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 X & Y Located in 23rd position (human) XX – female XY - male
Autosomes All other chromosomes
Mutations
Change in DNA Germ 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 Loss of a piece of chromosome
Inversion 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)
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 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
DNA Technology
Genetic Engineering 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.