Which of the following would you be unable to locate in xylem tissue?
A) Vessel elements
B) Sclerenchyma cells
C) Tracheids
D) Sieve tube elements
E) Cell walls with porous dimples called pits
D
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Double-stranded DNA absorbs less UV light than single-stranded DNAbecause:
A. base stacking in double-stranded DNA increases the absorbance of white light and causes a decrease in the amount of UV light it can absorb. This decrease in UV absorbance is called the hyperchromic effect. B. the bases are on the inside of the helix, inaccessible to the UV light in double-stranded DNA. C. in single-stranded DNA the bases are not interacting so more photons can be absorbed by the pentose rings. D. single-stranded DNA actually absorbs more of the UV light, making less light available to double-stranded DNA. E. of the hypochromic effect that results when hydrogen bonding and base stacking in double-stranded DNA limits resonance in the aromatic rings of the bases.
Roan cattle are the heterozygous hybrids of a cross
between a white individual and a red individual. If a roan bull were crossed with a red cow, their offspring would show which of the following ratios? a. all roan b. 1 red: 2 roan: 1 white c. 1 red: 1 white d. 1 red: 1 roan e. all red
A common method used to introduce rDNA into bacterial host cells is
A. plasmid transfer. B. viral infection. C. laser irradiation of cells in a fluid containing DNA. D. bacteriophage infection. E. microinjection of DNA.
DNA fragments can be separated by size on a gel, but then must be transferred to filters for probing
and further analysis. The technique used to transfer DNA to the filters is called ____________________. Fill in the blank(s) with the appropriate word(s).