Biology Flashcards: Explain Dna Sequence Encoding

What this deck covers

This deck focuses on Explain Dna Sequence Encoding, giving you a quick way to review the definitions, rules, and examples that matter most for Biology.

How to use these flashcards

Work through these flashcards in short sessions. Try to answer each prompt before flipping the card, then revisit any cards you miss until the explanation feels automatic.

Flashcard 1: What is a nonsense mutation in a protein-coding DNA sequence?

Answer: A base change that creates a premature stop codon. Creates early termination, usually destroying protein function.

Flashcard 2: How many nucleotides make up one codon in mRNA?

Answer: Three nucleotides. The triplet code allows 64 possible codon combinations.

Flashcard 3: What is the role of the ribosome in decoding genetic information?

Answer: It reads mRNA codons and catalyzes peptide bond formation. Ribosomes translate the mRNA code into protein sequences.

Flashcard 4: What is meant by the term "reading frame" in translation?

Answer: The grouping of mRNA nucleotides into consecutive, nonoverlapping codons. The reading frame determines which amino acids are produced.

Flashcard 5: What is a missense mutation in a protein-coding DNA sequence?

Answer: A base change that substitutes one amino acid for another. Changes one amino acid, potentially affecting protein function.

Flashcard 6: What is an operator in the operon model of prokaryotic gene regulation?

Answer: A DNA site where a repressor binds to block transcription. Operators control gene expression in bacterial operons.

Flashcard 7: Which RNA molecule carries amino acids to the ribosome during translation?

Answer: tRNA. tRNA molecules transport specific amino acids to ribosomes.

Flashcard 8: Identify the complementary DNA strand for the sequence 5'-GCTA-3'.

Answer: 3'-CGAT-5'. G pairs with C, T pairs with A in antiparallel strands.

Flashcard 9: How many different mRNA codons are possible using four RNA bases and triplets?

Answer: 64 codons. 4³ = 64 possible three-base combinations.

Flashcard 10: Which three codons function as stop codons in the standard genetic code?

Answer: UAA, UAG, and UGA. These codons signal the end of protein synthesis.

Flashcard 11: What is an exon in eukaryotic gene structure?

Answer: A sequence retained in mature mRNA after splicing. Exons contain the coding information for the final protein.

Flashcard 12: What is an enhancer in eukaryotic gene regulation?

Answer: A DNA sequence that increases transcription when bound by activators. Enhancers boost gene expression when regulatory proteins bind.

Flashcard 13: What is an anticodon, and where is it found?

Answer: A three-base sequence on tRNA that pairs with an mRNA codon. Anticodons ensure the correct amino acid is added.

Flashcard 14: What is the role of aminoacyl-tRNA synthetase in decoding genetic information?

Answer: It attaches the correct amino acid to its corresponding tRNA. This enzyme ensures accurate amino acid-codon matching.

Flashcard 15: What is a frameshift mutation, and what causes it?

Answer: A reading-frame shift caused by nucleotide insertion or deletion. Changes all downstream amino acids, severely affecting the protein.

Flashcard 16: What is a point mutation in a DNA base sequence?

Answer: A change in a single nucleotide base pair. The smallest possible DNA sequence change.

Flashcard 17: What is the central dogma sequence of information flow in cells?

Answer: DNA rightarrow RNA rightarrow protein. This describes the flow of genetic information in living cells.

Flashcard 18: What is meant by the term "coding region" (open reading frame) in a gene?

Answer: The nucleotide sequence translated into a polypeptide. This region contains the protein-coding information.

Flashcard 19: What is an allele in terms of DNA sequence?

Answer: An alternative DNA sequence version of the same gene. Different alleles produce different versions of the same protein.

Flashcard 20: What is the role of aminoacyl-tRNA synthetase in decoding genetic information?

Answer: It attaches the correct amino acid to its corresponding tRNA. This enzyme ensures accurate amino acid-codon matching.

Flashcard 21: Which direction is the DNA template strand read during transcription?

Answer: It is read in the 3' rightarrow 5' direction. RNA polymerase moves along the template in this direction.

Flashcard 22: What is an anticodon, and where is it found?

Answer: A three-base sequence on tRNA that pairs with an mRNA codon. Anticodons ensure the correct amino acid is added.

Flashcard 23: What is an operator in the operon model of prokaryotic gene regulation?

Answer: A DNA site where a repressor binds to block transcription. Operators control gene expression in bacterial operons.

Flashcard 24: What is a gene in terms of DNA sequence and biological function?

Answer: A DNA sequence that encodes a functional RNA or protein product. Genes are functional units that produce useful cellular products.

Flashcard 25: Which amino acid is specified by the start codon AUG in standard genetic code?

Answer: Methionine. AUG always codes for the first amino acid in proteins.

Flashcard 26: What is a codon in the context of the genetic code?

Answer: A three-nucleotide sequence in mRNA that specifies an amino acid or stop. Each triplet codes for one amino acid or termination signal.

Flashcard 27: What is a missense mutation in a protein-coding DNA sequence?

Answer: A base change that substitutes one amino acid for another. Changes one amino acid, potentially affecting protein function.

Flashcard 28: What is the immediate molecular product of gene expression for a protein-coding gene?

Answer: mRNA (a transcript that can be translated). mRNA carries the genetic code to the ribosome for translation.

Flashcard 29: What is the immediate molecular product of gene expression for a protein-coding gene?

Answer: mRNA (a transcript that can be translated). mRNA carries the genetic code to the ribosome for translation.

Flashcard 30: What are the four nitrogenous bases found in DNA?

Answer: Adenine, thymine, cytosine, and guanine. These four bases form all possible DNA sequences.

Flashcard 31: Identify the DNA coding strand sequence that matches the mRNA codon 5'-AUG-3'.

Answer: 5'-ATG-3'. The coding strand has the same sequence as mRNA (except T/U).

Flashcard 32: What is translation in gene expression?

Answer: Synthesis of a polypeptide using an mRNA template. The mRNA sequence determines the amino acid sequence.

Flashcard 33: What does it mean that the genetic code is "nearly universal"?

Answer: Most organisms use the same codon-to-amino-acid assignments. The genetic code is shared across nearly all life forms.

Flashcard 34: What does it mean that the genetic code is "degenerate"?

Answer: Most amino acids are specified by more than one codon. Multiple codons code for the same amino acid.

Flashcard 35: Which molecule directly links a specific mRNA codon to a specific amino acid?

Answer: tRNA (charged by aminoacyl-tRNA synthetase). tRNA carries amino acids and recognizes specific codons.

Flashcard 36: Identify the complementary DNA strand for the sequence 5'-ATCG-3'.

Answer: 3'-TAGC-5'. A pairs with T, C pairs with G in antiparallel strands.

Flashcard 37: What is the functional importance of the triplet nature of the genetic code?

Answer: Three bases specify one amino acid, enabling many codon combinations. Triplets provide enough combinations to code for all amino acids.

Flashcard 38: What does it mean that the genetic code is "nearly universal"?

Answer: Most organisms use the same codon-to-amino-acid assignments. The genetic code is shared across nearly all life forms.

Flashcard 39: What is translation in gene expression?

Answer: Synthesis of a polypeptide using an mRNA template. The mRNA sequence determines the amino acid sequence.

Flashcard 40: Which codon is the most common start codon for translation?

Answer: AUG. This codon initiates protein synthesis in most genes.

Flashcard 41: What is a silent mutation in a protein-coding DNA sequence?

Answer: A base change that does not alter the amino acid sequence. Code degeneracy protects against some mutations.

Flashcard 42: What is an exon in eukaryotic gene structure?

Answer: A sequence retained in mature mRNA after splicing. Exons contain the coding information for the final protein.

Flashcard 43: What is genotype in terms of genetic information encoded by DNA?

Answer: An organisms set of alleles (its DNA sequence variants). Genotype represents the genetic blueprint in DNA sequences.

Flashcard 44: What is genotype in terms of genetic information encoded by DNA?

Answer: An organisms set of alleles (its DNA sequence variants). Genotype represents the genetic blueprint in DNA sequences.

Flashcard 45: Identify the mutation type: insertion of one nucleotide early in a coding region.

Answer: Frameshift mutation. Single nucleotide insertion shifts the reading frame.

Flashcard 46: Which option best states how a DNA base substitution can alter a protein product?

Answer: It can change a codon, altering an amino acid or creating a stop signal. Base substitutions directly affect the codon sequence.

Flashcard 47: What is meant by the term "reading frame" in translation?

Answer: The grouping of mRNA nucleotides into consecutive, nonoverlapping codons. The reading frame determines which amino acids are produced.

Flashcard 48: How many different mRNA codons are possible using four RNA bases and triplets?

Answer: 64 codons. 4³ = 64 possible three-base combinations.

Flashcard 49: Which molecule directly links a specific mRNA codon to a specific amino acid?

Answer: tRNA (charged by aminoacyl-tRNA synthetase). tRNA carries amino acids and recognizes specific codons.

Flashcard 50: What is a silent mutation in a protein-coding DNA sequence?

Answer: A base change that does not alter the amino acid sequence. Code degeneracy protects against some mutations.

Flashcard 51: Which base is present in RNA in place of thymine found in DNA?

Answer: Uracil. RNA uses uracil instead of thymine found in DNA.

Flashcard 52: What does it mean that the genetic code is "unambiguous"?

Answer: Each codon specifies only one amino acid or a stop signal. No codon codes for multiple different amino acids.

Flashcard 53: Which DNA bases pair together by complementary base pairing?

Answer: A pairs with T; C pairs with G. Complementary pairing maintains the double helix structure.

Flashcard 54: Identify the DNA coding strand sequence that matches the mRNA codon 5'-AUG-3'.

Answer: 5'-ATG-3'. The coding strand has the same sequence as mRNA (except T/U).

Flashcard 55: How many nucleotides make up one codon in mRNA?

Answer: Three nucleotides. The triplet code allows 64 possible codon combinations.

Flashcard 56: Which RNA molecule carries amino acids to the ribosome during translation?

Answer: tRNA. tRNA molecules transport specific amino acids to ribosomes.

Flashcard 57: Which direction does RNA polymerase synthesize RNA during transcription?

Answer: It synthesizes RNA in the 5' rightarrow 3' direction. RNA polymerase adds nucleotides to the growing 3' end.

Flashcard 58: What is a point mutation in a DNA base sequence?

Answer: A change in a single nucleotide base pair. The smallest possible DNA sequence change.

Flashcard 59: What does it mean that the genetic code is "unambiguous"?

Answer: Each codon specifies only one amino acid or a stop signal. No codon codes for multiple different amino acids.

Flashcard 60: What is the central dogma sequence of information flow in cells?

Answer: DNA rightarrow RNA rightarrow protein. This describes the flow of genetic information in living cells.

Flashcard 61: Identify the mutation type: a single-base substitution changes one amino acid to another.

Answer: Missense mutation. One amino acid changes to another due to base substitution.

Flashcard 62: What type of bond holds complementary DNA bases together across the double helix?

Answer: Hydrogen bonds. These weak bonds allow DNA strands to separate during replication.

Flashcard 63: What is an intron in eukaryotic gene structure?

Answer: A noncoding sequence removed from pre-mRNA during splicing. Introns are removed during mRNA processing.

Flashcard 64: Identify the complementary DNA strand for the sequence 5'-ATCG-3'.

Answer: 3'-TAGC-5'. A pairs with T, C pairs with G in antiparallel strands.

Flashcard 65: What is the difference between a DNA coding strand and a DNA template strand?

Answer: Coding matches mRNA (T for U); template is complementary to mRNA. Only the template strand serves as the transcription template.

Flashcard 66: What is a nonsense mutation in a protein-coding DNA sequence?

Answer: A base change that creates a premature stop codon. Creates early termination, usually destroying protein function.

Flashcard 67: What is meant by the term "coding region" (open reading frame) in a gene?

Answer: The nucleotide sequence translated into a polypeptide. This region contains the protein-coding information.

Flashcard 68: What is an intron in eukaryotic gene structure?

Answer: A noncoding sequence removed from pre-mRNA during splicing. Introns are removed during mRNA processing.

Flashcard 69: Which option best states how a DNA base substitution can alter a protein product?

Answer: It can change a codon, altering an amino acid or creating a stop signal. Base substitutions directly affect the codon sequence.

Flashcard 70: Identify the mutation type: a base substitution changes a codon into UAA, UAG, or UGA.

Answer: Nonsense mutation. The mutation creates a premature stop codon.

Flashcard 71: What is a gene in terms of DNA sequence and biological function?

Answer: A DNA sequence that encodes a functional RNA or protein product. Genes are functional units that produce useful cellular products.

Flashcard 72: Which three codons function as stop codons in the standard genetic code?

Answer: UAA, UAG, and UGA. These codons signal the end of protein synthesis.

Flashcard 73: What is transcription in gene expression?

Answer: Synthesis of RNA from a DNA template. DNA serves as the template for making RNA copies.

Flashcard 74: Which base is present in RNA in place of thymine found in DNA?

Answer: Uracil. RNA uses uracil instead of thymine found in DNA.

Flashcard 75: What is an operon in prokaryotes?

Answer: A cluster of genes transcribed together under control of one promoter. Operons allow coordinated expression of related bacterial genes.

Flashcard 76: What is alternative splicing, and what does it change about gene output?

Answer: Different exon combinations produce different mRNAs from one gene. One gene can produce multiple protein variants through splicing.

Flashcard 77: What is a frameshift mutation, and what causes it?

Answer: A reading-frame shift caused by nucleotide insertion or deletion. Changes all downstream amino acids, severely affecting the protein.

Flashcard 78: Identify the mutation type: a base substitution changes a codon into UAA, UAG, or UGA.

Answer: Nonsense mutation. The mutation creates a premature stop codon.

Flashcard 79: What is phenotype in relation to DNA-encoded information?

Answer: Observable traits produced by gene expression and environment. Phenotype results from genotype expression plus environmental factors.

Flashcard 80: Which direction does RNA polymerase synthesize RNA during transcription?

Answer: It synthesizes RNA in the $5' \rightarrow 3'$ direction. RNA polymerase adds nucleotides to the growing 3' end.

Flashcard 81: Identify the mRNA complement transcribed from the DNA template sequence 3'-GGC-5'.

Answer: 5'-CCG-3'. C pairs with G, G pairs with C during transcription.

Flashcard 82: What is meant by the statement that DNA stores genetic information in its base sequence?

Answer: Information is encoded by the order of A, T, C, and G along DNA. The specific sequence of bases determines what proteins are made.

Flashcard 83: Which DNA bases pair together by complementary base pairing?

Answer: A pairs with T; C pairs with G. Complementary pairing maintains the double helix structure.

Flashcard 84: What is a promoter in a gene, and what is its main function?

Answer: A DNA region where RNA polymerase binds to start transcription. Promoters control where and when genes are transcribed.

Flashcard 85: Identify the mutation type: a single-base substitution changes one amino acid to another.

Answer: Missense mutation. One amino acid changes to another due to base substitution.

Flashcard 86: What is a codon in the context of the genetic code?

Answer: A three-nucleotide sequence in mRNA that specifies an amino acid or stop. Each triplet codes for one amino acid or termination signal.

Flashcard 87: What type of bond holds complementary DNA bases together across the double helix?

Answer: Hydrogen bonds. These weak bonds allow DNA strands to separate during replication.

Flashcard 88: What is a promoter in a gene, and what is its main function?

Answer: A DNA region where RNA polymerase binds to start transcription. Promoters control where and when genes are transcribed.

Flashcard 89: Which codon is the most common start codon for translation?

Answer: AUG. This codon initiates protein synthesis in most genes.

Flashcard 90: What are the four nitrogenous bases found in DNA?

Answer: Adenine, thymine, cytosine, and guanine. These four bases form all possible DNA sequences.

Flashcard 91: Identify the mRNA complement transcribed from the DNA template sequence 3'-TAC-5'.

Answer: 5'-AUG-3'. A pairs with U, T pairs with A during transcription.

Flashcard 92: What is transcription in gene expression?

Answer: Synthesis of RNA from a DNA template. DNA serves as the template for making RNA copies.

Flashcard 93: What is an operon in prokaryotes?

Answer: A cluster of genes transcribed together under control of one promoter. Operons allow coordinated expression of related bacterial genes.

Flashcard 94: Which direction is the DNA template strand read during transcription?

Answer: It is read in the 3' rightarrow 5' direction. RNA polymerase moves along the template in this direction.

Flashcard 95: What is the role of the ribosome in decoding genetic information?

Answer: It reads mRNA codons and catalyzes peptide bond formation. Ribosomes translate the mRNA code into protein sequences.

Flashcard 96: What is meant by the statement that DNA stores genetic information in its base sequence?

Answer: Information is encoded by the order of A, T, C, and G along DNA. The specific sequence of bases determines what proteins are made.

Flashcard 97: What is an enhancer in eukaryotic gene regulation?

Answer: A DNA sequence that increases transcription when bound by activators. Enhancers boost gene expression when regulatory proteins bind.

Flashcard 98: What is alternative splicing, and what does it change about gene output?

Answer: Different exon combinations produce different mRNAs from one gene. One gene can produce multiple protein variants through splicing.

Flashcard 99: Identify the complementary DNA strand for the sequence 5'-GCTA-3'.

Answer: 3'-CGAT-5'. G pairs with C, T pairs with A in antiparallel strands.

Flashcard 100: What is an allele in terms of DNA sequence?

Answer: An alternative DNA sequence version of the same gene. Different alleles produce different versions of the same protein.