Question

which of the following correctly describes the structure of dna?
a. coiled structure without nucleotides
b. triple - stranded helix
c. double - stranded helix
d. single - stranded helix
what is the function of mitochondrion’s dna?
a. encoding genetic information essential for cellular energy production
b. directing cell division
c. encoding genetic information for protein synthesis
d. controlling cell membrane structure
what does the term antiparallel refer to in dna structure?
a. the arrangement of dna strands running in opposite directions
b. the way bases pair with each other
c. the shape of the dna molecule
d. the direction of the sugar molecules

Explanation:

First Question (DNA Structure)

To determine the correct description of DNA structure:

• Option a: DNA is made of nucleotides, so "without nucleotides" is wrong.
• Option b: DNA is not triple - stranded; it has two strands.
• Option c: DNA has a double - stranded helix structure (discovered by Watson and Crick), which is correct.
• Option d: DNA is double - stranded, not single - stranded.

To find the function of mitochondrial DNA:

• Option a: Mitochondrial DNA encodes genes related to mitochondrial function, especially for cellular energy (ATP) production. Mitochondria are the powerhouses of the cell.
• Option b: Directing cell division is mainly related to nuclear DNA and cell cycle regulatory mechanisms, not mitochondrial DNA.
• Option c: Protein synthesis for most cellular proteins is directed by nuclear DNA. Mitochondrial DNA is for mitochondrial - specific proteins related to energy production.
• Option d: Controlling cell membrane structure is not a function of mitochondrial DNA.

To understand "antiparallel" in DNA:

• Option a: DNA's two strands run in opposite directions (one 5' - 3' and the other 3' - 5'), which is the meaning of antiparallel.
• Option b: Base pairing (A - T, G - C) is about complementary base pairing, not antiparallel.
• Option c: The shape of DNA is a double helix, not related to antiparallel.
• Option d: The direction of sugar molecules is part of the strand direction, but the term antiparallel refers to the overall strand orientation.

Answer:

c. Double - stranded helix

Second Question (Mitochondrial DNA Function)