Biological Principles Ch.7

what is the structure of DNA?

• composed of a double helix

• backbone is made of sugar and phosphate (PO4)

• ATGC

• wrapped in around protein YoYos called histones

histones

protein YoYos that DNA is wrapped in around

transcription

the process of copying genetic information from DNA to make a single stranded m-RNA

• happens in the nucleus

• m-RNA leaves the nucleus and finds the ribosomes (most often in the cytoplasm)

• 3 steps: initiation, elongation, and termination

• when regulating gene expression, all cells have ways to control the rate and timing of transcription

translation

RNA builds a protein

• cells translate the mRNA “message” into a sequence of amino acids

• requires ribosomes

• when regulating gene expression, eukaryotic cells often and control the rate and timing of translation

ribosomes

made of proteins and rRNA, where the cell builds a protein

• each ribosome has two parts: a small subunit and a large subunit

DNA process

DNA -> transcription -> mRNA -> translation -> protein

codon

a set of three nucleotides that encodes one amino acid on an mRNA strand

true or false: cells only express the genes they need to use?

true

mutation

a change in the nucleotide sequence of a cell’s DNA

what causes mutations?

some mutations occur spontaneously from errors in DNA replication, while others are caused by mutagens, external agents that change DNA structure

mutagens

external agents that change DNA structure

what are some examples of mutagens?

chemicals (such as smoking), radiation, and X-rays/ UV light

true or false: mutations are not usually harmful

true! most mutations are neutral, and some may be beneficial. Only a few mutations cause diseases