Replication, Transcription, Translation

Supplementary Material

Biological Molecules and Processes

1. DNA 2. RNA 3. Protein

Replication: 1 DNA molecule replicates (doubles) into 2 identical DNA copiesTranscription: DNA molecule transcribed (copied) into RNA moleculeTranslation: RNA molecule translated (the code is read and interpreted) to produce protein

Replication

When a cell divides, the entire DNA content in a cell needs to replicate in order for identical DNA information to be contained in both cells

Transcription/Translation

Proteins need to be created in cells to carry out many cellular functions, including carry out reactions and transport things• Example: hemoglobin is

a protein that is contained within red blood cells and delivers oxygen throughout our bodies

DNA/RNA molecules have 2 different “ends”

The shape of DNA is a double helix. If you were to unwind it, you would see two single strands of DNA that are connected by base pairs (A pairs with T, G pairs with C). Each of these single strands has a “LEFT” end and a “RIGHT” end.The two single strands of DNA have opposite orientation. So one strand reads from the “LEFT” end to the “RIGHT” end as you look at the sequence horizontally across the page. The other strand reads from the “RIGHT” end to the “LEFT” end

LEFT - TCCACAGTCTTG - RIGHT RIGHT - AGGTGTCAGAAC - LEFTDNA

Transcription• As DNA is transcribed into RNA, complimentary bases are added. G pairs with C

(and vice versa), T pairs with A, A pairs with U • Both single strands can be transcribed into RNA. The RNA is transcribed in the

LEFT to RIGHT orientation. *This means that bases are copied on the DNA from the RIGHT end to the LEFT end. So when you are copying DNA into RNA, start at the RIGHT end of the DNA strand and move toward the left. However, the RNA you are writing starts at the LEFT end.

• Arrows indicate the direction of transcription

UCAGAAC - LEFT LEFT - TCCACAGTCTTG - RIGHT RIGHT - AGGTGTCAGAAC – LEFTLEFT - UCCACA

DNA

1st RNA

2nd RNA

Transcription

After you copy the entire sequence, you will realize that each DNA strand has a RNA copy in the same end to end orientation, only with every T replaced by a U. We call the LEFT to RIGHT DNA strand the coding strand for the Blue RNA sequence shown below. The RIGHT to LEFT DNA strand is the coding strand for the Red RNA sequence.

RIGHT - AGGUGUCAGAAC - LEFT LEFT - TCCACAGTCTTG - RIGHT RIGHT - AGGTGTCAGAAC - LEFTLEFT - UCCACAGUCUUG - RIGHT

DNA

RNA

RNA

Translation• In translation, we read the RNA code to

determine what amino acids are chained together to form protein. The RNA is translated in the LEFT to RIGHT orientation.

• Boxes indicate the first three RNA bases that form a codon (CAA for the red, UCC for the blue). The codon table is used to determine what amino acid is added

RIGHT - AGGUGUCAGAAC - LEFT LEFT - UCCACAGUCUUG - RIGHT

Translation

RIGHT - AGGUGUCAGAAC - LEFT LEFT - UCCACAGUCUUG - RIGHT

• Arrows show the direction of translation. Unlike transcription, the amino acid sequence will be different for the two RNA molecules depending on which direction you are heading. So it is important that you start translation from the LEFT end of the RNA sequence.

Gly - Cys - Asp - Gln

Ser - Thr - Val - Leu

Practice Problems

You have unwound a double helix and exposed a single strand with the following sequence and orientation:LEFT – AGTTCATGCATCCGA – RIGHT1) During DNA replication, the molecule will once again

become double stranded. Provide the correct sequence and orientation to make a double stranded DNA helix.

2) Transcribe each strand of DNA to a molecule of RNA. Draw an arrow to show the direction that transcription proceeds

3) For each RNA molecule you made, translate it into the correct amino acid sequence. Draw an arrow to indicate the direction of transcription

Answers

1) LEFT – AGTTCATGCATCCGA – RIGHT RIGHT – TCAAGTACGTAGGCT – LEFT

2) LEFT – AGUUCAUGCAUCCGA – RIGHT RIGHT – UCAAGUACGUAGGCU – LEFT

3) Ser – Ser – Cys – Ile – Arg STOP – Ala – Asp – Ser

MutationsTwo main types of mutations1) Point mutations – when a single base is

substituted for a different base

2) Insertions/deletions – when single or multiple bases are added/subtracted

LEFT - UCCACAGUCUUG - RIGHT

LEFT - UCCACAGUCUUG - RIGHT

LEFT - UCCACCGUCUUG - RIGHT

LEFT - UCCA_ _GUCUUG - RIGHTLEFT - UCCAGUCUUG - RIGHT

Practice on Your Own!

Write out a random sequence of bases. This will represent your RNA to be translated1) Translate your sequence into a sequence of amino acids.2) Use a single point mutation to change the sequence. Does

this affect the amino acid sequence? Which point mutations will affect the sequence? Which mutations will not? (Hint: think about what position the mutation is at in the codon)

3) Try varying levels of insertions/deletions (indels) in your sequence. What numbers of indels are most likely to affect the amino acid sequence? What numbers of indels are least likely to affect the amino acid sequence?