Lecture 14 Genetics BIOL 302: Posttranslational Modifications and Chromosome Structure

Signal Sequence

First 15-20 Amino Acids of a protein that is labeled to directed to the correct cellular destinations

Cleavage

Removal or Splitting of protein to form different functions, is a posttranslational modification

Plasmids

Nonessential, Extrachromosomal DNA that can help guide DNA expression. Only found in Bacteria

Nucleoid

Region of DNA in a prokaryotic cell that consists of tightly packed chromosomes

Supercoiling

Twisting of bacterial DNA that allows it to condense. Occurs negatively in bacteria (against its helical twist)

Topoisomerase II

An enzyme that induces supercoiling in bacterial DNA

Histone

Molecule around which DNA is tightly coiled in chromatin

Chromatin

Strand of DNA associated with histones and functional proteins, roughly a 50/25/25 split respectively. Smallest unit of chromosomes, only 2nd to the actual DNA strand itself

Nucleosome

Repeating subunit of chromatin fibers, consisting of DNA coiled around histones. Only found in Eukaryotes

H1, H2A, H2B, H3, H4 Histones

Form polymer in which chromatin wraps around, creating the nucleosome. H2A-H2B and H3-H4 associate with each other, creating the polymer disc

Linker DNA

Region of DNA linking the nucleosomes together

Chromatid

Each half of the chromosome, composed of solenoids which are composed of nucleosomes. Are shaped by chromosome scaffolding.

Chromosome scaffolding

Non-Histone proteins that give the shape of chromatids