Exam 2- Pt 2

Front 1

Chain Facts!

Back 1

-Antiparallel
-Basses of opposite chains are paired:A-T, C-G
-Hydrogen bonds connecting bases
-bases are flat, lie perpendicular to axis, and stack

Front 2

Basepairing provides:

Back 2

Complimentarity of the two strands and chemical stability to the helix

Front 3

Hydrogen bonding between bases

Back 3

A-T base pairs form two hydrogen bonds and G-C base pairs form three hydrogen bonds

Front 4

Other DNA structures:

Back 4

-A-DNA-slightly more compact than 
B-DNA.
-B-DNA-believed to be the biologically significant form
-C,D,E-DNA-right-handed forms of DNA that are less compact than B-DNA.

Front 5

RNA FACTS!

Back 5

-Similar to DNA, but single Stranded
-Sub Ribose instead of Deoxyribose
-Sub U for T
-some RNAs form double-stranded regions as they fold into different secondary structures

Front 6

three classes of cellular RNAs

Back 6

-messenger RNA (mRNA): templates for protein synthesis
-ribosomal RNA (rRNA): components of ribosomes
-transfer RNA (tRNA): carry amino acids for protein synthesis

Front 7

Sedimentation:

Back 7

-Nucleic acids can be separated by gradient centrifugation procedures.
-Sedimentation equilibrium centrifugation separates by density gradient.

Front 8

Hyperchromic shift

Back 8

during DNA denaturation is used to determine the melting temperature (Tm).

Front 9

As DNA melts (denatures):

Back 9

both the UV absorption and buoyant density increases.

Front 10

Reassociation Kinetics

Back 10

provides information about the size and complexity of genomic DNA from an organism

Front 11

In molecular Hybridization:

Back 11

DNA strands (or DNA and RNA strands) can be renatured to each other.

Front 12

Fluorescent in situ hybridization (FISH)

Back 12

is used to identifying the chromosomal location of a DNA of interest.

Front 13

Nucleic Acid ELectrophoresis

Back 13

separates DNA and RNA fragments by size such that smaller fragments migrate through a gel at a faster rate than large fragments

Front 14

Three possible modes of DNA replication

Back 14

-Conservative-seperate to replicate, then rewind with original
-Semiconservative-STR, 1 new 1 old strand
-Dispersive-some old some new to both strands

Front 15

The Meselson-Stahl experiment

Back 15

-DNA replication is semi conservative
-each new DNA molecule consists of one old strand and one newly synthesized strand

Front 16

Taylor-Woods-Hughes experiment

Back 16

-Demonstrated semi conservative replication in eukaryotes
-Used root tips of Vicia fabia (excellent source of dividing cells)
-Monitored replication by labeling with H3-thymidine (radioactive)

Front 17

DNA Replication
BACTERIAL

Back 17

-Originates at ‘origins of replication’ in bacterial cells.
-Stands unwind during replication creating a ‘replication fork’.
-Replication is bidirectional
-Segment of DNA that is replicated is a ‘replicon’ – in bacteria this is the whole chromosome.

Front 18

Bidirectional replication creates

Back 18

two replication forks
that eventually merge at a termination region (ter).

Front 19

Bacterial DNA synthesis

Back 19

-involved 5 plymerases, and other enzymes
-Chain elongation direction:5-3, by addition of one nucleotide to 3 base end
-As the nucleotide is added, the two terminal phosphates are cleaved off