Small Scale Mutations & Gene Expression

LARGE MUTATIONS & GENETICS Quick Review

Gene: – section of a chromosome coded for a trait Example: – Gene 1 codes for your hair color Review: Genetics

Allele: different forms of a gene  Ex: TACCGTTCAC… = Brown hair or B allele  Ex: TAGCGTTCAC… = red hair or b allele Review: Genetics

Every organisms receives two alleles for traits Ex: Genotype: Bb Review: Genetics

The interaction of these alleles determines which individual trait will appear Example: – Genotype: Bb – Phenotype: Brown Hair Review: Genetics

Humans have ~20,000 genes throughout our 23 pairs of chromosomes. Example: – Gene 1 codes for: your hair color  – Gene 2 codes for: your ear shape  Review: Genetics

Large Scale Mutations Any change in chromosome number resulting from errors during gamete formation (meiosis)

Medium Scale Mutations Gene mutations: entire sections of DNA change

SMALL MUTATIONS & GENE EXPRESSION

DNA Replication For 3.5 b.y. DNA has been copying itself – usually perfectly (parent  offspring)

Mutation are Errors Sometimes DNA polymerase makes a mistake

Your DNA has 3-50 nucleotide mutations from your parent’s DNA You are a mutant!

Most of your DNA is noncoding

Your coding DNA Example: – DNA: TACCGTTCAC… – mRNA: AUGGCAAGUG… – Amino acid: met – glu – val… – Protein: Melanin – Trait: Brown hair

Small Scale Mutations Any change in the genome (nitrogen base sequence) resulting from errors during DNA replication and environmental conditions.

Point Mutations Changes occur in one nucleotide – Missense: wrong amino acid in protein – Silent: no change to amino acid sequence – Nonsense: amino acid codon to STOP codon

Frameshift Mutations Deletion: – removal of nucleotide(s) Insertion: – addition of nucleotide(s)

Ex: Sickle Cell Anemia – Missense mutation in the gene that codes for Hgb. Thymine replaced with adenine Results in valine instead of glutamine Hgb folds incorrectly RBCs become sickle shaped RBCs cannot carry O2

Ex: Cystic Fibrosis Deletion (3 bases) in gene that codes for CFTR – 508th amino acid phenylalanine is removed – Malfunctioning transport protein Cl- ions in membrane – Causes mucus buildup in lungs, digestive tract

Ex: Huntington’s Disease Repetition of a gene that codes for htt – Normal gene: 36 GAC repeats (glutamine) – Mutant htt gene: > 36 GAC repeats – Results in malfunctioning polyglutamine protein – Causes neurons to decay

Deletion of a gene that codes for CCR5 – Protein is important in immune function – Results in HIV resistance in homozygotes – Delayed onset of HIV infection in heterozygotes – Currently a research study being conducted to genetically modify T-cells so that they have this mutation Ex: Beneficial Mutation

We would not evolve!!!! We would all be clones!!! We wouldn’t have the ability to stick to walls! Without mutations