Which statement is untrue?

Question

Which statement is untrue??  
A. RNA is single-stranded.  
B. RNA contains uracil.  
C. DNA codes for proteins.  
D. DNA cannot be altered.

Accepted Answer

Correct Answer: (D)DNA cannot be altered.. 
Rationale: The statement “DNA cannot be altered” is untrue.DNA is not a static, unchangeable molecule. It can be modified by mutations, environmental factors, replication errors, recombination, and chemical damage, as well as regulated through epigenetic changes. These alterations are fundamental to genetic variation, evolution, disease development, and normal cellular processes.A) RNA is single-strandedRNA is typically single-stranded, unlike DNA which is double-stranded.Although RNA can fold back on itself to form secondary structures through internal base pairing, its fundamental structure consists of a single nucleotide chain. This property allows RNA to take on diverse functional roles, including messenger RNA (mRNA), transfer RNA (tRNA), and ribosomal RNA (rRNA).Therefore, this statement is true.B) RNA contains uracilRNA uses the nitrogenous base uracil (U) instead of thymine (T), which is found in DNA.Uracil pairs with adenine during transcription and translation. This substitution is one of the defining chemical differences between RNA and DNA.Thus, this statement is true.C) DNA codes for proteinsDNA contains genes, which are sequences of nucleotides that provide instructions for building proteins.These sequences are transcribed into messenger RNA and then translated by ribosomes into amino acid chains that fold into functional proteins. Proteins are essential for nearly all cellular structure and activity.Therefore, this statement is true.D) DNA cannot be alteredDNA can and does undergo changes.Alterations occur through:Mutations (point mutations, insertions, deletions, duplications)Chromosomal rearrangementsErrors during DNA replicationExposure to radiation or chemicals (mutagens)Recombination during meiosisEpigenetic modifications that affect gene expressionThese changes can be harmful, neutral, or beneficial and are the basis of genetic diversity and evolution. Because DNA is modifiable, the claim that it cannot be altered is false.This makes this statement the untrue one.Conclusion:RNA is single-stranded, RNA contains uracil, and DNA does code for proteins. However, DNA is not permanent or immutable; it is subject to change through multiple biological mechanisms.Therefore, the untrue statement is that DNA cannot be altered.

Which statement is untrue?

A
RNA is single-stranded.

B
RNA contains uracil.

C
DNA codes for proteins.

D
DNA cannot be altered.

The statement “DNA cannot be altered” is untrue.

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Related Questions

Which statement is untrue?

A RNA is single-stranded. B RNA contains uracil. C DNA codes for proteins. D DNA cannot be altered.

The statement “DNA cannot be altered” is untrue.

Topic Flashcards

Mini Quiz

Related Questions

A
RNA is single-stranded.

B
RNA contains uracil.

C
DNA codes for proteins.

D
DNA cannot be altered.