AP Biology : AP Biology

Study concepts, example questions & explanations for AP Biology

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Example Questions

Example Question #72 : Central Dogma

What is the process in which the DNA molecule separates into two strands then produces two new complementary strands following the rules of base pairing.

Possible Answers:

Reformation

Translation

Transcription

Replication

Correct answer:

Replication

Explanation:

Replication is the process in which the DNA molecule produces two new complementary strands. Transcription produces a messenger RNA, and translation produces a chain of amino acids that become a protein.

Example Question #37 : Understand Steps Of Replication

What is the primary enzyme involved in DNA replication?

Possible Answers:

DNA polymerase

ATP synthase

Transciptase

RNA polymerase

Correct answer:

DNA polymerase

Explanation:

DNA polymerase is the primary enzyme involved in DNA replication. It is responsible for adding nucleotides to the growing DNA chain in the 5' to 3' direction. This enzyme also has proofreading functionality, which allows it to remove nucleotides that are mispaired in the 3' to 5' direction and replace them with the correct nucleotide.

Example Question #38 : Understand Steps Of Replication

What DNA fragment would complement 5’ ATCGGTCAAT 3’ ?

Possible Answers:

5’ TAGCCAGTTA 3’

5’ GCTAACTGGC 3’

3’ ATCGGTCAAT 5’

3’ TAGCCAGTTA 5’

3’ GCTAACTGGC 5’

Correct answer:

3’ TAGCCAGTTA 5’

Explanation:

The correct answer must complementary base pair with the fragment in the 3’ to 5’ direction because the strands run anti-parallel to each other. Only three of the given options that will run anti-parallel, but only one complements the DNA properly.

Example Question #2351 : Ap Biology

In DNA replication, which enzyme is responsible for separating the two strands of DNA apart?

Possible Answers:

Polymerase III

Helicase

Polymerase I

Single-stranded binding proteins

Primase

Correct answer:

Helicase

Explanation:

The correct answer is Helicase because it is involved with the separation of the two strands of DNA by breaking the hydrogen bonds between them. Primase lays down the RNA primer so that the polymerase enzymes can attach and start adding complementary base pairs. SSBs are single stranded binding proteins which anchor the separated strands and keep them from annealing to each other.

Example Question #2352 : Ap Biology

A protein that ultimately functions in the plasma membrane of a cell is most likely to have been synthesized __________.

Possible Answers:

in the rough endoplasmic reticulum

by ribosomes on the nuclear envelope

by free cytoplasmic ribosomes

in the mitochondria

in the plasma membrane

Correct answer:

in the rough endoplasmic reticulum

Explanation:

The primary function of the ribosomes bound to the rough endoplasmic reticulum is to synthesize proteins for transport to the cell exterior or extracellular matrix. These ribosomes produce polypeptides that are packaged into vesicles by the Golgi apparatus and transported to the membrane. The vesicle then fuses with the membrane, either releasing proteins out of the cell or incorporating them into the cell membrane.

Nuclear ribosomes synthesize replication and transcription proteins into the nucleus, while cytoplasmic ribosomes produce cytoplasmic proteins.

Example Question #2353 : Ap Biology

Which of the following steps of DNA replication is inaccurate?

Possible Answers:

The enzyme topoisomerase creates breaks in the DNA backbone

A replication bubble with two replication forks is formed

The DNA strands are separated by the enzyme helicase

The primase enzyme lays down RNA primers

Okazaki fragments are joined by DNA polymerase

Correct answer:

Okazaki fragments are joined by DNA polymerase

Explanation:

During DNA replication, helicase is responsible for unwinding the DNA helix and topoisomerase cleaves portions of the sugar-phosphate backbone to release tension in the strands. DNA polymerase then enters the replication bubble created by helicase. The bubble has two sides, each with a leading strand and a lagging strand. The leading strand at one side of the bubble is the lagging strand at the other, since DNA is anti-parallel. DNA polymerase can only synthesize in the 5'-to-3' direction; the strand oriented in the 3'-to-5' direction at the replication fork is known as the lagging strand since it must be replicated in pieces in the reverse direction. These pieces are known as Okazaki fragments.

DNA ligase is the protein responsible for fusing breaks in the sugar-phosphate backbone. It repairs the bonds broken by topoisomerase and creates phosphodiester bonds between Okazaki fragments.

Example Question #2354 : Ap Biology

What is heterochromatin?

Possible Answers:

DNA that cannot be transcribed

DNA that is not being translated

DNA that is being translated

DNA that can be transcribed

Correct answer:

DNA that cannot be transcribed

Explanation:

Heterochromatin is “dark” chromatin that represents DNA that is not active in transcription. The fact that it is “dark” implies that it is condensed and inaccessible by polymerases. Heterochromatin is created when DNA is tightly wound around histones. This tight winding prevents transcription proteins from interacting with the DNA. Heterochromatin is most common in the nucleus during mitosis, when no transcription is taking place. In contrast, euchromatin is capable of being transcribed and is most common during interphase, when most cellular growth and production occurs.

Translation occurs outside of the nucleus and uses mRNA as a template, not DNA.

Example Question #1 : Understanding Prokaryotic Genes

What is the main difference between prokaryotic and eukaryotic genes?

Possible Answers:

Prokaryotic genes only have exons, but eukaryotic genes have exons and introns

Prokaryotic genes are not replicated, and only transcribed to RNA to then become protein

Prokaryotes have one large gene, but eukaryotes have many smaller genes

Prokaryotes do not have gene regulatory sequences, but eukaryotes do

Eukaryotes stores genes together in operons, but prokaryotes do not

Correct answer:

Prokaryotic genes only have exons, but eukaryotic genes have exons and introns

Explanation:

The correct answer is that prokaryotes only have exons, whereas eukaryotes have exons and introns. As a result, in eukaryotes, when mRNA is transcribed from DNA, the introns have to be cut out of the newly synthesized mRNA strand. The exons, or coding sequences, are then joined together. Prokaryotes do not have to process their mRNA to this extent. 

Example Question #1 : Understanding Prokaryotic Genes

A segment of prokaryotic DNA that binds transcription factors, usually as repressors that prevent transcription, are best known as __________.

Possible Answers:

Promoters

Exons

Untranslated regions

Enhancers

Operators

Correct answer:

Operators

Explanation:

The correct answer is operator. In most operons, repressors bind operators to prevent transcription of downstream genes.

Promoters are sequences of DNA upstream of genes that usually promote transcription by recruiting polymerases and other transcription factors. Enhancers are distant DNA sequences that promote transcription, whereas exons are the coding segments of a gene. 

Example Question #1 : Understand Regulation Of Transcription

What is the function of RNA polymerase in prokaryotes? 

Possible Answers:

Transcribe RNA from a DNA template

Translate RNA to protein

None of the other answers 

Replicate DNA during cell division

Repress transcription by binding operators

Correct answer:

Transcribe RNA from a DNA template

Explanation:

The correct answer is transcribe RNA from a DNA template. RNA polymerases are DNA-dependent, meaning that they require a DNA template; however, the new daughter strand that they create is composed of RNA. This RNA will then be translated into a functional protein by prokaryotic ribosomes. 

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