High School Biology : Genes and DNA

Study concepts, example questions & explanations for High School Biology

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Example Questions

Example Question #1 : Understand Regulation Of Transcription

What is the function of RNA polymerase in prokaryotes? 

Possible Answers:

None of the other answers 

Transcribe RNA from a DNA template

Replicate DNA during cell division

Translate RNA to protein

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. 

Example Question #1 : Understanding Prokaryotic Genes

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

Possible Answers:

Rho uses GTP as a source of energy

Rho attaches to a Rho recognition site on the DNA template 

None of the other answers

Rho unwinds the DNA-RNA helix at the transcription bubble

Rho is a nuclease that terminates transcription by cutting template DNA

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 #1 : Understanding Prokaryotic Genes

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

Possible Answers:

Promoter sequences

Operator sequences

Linked genes

Operons

Clusters

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 #1 : Understanding Prokaryotic Genes

Bacterial plasmids can __________.

Possible Answers:

be present in multiple copies

All of these

transfer between bacterial cells

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 #161 : Dna, Rna, And Proteins

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

Possible Answers:

Viral vectors

cDNA libraries

Restriction endonucleases

Watson-Crick base pairing

Sanger sequencing

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 #1 : Understand Regulation Of Transcription

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 frameshift mutation in the LacZ coding region

A mutation in the operator that blocks the activator from binding

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

A point mutation in the LacZ gene that abolishes enzyme activity

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 #1 : Understanding Prokaryotic Genes

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

Possible Answers:

operator

gene

terminator

promoter

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 #11 : Genes And Dna

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

Possible Answers:

a repressor

an inhibitor

an insulator

an activator

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 #12 : Genes And Dna

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:

Intron

Operon

Enhancer

Exon

Transcription factor

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 #131 : Genetics And Evolution

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 . . . introns

Introns . . . proteins

Exons . . . histones

Introns . . . exons

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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