Video Transcript
Which of the following parts of the genome can affect how well medicines work in
different people? (A) Sugar-phosphate backbone, (B) hydrogen bonds, (C) alleles, (D) mitochondrial
DNA.
The genome refers to the complete set of DNA in an individual. Let’s review the structure and function of DNA in order to answer this question.
Here’s a segment of DNA that shows its two strands wrapped up around each other to
form the familiar double helix shape. If we zoom in, we can see more details of DNA structure. The two strands are indicated here. Each strand is made up of repeating subunits called nucleotides. Each nucleotide is made up of three components: a phosphate group, a deoxyribose
sugar. The combination of the phosphate group and the deoxyribose sugar makes up the
sugar-phosphate backbone of DNA. And the third component of a nucleotide is a nitrogenous base.
In DNA, there are four nitrogenous bases: guanine, represented in orange; cytosine,
represented in blue; adenine, represented in green; and thymine, represented in
pink. These nitrogenous bases can bind with a complementary nitrogenous base on the
opposing DNA strand by hydrogen bonding, shown here as these black dots. The sequence of these nitrogenous bases can provide the instructions for different
proteins or functional units. We call these sequences genes.
Most individuals have a unique sequence of DNA in their genome and might have
different versions of genes that are slightly different from another individual. We can see this here boxed in black. These different versions of the same gene are called alleles, and alleles can produce
slightly different proteins. Different alleles can produce proteins that metabolize drugs differently. And these individuals can have different responses to a drug. Some might respond strongly to a medication, while another may respond poorly.
Therefore, the option that correctly identifies the part of the genome that can
affect how well medicines work in different people is given by answer choice (C),
alleles.
