Question 1
At the isoelectric point, an amino acid has what charges?
◦ + and -
◦ none
◦ + only
◦ - only
◦ multiple charges
Question 2
Below is a double stranded DNA composed of one strand containing
15N atoms and the other strand containing
14N atoms. If the cell which contains this DNA is grown for one generation (replication) on
15N medium and then transferred to
14N media for a second generation, what would the resulting double stranded DNA molecules look like?
◦ Four molecules; each containing one
14N strand and one
15N strand.
◦ Two molecules; one with a
15N and a
14N strand, the other with two
14N strands.
◦ Four molecules; three containing one
14N strand and one
15N strand and one molecule with two
14N strands.
◦ Four molecules; one with two
15N strands, two molecules with two
14N strands, and one molecule with one
14N and one
15N strands.
◦ Four molecules; all molecules have
14N strands.
Double pupils
Concentric double-pipe heat exchanger for co-current flow
The primase-polymerase switch during lagging strand synthesis
Atoms
Opener Bronze sculpture of the Watson–Crick model for double-helical DNA
Rosalind Franklin’s Photo 51, revealing DNA to be a double helix