Question

Complete the base sequence in a complementary DNA segment if a portion of the parent strand has each of the following base sequences: a. \(-\mathrm{T}-\mathrm{T}-\mathrm{T}-\mathrm{T}-\mathrm{T}-\mathrm{T}-\) b. \(-\mathrm{C}-\mathrm{C}-\mathrm{C}-\mathrm{C}-\mathrm{C}-\mathrm{C}-\mathrm{C}-\mathrm{C}-\mathrm{C}-\) c. \(-\mathrm{A}-\mathrm{T}-\mathrm{G}-\mathrm{G}-\mathrm{C}-\mathrm{A}-\) d. \(-\mathrm{A}-\mathrm{T}-\mathrm{A}-\mathrm{T}-\mathrm{G}-\mathrm{C}-\mathrm{G}-\mathrm{C}-\mathrm{T}-\mathrm{A}-\mathrm{A}-\mathrm{A}-\)

Short answer

a. \( -A-A-A-A-A-A- \) b. \( -G-G-G-G-G-G-G-G-G- \) c. \( -T-A-C-C-G-T- \) d. \( -T-A-T-A-C-G-C-G-A-T-T-T- \)

Step-by-step solution

Understanding DNA Base Pairing Rules

DNA is composed of four types of nucleotides, each containing a base: adenine (A), thymine (T), cytosine (C), and guanine (G). In DNA, adenine pairs with thymine, and cytosine pairs with guanine.

Determine Complementary Sequence for Part A

Given the parent strand: \( -\mathrm{T}-\mathrm{T}-\mathrm{T}-\mathrm{T}-\mathrm{T}-\mathrm{T}- \) The complementary strand will be: \( -\mathrm{A}-\mathrm{A}-\mathrm{A}-\mathrm{A}-\mathrm{A}-\mathrm{A}- \)

Determine Complementary Sequence for Part B

Given the parent strand: \( -\mathrm{C}-\mathrm{C}-\mathrm{C}-\mathrm{C}-\mathrm{C}-\mathrm{C}-\mathrm{C}-\mathrm{C}-\mathrm{C}- \) The complementary strand will be: \( -\mathrm{G}-\mathrm{G}-\mathrm{G}-\mathrm{G}-\mathrm{G}-\mathrm{G}-\mathrm{G}-\mathrm{G}-\mathrm{G}- \)

Determine Complementary Sequence for Part C

Given the parent strand: \( -\mathrm{A}-\mathrm{T}-\mathrm{G}-\mathrm{G}-\mathrm{C}-\mathrm{A}- \) The complementary strand will be: \( -\mathrm{T}-\mathrm{A}-\mathrm{C}-\mathrm{C}-\mathrm{G}-\mathrm{T}- \)

Determine Complementary Sequence for Part D

Given the parent strand: \( -\mathrm{A}-\mathrm{T}-\mathrm{A}-\mathrm{T}-\mathrm{G}-\mathrm{C}-\mathrm{G}-\mathrm{C}-\mathrm{T}-\mathrm{A}-\mathrm{A}-\mathrm{A}- \) The complementary strand will be: \( -\mathrm{T}-\mathrm{A}-\mathrm{T}-\mathrm{A}-\mathrm{C}-\mathrm{G}-\mathrm{C}-\mathrm{G}-\mathrm{A}-\mathrm{T}-\mathrm{T}-\mathrm{T}- \)

Key concepts

Nucleotide Pairing

DNA is made up of smaller units called nucleotides. Each nucleotide contains a sugar, a phosphate group, and a nitrogenous base. The four nitrogenous bases in DNA are adenine (A), thymine (T), cytosine (C), and guanine (G). Nucleotide pairing follows very specific rules: adenine always pairs with thymine, and cytosine always pairs with guanine. This is crucial because it ensures that DNA can be accurately replicated when cells divide. So, if you know the sequence on one strand, you can easily determine the sequence on the opposite, complementary strand.

Complementary DNA Strands

In DNA, two strands twist around each other to form a double helix. These strands are complementary, meaning that each base on one strand pairs with a specific base on the other strand. The rules of nucleotide pairing (A with T and C with G) guide this process.
For example, if one strand has the sequence \(\text{-A-T-G-C-}\), the complementary strand will have the sequence \(\text{-T-A-C-G-}\). This complementary nature of the DNA strands is vital for DNA replication and plays a key role in biological accuracy and function.

Adenine-Thymine Bond

The adenine-thymine bond is a specific type of nucleotide pairing in DNA. Adenine (A) pairs with thymine (T) through two hydrogen bonds, helping to stabilize the DNA structure. These hydrogen bonds are relatively weak compared to covalent bonds, but they provide enough stability to hold the two DNA strands together while still allowing them to separate during replication and transcription.
This specific bonding is critical for the accurate transmission of genetic information.

• Adenine (A) pairs with Thymine (T) through two hydrogen bonds.

Understanding this bond helps us to understand how mutations occur and how genetic information is faithfully passed from one generation to the next.

Cytosine-Guanine Bond

The cytosine-guanine bond is another specific type of nucleotide pairing in DNA. Cytosine (C) pairs with guanine (G) through three hydrogen bonds. This bond is stronger than the adenine-thymine bond due to the extra hydrogen bond, adding extra stability to the DNA molecule. The differences in bond strength between C-G and A-T pairs play a role in the functional aspects of DNA, such as the regulation of gene expression.
Key points include:

• Cytosine (C) pairs with Guanine (G) through three hydrogen bonds.

This stronger bond is part of what makes the genetic code reliable and helps prevent errors during DNA replication and repair processes.