A person who is HIV-positive and has a helper T (TH) cell count lower than __________ has AIDS.

A student carries out PCR using the following steps:   Step 1: 94°C for 1 minute Step 2: 60°C for 30 seconds Step 3: 72°C for 30 seconds Which of the following lists the CORRECT terms for these three steps?

Which of the following enzyme activities play a role in nucleotide-excision repair? Select all that apply.

14[14] 15[15]  

Which of the following DNA repair systems does NOT involve the activity of a DNA polymerase?

The R group for serine is -CH2-OH. In the ionized form, serine has the structural formula ________.

Assume that a base-pair substitution mutation converts a DNA triplet (AAT) to another DNA triplet (AAA). A second mutation now changes the AAA triplet to the GAA triplet. (UUA and CUU code for leucine and UUU codes for phenylalanine.) This second mutation is an example of a(n):

At a pH < 5, the ionized form for alanine (pI = 6) will have ________.

PCR (polymerase chain reaction) is an excellent method of generating copies of target DNA. If a single piece of double stranded DNA (dsDNA) is put into a PCR machine, how many dsDNA segments will there be after 3 rounds? 

Upon transposing to a new site, transposable elements: