High School Biology : Understanding Prokaryotic Genes

Study concepts, example questions & explanations for High School Biology

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Example Questions

Example Question #1 : Understanding Prokaryotic Genes

What is the main difference between prokaryotic and eukaryotic genes?

Possible Answers:

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

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

Eukaryotes stores genes together in operons, but prokaryotes do not

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

Prokaryotes do not have gene regulatory sequences, but eukaryotes do

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 #84 : Genetics Principles

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

Possible Answers:

Enhancers

Untranslated regions

Promoters

Operators

Exons

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 #694 : High School Biology

What is the function of RNA polymerase in prokaryotes? 

Possible Answers:

None of the other answers 

Translate RNA to protein

Repress transcription by binding operators

Transcribe RNA from a DNA template

Replicate DNA during cell division

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 #695 : High School Biology

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

Possible Answers:

Rho uses GTP as a source of energy

Rho unwinds the DNA-RNA helix at the transcription bubble

Rho is a nuclease that terminates transcription by cutting template DNA

None of the other answers

Rho attaches to a Rho recognition site on the DNA template 

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:

Clusters

Linked genes

Operator sequences

Operons

Promoter 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 #2 : Understanding Prokaryotic Genes

Bacterial plasmids can __________.

Possible Answers:

be present in multiple copies

carry antibiotic resistance genes

All of these

transfer between bacterial cells

integrate into the bacterial genome

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 #3 : Understanding Prokaryotic Genes

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

Possible Answers:

Watson-Crick base pairing

Restriction endonucleases

Viral vectors

cDNA libraries

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

A frameshift mutation in the LacZ coding region

A mutation in the operator that blocks the activator from binding

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 #5 : Understanding Prokaryotic Genes

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

Possible Answers:

promoter

gene

operator

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.

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