Intro to DNA

Question 1

deoxyribonucleic acids (DNA)

Answer 1

stores genetic code
responsible for transmission of code from parent to daughter cells and generation to generation

Question 2

ribonucleic acid (RNA)

Answer 2

intermediary between DNA and proteins
responsible for expressing the genetic code

Question 3

DNA replication

Answer 3

transmission of genetic information to daughter cells

Question 4

transcription

Answer 4

expression of genetic information contained in DNA through RNA

Question 5

DNA repair

Answer 5

corrects damage resulting from replication errors or environmental insults

Question 6

recombination

Answer 6

joins two parental DNA segments to form a hybrid molecule

Question 7

central dogma

Answer 7

genomic DNA -> mRNA -> protein

Question 8

nucleotides are made of

Answer 8

1) nitrogenous base (A, C, T, G, U)
2) 2’ deoxyribose sugar (DNA) or ribose sugar (RNA)
3) 5’ phosphate group

Question 9

which nucleotides are purines

Answer 9

A and G (2 rings)

Question 10

which nucleotides are pyrimidines

Answer 10

C, U, and T (1 ring)

Question 11

what distinguishes T from U

Answer 11

THYmine has a meTHYl group

Question 12

nucleoside

Answer 12

a nitrogenous base linked to a 5-carbon sugar via an N-glycosidic bond
-adenosine, guanosine, cytidine, uridine (RNA)
-deoxyadenosine, deoxyguanosine, deoxycytidine, deoxythymidine

Question 13

nucleotide

Answer 13

a nucleoside with 1, 2, or 3 phosphate groups at the 5’ C position of the sugar

Question 14

nucleic acid polymers

Answer 14

nucleotides are COVALENTLY bound together by 5’ to 3’ PHOSPHODIESTER BONDS, forming the DNA backbone

Question 15

3’-azido-2’-deoxythymidine (AZT)

Answer 15

-a thymidine analog (3’ OH group replaced by the N3 azido group)
-used to treat HIV infection
-inhibits the reverse transcription of the HIV RNA to DNA; gets incorporated but cannot be extended so replication stops

Question 16

acylovir (Zovirax)

Answer 16

-used to treat herpes simplex virus infections
-a guanosine analog
-incorporated into viral DNA chain, but cannot be extended

Question 17

primary structure of DNA

Answer 17

polynucleotide chain, linked by phosphodiester bonds between nucleotides
*DIRECTIONAL: 5’ phosphate to 3’ OH group

Question 18

endonucleases

Answer 18

enzymes that cleave INTERNAL phosphodiester bonds through hydrolysis

Question 19

exonucleases

Answer 19

enzymes that cleave phosphodiester bonds from the ENDS of the DNA (specific for 5’ or 3’ end)

Question 20

DNase treatment for cystic fibrosis

Answer 20

chops up the DNA that causes thick, sticky mucus buildup in the lungs

Question 21

secondary structure of DNA

Answer 21

double helix (B-form most common); has major and minor grooves; formed by base pairing between 2 polynucleotide chains with complementary sequences that run ANTIPARALLEL

Question 22

watson-crick base pairing

Answer 22

A and T - double hydrogen bond
C and G - triple hydrogen bond

Question 23

promoter

Answer 23

site for transcription factors and RNA polymerase to bind and begin transcribing RNA (common elements are TATA and CAAT boxes)

Question 24

enhancers/silencers

Answer 24

sequences that bind specific transcription factors that regulate transcriptional efficiency

Question 25

exons

Answer 25

contain sequence that will eventually be translated into peptide; CODING sequences

Question 26

introns

Answer 26

intervening sequences between exons; transcribed but removed during RNA processing

Question 27

5’ UTR

Answer 27

5’ untranslated region; responsible for binding to ribosome for translation

Question 28

3’ UTR

Answer 28

3’ untranslated region; contains poly-A binding sequence, which likely regulates mRNA stability

Question 29

myotonic dystrophy

Answer 29

autosomal dominant disease caused by mutations in DMPK or CNBP; trinucleotide repeat expansion; s/s include myotonia (slowed relaxation of muscles), muscle pain, etc

Question 30

trinucleotide repeat expansion diseases

Answer 30

-caused by unstable triplet repeat mutations
-number of repeats varies in everyone
-the repeat length correlates with the severity and/or age of onset of the disease
-demonstrate “genetic anticipation,” where earlier age of onset of more severe disease is observed in subsequent generations

Question 31

tertiary structure of DNA

Answer 31

DNA can be relaxed (B-form double helix) or supercoiled (when the double helix coils upon itself)

Question 32

DNA topoisomerases

Answer 32

relax supercoiling of DNA by introducing swivel points in the DNA helix; cause breaks and rejoin the strands without ATP

Question 33

topoisomerase I

Answer 33

cuts a single strand of the double helix to remove supercoiling

Question 34

topoisomerase II

Answer 34

cuts BOTH strands of DNA to remove supercoiling

Question 35

quinolone drugs

Answer 35

target a bacteria-specific topoisomerase II [DNA gyrase]
-blocks gyrase, inhibiting bacterial DNA synthesis
*eukaryotes do not have gyrase, so we are unaffected

Question 36

camptothecin (CPT)

Answer 36

-targets topo I and inhibits the reformation of the cleaved DNA
-leads to cell toxicity at DNA replication
*irinotecan/topotecan at derivates used as chemo

Question 37

etoposide

Answer 37

binds to topo II and prevents re-ligation of the break, leading to double stranded breaks and cell death

Question 38

nucleosome

Answer 38

contains ~146 bp of DNA and 2 copies of each of the core histones (H2A, H2B, H3, and H4)
-DNA is wrapped 1 3/4 turns around the outside of the histone octamer

Question 39

chromatosome

Answer 39

2-turn particle with H1
(contrast to nucleosome, which is 1 3/4 turns)

Question 40

histones

Answer 40

proteins with unusually high content of BASIC amino acids (Arg, Lys, and His), which are cationic and interact with the negatively charged DNA