Mutations. What is a mutation?. Any change in the DNA base sequence. What are the two different classes of mutations?. Gene Mutations Chromosomal Mutations. What is a gene mutation?. A change in the base sequence of one gene. What causes gene mutations?. Errors in DNA replication
What is a mutation? Any change in the DNA base sequence
What are the two different classes of mutations? • Gene Mutations • Chromosomal Mutations
What is a gene mutation? • A change in the base sequence of one gene
What causes gene mutations? • Errors in DNA replication • Chemicals • UV/X-ray Radiation
Types of Gene Mutations • Substitution • Deletion • Insertion Original DNA Strand
Two types of Gene Mutations Point mutation A change in ONE nitrogenous base, the overall number of bases stays the same (Substitution) Frame shift mutation A change in the number of overall nitrogenous bases in the genetic code (Insertion or Deletion)
Substitution Mutation • Substitution – One nitrogenous base is substituted for another.
Deletion and Insertion Mutations • Deletion– One or more nitrogenous bases are removed • Insertion – Extra nitrogenous bases are added to the genetic code.
How does a mutated protein affect a cell? • If the shape of the protein is altered, it MIGHTdisruptits normal activity OR (functioning).
How can gene mutations be passed down to future offspring? • ONLY IF THEY OCCUR IN THE SEX CELLS
What are some characteristics of gene mutations? • They can be dominant or recessive • They can occur on autosomal chromosomes (pairs 1-22) or sex chromosomes (pair 23) • People that are heterozygous for a recessive genetic disorder are called carriers • Carriers have one normal allele and one diseased allele; They do not show symptoms for the disease but may pass the allele to future offspring
COLORBLINDNESS: A SEX-LINKED DISORDER
Genetic Diseases caused by gene mutations: Cystic Fibrosis Faulty gene produces a defective protein that does not allow for the proper removal of mucous lining the cells of the lung and GI tract.
Gene Mutations: Tay-Sachs Disease Faulty gene produces a defective enzyme which cannot help remove fat from nerve cells.
Sickle-Cell Anemia: One base is substituted for another and this causes the production of a distorted hemoglobin molecule (protein) which cannot function properly.
What do these three gene mutations have in common? They all affect the shape of proteins!! If we change the shape of proteins (enzymes) they will not function properly and this will affect our phenotype.
How do we trace/identify gene mutations in a population or family? • Pedigree Charts: - A diagram that shows the presence or absence of a particular trait through each generation. • Genetic Testing: Ability to diagnose vulnerabilities to various genetic disorders
Recessive Gene Pedigree Chart Cc Cc cc
A – Dominant Allele; a - Recessive aa Aa Aa Aa aa aa Aa Aa aa ? aa ?
H – Dominant Allele; h - Recessive Hh hh hh Hh Hh hh hh hh hh hh hh hh hh Hh
What is a chromosomal mutation? • Any change in the number or structure of chromosomes
Chromosome Damage: Part of a chromosome is repeated. Part of a chromosome is missing. Reversing a fragment of the chromosome. A fragment of one chromosome attaches to a nonhomlogous chromosome.
Abnormal Numbers of Chromosomes • Polyploidy: Having many sets of chromosomes – 1.5n, 3n, 4n, 5n
Abnormal Numbers of Chromosomes • Aneuploidy: The addition or loss of a whole chromosome
How do these mutations occur? • NONDISJUNCTION: occurs when homologous chromosomes or sister chromatids fail to separate during meiosis.