• Have Graphs from Lab out and ready to be checked

Genetics

Definitions • Heredity- passing of characters from parents to offspring• Genetics- branch of biology that focuses on heredity• Monohybrid cross-is a cross that involves one pair of contrasting traits • P generation- first two individuals that are crossed • F₁ generation- is the offspring of the P generation• F₂ generation- is the offspring of the F₁ generation

Genetics•Explains the stability of inheritance and also variations between offspring from one generation to the next

•How long has Genetics been around?

How Old is Genetics

• From the first time man planted plants for food, to the taming of animals

• Genetics was originally thought of as the Blending concept• What changed and what was the Blending concept?

Blending Concept• Before the late 19th Century

• Offspring’s genetic makeup was intermediate to that of its parents • Ex. Red flower crossed with white flower would yield nothing but pink flowers• This could not explain why for example why pink flower plants produced both

red and white offspring This did not help Darwin explain how diverse forms evolve

What Changed?•Gregor Mendel•Austrian monk•One of the first to use mathematics in experiments•Particulate Theory•1860’s Garden Pea experiment •Considered the Father of Genetics

Particulate Theory • Based on the existence of minute particles or hereditary units• These units are now called Genes

• Two laws came from this theory• Law of segregation• Law of independent assortment

Garden Pea (Pisum sativum)

•Why was the Garden pea chosen •Many easy to identify traits• Easy to control pollination • Easy to maintain • Short generation time• Lead to obtaining True-breeding plants

True-Breeding •What is True-Breeding?• It is when the offspring are the same and exactly like the parents

Experiment • Started by choosing varieties that only differed by one trait• Like tall to short plants

• Generations • P-parents (true-Breeding)• F1 is offspring

• After first cross all offspring resembled tall parents • What did this mean

Experiment • F2 generation was ¾ were tall and ¼ was short • This lead to Mendel to deduce tall dominate over short

• This is referred to as a Monohybrid cross• Cross of a single trait • 3:1 ratio in F2 generation • This explains the Law of Segregation

Monohybrid Cross• Aa to Aa

A a

A

a

Monohybrid Cross• Cross between Aa to Aa

• Results 3:1

A a

A AA Aa

a Aa aa

Experiment• Law of Segregation• F1 parents contained two separate copies of each hereditary factor, one

dominate and the other recessive• Factors separated when the gametes were formed, and each gamete carried

only one copy of each factor• Random fusion of all possible gametes occurred upon fertilization

Definitions• Locus- location of a pair of chromosomes

• Alleles- alternative versions of same gene

• Dominant –fully functional protein

• Recessive-protein with little or no function

• Homozygous-two identical alleles

• Heterozygous-two different alleles

• Genotype –alleles an individual receives at fertilization(DNA)

• Phenotype-physical appearance of the individual (protein)• The protein that makes the phenotype is produced by the DNA that makes up

the Genotype

Definitions

• Two true-breeding plants with two different traits • Ex. Tall with green pods and short with yellow pods

• This is know as a dihybrid cross (9:3:3:1 phenotypic ratio)• Because the plants are hybrid in two ways

Mendel’s Second experiment

Experiment 2• Two possible out comes• If Dominant factors always segregate into F1 and recessive always stay

together than there will be two phenotypes in F2 plants• If the four factors segregate into F1 gametes independently, then there would

be four phenotypes among the F2 plants • Tall Green, Tall yellow, short green, short yellow

Experiment 2• Law of Independent Assortment• Each pair of factors segregate/assort independently of the other pair• All possible combinations of factors can occur in the gametes

• Note the law of independent assortment applies only to alleles on different chromosomes

Question

• Dihybrid cross AaBb with AaBb

Cross

Question

• 9 with dominate AB 3With Ab 3with aB and 1 with ab

AB Ab aB ab

AB AABB AABb AaBB AaBb

Ab AABb Aabb AaBb Aabb

aB AaBB AaBb aaBB aaBb

ab AaBb Aabb aaBb aabb

Review

Inheritance of traits• Pedigree- family history that shows how a trait is inherited over several

generations• Sex-linked gene’s- allele is located only on the X or Y chromosomes • Incomplete dominance- when a individual displays a phenotype that is

intermediate between two parents • Multiple alleles- genes with three or more alleles • Codominance- when two dominant alleles are expressed at the same

time• Crossing over- the exchange of genetic material between homologous

chromosomes that results in recombinant chromosomes

Pedigree

Pedigree

Sex-linked gene’s • Most sex-linked genes are carried on the X chromosome

• Who is most likely to exhibit these conditions?

• Why are males more likely to exhibit a sex-linked condition?

• Ex. Red-Green color blindness, Male pattern baldness, hemophilia

Incomplete Dominance • Predict the out come of a true breeding red snapdragon with a true breeding white snapdragon in incomplete dominance

Multiple Alleles• Ex. Blood types• Determined by the three alleles (Iᴬ, Iᴮ, i)

Codominance • Codominance and Incomplete dominance deferrer because both

traits are displayed in codominance • Ex. Type AB blood

Genetic disorders• Sickle Cell Anemia• Cystic Fibrosis• Hemophilia• Huntington’s Disease

• Abnormalities in Karyotypes• Trisomy • Monsomy

Abnormalities in Karyotypes

• Monosomy – chromosome having no homology, especially unpaired X chromosome• Turner’s syndrome- missing one sex chromosome

• Lethal

• Trisomy- three instances of a particular chromosome, instead of the usually two • Ex. Down syndrome there is an extra chromosome 21• Klinfelter’s syndrome were there is XXY sex chromosome

Sickle Cell Anemia • Recessive genetic disorder occurs in 1out of 500 births (mostly African

American)• Caused by mutated allele that produces a defective form of the protein

hemoglobin

• Side effects- red blood cells are sickle shaped, rupture easily, tend to get stuck in blood vessels • The recessive allele that causes sickle-shaped cells also helps protect

the cells of heterozygous individuals from the effects of malaria

Sickle Cell Anemia • malaria is a disease caused by a parasitic protozoan that invades red

blood cells

Cystic Fibrosis• Most common fatal, hereditary, recessive disorder among Caucasians

• Side effects- airways of lungs become clogged with thick mucus, and ducts of the liver and pancreas become blocked

• Treatments can relieve some of symptoms, but there is no know cure

Cystic Fibrosis• 1 in 25 Caucasians has at least one copy of a defective gene that

makes a protein necessary to move chloride into and out of cells about 1 in 2500 infants in US is homozygous for the cf allele

Hemophilia • Recessive genetic disorder in hemophilia • Impairs the blood’s ability to clot• Sex-linked trait

• Over a dozen genes code for the protein involved in blood clotting • Mutation on 1 of these genes on the X chromosome causes

hemophilia

Hemophilia• Most common in Males• 1 in 10,000

Huntington’s Disease• Genetic disorder caused by a Dominant allele located on an autosome

• Symptoms- mild forgetfulness and irritability appears in thirties to forties • Over time causes loss of muscle control, physical spasms, severe

mental illness, and eventually death

• 1 in 10,000