Inheritance & Human Genetic Patterns Chapter 12-13

WHY?? Thomas Hunt Morgan Early 1900’s Used fruit flies, Drosophila melanogaster to identify genetic patterns. Observed that only male fruit flies had white eyes WHY??

Linkage groups A group of genes located on one chromosome. These genes are usually inherited together. Example: Fruit flies have 4 pairs of chromosomes & four linkage groups. How many linkage groups do humans have?

Sex Determination Sex Chromosomes Autosomes X & Y Located in 23rd position (human) XX – female XY - male Autosomes All other chromosomes

Sex Linkage Traits that are linked to sex chromosomes.

Gene Maps Show the relative locations of each known gene on an organisms’ chromosome.

Mutations Change in DNA Germ cell mutation Somatic cell mutation Occurs in gametes Do no affect the organism May be passed on offspring Somatic cell mutation Occurs in body cells Not passed to offspring LETHAL MUTATIONS: cause death usually before birth

Gene mutations Involve a single nitrogen base or larger segment of DNA. Point Mutations Substitution, addition, or removal of a single nitrogen base Mutagen Environmental factor that damages DNA Ex. Carcinogens, tobacco, tars, UV radiation

Chromosome Mutations Deletion Inversion Loss of a piece of chromosome Chromosome section breaks off & reattaches in reverse orientation.

Chromosome Mutations cont… Translocation Chromosome section breaks off & reattaches to another, non-homologous chromosome Nondisjunction Failure of a chromosome to separate during meiosis.

Results of Nondisjunction Monosomy Zygote with 45 chromosomes Turners Syndrome (XO) Trisomy Zygote with 47 chromosomes Down Syndrome (Trisomy 21) Klinefelters Syndrome (XXY)

Trisomy 21

Genetic Traits & Disorders Single Allele Traits (dominant) Huntington’s Disease, Achondroplasia (Dwarfism), Cataracts, Polydactyly Single Allele Traits (recessive) Albinism, PKU, Cystic Fibrosis, Hereditary deafness, Sickle cell anemia

Genetic Traits continued… X-linked Traits Colorblindness, hemophilia, muscular dystrophy, ichthyosis simplex Multiple Allele Traits Blood Types Polygenic Traits Skin, hair, & eye color; foot size, nose length, height Sex-influenced Traits Male pattern baldness

Detecting Human Genetic Disorders Genetic Screening Examination of person’s genetic makeup Genetic Counseling Amniocentesis Removal of amniotic fluid from mother Chorionic Villi Sampling Villi contain same genetic makeup of fetus

Continued… Karyotype Ultrasound Pedigree Picture of an organisms’ chromosomes Ultrasound Bouncing sound waves off fetus to create an image Pedigree Family record that shows how traits are inherited over several generations

Pedigree

DNA Technology Genetic Engineering Uses of DNA Technology Used to identify genes for specific traits Transfer genes for a specific trait from one organism to another organism. Uses of DNA Technology Cure diseases Treat genetic disorders Improve good crops

Transplanting Genes Isolate a gene (ex. Insulin) Produce recombinant DNA A combination of DNA from 2 or more sources. Clone DNA Allow bacteria time to reproduce Transgenic animal: A host organism receiving recombinant DNA

The Human Genome Project Goals: To determine the nucleotide sequence of the entire human genome (approx. 3 billion nucleotide pairs or 100,000 genes) To map the location of every gene.

Gene Therapy Treating a disorder by introducing a gene into a cell or by correcting a gene defect in a cell’s genome.