HUMAN GENETICSHUMAN GENETICS

Chapter 12, Section 1Chapter 12, Section 1

PedigreePedigree PedigreePedigree = map of inheritance of genetic traits = map of inheritance of genetic traits

from generation to generationfrom generation to generation

Symbols on a PedigreeSymbols on a Pedigree Circle = FemaleCircle = Female Square = MaleSquare = Male Shaded = Affected Shaded = Affected Unshaded = UnaffectedUnshaded = Unaffected Adjoining line = Married/MatingAdjoining line = Married/Mating Connected by an adjoining line = OffspringConnected by an adjoining line = Offspring Roman Numeral = GenerationRoman Numeral = Generation

Recessive HeredityRecessive Heredity

Caused by Caused by recessive allelesrecessive alleles Attached earlobes, Cystic fibrosis Attached earlobes, Cystic fibrosis

(defective protein leads to excessive (defective protein leads to excessive mucus production in lungs), Albinismmucus production in lungs), Albinism

Individual will only display the Individual will only display the recessive recessive phenotypephenotype if its genotype is if its genotype is homozygous homozygous recessive (aa)recessive (aa)

Dominant HeredityDominant Heredity

Caused by Caused by dominant alleledominant allele Freckles, Widow’s peak, Hitchhickers thumb, Freckles, Widow’s peak, Hitchhickers thumb,

Huntington’s disease (brain degeneration, Huntington’s disease (brain degeneration, doesn’t appear until later in age), immunity to doesn’t appear until later in age), immunity to poison ivypoison ivy

Individual will display the Individual will display the dominant dominant phenotypephenotype if its genotype is if its genotype is heterozygous(Aa)heterozygous(Aa) oror homozygous homozygous dominant(AA)dominant(AA)

Textbook pg. 310 Fig. Textbook pg. 310 Fig. 12.212.2

With your lab partner answer the following questions on a With your lab partner answer the following questions on a separate sheet of paper.separate sheet of paper.

1.1.How many generations are shown?How many generations are shown?

2.2.How many offspring did I-1 and I-2 have?How many offspring did I-1 and I-2 have?

3.3.How many boys did III-3 and III-4 have?How many boys did III-3 and III-4 have?

4.4.How many girls did II-1 and II-2 have?How many girls did II-1 and II-2 have?

5.5.What kind of trait (dominant or recessive) is being passed What kind of trait (dominant or recessive) is being passed down?down?

6.6.What genotypes must I-1 and I-2 be in order to have a child What genotypes must I-1 and I-2 be in order to have a child with this trait?with this trait?

7.7.What is the probability that they would have this type of What is the probability that they would have this type of child? Show a Punnett squarechild? Show a Punnett square

When Heredity When Heredity Follows Different Follows Different

RulesRules

Chapter 12, Section 2Chapter 12, Section 2

Incomplete DominanceIncomplete Dominance Incomplete DominanceIncomplete Dominance = phenotype of a = phenotype of a

heterozygoteheterozygote is in between the dominant & is in between the dominant & recessive phenotypes, recessive phenotypes, appearance of a third appearance of a third phenotype.phenotype.

No Longer Upper and Lowercase letters No Longer Upper and Lowercase letters AA or or aa

Flowers known as Snapdragons come in 3 colors Flowers known as Snapdragons come in 3 colors but have 2 alleles, R and R’but have 2 alleles, R and R’

R’R’ = R’R’ = WhiteWhite R’R or RR’ = R’R or RR’ = PinkPink RR = RR = RedRed

Sample ProblemsSample Problems

Cross the following snapdragons and give the genotype and Cross the following snapdragons and give the genotype and phenotype ratios.phenotype ratios.

RedRed x x WhiteWhite – Phenotypic Ratio – Phenotypic Ratio

White White : : Pink Pink : : RedRed

Genotypic RatioGenotypic Ratio

R’R’R’R’: : R’R R’R : : RRRR

PinkPink x x PinkPink – Phenotypic Ratio – Phenotypic Ratio

White White : : Pink Pink : : RedRed

Genotypic RatioGenotypic Ratio

R’R’R’R’: : R’R R’R : : RRRR

Text pg. 316 Figure 12.7Text pg. 316 Figure 12.7

RedRed x White = all x White = all pinkpink PinkPink x x PinkPink = 1 = 1RedRed: 2: 2PinkPink: 1White: 1White

Genetics ReviewGenetics Review

Mendelian Genetics – Simple Dominant Mendelian Genetics – Simple Dominant & Recessive Traits (Tall TT or Tt or short & Recessive Traits (Tall TT or Tt or short tt)tt)

Incomplete Dominance – 3 phenotypes Incomplete Dominance – 3 phenotypes (FF = red, FF’ = pink, F’F’ = white)(FF = red, FF’ = pink, F’F’ = white)

Pedigree – Map to show how traits are Pedigree – Map to show how traits are passed from parent to offspring (not passed from parent to offspring (not shaded – doesn’t have trait, half shaded shaded – doesn’t have trait, half shaded – carrier, shaded – has trait– carrier, shaded – has trait

CodominanceCodominance

BothBoth alleles for a gene are expressed in a alleles for a gene are expressed in a heterozygous individualheterozygous individual•Black Feathers FBFB = Black Feathers•White Feathers FW FW = White•When the 2 alleles are combined a chicken with both black and white feathers is created.•Erminette chickens FBFW = Black & White•Neither allele is dominant or recessiveNeither allele is dominant or recessive

Codominance Practice ProblemsCodominance Practice Problems

Cross a chicken that is homozygous for Cross a chicken that is homozygous for the black alleles with a chicken that is the black alleles with a chicken that is homozygous for the white alleles.homozygous for the white alleles.

What color feathers did the offspring What color feathers did the offspring have?have?

Cross 2 chickens from the F1 generation Cross 2 chickens from the F1 generation to make the F2 generation?to make the F2 generation?

What color feathers did the offspring What color feathers did the offspring have?have?

Blood TypesBlood Types

BLOOD TYPE.ppt

Genetic TestingGenetic Testing Genetic Tests are now available that can tell you Genetic Tests are now available that can tell you

the probability that an individual will have a certain the probability that an individual will have a certain disorder. Write disorder. Write Yes or No Yes or No on the whiteboard to on the whiteboard to answer the following questions.answer the following questions.

Would you want to be tested? Would you want to be tested? Would you have a significant other tested? Would you have a significant other tested? Would you have your child tested? Would you have your child tested? Would you agree to be tested if you are an Would you agree to be tested if you are an

employee? employee? Would you as an employer require job applicants to Would you as an employer require job applicants to

take a test? take a test?

Sex Determination & Sex-Sex Determination & Sex-linked Inheritancelinked Inheritance

Combination of Combination of sex chromosomes (X and sex chromosomes (X and Y)Y) determine an individual’s gender determine an individual’s gender

Males XYMales XY, , X chromosome comes from X chromosome comes from mom & Y chromosome comes from dadmom & Y chromosome comes from dad

Females XXFemales XX, , both mom & dad give an X both mom & dad give an X chromosomechromosome

Sex-linked TraitsSex-linked Traits = traits controlled by = traits controlled by genes on sex chromosomesgenes on sex chromosomes

Examples of X Linked TraitsExamples of X Linked Traits

Red-Green colorblindness Red-Green colorblindness Hemophilia (blood doesn’t clot properly)Hemophilia (blood doesn’t clot properly) Duchenne Muscular Distrophy (muscular Duchenne Muscular Distrophy (muscular

degeneration leading to eventual degeneration leading to eventual paralysis)paralysis)

Most of sex-linked traits are found on Most of sex-linked traits are found on genes on the genes on the X chromosomeX chromosome (X-linked (X-linked trait)trait) because it is larger than the because it is larger than the Y Y chromosomechromosome

X-linked traits display more in males X-linked traits display more in males because they only have 1 X because they only have 1 X chromosome, whereas females get 2 X chromosome, whereas females get 2 X chromosomes so they can be carriers of chromosomes so they can be carriers of the trait but not display the phenotypethe trait but not display the phenotype

Color Blindness - Recessive TraitColor Blindness - Recessive Trait B = Normal b = color blind B = Normal b = color blind

MalesMales

XXBBY = NormalY = Normal XXbbY = Color BlindY = Color Blind FemalesFemales

XXBBXXBB = Normal = Normal

XXBBXXbb = Carrier (Normal) = Carrier (Normal)

XXbbXXbb = Color Blind = Color Blind

Can males be carriers for color blindness? Can males be carriers for color blindness? Why or why not?Why or why not?

Sex Linked CrossesSex Linked Crosses

Cross a color blind male with a carrier Cross a color blind male with a carrier female?female?

What is the probability you will get a color What is the probability you will get a color blind child?blind child?

What is the probability you will get a color What is the probability you will get a color blind male? Only look at males.blind male? Only look at males.

What is the probability you will get a What is the probability you will get a carrier female? Only look at the femalescarrier female? Only look at the females

Polygenic InheritancePolygenic Inheritance Characteristics that are influenced by Characteristics that are influenced by

several genesseveral genes