DNA to Protein & Mutation Lab

Follow the central dogma of molecular biology from DNA through mRNA to protein. Explore reading frames, codon translation, and how different types of mutations affect protein structure.

Guided Experiment: Central Dogma and Codon Reading

Hypothesis

Setup

Run Experiment

Analyze

Conclude

How does the reading frame affect the protein produced from the same DNA sequence? Will shifting the reading frame by one base produce a completely different protein?

Write your hypothesis in the Lab Report panel, then click Next.

3' Template

TACCTCGACTGA

5' Coding

ATGGAGCTGACT

Transcription (T → U)

5' mRNA

AUGGAGCUGACU

Translation (Reading Frame 1)

AUG

Met(M)

GAG

Glu(E)

CUG

Leu(L)

ACU

Thr(T)

Protein (4 amino acids)

Met-Glu-Leu-Thr

MELT

Start (AUG) at codon position 1

Controls

Mode

Presets

DNA Template Strand (3' to 5')

12 bases (4 complete codons). Only A, T, G, C accepted.

Reading Frame

Central Dogma

\text{DNA} \xrightarrow{\text{Transcription}} \text{mRNA} \xrightarrow{\text{Translation}} \text{Protein}

Process Summary

Template Strand

12 bases

Codons

Amino Acids

Codon Table

Ala (A)

GCU, GCC, GCA, GCG

Arg (R)

CGU, CGC, CGA, CGG, AGA, AGG

Asn (N)

AAU, AAC

Asp (D)

GAU, GAC

Cys (C)

UGU, UGC

Gln (Q)

CAA, CAG

Glu (E)

GAA, GAG

Gly (G)

GGU, GGC, GGA, GGG

His (H)

CAU, CAC

Ile (I)

AUU, AUC, AUA

Leu (L)

UUA, UUG, CUU, CUC, CUA, CUG

Lys (K)

AAA, AAG

Met (M)Start

AUG

Phe (F)

UUU, UUC

Pro (P)

CCU, CCC, CCA, CCG

Ser (S)

UCU, UCC, UCA, UCG, AGU, AGC

Thr (T)

ACU, ACC, ACA, ACG

Trp (W)

UGG

Tyr (Y)

UAU, UAC

Val (V)

GUU, GUC, GUA, GUG

Stop (*)

UAA, UAG, UGA

Data Table

(0 rows)

#	Trial	DNA Sequence	mRNA	Protein	Length (aa)	Mutation Type	Changed Positions

Hypothesis

0 / 500

Observations

0 / 500

Conclusions

0 / 500

Reference Guide

Transcription

Transcription copies the DNA template strand into messenger RNA (mRNA). RNA polymerase reads the template 3' to 5' and builds the mRNA 5' to 3'. Each thymine (T) in DNA becomes uracil (U) in RNA.

\text{DNA Template: } 3'\text{-TAC CTC GAC-}5' \rightarrow \text{mRNA: } 5'\text{-AUG GAG CUG-}3'

The coding strand has the same sequence as the mRNA (with T instead of U) and runs antiparallel to the template strand.

Translation and the Codon Table

Ribosomes read mRNA in three-base units called codons. Each codon specifies one amino acid. Translation begins at the start codon AUG (methionine) and ends at a stop codon (UAA, UAG, or UGA).

\text{AUG} \rightarrow \text{Met (start)} \quad \text{UAA, UAG, UGA} \rightarrow \text{Stop}

The genetic code is degenerate, meaning multiple codons can encode the same amino acid. For example, both GAG and GAA code for glutamic acid (Glu). This redundancy helps buffer against harmful mutations.

Reading Frames

An mRNA sequence can be read in three different reading frames depending on the starting position. Each frame groups the bases into completely different codons, producing different proteins.

\text{Frame 1: } \underbrace{\text{AUG}}_{\text{Met}}\underbrace{\text{GAG}}_{\text{Glu}}\underbrace{\text{CUG}}_{\text{Leu}}

\text{Frame 2: } \text{A}\underbrace{\text{UGG}}_{\text{Trp}}\underbrace{\text{AGC}}_{\text{Ser}}\underbrace{\text{UG...}}

The start codon AUG establishes the correct reading frame for translation. Only one frame produces the intended protein.

Mutation Types

Point mutations change a single base pair. They are classified by their effect on the protein.

Silent - DNA changes but the amino acid stays the same (wobble position)
Missense - One amino acid is replaced by another (e.g., sickle cell: Glu to Val)
Nonsense - A codon becomes a premature stop codon, truncating the protein

Frameshift mutations result from insertions or deletions that shift the reading frame. Every codon downstream is altered, usually producing a nonfunctional protein.