Ch. 13 - The Genetic Code and Transcription

Klug - Concepts of Genetics 12th Edition

Klug12th EditionConcepts of GeneticsISBN: 9780135564776Non è quello che usi tu?Cambia libro di testo

Klug 12th Edition

Ch. 13 - The Genetic Code and Transcription

Problema 29a

Capitolo 13, Problema 29a

Shown here are the amino acid sequences of the wild-type and three mutant forms of a short protein.
___________________________________________________
Wild-type: Met-Trp-Tyr-Arg-Gly-Ser-Pro-Thr
Mutant 1: Met-Trp
Mutant 2: Met-Trp-His-Arg-Gly-Ser-Pro-Thr
Mutant 3: Met-Cys-Ile-Val-Val-Val-Gln-His _

Use this information to answer the following questions:
Using the genetic coding dictionary, predict the type of mutation that led to each altered protein.

Guida verificata passo dopo passo

Step 1: Understand the wild-type amino acid sequence and the mutant sequences given. The wild-type sequence is Met-Trp-Tyr-Arg-Gly-Ser-Pro-Thr, and the mutants show changes in length and amino acid composition.

Step 2: Recall that mutations can be classified as nonsense, missense, frameshift, or silent mutations. Nonsense mutations introduce a premature stop codon, truncating the protein. Missense mutations change one amino acid to another. Frameshift mutations result from insertions or deletions that shift the reading frame, altering downstream amino acids. Silent mutations do not change the amino acid sequence.

Step 3: Analyze Mutant 1, which has only Met-Trp compared to the full wild-type sequence. Since the protein is truncated early, this suggests a nonsense mutation that introduced a premature stop codon after the second amino acid.

Step 4: Analyze Mutant 2, which has Met-Trp-His-Arg-Gly-Ser-Pro-Thr. Compared to the wild-type, the third amino acid is His instead of Tyr, but the rest of the sequence is unchanged and the length is the same. This suggests a missense mutation where a single nucleotide change altered one codon, changing Tyr to His.

Step 5: Analyze Mutant 3, which has a completely different sequence: Met-Cys-Ile-Val-Val-Val-Gln-His. The sequence is different in multiple amino acids and length, indicating a frameshift mutation caused by an insertion or deletion that shifted the reading frame, changing all downstream amino acids.

Risposta video verificata per un problema simile:

Questa soluzione video è stata consigliata dai nostri tutor come utile per risolvere questo problema.

Durata del video:

Concetti chiave

Ecco i concetti essenziali che devi comprendere per rispondere correttamente alla domanda.

Types of Mutations

Mutations are changes in the DNA sequence that can alter the resulting protein. Common types include point mutations (single nucleotide changes), insertions or deletions (which can cause frameshifts), and nonsense mutations (introducing premature stop codons). Understanding these helps predict how the amino acid sequence changes.

Video consigliato:

Percorso guidato

10:48

Mutations and Phenotypes

Genetic Code and Codon Translation

The genetic code translates nucleotide triplets (codons) into amino acids. Each codon corresponds to a specific amino acid or a stop signal. Using the genetic code dictionary allows prediction of amino acid sequences from DNA or mRNA sequences and helps identify how mutations affect protein sequences.

Video consigliato:

Percorso guidato

11:43

The Genetic Code

Effects of Mutations on Protein Structure

Mutations can lead to truncated proteins, altered amino acid sequences, or extended proteins, affecting function. For example, a nonsense mutation causes early termination, while a frameshift changes downstream amino acids. Recognizing these effects aids in classifying mutations based on observed protein changes.

Video consigliato:

Percorso guidato

05:05

Proteins

Pratica correlata

Domanda del libro di testo

Shown here are the amino acid sequences of the wild-type and three mutant forms of a short protein.

___________________________________________________

Wild-type: Met-Trp-Tyr-Arg-Gly-Ser-Pro-Thr

Mutant 1: Met-Trp

Mutant 2: Met-Trp-His-Arg-Gly-Ser-Pro-Thr

Mutant 3: Met-Cys-Ile-Val-Val-Val-Gln-Hi

___________________________________________________

Use this information to answer the following questions:

For each mutant protein, determine the specific ribonucleotide change that led to its synthesis.

479

views

Domanda del libro di testo

Shown here are the amino acid sequences of the wild-type and three mutant forms of a short protein.

__________________________________________________

Wild-type: Met-Trp-Tyr-Arg-Gly-Ser-Pro-Thr

Mutant 1: Met-Trp

Mutant 2: Met-Trp-His-Arg-Gly-Ser-Pro-Thr

Mutant 3: Met -Cys-Ile-Val-Val-Val-Gln-His

______________________________________________

Use this information to answer the following questions:

The wild-type RNA consists of nine triplets. What is the role of the ninth triplet?

500

views

Domanda del libro di testo

In a mixed copolymer experiment, messages were created with either 4/5C:1/5A or 4/5A:1/5C. These messages yielded proteins with the following amino acid compositions.

Using these data, predict the most specific coding composition for each amino acid.

931

views

Domanda del libro di testo

Shown here are the amino acid sequences of the wild-type and three mutant forms of a short protein.

___________________________________________________

Wild-type: Met-Trp-Tyr-Arg-Gly-Ser-Pro-Thr

Mutant 1: Met-Trp

Mutant 2: Met-Trp-His-Arg-Gly-Ser-Pro-Thr

Mutant 3: Met-Cys-Ile-Val-Val-Val-Gln-Hi

___________________________________________________

Use this information to answer the following questions:

Of the first eight wild-type triplets, which, if any, can you determine specifically from an analysis of the mutant proteins? In each case, explain why or why not.

566

views

Domanda del libro di testo

It has been suggested that the present-day triplet genetic code evolved from a doublet code when there were fewer amino acids available for primitive protein synthesis.

As determined by comparisons of ancient and recently evolved proteins, cysteine, tyrosine, and phenylalanine appear to be late-arriving amino acids. In addition, they are considered to have been absent in the abiotic Earth. All three of these amino acids have only two codons each, while many others, earlier in origin, have more. Is this mere coincidence, or might there be some underlying explanation?

848

views

Domanda del libro di testo

An early proposal by George Gamow in 1954 regarding the genetic code considered the possibility that DNA served directly as the template for polypeptide synthesis. In eukaryotes, what difficulties would such a system pose? What observations and theoretical considerations argue against such a proposal?

597

views