High School Biology : Genetics Principles

Study concepts, example questions & explanations for High School Biology

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Example Questions

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Example Question #2 : Understanding Prokaryotic Genes

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

Possible Answers:

promoter

operator

gene

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 #91 : Genetics Principles

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

Possible Answers:

a repressor

an activator

an insulator

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 #131 : Genetics And Evolution

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

Enhancer

Transcription factor

Operon

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 #1 : Understanding Gene Regulation

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

Exons . . . histones

Introns . . . proteins

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.

Example Question #702 : High School Biology

Which of the following best describes the interaction between tRNA and mRNA during protein synthesis?

Possible Answers:

tRNA semi-randomly adds amino acids to the ribosome, and the ribosome sorts them later by binding mRNA codons and building the correct protein chain sequence.

mRNA does not interact with tRNA because mRNA is a nucleic acid that is only utilized during transcription.

mRNA anti-codons directly bind tRNA codons to form a chain of amino acids. Once all amino acids are joined, mRNA and tRNA are degraded.

tRNA anti-codons are matched to the mRNA codons during translation in the ribosome to build the correct protein. tRNA molecules carry the amino acids to the ribosome in the correct order as prescribed by the mRNA transcript.

mRNA provides the code for the proper amino acid chain order and the ribosome creates the links in the chain (peptide bonds). tRNA is then responsible for folding the chain to give a protein its 3-dimensional structure.

Correct answer:

tRNA anti-codons are matched to the mRNA codons during translation in the ribosome to build the correct protein. tRNA molecules carry the amino acids to the ribosome in the correct order as prescribed by the mRNA transcript.

Explanation:

The ribosome is where translation happens, but it requires both mRNA and tRNA. mRNA provides the "recipe" for the order of the amino acids in its codons, each of which corresponds to a specific amino acid in the chain, and the tRNA molecules come in and bind appropriately when their anti-codons are complementary to the mRNA codons. tRNA molecules carry the amino acids to the ribosome, where the actual protein chain is then synthesized.

Example Question #1 : Understanding Gene Regulation

What type of protein binds to the the regulatory region of genes in eukaryotic cells to regulate gene expression?

Possible Answers:

RNA polymerase

Transcription factors

Tyrosine recombinases

TATA-box binding protein

Correct answer:

Transcription factors

Explanation:

Transcription factors are proteins that bind to the regulator region of genes in eukaryotes and regulate whether a gene is expressed or not. A TATA-box binding protein is recruited after the transcription factors bind to the regulator region, and it eventually recruits RNA polymease. Tyrosine recombinases are not involved in initating eukaryotic gene expression.

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