DNA Structure and Replication

Which sequence of DNA bases would pair with this partial strand:
CAT TCA CTG

• ATG TGA CAG

• TAC ACT GTC

• GTA AGT GAC

• CAT TCA CTG

Answer explanation

The DNA base pairing follows the rule A-T and C-G. The given strand CAT TCA CTG pairs with GTA AGT GAC, where C pairs with G, A with T, and T with A, confirming it as the correct complementary sequence.

DNA replication results in two DNA molecules,

• each with two original strands

• each with two new strands

• each with one new strand and one original strand

• one with two new strands and the other with two original strands

Answer explanation

During DNA replication, each new DNA molecule consists of one original strand and one newly synthesized strand, a process known as semi-conservative replication. Thus, the correct answer is that each molecule has one new strand and one original strand.

Order of DNA replication:

• 3, 4, 2, 1

• 3, 1, 4, 2

• 2, 1, 4, 3

• 3, 4, 1, 2

Answer explanation

The correct order of replication is 3, 4, 1, 2. This sequence accurately reflects the steps involved in the replication process, ensuring clarity and correctness in the biological context.

Tags

NGSS.HS-LS3-2

A process in which DNA has the unique ability to make an exact copy of itself.

• Replication

• Translation

• Transcription

Answer explanation

Replication is the process by which DNA makes an exact copy of itself, ensuring genetic information is passed on during cell division. Translation and transcription are related to protein synthesis and RNA production, respectively.

Tags

NGSS.HS-LS3-2

The process of DNA replication is called semi-conservative because it results in:

• None of these

• Two DNA molecules: one original molecule and one with two new strands

• Two exact copies with new strands

• Two identical molecules, each with one original strand and one new strand.

Answer explanation

DNA replication is termed semi-conservative because each of the two resulting DNA molecules contains one original strand and one newly synthesized strand, ensuring genetic fidelity.

What is DNA replication called when the new DNA consists of one parent strand and one new strand?

• Conservative 

• Semiconservative 

• Dispersive

Answer explanation

DNA replication is termed semiconservative because each new DNA molecule consists of one original (parent) strand and one newly synthesized strand, ensuring that genetic information is accurately preserved.

What is the backbone of DNA composed of?

• Nitrogen bases

• Amino acids

• Double H

• Sugar & phosphate

Answer explanation

The backbone of DNA is composed of sugar and phosphate molecules. These form the structural framework, while nitrogen bases attach to the sugar, but they are not part of the backbone itself.

Why is it crucial for living things to be able to replicate their DNA?

• Each cell must have its own DNA

• Fewer copies of DNA are needed when a new cell is created

• A cell needs multiple copies of DNA

• Only muscle cells need DNA

Answer explanation

It is crucial for living things to replicate their DNA so that each cell has its own complete set of genetic information. This ensures proper functioning and development, as every cell requires its own DNA to operate effectively.

If 30% of DNA is made up of Thymine, what is the correct percentage of Guanine?

• 30

• 15

• 20

• 60

Answer explanation

In DNA, the base pairing rules state that Adenine pairs with Thymine and Guanine pairs with Cytosine. If Thymine is 30%, then Adenine is also 30%. The remaining percentage (100% - 60%) is divided equally between Guanine and Cytosine, giving 20% for Guanine.

What is responsible for holding the two strands of the DNA double helix together?

• hydrogen bonds

• alleles

• London dispersion forces

• deoxyribose sugars

Answer explanation

Hydrogen bonds are responsible for holding the two strands of the DNA double helix together. These weak bonds form between the nitrogenous bases of the strands, allowing the DNA to maintain its structure while being flexible.