chapter 16 Flashcards
(25 cards)
What hypothesis did Beadle and Tatum propose?
The one-gene, one-enzyme hypothesis, suggesting each gene contains the information to produce a specific enzyme.
What organism did Beadle and Tatum use in their experiments?
The bread mold Neurospora crassa.
What did Srb and Horowitz contribute to the one-gene, one-enzyme hypothesis?
They demonstrated that each gene in a metabolic pathway is responsible for producing one specific enzyme.
How has the one-gene, one-enzyme hypothesis been updated?
It is now called the one-gene, one-polypeptide hypothesis, as not all proteins are enzymes, and some proteins consist of multiple polypeptides.
What is the central dogma of molecular biology?
The flow of genetic information:
DNA → RNA → Protein.
What is transcription?
The process of synthesizing RNA from a DNA template.
What is translation?
The process of synthesizing RNA from a DNA template.
What is translation?
The process of using the information in mRNA to synthesize proteins by converting nucleotide sequences into amino acid sequences.
How do genotype and phenotype relate according to the central dogma?
Genotype: The sequence of DNA.
Phenotype: The physical traits, which result from the proteins produced by the genotype.
What are exceptions to the central dogma?
Some genes code for RNAs that are not translated into proteins.
Viruses with reverse transcriptase can flow information from RNA → DNA.
What is the genetic code?
A set of rules that define how nucleotide sequences in mRNA specify amino acids in proteins.
What is a codon?
A group of three nucleotide bases that codes for a specific amino acid.
How many codons are there?
64 codons:
61 code for amino acids.
1 start codon (AUG).
3 stop codons (UAA, UAG, UGA).
What are the key properties of the genetic code?
Redundant: Most amino acids are encoded by multiple codons.
Unambiguous: Each codon specifies only one amino acid.
Non-overlapping: Codons are read one at a time.
Nearly universal: Shared by almost all organisms.
*Conservative: Codons for the same amino acid often share the first two bases.
How was the genetic code deciphered?
Nirenberg and Matthaei used synthetic RNA sequences in a test tube to identify which amino acids were coded by specific triplets.
What is a mutation?
A permanent change in DNA that alters an organism’s genotype and potentially its phenotype.
What are the types of point mutations?
Missense mutation: Changes one amino acid in a protein.
Silent mutation: Does not change the amino acid sequence.
Frameshift mutation: Shifts the reading frame, altering all downstream codons.
Nonsense mutation: Converts an amino acid codon into a stop codon.
What are the impacts of point mutations on fitness?
Beneficial: Increases fitness.
Neutral: No effect on fitness.
Deleterious: Decreases fitness.
What are chromosome-level mutations?
Inversion: A chromosome segment flips and rejoins.
Translocation: A segment attaches to a different chromosome.
Deletion: A segment is lost.
Duplication: A segment is copied.
How are chromosome mutations detected?
Through karyotype analysis, which visualizes the complete set of chromosomes.
Why are mutations significant in cancer?
Chromosome mutations such as aneuploidy, inversions, and translocations are commonly associated with cancer cells.
What is the significance of AUG in protein synthesis?
AUG is the start codon and codes for methionine, signaling the beginning of translation.
Why is redundancy in the genetic code beneficial?
It minimizes the impact of mutations by allowing multiple codons to code for the same amino acid.
What are null alleles or loss-of-function alleles?
These are defective alleles that do not produce a functional protein, often leading to a mutant phenotype when studied.
