Chapter 11: Introduction into Genetics Mr. Freidhoff

Genetics Genetics: is the branch of science that studies how the characteristics of living organisms are inherited.

Traits Trait: Distinguishing characteristic or quality that’s determined by DNA. – Traits of eye color, hair color, height, etc. – Inherit traits from parents and pass onto offspring.

Alleles An allele is a specific version of a gene. – Examples: eye color, hair color, earlobe type.

Fundamentals of Genetics The two different alleles are on the same part of a chromosome. The interaction of alleles determines the appearance of the organism.

Genotype – The genotype of an organism is the combination of alleles that are present in an organism’s cells. Ex. BB, Bb, bb Homozygous: two identical alleles. Heterozygous: two different alleles.

Dominant Vs. Recessive Dominant: Stronger of two genes expressed in the genotype. – Represented by a capital letter (R). Recessive: Gene that is masked by the dominant gene. – Represented by a lowercase letter (r).

Fundamentals of Genetics BB – Homozygous Dominant bb – Homozygous Recessive Bb – Heterozygous

Fundamentals of Genetics – The PHenotype of an organism is the PHysical appearance due to the organism’s genotype. Blue eyes Brown eyes Green eyes Grey Eyes

Dominant Vs. Recessive – When the dominant gene is present, the dominant phenotype will be shown. R = Purple Flower r = White Flower – RR – Purple Flower Rr – Purple Flower rr – White Flower

Genotype vs Phenotype Aa  Purple Flower Genotype Phenotype

Fundamentals of Genetics Purebred: Homozygous – Dominant and Recessive – AA, aa Hybrid: Heterozygous – Aa

Blending Hypothesis Pre-1800s. Blending in offspring. Red Flower crosses with a Yellow flower. – Creates an Orange flower. Incorrect.

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Gregor Mendel ( ) Austrian Monk. “The Father of Genetics" Experimented with pea plants. Understood that there was something that carried traits from one generation to the next.

Gregor Mendel He studied physics and botany at the University of Vienna. Work with pea plants took 8 years. Tested some 28,000+ pea plants.

Site of Mendel’s experimental garden in the Czech Republic

Generations Generations: – P = Parental generation. – F1 = 1st generation, offspring of the P generation.

Generations −Crossed purple flower pea plant with white flower pea plant. −P-Generation. −Offspring was all purple flower. −F1-Generation. −Where did the white color go? −Why did it not blend?

WHAT DID MENDEL FIND OUT FROM THIS?

F2 Generation White flowers appeared again in F2 generation. Blending hypothesis was incorrect. Something controlled the phenotype of an organism.

: Statistics indicated a pattern.

Particulate hypothesis created. With more information, particulate hypothesis discovered untrue. Chromosomal Theory is what evidence supports today. Heritable factors are located on chromosomes. Particulate Hypothesis

Punnett Square: A tool we use for predicting the traits of an offspring. – Letters are used as symbols to designate genes. – Genes always exist in pairs. Punnett Squares

F1 Generation Genotype Ratio: BB: 0 Bb: 4 bb: 0 Purple: BB White: bb

F2 Generation Genotype Ratio: BB: 1 Bb: 2 bb: 1 Purple: Bb

Mendel’s Work Published findings in the local natural history journal in Mendel’s last words were “my time will come.” Mendel’s results were forgotten until the early 20th century. Link

Punnett Squares -Monohybrid cross: Cross involving a single trait e.g. flower color Dihybrid cross: Cross involving two traits e.g. flower color & plant height

Dihybrid Cross Punnett square looks at 2 different alleles. – One for each trait. Offspring have 4 allele. 16 different possibilities. 4x4 box

Dihybrid Punnett Square AaBbAaBb ABABAbAbaBaBabab Gamete #1Gamete #2Gamete #3Gamete #4

AB aB ab aB Ab AB ab Ab Fur Color: A: Purple a: White Coat Texture: B: Tall b: Short AaBb x AaBb Dihybrid Cross

How many of the offspring would be Purple and Tall? How many of the offspring would have a Purple and Short? How many of the offspring would have a White and Tall? How many of the offspring would have a White and Short? Flower Color A: Purple a: White Plant Height B: Tall b: Short Phenotypic Ratio 9:3:3:1 AB aB ab aB Ab AB ab Ab AABBAABb AaBBAaBb AABbAAbb AaBbAabb AaBBAaBb aaBBaaBb AaBbAabb aaBbaabb

Mendel’s 3 Laws

1. Law of Dominance If an organism has one dominant allele, the dominant phenotype will be produced. – AA, Aa will show dominant trait. – aa will show recessive trait.

2. Law of Segregation: Two alleles for each trait separate when gametes form. Parents pass only one allele for each trait to each offspring.

Where does the separation come from?

3. Law of Independent Assortment: Genes for different traits are inherited independently of each other. No order in gene selection. – Random!

Non-Mendelian Genetics Oh come on! That’s “allele” funny…

Intermediate Dominance Heterozygotes have a phenotype that is intermediate between the phenotypes of the two homozygotes. Neither allele is dominant or recessive. Wrote as superscript.

Intermediate Dominance

Codominance Codominance: Situation in which both alleles of a gene contribute to the phenotype of the organism. Expressed with capital letters

Blood Type A person’s blood type is regulated by multiple alleles. 3 Different Alleles types. – A, B, O I A = A allele I B = B allele i = O allele

Blood Type In humans, blood types A and B are equally dominant (codominant). Both types of blood are dominant to O. 4 different phenotypes: – A, B, AB, O

Blood Typing Problem A man with type AB blood marries a woman with type O blood. Give the genotypes and phenotypes of all possible offspring.

Blood Type

Type O is the universal donor. – No Antigens to react with. Type AB blood is universal receiver. – No Antibodies to react with foreign blood.

Rh Factor More antigens. Positive (+) represents presence of antigens. Negative (-) represents no antigens.

Who can donate to who?

Polygenic Inheritance Several Alleles contribute to phenotype. Large amount of phenotypes.

Bell Curve (Draw in notes)

If a trait, say height, is controlled by two loci, A and B, and each locus has two alleles, one regular and one prime allele, what are the possible genotypes and phenotypes? AABB short AABB semi-short AABB average AABB semi-tall AABB tall

AABB AABBAABB short semi- short average semi- tall 01234

Sex-Linked Genes Sex chromosomes determine the sex of the organism. Humans: 23 rd Chromosome – XX: Female – XY: Male X: 1500 genes Y: 80 genes

Sex-Linked Genes Sex-linked Gene: Any gene that is located on a sex chromosome. In humans, most sex- linked genes are found on the X- Chromosome.

Sex-Linked Disorders Males only need 1 copy of a sex- linked disorder on a X- chromosome to produce the phenotype. Females need two X- chromosomes with disorder. – X h, X H

Colorblindness Colorblindness is recessive and X-linked. Affected males can only receive disorder from mother. – Why? – Males receive X from mother and Y from father.

How Color-Blind People See Things What people with normal color vision see. What a red-green color-blind person sees.

Colorblind Test