Medelian Genetics

Traits blend evenly in offspring through mixing of parents blood Explains intermediate traits

• removed stamens from purple flower and transferred pollen to white flower • control self fertilization and cross fertil. • P was homozygous • F1 was all purple, not pure breed. Heterozygous • F2 both purple and white

• inheritance of single character • genes exist in alternative versions called alleles • for each characteristic, organism inherits 2 alleles one from each parent • alleles differ, dominant determines organisms appearance • allele pairs separate during gamete production

• expressed when both are recessive homozygous - Aa brown mice can pass a allele so they carriers

To determine unknown genotypes • mating between individual of unknown genotype and homozygous recessive Individual • will show whether unknown genotype includes recessive allele • identify dominat phenotype genotype

Alleles at different loci (on different chromosomes) are inherited independently -experiment with 2 or more different traits

-if calculated value is smaller than tabulated value at the .5 probability than independent assortment is supported

Single character many genes

Allele is not completely dominant, the other allele will have effect Ex: snapdragons: pink F1 generation, heterozygote phenotype is different from either parent -1 allele produces functioning protein. Other non-functional

Both alleles produce protein that creates trait

Ex:sickle cell -affects type of hemoglobin produced and shape RB -causes anemia and organ damage Single gene many phenotypes!!! -Marfans syndrome: dominant allele ( responsible for tall. Curved spine. Elongated fingers)

• gene at one locus alters expression of a gene at another • regulatory genes may give rise to epigenetics: turning on and off genes • mice, black is B dominant. b is brown recessive. • presence of second allele C determines pigment is expressed • C is color expression. c is color inhibition. CC and Cc have black or brown. cc are white.

• sickle cell. Cystic fibrosis. Albinism. Methemoglobinemia • problem with recessive allele • even though not expressed. Parents can be carriers.

• one faulty dominant allele causes disorder • Huntingtons, polydactyl, brittle bone • person with disorder can be homo or hetero

Faulty allele on X chromosome • faulty recessive allele • mother to son and daughter • father to daughter • color blind, hemophilia, duchenne • male with faulty allele x have no other allele on Y to mask effect

Chromosome pair fail to separate during meiosis. -monosomy: chromosome with no pair -trisomy: 3 copies of chromosome Non disjunction: in meiosis 1 100% abnormal. Meiosis 2 50%

Gametes with too many or too few chromosomes

Turners syndrome • non disjunction in 23 pair • only X chromosome present • 95% die

Down syndrome -impotency in male -21 non disjunction XXX super female XYY super male -delayed walking emotional difficulties XXY: Klinefelter syndrome

• result of two loci being located close together on same chromosome. Causes departure from independent assortment • causes certain combo of genes to be over represented in indivdiaul gametes • F1 wild type, • no linkage expected 25%

• tell how far apart loci are by proportion of F2 from a test cross that are recominants • take number of recombinants and divide by total • recombinants are F2 that do not resemble grandparents • from r get distance between loci by multiplying r by 100 in map units • farther away, higher r, more recominants