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Genetics:

Genetics:. Branch of biology dealing with genes and heredity Genes: bits of DNA on chromosomes Usually 2 genes for a trait Dominant Gene: always seen in the population – represented by a capital letter Recessive Gene: overpowered by the dominant gene – represented by a small letter

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Genetics:

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  1. Genetics: • Branch of biology dealing with genes and heredity • Genes: bits of DNA on chromosomes • Usually 2 genes for a trait • Dominant Gene: always seen in the population – represented by a capital letter • Recessive Gene: overpowered by the dominant gene – represented by a small letter • Trait: a feature or characteristic (eye color, hair color) • Alleles: different forms of a gene on a homologous chromosome

  2. Gregor Mendel (1822-1884)The “Father of Genetics” • Austrian monk who worked with pea plants (28,000 plants in a 10 year span) • Use of favorable material (easy to raise) • Self-pollination (creation of pure strains) and cross-pollination possible • Discontinuous traits (2 contrasting forms) • Could study 1 trait at a time • Large numbers of offspring produced

  3. Mendel’s Three Laws: • Law of Dominance: One gene can mask another gene (dominant versus recessive) • Phenotype: the appearance of the organism • Genotype: the arrangement of genes • Homozygous Dominant (FF) • Homozygous Recessive (ff) • Heterozygous (Hybrid) (Ff) • Law of Segregation: In gamete formation, genes are separated • Rule for # of gametes: 2n (n= # of hybrids) • Law of Independent Assortment: In gamete formation, genes separate independent of each other • Exception: linkage (blonde hair, blue eyes)

  4. Rules for Problem-Solving: • Write down dominant and recessive genes • Write down parents’ genes (P generation) • Get parents’ gametes • Do the cross on a punnett square (board for offspring possibilities – F1 generation) • Get results and label answer

  5. Types of Problems: • Simple 1 trait cross • Monohybrid Cross (Ff X Ff) • Genotype: 1:2:1 Phenotype: 3:1 • Simple 2 trait cross • Dihybrid Cross (FfDd X FfDd) • Phenotype: 9:3:3:1 • Incomplete Dominance (3 phenotypes present) • Andalusian Fowl FF (black) ff (white) Ff (blue) • Roan Cattle FF (brown/reddish) ff (white) Ff (brown with white) • Four O’Clock Flowers FF (red) ff (white) Ff (pink)

  6. Multiple Alleles: traits with more than one pair of alleles • Examples: Rabbits (coat color) Humans (blood groups) • Human Blood Groups Karl Landsteiner • Also calledCodominance (2 dominant alleles/1 recessive allele) • A and B = dominant O = recessive • 4 Human Blood Types: A B AB O (phenotypes) • Type A: AA AO (genotypes) • Type B: BB BO (genotypes) • Type AB: AB (genotype) • Type O: OO (genotype) • Test Cross: used to determine the genotype of an organism • Use homozygous recessive X the unknown genotype

  7. 1903 Walter Sutton: factors as genes • 1909 Thomas Hunt Morgan: Colombia University - used Drosophila melanogaster as a research animal • Easy to raise • Eat simple food • Life cycle (10-15 days) many generations • Easy to distinguish the sexes • 4 pairs of chromosomes (3 pairs of autosomes) • Large salivary gland chromosomes • Easy storage • 1 pair of sex chromosomes with sex-linked traits (white eyes) XX, XY • Genetic Maps: specific location of genes on chromosomes • Crossing over of genes (“jumping genes”) • Barbara McClintock: research with corn

  8. Mutations • A change in DNA(a “mistake” in DNA) • Add diversity • Most are recessive • Not usually positive • Inherited • Caused by mutagens (chemicals, food additive, radiation, viruses) • Somatic Mutation: in body cells (not passed on) • Germ Mutation: in sex cells (passed on) • Gene Mutation: • Deletion (a gene is omitted) agethol agetol • Insertion (a gene is added) agethol agethoyl • Frameshift (a section is reversed) agethol aolgeth

  9. Chromosomal Mutation: • Inversion: piece of a chromosome breaks off and reattaches itself to the same chromosome backwards • Translocation: piece of one chromosome breaks off and reattaches itself to a different chromosome (Stillbirths) • Human chromosome number = 46 (2n) • n = # of chromosomes in a sperm or egg • Aneuploidy = 1+ or - the 2n number (either 45 or 47 chromosomes) • Monosomy: 45 (2n-1) • Turner’s Syndrome (X_) Sterile female underdeveloped • Trisomy: 47 (2n+1) • Down’s Syndrome (extra #21 chromosome) • Kllinefelter’s Syndrome (XXY) Sterile male feminized • (XYY) Tall male with acne (criminal tendencies) • (XXX) Fertile female (mentally challenged)

  10. Polyploidy: whole sets of chromosomes are inherited (3n, 4n, etc.) plants • Human chromosome number = 46 (2n) • n = # of chromosomes in a sperm or egg cell • Sex Linked Condition: recessive abnormality on the X chromosome Hemophilia: XHXH XHXh XhXh XHY XhY • Colorblindness XCXC XCXc XcXc XCY XcY • Sex Influenced Condition:not sex linked; not attached to the X chromosome; patterned baldness (influenced by female hormones) • Genetic Abnormalities: • PKU: affects infants; lack an enzyme; problems with amino acids • Sickle Cell Anemia: Pain at joints, fatigue; affects Black Americans; red blood cell shape of sickle; (1 in 500 is a carrier) • Cystic Fibrosis:Caucasian disease; excess mucus during digestion • Tay Sachs:Jewish infants (1 in 3 is a carrier)

  11. Galactosemia: problems with sugar breakdown • Huntington’s Disease: causes insanity; dominant gene • Genetic Counseling: • Sonagrams of fetuses • Amniocentesis: technique in which amniotic fluid is extracted and examined • Karyotype: a picture of the chromosomes • Pedigree: a family history of genes • Genetic Engineering: • Cloning/Gene splicing • Human Genome Project • “Green Revolution”

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