High School Biology : Genes and DNA

Study concepts, example questions & explanations for High School Biology

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Example Questions

Example Question #3 : Understanding Prokaryotic Genes

What is the function of RNA polymerase in prokaryotes? 

Possible Answers:

Replicate DNA during cell division

Repress transcription by binding operators

None of the other answers 

Translate RNA to protein

Transcribe RNA from a DNA template

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. 

Example Question #11 : Transcription

Which of the following is true of Rho-dependent transcription termination in prokaryotes?

Possible Answers:

None of the other answers

Rho attaches to a Rho recognition site on the DNA template 

Rho uses GTP as a source of energy

Rho is a nuclease that terminates transcription by cutting template DNA

Rho unwinds the DNA-RNA helix at the transcription bubble

Correct answer:

Rho unwinds the DNA-RNA helix at the transcription bubble

Explanation:

Rho attaches to a Rho recognition site on the mRNA strand and uses ATP to move along the mRNA strand towards RNA polymerase. When RNA polymerase pauses at the terminator, Rho unwinds the DNA-RNA hybrid. RNA polymerase, Rho, and the newly synthesized mRNA are released. 

Example Question #5 : Understanding Prokaryotic Genes

Prokaryotic genes are often grouped together based on function. What are these groups of genes called?

Possible Answers:

Clusters

Linked genes

Operons

Promoter sequences

Operator sequences

Correct answer:

Operons

Explanation:

Bacteria organize some of their genes into operons. Operons contain genes of a similar function grouped together, and these genes are all transcribed together. For example, the lac operon involves the three genes required for breaking down lactose. There is no point in only transcribing one or two of the three genes since they are all required to break down lactose. Thus, they are under the control of a single operator and are all transcribed when the operator is active.

Example Question #6 : Understanding Prokaryotic Genes

Bacterial plasmids can __________.

Possible Answers:

transfer between bacterial cells

All of these

be present in multiple copies

integrate into the bacterial genome

carry antibiotic resistance genes

Correct answer:

All of these

Explanation:

Plasmids are small pieces of DNA that are not part of a bacteria's genome. The genes contained on plasmids are not necessary for proper function of the bacteria. However, bacterial plasmids can carry genes to confer antibiotic resistance, and commonly do. Plasmids can be transferred between bacteria via conjugation, and can be integrated into their genomic DNA.. Plasmids are usually present in more than one copy per cell.

Example Question #81 : Genetics Principles

Which of the following technological advances allows for the creation of a “recombinant plasmid”? 

Possible Answers:

cDNA libraries

Restriction endonucleases

Watson-Crick base pairing

Sanger sequencing

Viral vectors

Correct answer:

Restriction endonucleases

Explanation:

Restriction Endonucleases, or otherwise known as restriction enzymes, allows biologist to “cut and paste” different DNA sequences together. The use of restriction endonucleases is critical for the creation of recombinant plasmids. Viral vectors is incorrect, as viral vectors are useful in the application of recombinant DNA plasmids, delivery to host cell, but not in forming.

Example Question #8 : Understanding Prokaryotic Genes

A mutation in the bacterial cell escherichia coli makes it unable to break down the sugar lactose. Which of the following is not a potential mutation that could result in this phenotype?

Possible Answers:

A point mutation in the LacZ gene that abolishes enzyme activity

A mutation in the operator that blocks the activator from binding

A mutation in the region DNA polymerase binds to in the promoter

A frameshift mutation in the LacZ coding region

Correct answer:

A mutation in the region DNA polymerase binds to in the promoter

Explanation:

DNA polymerase is not involved in the process of transcription. The incorrect answer could be corrected if it was rewritten as "a mutation in the promoter region where the RNA polymerase binds to."

Example Question #9 : Understanding Prokaryotic Genes

When a repressor binds to the __________, the LacZ gene does not get expressed. 

Possible Answers:

operator

gene

promoter

terminator

Correct answer:

operator

Explanation:

The region of a gene where activator/repressors bind in prokaryotic organisms is called an operator. The protein that's bound to the operon strongly influences the level of gene expression.

Example Question #1 : Understanding Gene Regulation

A protein that binds to a DNA sequence and reduces transcription of a target gene is referred to as __________.

Possible Answers:

an activator

an insulator

a repressor

an inhibitor

Correct answer:

a repressor

Explanation:

A repressor is a transcription factor that negatively regulates expression of a target gene. An activator is a transcription factor that enhances expression of a target gene. Activators and repressors often bind to the same genomic sequence to precisely regulate transcription.

An inhibitor is a factor that modulates a biological or chemical process, such as a cell signaling pathway or an enzymatic reaction, but does not generally bind directly to DNA. An insulator is a protein that forms boundaries between active and inactive genomic regions, but generally does not have a direct effect on a target gene.

Example Question #2 : Understanding Gene Regulation

What is the functional unit in which numerous adjacent genes are under the control of the same promoter and regulated by the same operator?

Possible Answers:

Exon

Operon

Transcription factor

Enhancer

Intron

Correct answer:

Operon

Explanation:

The correct answer is operon. Found in prokaryotes and a few eukaryotes, operons allow transcription and translation of all the genes downstream of a promoter simultaneously. This is advantageous because these organisms are able to express a subset of related genes rapidly in response to external or internal stimuli. 

Example Question #91 : Genetics Principles

Fill in the blanks with the best answers:

__________ are DNA segments that carry information that will ultimately not be transcribed into mRNA. These regions occur between __________, which are the DNA segments containing the genes to be transcribed and translated.

Possible Answers:

Introns . . . codons

Exons . . . histones

Exons . . . introns

Introns . . . exons

Introns . . . proteins

Correct answer:

Introns . . . exons

Explanation:

This is simply a matter of vocabulary. Introns do not contain coding sequences, while exons do. "Intron" comes from the word "intragenic," meaning between genes, and therefore between exons. During post-transcriptional modification, introns are spliced out of the initial RNA transcript.

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