Gene Expression- Translation POGIL

What do the letters U, C, A, and G represent in Model 1?

mRNA nucleotides

What do abbreviations such as Phe, Ile, Ala, and Gly represent in Model 1?

Amino acids

The language of mRNA is often described as a "triplet code". Explain the significance of this reference.

Three nucleotides are needed to code for one amino acid.

If a mRNA molecule had 300 nucleotides in the coding region of the strand, how many amino acids would be in the polypeptide that was synthesized? Show mathematical work to support your answer.

300/3= 100

How many different codons (triplets) code for the amino acid Proline (Pro)?

4

Compare all of the codons for Proline. What are the similarities and differences?

All the proline codons are the same starting with CC. The difference is the third base.

Considering the mistakes that can occur during transcription and DNA replication, what advantage is there for an organism to have multiple mRNA sequences code for the same amino acid?

In case one codon makes a mistake/fails the mRNA will still translate properly into the amino acid.

Using the mRNA codon chart in Model 1, complete the following:

DNA-> TAC CTT CGG ATG CTG ACT
mRNA-> AUG GAA GCC UAC CAG UGA
polypeptide seq.-> met (start) Glu Ala Tyr Gln

According to the table in Model 1, what amino acid is at the beginning of every polypeptide?

AUG (start codon) methionine.

The codon showed in Model 1 are used in all species on Earth with very little variation. What might scientists conclude from this?

All species come from.a common ancestor and the theory of evolution.

What are the three stages of translation?

Initiation, elongation, termination.

Define each of the terms used in your answer to part A as they are used in everyday language.

Initiation- to start
Elongation- to make longer, to add on
Termination- to end

According to Model 2, when the mRNA leaves the nucleus, to which cellular organelle does it attach?

The ribosome.

The mRNA attaches to the organelle at the sequence AUG. What is the significance of this sequence of nucleotides?

AUG is the start codon.

Describe the movement of the ribosome as translation occurs.

The ribosome moves along the mRNA chain from 5 to 3.

Find the tRNA in Model 2 that is carrying the Histidine (His). What sequence of nucleotides makes the anticodon on this tRNA molecule?

GUA

What codon on mRNA would match this anticodon?

CAU

What anticodon would be found on a tRNA molecule carrying Glycine (Gly) (There are multiple answers)

CCA CCU CCG CCC

The "t" in tRNA is short for transfer. In a complex sentence, explain why this molecule is called transfer RNA.

It transfers the correct amino acid in the correct sequence to the ribosome to produce the functional protein.

During elongation, how many tRNA molecules are held in the ribosome at the same time?

2

What will happen to the unattached tRNA once it has delivered the amino acid?

It is released from the ribosome and is free to pick up and carry another amino acid.

Describe two things that occur during termination as illustrated in Model 2.

A release factor binds to the last codon which stops the process of adding more amino acids to the polypeptide. A water molecule is added to the end of the amino acid chain.

Explain how the term "translation" applies to the synthesis of proteins from the DNA instructions.

The language of DNA in the form of nitrogen bases read in a set of three called codons is being translated into the language of proteins, i.e., amino acids.

Show mathematically that there are 64 permutations possible when three bases are used.

4x4x4= 64

Show mathematically that two bases as a codon would not be sufficient to code all 20 known amino acids.

2x2x2=8

A silent mutation is one that does not affect protein structure. Write a code for an original DNA strand containing at least 12 bases, and then mutate the original DNA so that the final protein is unaffected.

Original-> TAC AAA CCC GGA
Mutated-> TAC AAG CCC GGA

In prokaryotic cells, translation begins before transcription is finished. Give two reasons why this would not be possible in eukaryotic cells.

Eukaryotic cells have a nucleus and prokaryotic cells do not. Transcription takes place in the nucleus while translation takes place on the ribosomes in the cytoplasm. Eukaryotic cells have introns that must be removed from the pre-mRNA before translation can occur.