2 The branch of Biology that studies heredity Heredity and GeneticsWhat is Heredity? The passing of genetic traits from parent to offspringWhat is Genetics?The branch of Biology that studies heredity
3 Gregor Mendel The Father of Genetics Gregor Mendel studied genetics in the 1800’s.He was born in Austria to peasant parents who worked as gardeners.He studied at the University of Vienna and later became a monk.The Father of GeneticsConducted experiments in the garden studying traits in pea plants.Observed & recorded traits passed from parents to offspring.
4 What were Mendel’s Experiments? What characteristics did Mendel study? Mendel BrainstormWhat were Mendel’s Experiments? What characteristics did Mendel study?
5 Mendel’s ExperimentsGregor Mendel carried out a series of experiments related to how certain characteristics are inherited in pea plants.The characteristics that Mendel studied include…flower colorflower positionplant heightpod appearancepod colorseed textureseed color
6 So why did Mendel pick pea plants? 1. Many traits exist in two clearly different forms 2. The mating or crossing of two plants can easily be controlled 3. Pea plants are small, easy to grow, mature quickly, and produce many offspring
7 Mendel’s Experiments P Generation (Parental Generation) Mendel allowed two plants to self-pollinate until all offspring displayed only one characteristic (example, all purple) – this is called true breeding.A true breeding plant will only allow one trait to show through because it should be either 100% homozygous dominant (purple) or 100% homozygous recessive (white).
8 Mendel’s ExperimentsHe then picked two parents, each with contrasting traits (one purple and one white) and cross-pollinated them.F1 GenerationThe offspring of the Parental Generation which Mendel cross-bred; this generation only expressed one trait (the dominant trait, purple)
9 Mendel’s ExperimentsNext, he allowed F1 generation plants to self-pollinate.F2 GenerationThe self-pollinating offspring of the F1 Generation; this generation expressed both traits again, although the dominant (purple) trait was expressed more often (3:1)
11 Mendel’s Experiments - Hypotheses Allelesthe different versions of the gene; represented by lettersOne allele is dominant, one is recessive…Dominant: expressed form of trait (capital allele)Recessive: not expressed form of trait (lower case allele)An individual has two copies of a gene – one from each parent.There are different versions of each gene.For example, the gene for flower color in pea plants can either be purple or white, represented by letters; P = purple and p = white.
12 Mendel’s Experiments - Conclusions HomozygousHaving identical alleles for a trait; either two dominant alleles or two recessive allelesHomozygous Dominant = BB or TT or QQHomozygous Recessive = bb or tt or qqHeterozygousHaving two different allelesBb or Tt or QqGenotypethe set of alleles that an individual has (the actual genes)Ex: BB, Tt, or qqPhenotypethe physical appearance of a trait (how it actually appears)Ex: Brown eyes or blue eyes; tall or short
13 Mendel’s BIG Conclusions… The Laws of Heredity Law of SegregationTwo alleles for a trait separate when gametes are formedLaw of Independent AssortmentThe inheritance of one trait does not influence the inheritance of another traitThese both occur during Meiosis!
14 Mendel’s Contributions On the left side of your IN, write a short paragraph about the importance of Mendel’s research.
16 What is the genotype of parent 1? What is the genotype of parent 2? Punnett SquareSimple diagram used to predict expected result of a genetic crossGenetic CrossHh x hhWhat is the genotype of parent 1?What is the genotype of parent 2?Punnett Squares consider all possible combination of gametes for that particular crossHhhhHomozygous RecessiveHeterozygousHhhh
17 Punnett Squares – Monohybrid Cross What is the probability that the offspring is heterozygous?50%What is the probability that the offspring is homozygous recessive?25%A cross that considers ONE pair of contrasting traits between two individualsCross the following!Heterozygous Male x Heterozygous FemaleGg x GgWhat is the probability that the offspring is green?75%What is the probability that the offspring is brown?25%GgFrog Color KeyG – Greeng- brownGGGgGgGggg
18 Punnett Squares – Monohybrid Cross Cross the following!Heterozygous Female x Homozygous Recessive MaleGg x ggWhat is the probability that the offspring is green?50%What is the probability that the offspring is brown?GgFrog Color KeyG – Greeng- browngGggggggGg
19 Punnett Squares – Monohybrid Cross What is the genotype of all of the offspring?HeterozygousWhat is the probability the offspring’s phenotype is Round?100%Cross the following!Homozygous Dominant Female x Homozygous Recessive MaleRR x rrrrSeed of Pea PlantsKeyR – Roundr- WrinkledRRrRrRrRrR
20 Punnett Squares – Monohybrid Cross How many offspring would you expect to have the:Genotype RR1/4 or 25%Genotype Rr2/4 or 1/2 or 50%Genotype rrHow many offspring would have the following phenotype?Round Seeds3/4 or 75%Wrinkled Seeds1/4 or 25%Try 1 more cross!Heterozygous Male x Heterozygous FemaleRr x RrWhat is the phenotypic ratio?3:1What is the genotypic ratio?1:2:1RrSeed of Pea PlantsKeyR – Roundr- WrinkledRRRRrrRrrr
21 Test CrossA test cross can be performed to determine whether a parent with a dominant phenotype is homozygous dominant or heterozygous.In a test cross, an individual whose phenotype is dominant, but whose genotype is unknown, is crossed with a homozygous recessive individual. One can then look at the offspring to determine the genotype of the parent.
22 So if we get 4 purple offspring, what must the other allele be? Test Cross - examplesPea Plant Flower ColorP = purplep = whiteUnknown withdominant phenotypeP?PSo if we get 4 purple offspring, what must the other allele be?Pp=pPp=purplepurpleHomozygous recessivepPp=Pp= purplepurple