Video Transcript
Which of the following is not an
adaptation that DNA has in order to carry out its primary functions? (A) DNA is very stable, so it can
be passed from generation to generation with changes being rare. (B) The hydrogen bonds joining
bases together can be easily separated to allow DNA replication. (C) DNA usually exists as a single
strand, ready to be replicated and passed on. (D) DNA is a relatively large
molecule and can carry a lot of information. Or (E) DNA has a strong
sugar–phosphate backbone to provide support and protection.
Let’s begin by reviewing some of
the primary functions of DNA. DNA, or deoxyribonucleic acid, is a
molecule found in the cells of all living organisms. DNA carries genetic
information. It is responsible for preserving
this information and passing it on from one generation to the next.
A molecule of DNA is composed of
two strands of nucleotides. A single nucleotide has three
components: a deoxyribose sugar, a phosphate group, and a nitrogenous base. The sugar molecule of each
nucleotide forms a bond with the phosphate group of the next. This forms a stable sugar–phosphate
backbone. The two strands of DNA are joined
together through hydrogen bonds, which form between the nitrogenous bases on one
strand and the nitrogenous bases on the other strand.
With this in mind, let’s answer our
question by figuring out which of the statements about the adaptations of DNA is not
true.
Answer choice (A) states that DNA
is very stable, so it can be passed from generation to generation with changes being
rare. This is true. DNA exists as a stable,
double-stranded molecule. This helps maintain the integrity
of the genetic information as it is passed from one generation to the next. This means that option (A) cannot
be the correct answer to this particular question.
Answer choice (B) states that the
hydrogen bonds joining bases together can be easily separated to allow DNA
replication. This statement is also correct. When a cell divides, DNA first must
replicate itself. A special enzyme breaks the
hydrogen bonds and separates the two strands. This allows two new strands to be
synthesized. With this information, we can
eliminate option (B) too.
Answer choice (C) states that DNA
usually exists as a single strand, ready to be replicated and passed on. As we know, DNA usually exists as a
double-stranded molecule. This statement is therefore
incorrect and could be the answer we are looking for. Let’s bear this in mind while we go
over the last two answer choices.
Answer choice (D) states that DNA
is a relatively large molecule and can carry a lot of information. This is true. Did you know that human DNA
contains around three billion nitrogenous base pairs? It stores twenty to twenty-five
thousand genes, which are mostly responsible for the synthesis of proteins. Therefore, this cannot be the
correct answer.
Finally, answer choice (E) says
that DNA has a strong sugar–phosphate backbone to provide support and
protection. Well, as we learned earlier, this
is true. Each strand of DNA has a backbone
made of sugar and phosphate. So, this option must also not be
the correct response to this question.
Through the process of elimination,
we can now confirm which of the statements is incorrect. The answer choice that is not an
adaptation of DNA is (C): DNA usually exists as a single strand, ready to be
replicated and passed on.
