Chapter 9 9-1 Gregor Mendel (1850’s)- used pedigree in his studies of .

Always recorded his data. Studied Statistics in college.

Mendel's experiments tell and show us how are responsible for traits being passed from gen. to gen. I. Genetic Terms A. Heredity - the passing on of traits from parents to offspring (DNA) B. Environment - is all of the outside forces that act on an organism. (Some may change the blueprints as in virus, carcinogens, and radiation). You may have the to be tall but you end up not as tall. Hearing and Sight C.Trait – a genetically determined characteristic.

ex) eye color, skin color, hair color II. Mendel’s Exp. A. Reason for using pea plants. Seven pairs of contrasting traits.(See p. 176)

Tall------Short (size) Axial flower----Terminal flower (flower arrangement) Round seeds------Wrinkled seeds (shape) Yellow seeds------Green seeds (color) Colored flower------White flowers Inflated Pods------Constricted Pods Green pod color----- Yellow pod color.

(Why not people?)

Today scientist use round worms (3 days), and fruit flies (2 weeks) B. True Breeding (Pure trait) - a trait that always produces an offspring with that trait. C.Strain - all plants pure for a specific trait.

How did he accomplish this? D.Self-Pollination - pollination occurs within a single . 1. Stamen – male - carry haploid pollen 2. Pistil - female - haploid egg 3. Pollination - transfer of pollen to stigma. E. Cross-Pollination - pollen from an anther to stigma of another. 1. Parental Generation (P for short) - the first two individuals that are crossed. 2. First filial generation (F1 for short) - offspring from P 3. Second filial generation (F2 for short) - offspring from self pollinated F1 F. Results 1. Crossed two traits (2 P’s - Purple & White) 2. F1 were all Purple.

if stopped here, what might have been his conclusions? 3. Self-pollinated the F1 a. 3/4 were Purple b. 1/4 were White When Mendel crossed strains, one of the P traits vanished from all F1, but reappeared in the F2 at a 3:1 ratio.

4. Mendel called the trait that appeared in F1 - Dominant trait. 5. The trait that disappeared in F1 but reappeared in F2 he called the Recessive trait. III.Mendel’s Three Principles A. The principle of and recessiveness. -where one factor in a pair may mask the other factor. B. The principle of segregation. - each pair of factors separate during sex cell (gamete) formation (meiosis). C.The principle of independent assortment. - each pair of factors is distributed independently. IV. Chromosomes & Genes A. - segment of DNA on a that controls a hereditary trait. Genes occur in pairs (because chromo. occur in pairs). B. (“factor”) - each of the alternative forms of a gene B. Allele (“factor”) - each of the alternative forms of a gene 1. letters are used to represent . CAPITAL = dominant trait lowercase = recessive trait

2. During fertilization, the offspring receives one allele for a given trait from each parent. C. – the study of the structure and function of chromosomes and genes. 9-2 Genetic Crosses I. - genetic makeup II. - external appearance III.Homozygous - when both alleles of a pair are the same ex) TT or tt IV. Heterozygous - two alleles are not the same. ex) Tt V. Multiple Alleles - when three or more alleles control a trait. ex) Blood type A, B, AB, O

Human blood type is controlled by three alleles: LA, LB, and LO (L is for Landstainder). The possible involving these alleles are LALA, LBLB, LALB, LALO, and LBLO. Both LA and LB are dominant to LO. However, neither LA nor LB is dominant over the other. Therefore, four blood types are possible---A, B, AB, and O. These are the . Phenotype Genotype A AA, AO B BB, BO AB AB O OO

Question: What is the most common blood type?

O-positive: 38 percent O-negative: 7 percent A-positive: 34 percent A-negative: 6 percent B-positive: 9 percent B-negative: 2 percent AB-positive: 3 percent AB-negative: 1 percent VI. Probability - the likelihood that a specific event will occur. Probability = number of one kind of event number of all events ex) heads vs tails - need several tries to get 50 – 50 VII. Monohybrid cross - one pair of contrasting traits. Punnet square - method used to predict probabilities A. Homozygous (TT) X Homozygous (tt) Genotype = Phenotype = B. Homozygous (TT) X Heterozygous (Tt) Genotype = Phenotype = C.Heterozygous X Heterozygous Genotype = Phenotype = VIII. – where two characteristics are tracked. (“F.O.I.L” – First, Outside, Inside, Last) A. Homozygous (TTGG) X Homozygous (ttgg) T – tall t – short G – green g – yellow

Genotype =

Phenotype = B. Heterozygous (TtGg) X heterozygous (TtGg) Genotype =

Phenotype =

Should have a 9:3:3:1 ratio C.Heterozygous (TtGg) X Homozygous (ttgg) Genotype =

Phenotype = This an example I will cover later. No NOTES from this slide

BLACK, brown / ROUGH COAT, smooth coat Guinea Pig

Hetero for color and coat Crossed with Hetero for color and smooth coated. IX. Testcross - procedure in which an unknown genotype is crossed with a homozygous recessive individual. ex) cross (tt) X (Tt) = results? some Tall, some Short

or cross (tt) X (TT) = results? all Tall X. Incomplete dominance (“Blending”) - Results in a trait intermediate between dominance and recessive. ex) Japanese four o’clocks R = red r = white

RR = rr = Rr =

XI. Codominance - Both alleles are expressed in a heterozygous offspring. ex) roan horse - has both red and white coat color. R = red R’ = white RR’ = white & red

Red Roan Horse Red Roan Horse

Blue Roan Horse XII. Polygenic inheritance – when several genes influence a trait. ex) eye color, height, weight, hair & skin color. XIII – Genetic Disorders A. Sickle cell anemia – recessive disorder of the red blood cells. 1 in 500 African Americans - the recessive allele protects individuals from Malaria (parasitic protozoan that invades red blood cells)

B. Cystic Fibrosis – C.Hemophilia D.Huntington’s Disease XIV Gene Therapy – replacing defective genes with copies of healthy ones. - using a virus.

XV Treating a disorder if diagnosed early. ex: Phenylketonuria (PKU) causes severe retardation due to a lack of a certain enzyme. (1/10,000 babies)