16 protein synthesis

study guide 16

What is the difference between transcription and translation?

Transcription: is transferring the message encoded in DNA to messenger RNA (mRNA)

Translation: is decoding the message in mRNA to make proteins using transfer RNA (tRNA), ribosomal RNA, amino acids, and specific enzymes.

Where does transcription occur?

inside the cell nucleus

what happens to the product molecule of transcription before it becomes an mRNA?

It gets edited in two ways: a 5’ cap and a 3’ poly-A tail are added to the RNA to stabilize it, and then the RNA goes through a process of cut-and-paste in which introns are removed, and the remaining exons are spliced together

introns

non coding sequences of DNA/RNA that are cut out and discarded during RNA processing.

exons

coding sequences that remain in the mature mRNA and are expressed (traslated) into a protein.n

What is alternative gene splicing?

When one single RNA sequence can produce multiple unique mRNA versions, which are then used to build several different polypeptide chains.

where does translation occur?

in the cytoplasm

what is a codon?

three consecutive letters in mRNA that code for a particular amino acid

What does it mean when we say that the genetic code is redundant?

For nearly every amino acid, there is more than one codon.

what 5 things are needed for tranlation?

Genetic code, ribosomes, transfer RNA (tRNA), Amino acids, and the mechanism.

write the 3 amino acid sequence that would be produced by this set of codons: AUG, UCH GGC

Methionine

Serine

Glycine

what is a ribosome?

a ribosome is a celluar machine that synthesizes proteins by translating messenger RNA (tRNA) molecules into polypeptide chains.

what are the two active sites on a tRNA?

1. One site is a 3-base sequence called an anticodon.

2. The other is where an amino acid attaches to the tRNA.

What is the anticodon for the codon GAC?

The anticodon for the codon GAC is CUG.

Explain the difference between a silent mutation, a missense mutation, and a nonsense mutation.

A silent mutation does not change the amino acid produced,

a missense mutation results in a different amino acid

a nonsense mutation introduces a premature stop codon.

What is a frameshift mutation?

Occurs if one or more base pairs are either inserted into or deleted from the normal sequence during DNA replication or transcription.

What are 2 ways in which a nonsense mutation could occur?

a single base substitutioin or frameshift mutation

what is a gene?

A segment of DNA that contains the necessary information to produce a functional product, usually a protein.