Topic 7 - Nucleic Acids

Question 1

Hershey + Chase

Answer 1

Used radioisotopes to confirm that DNA is the genetic material of life.

Question 2

Bacteriophage

Answer 2

Virus with a protein outer coat + an inner core of DNA or RNA.

Question 3

Bacteriophages in the Hershey-Chase experiment

Answer 3

Radioactivity: bacteriophage with phosphorus-32 in DNA

No radioactivity: bacteriophage with sulfur-35 in protein coat

Question 4

Composition of DNA strand

Answer 4

Alternating phosphate + deoxyribose molecules, held together by phosphodiester bonds.

Question 5

Where do phosphodiester linkages form?

Answer 5

Between a hydroxyl on the 3’ carbon of deoxyribose + the phosphate group attached to the 5’ carbon of deoxyribose.

Question 6

Condensation

Answer 6

Reaction between phosphate group (5’ end) and hydroxyl group (3’ end)

Question 7

Nitrogenous bases

Answer 7

Linked by hydrogen bonds, attach the sugar/phosphate backbones together.

Question 8

Purines

Answer 8

Double ring structures; adenine + guanine

Question 9

Pyrimidines

Answer 9

Single ring structures; cytosine + thymine

Question 10

Complementary base pairings

Answer 10

Adenine/thymine (2 H-bonds), guanine/cytosine (3 H-bonds)

Question 11

Histones

Answer 11

Proteins used in DNA packaging

Question 12

Nucleosome

Answer 12

Packaged DNA; 8 histones + H1 to maintain it, wrapped DNA, linker DNA.

Question 13

Charges in DNA packaging

Answer 13

DNA has a negative charge, histones have a positive charge; attraction!

Question 14

DNA Packaging - Purpose

Answer 14

DNA is inaccessible to transcription enzymes; regulates transcription process.

Question 15

Highly repetitive sequences

Answer 15

No coding functions, can move between locations in genome.

Question 16

Protein-coding genes

Answer 16

Provide base sequences for protein production at ribosomes.

Question 17

Exons

Answer 17

Coding fragments of genes.

Question 18

Introns

Answer 18

Non-coding fragments of genes.

Question 19

Structural DNA

Answer 19

Highly coiled, has no coding functions (possibly due to mutation)

Question 20

Short tandem repeats

Answer 20

Short, repeating DNA sequences

Question 21

Polymorphisms

Answer 21

DNA regions that show a lot of variation; analyzed in DNA profiling.

Question 22

Bacterial DNA

Answer 22

Circular, no histones, single origin

Question 23

Eukaryotic DNA

Answer 23

Linear, histones, thousands of origins

Question 24

Origin of replication

Answer 24

Site where replication starts; separation of strands creates a ‘bubble.’

Question 25

Helicase

Answer 25

Enzyme; acts on H-bonds between nucleotides to separate strands.

Question 26

Replication fork

Answer 26

Location at the end of each ‘bubble’ where double-stranded DNA opens to make the two parental DNA strands available as templates.

Question 27

Direction of replication process

Answer 27

Bidirectional

Question 28

Bubbles fuse with each other to…

Answer 28

…produce 2 identical daughter DNA molecules.

Question 29

Primer

Answer 29

Short (5-10 nucleotides) RNA sequence, produced at replication fork.

Question 30

Primase

Answer 30

Enzyme; causes production of primer and let RNA nucleotides join together at the point of replication.

Question 31

DNA polymerase III

Answer 31

Enzyme; allows addition of molecules to produce DNA strand (5’ to 3’ direction)

Question 32

DNA polymerase I

Answer 32

Removes the primer from the 5’ end, replaces it with DNA nucleotides

Question 33

Deoxynucleoside triphosphate (dNTP)

Answer 33

Nucleotides added to elongating DNA chain; loss of two phosphates in the process provides energy for chemical bonding of nucleotide.

Question 34

Leading strand

Answer 34

DNA forms in 3’ to 5’ direction; continuous/fast process.

Question 35

Lagging strand

Answer 35

DNA forms in 5’ to 3’ direction; fragmented/slow process