Molecules and Cells Unit 3

Particulate inheritance

Hereditary determinants are discrete, unchanging particles

Linkage

Genes are inherited together because they’re on the same chromosome

Multiple allelism

More than 2 alleles of a gene in a population

• Blood type

Incomplete dominance

Intermediate phenotype; traits mix

Co-dominance

2 equally dominant alleles exist

Pleiotropic

One gene affects multiple traits

Epistasis

Multiple genes affect 1 trait

Helicase

Opens double helix by breaking H-bonds

Topoisomerase

Relives twisting made by helicase by cutting and bonding strands

Single strand binding protein

Attach to open strand to stop them from closing

DNA Polymerase III

Catalyze synthesis 5’ → 3"‘

DNA Polymerase I

On lagging strand, removes primer at the start of each OF and fills gaps

DNA Ligase

On lagging strand, joins OF

Telomeres

At the end of the lagging strand, extend it with bases so DNA polymerase can finish

Exonuclease

Used by polymerase to correct misplaced bases; Removes base by breaking phosphodiester bond

Primer

Needed for DNA synthesis, gives polymerase a place to start

Mismatched repair

Fixes bases that got through polymerase proofreading

Nucleotide excision repair

Replaces bases that were kinked by UV light

Point mutation

Changes 1 base

Silent mutation

Doesn’t change the AA

Nonsense

Changes to a stop codon

Missense conservative

Changes AA to one with similar chemical properties

Missense non-conservative

Changes AA to one with different chemical properties

Frameshift

Add or removes bases, changes entire sequence after

Chromosome level mutation

Changes the number of chromosomes

Sigma proteins

Bind RNA polymerase to the template strand at the promoter sequence in bacterial transcription

Basal transcription factors

Bind RNA polymerase to the template strand at the promoter sequence in eukaryotic transcription

Exons

Coding regions in eukaryotic cells

Introns

Non-coding regions in eukaryotic cells

Spliceosomes

Remove introns in eukaryotes

5’ Cap and Poly A tail

Added to mRNA to make it more stable

Polyribosomes

Attach to and translate mRNA in bacteria; multiple on each strand

Wobble Hypothesis

Each tRNA can read multiple codons, usually the last letter is different

Ribosome binding site

Sequence on mRNA that binds to small ribosomal subunit

Release factor

When terminating translation, it enters the A site, hydrolyzes the bond between the tRNA and it’s AA in the P site

Post translation modification

Modifications that proteins go through after creation

Molecular chaperons

Speed up folding of a protein

Transcriptional control

Changes rate of transcription, slow but efficient

Translational control

Change translation rate, quicker than transcriptional control

Post-translational control

Activate or inhibit protein, fastest but uses lots of E

Negative control

Regulatory protein shuts down transcription

Positive control

Regulatory protein triggers transcription

Operon

Group of genes that share a promoter

• Increase efficiency

• Usually related by pathway

Regulon

Set of genes that have the same regulatory protein

• Can be turned on/off with the same regulator

Chromatin remodeling

Form of control in euk., DNA near promoter is released from tight interaction w/ histones before transcription

mRNA Stability

Form of control in euk., life span of mRNA is used to control gene expression

Acetylation

Add acetyl group to histones, activate gene

Methylation

Add methyl group to histones, deactivate genes

Enhancers

Regulatory sequences in euk, far downstream from promoter, or in gene they regulate

Silencers

Similar to enhancers, but function in negative control

Alternative splicing

In euk., on the same gene, different parts are spliced out for different cells/functions

RNA Interference

Regulates mRNA stability in euk., proteins break down mRNA