DNA and Biotechnology

Question 1

1° Structure: Nucleic Acids

Answer 1

Linear sequence of nucleotides.

Question 2

2° Structure: Nucleic acid (DNA)

Answer 2

Interactions between bases within the same molecule. In
DNA, the bases are held together by hydrogen bonds. 2°
structure is responsible for the shape of nucleic acid.

Question 3

2° Structure: Nucleic Acids (RNA)RNA 2°

Answer 3

structure has 4 basic elements: Loops, helices, bulges,
and junctions. Loops include stem-loops (hairpin loops),
tetraloops, and psuedoknots

Question 4

Nucleoside

Answer 4

: 5-carbon sugar + nitrogenous base. NO PHOSPHATE groups.

Question 5

Nucleotide:

Answer 5

A nucleoside with 1 to 3 phosphate groups added.
Nucleotides in DNA contain deoxyribose; in RNA they
contain ribose. Adenine (A), Thymine (T), Guanine (G),
Cytosine (C), Uracil (U). In RNA, U replaces T, so A pairs with
U via 2 h-bonds.

Question 6

Watson-Crick

Model:

Answer 6

Backbone of alternating sugar/phosphate groups. Always
read 5’ –> 3’. Two strands with antiparallel polarity wound
into a double helix.

Question 7

B-DNA vs Z-DNA

Answer 7

Most DNA is B-DNA, forming a right-handed helix. Low
concentrations of Z-DNA, with a zigzag shape, may be seen
with high GC-content or high salt concentration

Question 8

Oncogenes

Answer 8

Develop from mutations of proto-oncogenes, and
promote cell cycling. May lead to cancer.
Oncogenes = stepping on gas pedal

Question 9

Tumor Suppressor

Genes

Answer 9

Genes:
Code for proteins that reduce cell cycling or promote
DNA repair.
Mutated Tumor Suppressor genes = cutting the brakes

Question 10

Proofreading:

Answer 10

DNA Polymerase proofreads its work and excises
incorrectly matched bases. The daughter strand is
identified by its lack of methylation and corrected
accordingly.

Question 11

What phase of the cell cycle does mismatch repair occur?

Answer 11

G2 phase using the genes MSH2 and MLH1

Question 12

Nucleotide

Excision Repair

Answer 12

Fixes helix-deforming lesions of DNA such as Thymine

dimers. A cut-and-patch process. Excision Endonuclease.

Question 13

Base Excision

Repair

Answer 13

Fixes nondeforming lesions of the DNA helix such as
cytosine deamination by removing the base, leaving
apurinic/apyrimidinic (AP) site. AP Endonuclease then
removes the damaged sequence, which can be filled in
with the correct bases.

Question 14

Heterochromatin

Answer 14

Dark, dense, and silent

Question 15

Euchromatin

Answer 15

Light, uncondensed, and expressed

Question 16

Telomeres

Answer 16

: Ends of chromosomes. Contain high GC-content to prevent
unraveling of the DNA. During replication, telomeres are
shortened, but this can be partially reversed by telomerase

Question 17

Centromeres:

Answer 17

Located in the middle of 
chromosomes and hold 
sister chromatids 
together until they are 
separated during 
anaphase in mitosis. 
High GC-content to 
maintain a strong bond 
between chromatids.

Question 18

Acrocentric

Chromosome

Answer 18

When the centromere is located near one end of the

chromosome and not in the middle

Question 19

Recombinant DNA

Answer 19

DNA composed of nucleotides from 2 different sources

Question 20

Hybridization

Answer 20

The joining of complementary base pair sequences.

Question 21

Cytosine structure

Answer 21

Question 22

Thymine

Answer 22

Question 23

Uracil

Answer 23

Question 24

Guanine

Answer 24