Introduction to Genetics Genes= set of instructions for one protein; section of chromosome –region of DNA that controls a hereditary characteristic (by making a particular PROTEIN!!)

Introduction to Genetics Trait= characteristic that is expressed and may vary from one individual to another Heredity= passage of genetic information from parents to offspring

Allele: different forms of a gene found on homologous chromosomes

Heterozygous: Having two different alleles for a single trait. Homozygous: Having identical alleles for a single trait. Genotype:The genetic makeup of an organism Phenotype: An organism's expressed physical traits.

Remember…these are separated during meiosis!! Homologous chromosomes Alleles

But before all this cool stuff was known….. It all started with a monk and his pea plants …..

Began with Mendel

The modern science of genetics was founded by an Austrian monk named Gregor Mendel. Mendel was in charge of the monastery garden, where he was able to do the work that changed biology forever. Mendel carried out his work with ordinary garden peas, partly because peas are small and easy to grow. A single pea plant can produce hundreds of offspring. Today we call peas a “model system.”

Cross-pollination allowed Mendel to breed plants with traits different from those of their parents and then study the results.

Gregor Mendel…the “father” of genetics

Mendel’s Conclusions

Dominant Trait : the trait will always appear if the gene is present (Capital letter) (Dominant allele= dominant gene) Recessive Trait: the trait that will appear if there are two copies of a gene…..otherwise this trait will be hidden by the dominant trait!! (lower case letter) (Recessive allele=recessive gene….the one that can be covered up)

Principle of Segregation – Allele pairs separate or segregate during formation of gametes (MEIOSIS) and recombine during fertilization

Meiosis Explains this

Principle of Independent Assortment Alleles for different traits are separated independently of each other

Mendel’s Principles The inheritance of biological characteristics is determined by individual units called genes. When two or more forms (allele) of the gene for a single trait exist, some alleles may be dominant or recessive In most sexually reproducing organisms, each adult has two copies of each gene– one from each parent. These genes segregate from each other when gametes are formed. Alleles for different traits usually separate independently of each other

Punnett SquaresSquares chart which shows/predicts all possible gene combinations in a cross of parents (whose genes are known). Actually…..shows possible alleles parents may contribute!!

Dihybrid Cross

Probability and Punnett squares Why are the principles of probability able to be used to predict the outcome of genetic crosses? Think about the “segregation of alleles”!!“segregation of alleles”!!

Heterozygous: Having two different alleles for a single trait. Homozygous: Having identical alleles for a single trait. Genotype:The genetic makeup of an organism Phenotype: An organism's expressed physical traits.

Inheritance of Traits During fertilization…the male and female parents each contribute genetic information…to create the zygote Zygote: fertilized egg; cell formed by union of gametes

Species chromosome number: the number of chromosomes normally in the body cell of the organism – Same from generation to generation

Karyotype: photograph/chart of chromosomes in an organism arranged in pairs Can tell gender….and certain diseases

Kleinfelters Syndrome

Genetics so far…… Simple dominant/recessive one trait crosses! Now…… Incomplete Dominance: a blending of traits; neither allele is completely dominant Codominance: Each trait is expressed; both alleles are dominant

Incomplete Dominance Alleles are neither dominant or recessive The heterozygote phenotype is a blending (lies somewhere between the two)

Codominance In a heterozygote…..both traits are expressed separately…both are dominant Example…..

Codominance Codominance helps to explain the inheritance of Human Blood Types

Human Blood Typing Blood type is determined by antigen found on red blood cell

Codominance and Multiple Alleles!! There are more than two alleles (gene possibilities) (Multiple Alleles) A (I A ), B (I B ), and O(i) Both A and B are dominant(Codominant) O is recessive

If an antigen is introduced to a person that cannot recognize it…they will make antibodies against it…..and attack it! This will cause the blood to clump…clots... So blood types need to be matched If the person can recognize it…they can have it!!

Blood Typing Process!!

Pedigree Chart Traces the pattern of inheritance through many generations

Female Affected Female Male Affected male

Tay Sach’s

Sickle-cell Anemia

Human Genetic Diseases PKU: an enzyme needed to metabolize a particular amino acid is absent; if not detected early mental retardation may occur Sickle-cell Anemia: formation of abnormal hemoglobin; makes RBC’s fragile and gives them a sickle shape Tay-Sachs: an enzyme is not synthesized and that allows for an accumulation of a fatty material on nervous tissue; fatal disease Cystic Fibrosis: a non-secretion of digestive enzymes; allows for a abnormal build-up of mucus (recessive) (chromosome 7) Specific disorders Information from Genome Project

Albinism: inability to produce melanin (recessive) Huntington's Disease: adults lose muscle control, convulsions, nervous degeneration causes death (chromosome 4) (dominant) Polydactyly: dominant disorder that causes extra fingers and toes

Sex determination Sex chromosomes: 1 pair of chromosomes…..responsible for determining gender (X or Y) Autosomes: the other 22 pairs of chromosomes ( not sex)

Sex chromosomes are represented by X and Y Egg cells carry only X chromosomes Sperm cells carry either an X or Y At fertilization: XX=female » XY=male

Sex-Linked Inheritance Several genes found on X chromosome but not on Y….X is larger!! Sometimes these genes on the X carry genetic diseases and are called sex-linked genes Usually recessive Females who have one recessive gene and one normal gene are called carriers

Polygenic Inheritance Traits controlled by more than one gene pair (allele) Most human traits are polygenic – Skin color, height Resulting phenotypes show range of differences!!