creates mRNA to send info to ribosome
Translation: Creates polypeptide chain from ribosome

Question 24

Types of DNA + functions

Answer 24

Exons: Code for polypeptides
Introns: idk
Structural DNA: Joins to centromeres

Question 25

What are the sense and anti-sense strands

Answer 25

The anti-sense strand is transcribed by RNA polymerase. | The sense strand is complementary to the anti-sense strand, therefore RNA polymerase effectively copies it.

Question 26

Why do humans only have around 30000 genes

Answer 26

Genes can be modified after transcription and proteins can be modified after translation, so one DNA sequence can code for more than one protein

Question 27

Steps of a polymerase chain reaction

Answer 27

To unwind, heat DNA to 95C --> Cool to 40C and add primers --> Add DNA polymerase (III) at 72C --> Repeat 20 times

Question 28

Types of inhibitors + explanation

Answer 28

Competitive: Similar shape to substrate | Non-competitive: Binds to enzyme and changes active site shape

Question 29

Stages of translation + explanation?

Answer 29

- Initiation: mRNA and tRNA bind to ribosome - Elongation: amino acids brought to ribosome in order - Trans-location: amino acids form polypeptide chain - Termination: Translation ends, pelypeptide released

Question 30

Structure of tRNA?

Answer 30

- Held together by complementary base pairing - 3 loops (middle one is anticodon loop) - Amino acid attached to 3' end at CCA

Question 31

Role of ATP in transcription?

Answer 31

Binds to tRNA, then phosphate used to form ester bond b/w amino acid and tRNA

Question 32

How are peptide bonds formed and broken?

Answer 32

Formed by dehydration synthesis | Broken by hydrolysis