The ________ valves prevent blood from flowing back into the heart once it has left the ventricles
Fill in the blank(s) with correct word
semilunar
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Where is the central pacemaker that controls circadian rhythm found in many animals?
a. in the suprachiasmatic nucleus b. in the eye c. in the skin d. in the optic nerve
How do different strains of E. coli can reveal different linkage arrangements of genes in Hfr crosses?
A) In different Hfr strains, different genes will be transferred based on where the centromere resides. B) Different strains may have different F factors and therefore different initiation points for chromosome transfer. C) They do not. All Hfr strains are identical. D) Hfr strains will demonstrate different areas of recombination, due to dominance and recessiveness of genes. E) In different Hfr strains, genes can be in different order on the chromosome.
Imagine you were working on a vaccine against HIV viruses. Which part of the virus particle would you try to target as an epitope for the vaccine?
a. the part that shows the strongest positive selection b. the part that interacts with the host immune system c. the part with the highest mutation rate d. the part that shows the strongest purifying selection
Which of the following is a proposed hypothesis for the origin of genetic information?
a. Early DNA molecules coded for RNA, which then catalyzed the production of proteins. b. Early polypeptides were the first "genes," followed by RNA and then DNA. c. As protocells grew and split, they distributed copies of their molecules to their offspring. d. Early RNA molecules coded for the order of amino acids in a polypeptide. e. Short RNA strands were capable of self-replication and evolved by natural selection.