DNA & Biotechnology

Question 1

What is the difference between nucleosides & nucleotides ?

Answer 1

Nucleosides: composed of pentose & nitrogenous base (covalently linked @ C1)
Nucleotide: amount of phosphate groups attached to nucleoside (attached @ C5)

Question 2

What is the difference between ribose & deoxyribose?

Answer 2

Ribose has -OH @C2 while deoxyribose has -H @C2

Question 3

What is the overall charge of DNA & RNA, & why ?

Answer 3

Negative due to phosphates

Question 4

Which bases are classified as purines & pyrimidines and how do they differ ?

Answer 4

Purines: adenine, guanine (2 ring structures)—> both found in RNA & DNA
Pyrimidines: cytosine, uracil, thymine (1 ring structures)—-> C in both but U only in RNA & T only in DNA

Question 5

What properties are needed for a molecule to be considered aromatic ?

Answer 5

1. Planar
2. Cyclic
3. Conjugated
4. 4n +2 pi electrons (Huckel’s rule)

Question 6

How are nitrogenous bases paired via complementary base pairing ?

Answer 6

A-T (2 H+)

C-G (3H+)—> stronger due to more bonds

Question 7

The idea that the total amount of purines will be equal to the total amount of pyrimidines based on complementary pairing is based on what ?

Answer 7

Chargaff’s rules

Question 8

What is the difference between nucleosome and chromatin ?

Answer 8

Chromatin is a whole structure of complex DNA and proteins while nucleosome is a basic unit of chromatin

Question 9

What is the difference between heterochromatin & euchromatin ?

Answer 9

Heterochromatin is a small part of chromatin that remains compact during interphase & often consists of DNA w/ highly repetitive sequences.
Euchromatin is dispersed and contains genetically active DNA

Question 10

What does the replisome/replication complex function as ?

Answer 10

Assisting proteins to DNA polymerases

Question 11

What is the enzyme responsible for unwinding DNA ?

Answer 11

Helicase

Question 12

Proteins that hold single stranded DNA apart to prevent rekindling or degradation are known as ?

Answer 12

Single-stranded DNA-binding proteins

Question 13

What enzyme works ahead of helicases to add negative supercoils to relieve the torsional strain that comes with the positive supercoiling effect due to DNA unwinding ?

Answer 13

DNA topoisomerases

Question 14

The enzyme responsible for reading the DNA template in the 3’-5’ direction and synthesizing new DNA from it is known as ?

Answer 14

DNA polymerases

Question 15

Primase consists of what type of sequences ?

Answer 15

RNA

Question 16

What are the functions & differences between the DNA polymerases ?

Answer 16

B, E, & S: work together to synthesize new DNA on both the leading & lagging
S: fills in gap left after removal of RNA sequence/primer
Y: replicates mitochondrial DNA
B & E: essential for DNA repair
S & E: assisted by PCNA protein to strengthen interaction between polymerases and template strand
*RNase H: removes rna primer sequence

Prokaryotes:
III: synthesis of DNA
I: replaces RNA primer sequence with DNA sequence

Question 17

Mutated genes that cause cancer are known as ?

Answer 17

Oncogenes (referred to as proto-oncogenes BEFORE mutated)

Question 18

Tumor suppressor genes that function to stop tumor progression are known as ?

Answer 18

Antioncogenes (Ex: p53 or Rb)

Question 19

Genomic libraries consist of what ?

Answer 19

Large fragments of DNA that include both exons (coding region) & introns (noncoding region) of the genome.

Question 20

cDNA libraries consist of ?

Answer 20

Reverse-transcribed mRNA & include only genes that are expressed in the tissue they were derived from

Question 21

The joining of 2 single stranded sequences is a tool known as ?

Answer 21

Hybridization

Question 22

How do transgenic and knockout mice compare ?

Answer 22

Transgenic mice are altered @germ line via fertilized ova or embryonic stem cells
Knockout mice intentionally have a deleted gene
Both are useful for studying human diseases