Genetics

Objectives  ________’s Experiments and Laws Inheritance  ________ Square to determine genotype and phenotype ratios of a cross  Types of Inheritance: .

Heredity and Genetics  Heredity is the passing of traits from _________ to _________  Traits are controlled by _________, so…  Genetics is the study of how traits are _________ through the action of _________

Gregor Mendel: Father of Genetics  Mendel, an Austrian monk (born in1822) is responsible for the laws governing the i _________ of traits  Mendel cultivated and tested over 28,000 _________ plants  Mendel performed _______________ by transferring pollen from one plant to selected ova of other plants, thereby controlling which plants mixed

Traits Observed

Traits Continued

Genetics Vocab  Traits: any characteristic that can be passed from parents to _________  Heredity: the _________ of traits from _________ to offspring  Alleles: a type of gene, either _________ or _________

Complete (Single) Dominance  Complete Dominance: _________ gene with the possibility of _________ alleles  _________

Dominant vs. Recessive  Dominant : an allele whose effects mask the effects of a _________ allele  represented by a _________ letter.  Ex: Brown hair: _________  Recessive : an allele whose effects are masked by the _________ allele  represented by a _________ letter  Ex: blond hair: _________

Heterozygous v. Homozygous  “Purebred” species have two of the same alleles; this is also called _________  Homozygous: species with two of the _________ alleles:  _________ (homozygous dominant)  _________ (homozyg ous recessive)  Heterozygous: Species with two _________ alleles  _________

Genotype v. Phenotype  Genotype : the alleles present in the organism, i.e., _________, _________ or _________  Phenotype : the physical expression of the genes; what is _________

Genetic Crosses  Monohybrid Cross : cross involving _________ trait  Ex: eye color  Dihybrid Cross : cross involving _________ traits  Ex: Shape and Color of Fruit  Offspring’s genotype and phenotype is determined using a _________ square

Punnett Squares  Punnett squares can be used to determine the probabilities for _________ (genetic information) and _________ (expression of gene) combinations in _________ crosses.

Genotypes and Phenotypes in Flowers  All genes occur in pairs, so _________ alleles affect a trait.  Possible combinations if: R = Red flower r = Yellow flower  Possible Genotypes _________ _________ _________  Phenotypes _________ _________ _________

Punnett Square: Example  A father has brown hair and is heterozygous  What is his phenotype?_______  What is his genotype? ________  He is ________________________  A mother has brown hair and is homozygous  What is her phenotype?_______  What is her genotype? ________  She is ________________________________

Punnett Square: Example  What are the possible phenotypes and genotypes for their child?  Genotypic Ratio: ________  Phenotypic Ratio: __________

More Punnett Square Examples

Incomplete Dominance and Codominance

Incomplete Dominance  Incomplete Dominance: _________ allele for a trait (gene) is completely dominant over the other _________ Results in the heterozygous genotype having a _________ phenotype

Incomplete Dominance  F1 hybrids have an appearance somewhat _________ the phenotypes of the two parental varieties.  Example: snapdragons (flower) red (RR) x white (WW) RR = red flower WW= white flower

Incomplete Dominance 21 RW R R r All RW = _________ ( _________ pink) produces the r copyright cmassengale

Incomplete Dominance

Codominance  Both alleles for a gene are expressed in the phenotype of an individual with the _________ genotype  Example: Coat color in cattle

Codominance Example  In some cattle, the genes for brown hair (B) and for white hair (W) are codominant. Cattle with alleles for both brown and white hair, have both brown and white hair. This condition is this combination of two separate hair colors is called Roan. It’s genotype is BW. Cross a Roan Cow and a white bull. Give the phenotypic and genotypic ratios for the offspring.

Codominance Example Cont.  Genotypic Ratios: __________________  Phenotypic Ratios: ___________________

Multiple Alleles  Multiple Allele Traits: The trait is determined by genes that have more than _________ alleles  Ex:  Humans: _________ blood groups  Rabbits: Fur Color

Multiple Alleles  Blood type in humans is determined by one gene and three alelles  Each person inherits 2 alleles  _________ : I A  _________ : I B  _________ : i  Possible Combinations:  1.type A= _________ or _________  2.type B= _________ or _________ 3.type AB= _________  4.type O= _________

Multiple Alleles Problem 1  A man with Type AB blood is marries to a woman who is also Type AB blood. What is the potential of each of the following blood types?  Type A:  Type B  Type AB:  Type O:

Multiple Alleles Problem 2  A man who is homozygous for Type B blood is married to a woman who is Type O blood.  What blood type will all of the children have?

Multiple Alleles Problem 3  A woman with Type O blood is claiming that a man with Type AB blood is the father of her child who is Type AB blood. Could this man be the father of her child? Show the Punnett square and explain your result.

Sex Linked Traits  Genes Reside on Chromosomes  Sex-Linked Traits : the trait is determined by the gene on the _________ chromosomes  Most are located on the _________ chromosomes  Sex-linked traits in humans are usually defects or diseases that are _________  Ex: _________, _________, _________

Ex: Sex-Linked Traits  Hemophilia (H: Normal blood clotting, h: hemophilia) XX chromosome - femaleXy chromosome - male Hemophilia

Sex-Linked Traits  Sex-Linked Genes and Traits  Because males have only one X chromosome, a male who carries a recessive allele on the X chromosome will exhibit the sex-linked trait.  Many sex-linked traits carried on X chromosome

Sex Linked Trait Example 34  Cross a homozygous normal female with a male who has hemophilia.  Female Genotype:  Male Genotype:  Probability of Producing female child with hemophilia?  Probability of Producing female child with hemophilia copyright cmassengale

Sex-Linked Problem 2  Cross a carrier female with a normal male?  Female Genotype:  Male Genotype:  Probability of Producing female child with hemophilia?  Probability of Producing female child with hemophilia

Female Carriers  In sex- linked traits (ie. hemophilia), women are _________ (they have the gene, but it is not expressed) and men have the phenotype more often. Can you explain why?

Polygenic  Polygenic:  _________ than two genes control a trait (“_________ genes”)  Results in a wide range of _________  Ex: _________, _________, _________

Mendel’s Law of Segregation  Mendel’s Law of Segregation : _________ of alleles during _________ formation  This is seen with _________ squares

Mendel’s Law of Independent Assortment  Mendel’s Law of Independent Assortment Genes for different traits are inherited _________ from each other (ie. your eye color does not depend on the shape of your eyes)

Dihybrid Crosses  A breeding experiment that tracks the inheritance of _________ traits  Mendel’s “Law of Independent Assortment”  Each pair of alleles segregates _________ during gamete formation  Formula: 2 n (n = # of heterozygotes) Example: 1. RrYy: 2 n = 2 2 = _________ possible gametes _________ _________ 2. AaBbCCDd: 2 n = 2 __ = ____ gametes _________ _________ _________ _________ _________ _________ _________ _________

Dihybrid Crosses  Traits: Seed shape & Seed color  Alleles:  Alleles: R round r wrinkled Y yellow y green RrYy x RrYy ___ ___ ___ ___ All possible gamete combinations ____ ___ ____ ____

Dihybrid Cross: With Ratio 42RYRyrYry RYRy rY ry copyright cmassengale

Dihybrid Cross 43 RRYY RRYy RrYY RrYy RRYy RRyy RrYy Rryy RrYY RrYy rrYY rrYy RrYy Rryy rrYy rryy Round/Yellow: 9 Round/green: 3 wrinkled/Yellow: 3 wrinkled/green: 1 9:3:3:1 phenotypic ratio RYRyrYryRY Ry rY ry copyright cmassengale

Dihybrid Cross Round/Yellow: 9 Round/green: 3 wrinkled/Yellow: 3 wrinkled/green: 1 9:3:3:1

Inheritance of Traits  Pedigrees  Geneticists use _________ to trace _________ or traits through families.  Pedigrees are diagrams that reveal _________ patterns of _________

Pedigree for Cystic Fibrosis

Some Important Genetic Disorders