The relationship between genomes and epigenomes reveals how cells with identical DNA develop different _____ whereas the genome in each...

Let's begin by understanding the meaning of this sentence. We'll use our understanding of pause points and segment the sentence as shown - understanding and assimilating the meaning of each segment bit by bit!

Sentence Structure

• The relationship between genomes and epigenomes
• reveals how cells with identical DNA
  • develop different functions [?]
• whereas the genome in each cell
  • contains a complete DNA sequence,
• the epigenome
  • consists of chemical compounds
    • that determine which traits in the sequence will be expressed.
• [?] = A: (nothing) | B: , | C: , and | D: :

Understanding the Meaning

The sentence starts by telling us what a certain relationship reveals:

• "The relationship between genomes and epigenomes reveals how cells with identical DNA develop different functions"

This is saying: even though cells have identical DNA, they develop different functions. Interesting! But how does this happen?

This is where we have the blank. Let's look at the choices:

• They're asking what punctuation (if any) should follow "functions"
• Options are: nothing, a comma, a comma with "and", or a colon

To see what works here, let's read the rest of the sentence and understand what it's saying!

The sentence continues:

"whereas the genome in each cell contains a complete DNA sequence, the epigenome consists of chemical compounds that determine which traits in the sequence will be expressed."

Now let's understand what this is telling us:

• "the genome in each cell contains a complete DNA sequence"
  • The genome (DNA) is the same in every cell - complete and identical
• "the epigenome consists of chemical compounds that determine which traits in the sequence will be expressed"
  • The epigenome acts like a controller
  • It determines which parts of that identical DNA actually get used
  • Different cells can express different traits from the same DNA

So the complete picture is:

• The first part says: cells with identical DNA develop different functions
• The second part explains HOW this happens: the epigenome controls which traits from that identical DNA get expressed

What do we notice about the structure here?

• Before the blank: we have a complete statement that raises a question
  • "Cells with identical DNA develop different functions" - but how?
• After the blank: we have a complete statement that answers that question
  • It explains the mechanism - the epigenome determines which traits are expressed
• The second part is elaborating on and explaining the first part
  • It's giving us the details of how the phenomenon works

When we have one complete thought followed by another complete thought that explains or elaborates on the first, we need a colon. The colon signals: "here comes the explanation for what I just said."

So we need a colon after "functions."

The correct answer is D.

GRAMMAR CONCEPT APPLIED

Using Colons to Introduce Explanations

When you have a complete statement followed by material that explains, elaborates on, or provides details about that statement, use a colon to introduce the explanatory material. The colon signals to the reader: "what follows will clarify or expand on what I just said."

Pattern:

• Statement: [Complete thought that sets up expectation]: [Explanation or elaboration]

Example 1:

• The study revealed a surprising finding: students who took breaks every 30 minutes retained more information than those who studied continuously.
• First part: mentions a finding (creates expectation)
• After colon: explains what that finding was

Example 2:

• The coach explained his strategy: the team would focus on defense in the first half and switch to offense after halftime.
• First part: says there's a strategy (creates expectation)
• After colon: details what that strategy is

In our question:

• Cells with identical DNA develop different functions: whereas the genome in each cell contains a complete DNA sequence, the epigenome consists of chemical compounds that determine which traits in the sequence will be expressed.
• First part: states the phenomenon (cells with same DNA differ)
• After colon: explains the mechanism (epigenome controls expression)

The colon (called a colon in punctuation terms) is perfect when the second part unpacks or clarifies the first part. It creates a clear relationship between the setup and the payoff.