CHAPTER 14: Genes in Action
Essential Ideas-VOCABULARY
Gene-a segment of DNA whose nucleotide sequence codes for a protein.
Mutation - Changes in the nucleotide sequence of a gene’s DNA
Mutagens cause mutations, include environmental factors ike chemicals, X-rays, and UV light
Genetic Mutations – single or small changes to individual genes DNA sequence
Point mutations include; silent, missense and nonsense
SILENT mutation - the change in the codon results in the same amino acid- UAU  UAC both code for tyrosine
NONSENSE mutation - a codon is changed to a stop codon; protein may be too short to function -UAC  UAG (a stop codon)
MISSENSE mutation - involves the substitution of a different amino acid,
Frameshift mutations may be caused by additions or deletions, they create missense or nonsense mRNA
Genetic Diseases ( aka genetic disorders) like: CF, Duchennes MD, ColorBlindness are caused by point or frameshift mutations
Sickle Cell Anemia: MISSENSE MUTANT -Defective Hemoglobin Gene-You can’t carry oxygen well
Cystic Fibrosis: DELETION MUTANT -Defective Protein is made that creates excess mucus; clogs lungs.
Color Blindness: SEX LINKED - Inablity to distinguish colors (8% of male population)
Hemophilia: SEX LINKED - Inablity of blood to clot
Muscular Dystrophy: SEX LINKED -Loss of muscle that begins in early childhood
Chromosomal Mutations. Large scale change in the gene sequence including deletion, duplication, inversion, translocation
Tetrad formation in Prophase I of Meiosis- when Chromosomal changes occur
Chromosomal or Genetic Syndromes – caused by chromosomal mutations, include; Williams, Alagille, or Downs
Chromosomal Deletion : Chromosome loses a segment, ex. Williams Syndrome- Chromosome 7 loses an end piece
Chromosomal Duplication: chromosome segment being REPEATED in the same chromosome, ex inv Dup 15 syndrome
Chromosome Translocation: exchange of chromosomal segments between two, NON-HOMOLOGOUS chromosomes. ex.Alagille Syndrome
Chromosome Inversion- a segment of a chromosome being turned 180 degrees.
Williams Syndrome- Children have a pixie look Poor academic skills, good verbal and musical abilities-Chromosomal Deletion
inv Dup 15 syndrome- Poor muscle tone, mental retardation, seizures, curved spine, and autistic characteristics, Chromosomal Duplication
Alagille Syndrome- Distinctive face, abnormalities of eyes & internal organs, and severe itching. Translocation
Saethre-Chotzen syndrome- Chromosome Inversion
Polyploidy when extra chromosomes are found in an individual, for example trisomy 21 or Downs syndrome
Non disjunction event during Anaphase of Meiosis in which chromosomes fail to separate that can lead to polyploidy
DOWNS SYNDROME =TRISOMY21 (3 copies of a chromosome 21) mental delays, changes in blood vessels and connective tissue
DNA Technology - Genetic Engineering – the use of technology to understand and change gene function
The Human Genome Project Decoded an entire length of DNA in 2003
Genetic Sequencing – decoded nucleotide sequence for the 23,000+ human genes, allows for the detection and treatment of genetic disease
and cancer.
Gene Therapy -good copies of a gene are introduced into those individuals affected by genetic disease, often using viruses
Virus – a non-living vector that infects cells with DNA and uses the cells machinery to reproduce toil the cell lyses or explodes