Genetics

Mendelian Genetics The passing of traits to the next generation is inheritance or heredity Mendel- a monk who work with pea plants Studied various traits in the peas

P, F1, and F2 Generations Parent generation - P generation P x P - F1 generation or first filial generation F1 x F1 - F2 generation or second filial generation

Genes in Pairs Allele- alternative form of a single gene Dominant- able to mask Recessive- is masked

Dominance Homozygous- two of the same alleles Homozygous dominant (both dominant alleles) Homozygous recessive (both recessive alleles) Heterozygous- two different alleles Genotype- an organisms pair of alleles Phenotype- observable characteristic

Mendel’s Law of Segregation Two alleles separate during meiosis You have a 50-50 chance of giving each allele

Monohybrid Cross Cross a homozygous dominant plant and with a homozygous recessive plant tall - dominant dwarf - recessive What do we expect the F1 and F2 Generations to look like?

F1 Generation

F2 Generation

Dihybrid Cross Dihybrid Cross Law of Independent Assortment Simultaneous inheritance of 2 traits in the same organism Must be on different chromosomes Different chromosomes separate independently Genes on different chromosomes separate independently

Cross two pea plants that are each hybrid for height (Tt) and also hybrid for pod color (T-Tall and t- dwarf) (Y=yellow and y=green)

What would happen? What would happen if two genes were on the same chromosome? (Circle one) A. They sort independently of each other B. They don’t sort independently of each other Why

Complex Inheritance and Human Heredity Albinism Can affect only the eyes, skin, or hair or be complete

Complex Inheritance and Human Heredity Sickle Cell Anemia Autosomal Recessive Red blood cells- sickle shape heterozygotes have both normal and sickle-shaped cells Heterozygotes protected from malaria HH- no SCA/ get malaria Hh- no SCA/ don’t get malaria hh- afflicted with SCA 7766x Sickle cell

Pedigrees A diagram that traces inheritance Can be used to predict genetic disorders in families

Incomplete Dominance The heterozygote phenotype is a blend between the two homozygous phenotypes

Codominance Both alleles are expressed at the same time

Complex Inheritance and Human Heredity Epistasis One allele can hide the effects of another allele eebb eeB_ E_bb E_B_ No dark pigment present in fur Dark pigment present in fur

Sex Determination (mammals) Sex Chromosomes XX- female XY- Male Sex chromosomes determine gender

Sex Linked Traits Located on the X chromosome Affects mostly males Red Green Colorblindness Hemophilia

Polygenic Traits Trait determined by many genes at many loci Loci – locations on different chromosomes

Explain The Twins

Environmental Influences Diet Exercise Sunlight and water Temperature

Look at you: nice work, human!

Identical Twin Studies Helps separate genetic contributions from environmental contributions Traits that affect both twins are controlled partially by heredity Traits expressed differently in identical twins are strongly influenced by the environment

Karyotype Studies Picture of the chromosomes arranged in decreasing size Chromosomes are stained Look for abnormalities Number of chromosomes Missing parts to chromosomes

Male or Female?

See anything different?

Nondisjunction During meiosis- sister chromatids fail to separate properly Down syndrome Sex Chromosomes

Down Syndrome Trisomy 21 46+ #21 = 47 Turners Syndrome 46 – X=45 XO