Don’t let this happen to you!!

HOOK EM’ HORNS!!!

MUTATIONS Changes in DNA that affect genetic information

Gene Mutations  Point Mutations – changes in one or a few nucleotides  Substitution  THE FAT CAT ATE THE RAT  THE FAT HAT ATE THE RAT  Insertion  THE FAT CAT ATE THE RAT  THE FAT CAT XLW ATE THE RAT  Deletion  THE FAT CAT ATE THE RAT  THE FAT ATE THE RAT

 If purine (A/G) or pyrimidine (T/C) substitutes for itself = transition substitution  If purine substitutes for pyrimidine or vice versa = transversion substitution

Results of point mutations  Silent mutations = due to redundancy of the Genetic Code, most point mutations are silent – do not code for a different amino acid  Missense mutations = produces change in amino acid in protein but does not change the function of the protein  Nonsense mutations = produces a STOP codon in the midst of the mRNA transcript; can produce a non-functional protein

Sample outcome of DNA code Methionine, proline, threonine, arginine, stop

Silent mutation Due to redundancy of Genetic Code, no change in amino acid sequence is produced!!

Missense mutation Missense mutation produces a change in amino acid sequence in protein product (Histidine in for Arginine); may change function of protein or may not!

Nonsense mutation Bad news! – nonsense mutation produces a STOP codon within the mRNA transcript leading to a truncated protein. How short the protein product depends on where the STOP codon was produced within the mRNA transcript.

Gene Mutations  Frameshift Mutations – shifts the reading frame of the genetic message so that the protein may not be able to perform its function.  Insertion  THE FAT CAT ATE THE RAT  THE FAT HCA TAT ETH ERA T  Deletion  THE FAT CAT ATE THE RAT  TEF ATC ATA TET GER AT H H

Chromosome Mutations  Changes in number and structure of entire chromosomes  Original Chromosome ABC * DEF  DeletionAC * DEF  DuplicationABBC * DEF  InversionAED * CBF  TranslocationABC * JKL GHI * DEF

Deletions to chromosome If too much information is lost, it may be fatal to the organism and may result in early death (e.g., Cri-du-chat syndrome – large deletion from chromosome #5)

Duplications within chromosome Effect of base duplications depend on location within the chromosome – whether or not duplication resides in coding or non- coding region of DNA

Inversions within chromosome

Translocations within chromosome Can be caused due to abnormal synapsis event at Meiosis I by incorrect chromosomes coming together. Associated with 2 forms of leukemia – oncogenes translocated to incorrect regions within chromosomes of leukocytes (white blood cells)

Significance of Mutations Most are neutralMost are neutral Eye colorEye color Birth marksBirth marks Some are harmfulSome are harmful Sickle Cell AnemiaSickle Cell Anemia Down SyndromeDown Syndrome Some are beneficialSome are beneficial Sickle Cell Anemia to MalariaSickle Cell Anemia to Malaria Immunity to HIVImmunity to HIV

What Causes Mutations?  There are two ways in which DNA can become mutated:  Mutations can be inherited.  Parent to child  Mutations can be acquired.  Environmental damage  Mistakes when DNA is copied

Chromosome Mutations  Down Syndrome  Chromosome 21 does not separate correctly.  They have 47 chromosomes in stead of 46.  Children with Down Syndrome develop slower, may have heart and stomach illnesses and vary greatly in their degree of inteligence.

Chromosome Mutations  Cri-du-chat  Deletion of material on 5 th chromosome  Characterized by the cat-like cry made by cri-du-chat babies  Varied levels of metal handicaps

Sex Chromosome Abnormalities  Klinefelter’s Syndrome  XXY, XXYY, XXXY  Male  Sterility  Small testicles  Breast enlargement

Sex Chromosome Abnormalities  XYY Syndrome  Normal male traits  Often tall and thin  Associated with antisocial and behavioral problems

Sex Chromosome Mutations  Turner’s Syndrome  X  Female  sex organs don't mature at adolescence  sterility  short stature

Sex Chromosome Mutations  XXX  Trisomy X  Female  Little or no visible differences  tall stature  learning disabilities  limited fertility

Some mutations even make it on SNL!