Chapter 11: Introduction to Genetics

11-1: The Work of Gregor Mendel heredity: set of characteristics an organism receives from its parents genetics: study of heredity

Gregor Mendel http://www.biography.com/#!/people/gregor-mendel-39282#synopsis

Reproduction in Pea Plants pollen is the male sex cell eggs are the female sex cells Able to reproduce…. self pollination: pollen fertilizes an egg from the same plant cross pollination: pollen from one plant fertilizes an egg from another plant

Pea Plant Traits Seven traits with two options Crossed plants with different characteristics of same trait tall with short green seeds with yellow seeds round seeds with wrinkled seeds alleles: different forms of a gene

True-Breeding True-breeding plants AA, bb Only have one allele per trait AA, bb What is another name for a true-breeding plant? Only produce identical offspring TALL plants produce TALL plants Green seeded plants produce Green seeded plants

Mendel’s First Experiment What did Mendel do in his experiments? Prevented self pollination Controlled cross pollination Removed male flower parts Pollen from plant A with egg from plant B used purebreds Seed color or plant height

Mendel’s Results offspring were hybrids: organisms produced by crossing parents with differing characteristics all hybrids had the characteristics of only one parent

Mendel’s Second Experiment Crossed F1 hybrid plants P generation: purebred group F1 generation: hybrid group F2 generation: offspring of hybrids F2 plants - the recessive traits reappeared

Mendel’s Results Ratios of Mendel’s Crosses phenotype: physical characteristics genotype: genetic makeup homozygous: two identical alleles for a particular trait TT, homozygous dominant tt, homozygous recessive heterozygous: having two different alleles for the same trait Tt

Genes and Alleles genes: unit that determines traits alleles: different forms of a gene have two alleles for each trait one from each parent sex cells contain one allele when sex cells combine, create cells with two sets of genes

DO NOW DEC 8 Solve the following problem… Cross a Heterozygous Long-clawed panther with a short-clawed panther. 1. List all of the possible genotypes and their phenotypes. 2. What percentage of panther cubs will have short claws?

Solution Dec 8 L l Ll ll L = LONG CLAW l = short claw 1. Genotype = Ll Phenotype = LONG claw ll short claw 2. 50% Genotype ll L l Ll ll

Independent Assortment Principle in which alleles separate independently of one another as they are passed down from parent to offspring. Interpret this statement. How does this process occur? Why is this process valuable to a species?

Independent Assortment Interpret this statement. The passing down of alleles is a random process. How does this process occur? Meiosis Crossing over, Independent Association, Gamete Formation in Females Why is this process valuable to a species? Provides Genetic Variation to organisms. Necessary for survival.

Interpreting Genotypes and Phenotypes Determine the possible genotypes of a pea plant that is Tall and has white flowers. TALL is dominant over short PURPLE is dominant over white flowers

Identifying Genotypes Possible Genotypes TT pp where T = Tall P = Purple t = short p = white Tt pp

Dihybrid Crosses Perform a cross between two heterozygous round and heterozygous yellow seed plants. R = Round seed Y = Yellow seed r = wrinkled seed y = green seed What do you need to determine from the information you are given?

Dihybrid Crosses Solving for two different traits. Parents RrYy x RrYy R = Round seed Y = Yellow seed r = wrinkled seed y = green seed

F=first O=outer I=inner L=last Allele Combinations Use the FOIL method to determine all of the possible genotypes of the parents. F=first O=outer I=inner L=last

Allele Combinations Parent Genotypes – RrYy Use FOIL Method to find parent allele combinations. F – RY O – Ry I – rY L – ry Allele Combinations RY Ry rY ry

Analyzing Results Answer the following question using your Punnett Square results. What is the ratio of offspring having a round and green seed?

Identifying the Phenotypes of the Offspring Parent Allele Combinations RY Ry rY ry RRYY RRYy RrYY RrYy RRyy Rryy rrYY rrYy rryy

Step by Step Procedure 1. Identify the parent genotypes 2. Assign letters to represent alleles 3. Use FOIL to determine allele combinations 4. Set up and Solve your Punnett Square 5. Identify information you need to answer questions. Write down genotypes / phenotypes 6. Analyze data from the results of your Punnett Square. Calculate genotypic and phenotypic ratios Answer questions using results

Punnett Square REVIEW A poodle that is heterozygous for white, curly fur is crossed with a poodle having black, straight fur. What are the chances one of their puppies will have white, straight fur?

WwCc x wwcc Parent Allele Combinations WC Wc wC wc WwCc Wwcc wwCc wwcc

Punnett Square REVIEW What are the chances one of their puppies will have white, straight fur? White Curly DOMINANT Genotypes for White, Straight fur WWcc or Wwcc 4/16 puppies

Mendel’s Conclusions 1. individual factors, called genes, control each trait 2. principle of dominance: some factors or alleles are dominant whereas others are recessive

11-2: Probability and Punnett Squares probability applies to genetics because the formation of gametes depends on random events

Probability and Punnett Squares probability: the likelihood that a particular event will occur # of times event occurs ÷ by the total # of occurrences

Predicting Averages Probabilities predict the average outcome of a large number of events. Cannot predict the precise outcome of a single event. Also true for genetics. Larger numbers of offspring will produce results closer to the expected values/ratios. Only 3 or 4 (F2) offspring may not equal the predicted ratio However, hundreds/thousands of offspring will produce ratios very close to results.

Segregation the separation of alleles during gamete formation New random combinations formed through meiosis monohybrid cross: crossing one trait

Segregation What are the genotypes of the F1 plants? When crossed, the recessive trait reappears in the F2 Gen

A Summary of Mendel’s Work genes control heredity genes are inherited from each parent some forms of the gene may be dominant and others may be recessive segregation occurs during the formation of reproductive cells genes for different traits may sort independently of one another

Dihybrid Crosses Homework Review Question 3 BE Be bE be BbEe Bbee bbEe bbee

Dihybrid Crosses Homework Review Question 6 TP Tp TTPp TTpp tp TtPp Ttpp

11-3: A Closer Look At Heredity Incomplete dominance: neither allele is completely dominant or recessive The phenotype for a heterozygous offspring is a blending of both alleles.

Incomplete Dominance Cross a Red Flowered plant with a White Flowered plant. What are the genotypes and phenotypes of the offspring? What percent of the offspring will have White Flowers?

Punnett Square Solution Incomplete Dominance

Codominance codominance: both alleles are expressed and contribute to the phenotype Example: Roan horse CWCW  White Coat CRCR  Red Coat CRCW  Roan Coat Cross a Roan Horse with a Red coated Horse.

Solution CR CW x CR CR  RW x RR How many horses have a white coat? R

Multiple Alleles Polygenic Traits a trait that has more than two alleles eye color blood type traits that are controlled by more than one gene facial appearance

Multiple Alleles Polygenic Traits Blood types in humans. A B AB O ALLELES: A, B, O Coat color in rabbits Four different alleles Skin color in humans Eye color is various organisms Fruit flies

BLOOD TYPES Controlled by 3 Alleles A and B are codominant A (IA), B (IB) and O (ii) A and B are codominant Both dominant over O

Blood Type Punnett Squares

11-5 Gene Linkage 1910 - Thomas Hunt Morgan conducted many experiments with the Drosophilia fruit fly. Many groups of genes were “linked” together. Reddish eyes and miniature wings Two conclusions. 1. Chromosomes are actually groups of linked genes 2. Chromosomes assort independently (not single genes)

11-5 Gene Mapping Crossing over can separate and exchange linked genes. Creates genetic diversity The farther apart 2 genes are from one another, the greater chance they would be separated by crossing over. Gene Locus – Location of a gene on a chromosome

Codominance A farmer has been told by his friend that white-coated horses are worth more money than red or roan coated horses. He decides to breed his own by crossing two Roan coat horses. Is he successful? List the genotypes and phenotypes of all the offspring. List the percentage of each phenotype.

Incomplete Dominance What is the genotype of a pink flower? If two pink flowers were crossed, what are the possible genotypes and phenotypes of the offspring?