The two strands of a DNA double helix are held together by _____ that form between pairs of nitrogenous bases
a. ionic bonds
b. covalent bonds
c. hydrophilic interactions
d. S—S bonds
e. hydrogen bonds
Ans: hydrogen bonds
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The nucleolus is a highly active region of the nucleus that is required for synthesis of ribosomes.
Answer the following statement true (T) or false (F)
Soil particles composed of decomposing organic matter are called ____
a. sand b. humus c. silt d. clay e. mineral
What is post-transcriptional gene regulation?
a. regulation after translation b. regulation when the DNA is uncoiled and loosened at the nucleosomes to bind transcription factors c. regulation when RNA is processed and exported to the cytoplasm after it is transcribed d. regulation when RNA is translated to protein
A patient has come to you for a second opinion. "I have these mysterious lumps in my right armpit," he says, "The other doctor says we may have to remove them. What do you think?"You notice red scratches on the patient's right arm. "You must have a new kitten. Cat scratch disease, from the bacterium Bartonella," you say, "And we certainly won't remove those lumps, they are really important! Those are your..."
A. "thymus glands, where naive B and T cells encounter antigens and become activated." B. "lymph nodes, where naive B and T cells encounter antigens and become activated." C. "lymph nodes, where T-cell receptor genes are rearranged as T cells mature." D. "spleen, where hematopoietic stem cells produce lymphoid and myeloid progenitors."