What a Difference an 'A' Makes!!                                                                                                                  

This activity is designed to follow the Protein Synthesis Simulation where students have walked through the coding of a protein in order to understand how codons and anticodons work inside a living cell - a concrete example of a complex concept!! The exercise is considerably more abstract and will ultimately let you know who understands the mechanisms of this process.

I. DNA and RNA The model on the left side of the chart represents a segment of a single strand of DNA that has separated from its partner. Using the pictured strand as the original template, construct the following:

  1. the sequence of bases in the new strand of DNA if the original strand were to replicate
  2. the sequence of bases in the mRNA produced from the original DNA
  3. the sequence of bases needed by the tRNA's if they were to pair with the mRNA in #2 above
  4. the sequence of amino acids that would be assembled in the polypeptide chain. (NOTE: use a chart of mRNA codons such as those found in Miller/Levine Biology).

II. MUTATION

(A) Assume that the base in position 6 of the original DNA strand mutates to an "A." How will the sequence of 1,2,3, and 4 be affected?
(B) Suppose the base in position 2 gets shifted to position 16; how will the sequence of 1,2,3 and 4 (above) be affected?
(C) If the base in position 6 is changed to a "T," how will the sequence of 1,2,3 and 4 (above) be affected?

(D) Suppose the base in position 4 is removed. What happens to the strand? What kind of mutation is this?

The RNA Codons

 

 

U

C

A

G

U

UUU Phenylalanine (Phe)

UCU Serine (Ser)

UAU Tyrosine (Tyr)

UGU Cysteine (Cys)

U

UUC Phe

UCC Ser

UAC Tyr

UGC Cys

C

UUA Leucine (Leu)

UCA Ser

UAA STOP

UGA STOP

A

UUG Leu

UCG Ser

UAG STOP

UGG Tryptophan (Trp)

G

C

CUU Leucine (Leu)

CCU Proline (Pro)

CAU Histidine (His)

CGU Arginine (Arg)

U

CUC Leu

CCC Pro

CAC His

CGC Arg

C

CUA Leu

CCA Pro

CAA Glutamine (Gln)

CGA Arg

A

CUG Leu

CCG Pro

CAG Gln

CGG Arg

G

A

AUU Isoleucine (Ile)

ACU Threonine (Thr)

AAU Asparagine (Asn)

AGU Serine (Ser)

U

AUC Ile

ACC Thr

AAC Asn

AGC Ser

C

AUA Ile

ACA Thr

AAA Lysine ( Lys)

AGA Arginine (Arg)

A

AUG Methionine (Met) or START

ACG Thr

AAG Lys

AGG Arg

G

G

GUU Valine Val

GCU Alanine ( Ala)

GAU Aspartic acid (Asp)

GGU Glycine (Gly)

U

GUC (Val)

GCC Ala

GAC Asp

GGC Gly

C

GUA Val

GCA Ala

GAA Glutamic acid (Glu)

GGA Gly

A

GUG Val

GCG Ala

GAG Glu

GGG Gly

G

 

Protein Synthesis Activity

 

TACCCCTAGCAACTTGTTACAACGCGGAGTCAAACATCATATATAGTCGAACTCTTAATGACGTTG AAACATTTGGTTGTAAACACACCCAGGGTGGATCAACTCCGGAATATAAACCACACACCACTTTCT CCGAAAAAGATATGGGGCTTTCGTATC

 

The triplet codons above code for one of the smallest proteins in humans, the hormone insulin. The job of insulin is to remove excess sugar from your blood and take it to your liver where it can be converted into glycogen. (The gene for this protein is turned on shortly after one has completed a meal). In this activity, you are to complete the following:

1. Build the DNA molecule using the appropriate nucleotides/codons.

2. Transcribe/build an mRNA molecule that is complimentary to the DNA above.

3. Translate/determine the amino acid sequence.

4. Build the insulin molecule using the appropriate amino acids.

 

Helpful Web Sites:

http://nobel.scas.bcit.ca/resource/dna/station2.htm

http://gslc.genetics.utah.edu/units/basics/transcribe/

http://nobelprize.org/medicine/educational/dna/index.html

http://www.rothamsted.bbsrc.ac.uk/notebook/courses/guide/