Transcription, Translation, and Mutations

Transcription

A process occuring in the nucleus where RNA polymerase uses a single strand of DNA to form an mRNA transcript, synthesizing RNA from 5’—>3’ and using the 3’—>5’ strand of DNA as a template

Splicing

A process occuring before the mRNA transcript leaves he nucleus, removing unneeded sequences called introns to put together exons—sequences that will be put together and later expressed

Translation

A process following splicing, occuring on ribosomes as a sequence of nucleotides are read to build the sequence of amino acids in proteins, forming its primary structure.

Steps of Translation

first, small ribosomal subunits bind to mRNA and scan for the start codon (AUG), ensuring translation begins at the right site. Next, the polypeptide chain increases in length as the ribosome moves along mRNA to add amino acids, with anticodons on the tRNA molecule transfering the corresponding amino acids to the ribosome. Lastly, ribosomes ends the newly synthesized polypeptide chain upon reaching a stop codon (UAA, UAG, UGA)

What are mutagens?

factors that cause mutations, including UV radiation, general radiation, chemicals from burning, errors during replication, and viral infections from bacteria/retroviruses

Substitution

a type of mutation where a nucleotide in DNA is replaced by another nucleotide, causing a single codon to change. This can have no effect, due to amino acid redundancy, or could be fatal

Insertion

a type of mutation where one or more nucleotide base pairs are added into a DNA sequence. Also known as a frameshift mutation, as it disrupts the original sequence, thus altering how the codons are read

Deletion

a type of mutation where one or more nucleotide base pairs are removed or “deleted” from the sequence. Also known as a frameshift mutation, as it disrupts the original sequence, thus altering how the codons are read.