Biol 2051- Exam 2: Ch. 7

Front 1

Molecule of heredity

Back 1

Deoxyribonucleic acid (DNA)

Front 2

Gene

Back 2

sequence of nucleotides in DNA that codes for a single polypeptide

Front 3

Three (3) Key Processes of Macromolecular Synthesis

Back 3

(1) DNA replication
(2) transcription
(3) translation

Front 4

Two (2) Major Differences between Prokaryotic and Eukaryotic genomes

Back 4

(1) Eukaryotes have non-coding regions called introns
(2) Single prokaryotic mRNA often contains more than one coding region

Front 5

DNA base pairing

Back 5

Adenine = thymine (A=T)
Guanine =- cytosine (G=-C)

> hydrogen bonds hold the two strands together

Front 6

Deoxyribonucleotide

Back 6

sugar deoxyribose +
nitrogenous base +
phosphate

Front 7

Bonds linking deoxyribonucleotides

Back 7

covalent phosphodiester bonds

Front 8

Purines

Back 8

Adenine (A) and Guanine (G)

Front 9

Pyrimidines

Back 9

cytosine (C) and thymine (T)

Front 10

Size of DNA (bacterial nucleoid) compared to cell

Back 10

E. coli circular dsDNA is

1500x the size of the cell

> prokaryotic circular DNA is supercoiled

Front 11

Supercoiling

Back 11

methods of compacting DNA by breaking and resealing DNA

> DNA gyrase/topoisomerase

Front 12

Genetic elements in cells

Back 12

(1) DNA
(2) plasmids
(3) mitochondria/chloroplasts
(4) transposable elements

Front 13

Effect of Temp on DNA Structure

Back 13

> hydrogen bonds weak
> covalent phosphodiester bonds strong

Apply heat = H bonds break, not covalent
= denaturing of DNA

Front 14

DNA replication is ________.

Back 14

Semi-conservative

> both DNA strands serve as templates for new strands

Front 15

DNA replication in Prokaryotes

Back 15

begins at origin of replication (oriC)
ends at terminus (ter site)

> Prokaryotes have single oriC (Eukaryotes many)
> bidirectional replication (in both directions) = starts at oriC, ends at ter site halfway around

Front 16

Major Enzymes in DNA replication

(in order)

Back 16

(1) Helicase (unwinds)
(2) Primase (primes)
(3) DNA polymerase III
(4) DNA polymerase I (excises primer)
(5) Ligase (seals nicks)

Front 17

Helicase

Back 17

unwinds helix at replication fork

Front 18

Primase

Back 18

primes strands of DNA with RNA primer

Front 19

DNA polymerase III

Back 19

adds deoxyribonucleotides to the 3' OH end

> 5' -> 3' (only add on to 3')
> cannot begin new DNA strand (must have primer)

Front 20

DNA polymerase I

Back 20

excises RNA primer and fills gap

Front 21

Ligase

Back 21

seals nicks (absence of phosphodiester bond) in DNA

Front 22

Leading strand

Back 22

in DNA replication, the strand made toward the replication fork

Front 23

Lagging strand

Back 23

in DNA replication, the strand made away from the replication fork

Front 24

What bonds are formed when DNA is synthesized?

Back 24

(1) covalent phosphodiester bonds between the sugar of one nucleotide and the phosphate of the next (DNA polymerases)
(2) hydrogen bonds

Front 25

Okazaki fragments

Back 25

lagging strand fragments that contain both DNA and RNA primer

> DNA polymerase III builds DNA up to the fragment, then DNA polymerase I removes RNA primer and fills in with DNA

Front 26

Accuracy of DNA replication

Back 26

Error: 1 per 10^9 nucleotides

(1) proofreading by DNA polymerase III (exonuclease removes and replaces)
(2) complementary base-pairing

Front 27

Plasmids

Back 27

extrachromosomal pieces of DNA

low-copy-number plasmids (1 or 2 per cell)
high-copy-number plasmids (up to 50 per cell, divide continuously)

Front 28

Plasmid Replication

Back 28

(1) bidirectional replication
(2) unidirectional ("rolling circle") replication - used by many bacteriophages
(may produce concatemers)

Front 29

Concatemer

Back 29

long continuous DNA molecule that contains multiple copies of the same DNA sequences linked in series by cos sites

Front 30

Cos sites

Back 30

a protein binding nucleotide sequence that occurs once in each copy of the genome (linking DNA sequences in a concatemer)

Front 31

Determining DNA Base Sequences

Back 31

(1) Restriction enzymes cut DNA; reveal locations of specific sequences
(2) PCR [primers bind to complementary DNA sequences, Taq polymerase (archaeal) synthesizes DNA, rapidly amplifies segment]
(3) Sanger method (determines up to 1000 bases)

Front 32

What prevents the DNA strands from annealing during replication?

Back 32

single-strand binding protein (ssb)

Front 33

Benefit of Plasmids

Back 33

Genes for...
> antibiotic-resistance
> resistance to toxic metals
> proteins to metabolize rare food sources
> allow pathogenesis (virulence genes)
> allow symbiosis