Which of the following characteristics of the structure of DNA was determined directly from X-ray diffraction photographs of crystallized DNA?
A. the double helical structure
B. the length of a given DNA molecule
C. the frequency of A versus T nucleotides
D. the sequence of nucleotides
Ans: A. the double helical structure
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Answer the following statements true (T) or false (F)
1. All plant cells contain centrioles. 2. The presence of a cell wall and chloroplasts are two features that distinguish a plant cell from an animal cell. 3. The genome rather than proteome most specifically determines how a cell looks and functions. 4. The glycocalyx is a protective coating that prevents bacteria from dehydration and potential destruction by the host organism.
Disulfide bonds are often found to stabilize which of the following levels of protein structure?
A) primary B) secondary C) tertiary D) all of the above E) none of the above
A human diploid cell has ____
a. 23 chromosomes b. n sets of chromosomes c. only the X or Y chromosome d. 23 pairs of homologous chromosomes e. 46 different chromosomes
The first step in urine formation is when blood pressure forces protein-free plasma out of glomerular capillaries and into ____.
A. Bowman’s capsule B. the loop of Henle C. the proximal tubule D. the distal tubule E. the plasma