All flashcards
Flashcard 1: What is transcription in gene expression?
Answer: Synthesis of RNA from a DNA template. DNA serves as the template for making RNA copies.
Flashcard 2: 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 3: Which codon is the most common start codon for translation?
Answer: AUG. This codon initiates protein synthesis in most genes.
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 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 6: 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 7: 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 8: 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 9: 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 10: 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 11: 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 12: 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 13: 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 14: 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 15: 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 16: 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 17: 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 18: 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 19: 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 20: 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 21: Identify the mutation type: insertion of one nucleotide early in a coding region.
Answer: Frameshift mutation. Single nucleotide insertion shifts the reading frame.
Flashcard 22: 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 23: 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 24: 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 25: 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 26: 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 27: 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 28: 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 29: 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 30: 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.