BIOL 1441 1st Edition Lecture 23 Outline of Last Lecture I. MeiosisII. Stages of Meiosis IIII. Stages of Meiosis IIIV. Meiosis and diversityV. HeredityVI. Chromosomes-somatic cells/gametesVII. TwinsVIII. Asexual/sexual reproductionIX. Genetic variationOutline of Current Lecture I. Gregor MendelII. Theories of inheritanceIII. GenesIV. Mendel’s laws of inheritanceV. Law of segregationVI. Punnett squareVII. Test CrossesVIII. Law of independent assortmentThese notes represent a detailed interpretation of the professor’s lecture. GradeBuddy is best used as a supplement to your own notes, not as a substitute.Current LectureI. Gregor Mendela. Father of Geneticsb. Austrian monk & scientistc. Studied heredity of physical traits in pea plantsII. Theories of Inheritancea. Blending hypothesis- idea that genetic material from the two parents blends together i. Blue and yellow paint blend to make greenb. Particulate hypothesis- idea that parents pass on discrete heritable units (genes)i. Mendel documented a particulate mechanism through his experiments with garden peasIII. GenesIV. What are they?a. Nucleotidesi. Phosphate + Deoxyribose (DNA sugar) + nitrogen base (A,T,C,G)ii. Adenine-thymine = 2 H bondsiii. Guanine-cytosine = 3 H bondsb. DNA ® mRNA ® Proteinc. Codon- 3 DNA bases encode for 1 amino acidd. Amino acids string together to form proteinse. Genes- segments of DNA that code for a specific proteinsi. Allele- variants of the geneii. Gene for eye color1. Alleles: blue, green, brown, hazel, etc.f. Each gene resides at a specific locus (location) on a chromosomeg. One allele is dominant over the other and affects its expression (what you see)h. Gene Expressioni. Alleles are dominant or recessiveii. Dominant allele masks the expression of the recessive allele1. Dominant- 1 allele for expression2. Recessive- 2 alleles for expressioniii. Gene for hair color1. Alleles: brown and blond2. Dominant allele: brown color3. Recessive allele: blond colori. Genotypesi. Homozygous- organism with two identical alleles for a gene ii. Heterozygous- organism that has two different alleles for a geneV. Mendel’s Laws of Inheritancea. Law of segregation- two alleles in a pair segregate (separate) into different gametes during gamete formationi. Only one allele is put on one gameteb. Law of independent assortment- each pair of alleles sort independently of each other during gamete formationi. (metaphase I meiosis- homologous chromosomes align and randomly divide)c. Mendel discovered the basic principles of heredity by breeding garden peas in carefully planned experimentsd. Picked traits only had 2 possible outcomesi. White flower or purple flowerii. Wrinkled seed or a smooth seede. Observable feature- character (characteristic)f. Variants of character- traitsg. Mendel’s Experimental Approachi. True-breed- plants that produce offspring of the same variety when they self-pollinate (pollinate flowers on same plant)ii. Homozygous for trait1. Both alleles same2. Flower color- purple &purpleiii. Typical experiment, Mendel mated two contrasting, true-breeding varieties- hybridization1. Heterozygote = hybrid2. True-breeding parents- parental generation3. Hybrid offspring - F1 generation4. Self-pollinate F1 individuals- produce F2 generationh. Mendel’s Observationi. Mendel discovered a ratio of about three to one, purple to white flowers, in the F2 generationii. White flower trait did not disappear, it was masked or hidden in F1 generationi. Mendel’s Modeli. Mendel developed a hypothesis to explain the 3:1 inheritance pattern he observed in F2 offspringii. 2 alleles for every gene- one from each parent1. Purple + purple 2. Purple + white3. White + whitej. Dominant vs Recessive Traitsi. Dominant trait hides or masks the recessive trait in F1 generationii. Recessive trait reappears in F2 generation- need two recessive genes to be expressedVI. Law of Segregationa. Two alleles in a pair segregate into different gametesb. Two alleles for a gene separate (segregate) during gamete formation and end up in different gametesc. Egg or a sperm receives only one of the two alleles that are present in the somatic cells of an organismd. Segregation of alleles corresponds to the distribution of homologous chromosomes to different gametes in meiosisVII. Punnett Squarea. Possible combinations of sperm and egg can be shown using a Punnett squareb. Diagram for predicting the results of a genetic cross between individuals of known genetic makeupc. Capital letter- dominant allelei. P- purpled. Lowercase letter- recessive allelei. p -whitee. Genotypesi. Homozygous- organism with two identical alleles for a gene 1. PP – purple, purple2. pp- white, whiteii. Heterozygous- organism that has two different alleles for a gene1. Pp- purple, whitef. Genotype or Phenotypei. Organism’s traits do not always reveal its genetic composition (genotype)1. PP- purple2. Pp- purpleii. Distinguish between an organism’s physical appearance and it’s genetic makeupiii. Genotype -genetic makeup (PP or Pp or pp)iv. Phenotype- physical appearance (purple or white)VIII. Testcrossa. How can we tell the genotype of an individual with the dominant phenotype? i. Homozygous dominant (PP)ii. Heterozygous (Pp)b. Testcross: breeding the mystery individual with a homozygous recessive (pp) individualc. If any offspring display the recessive phenotype, the mystery parent must be heterozygousd. Types of Crossesi. Test cross- tell you the genotype of a dominant trait1. PP x pp or Pp x ppii. Monohybrid cross- cross 2 heterozygous individuals for one trait1. Pp x Ppiii. Dihybrid cross- cross 2 heterozygous individuals for two traits1. PpYy x PpYye. Monohybrid Crossi. Monohybrid- individuals that are heterozygous for one characterii. A cross between heterozygotes is called a monohybrid cross1. (crossing F1 generation)f. Dihybridsi. Crossing two, true-breeding parents differing in two characters producesdihybrids in the F1 generationii. Heterozygous for both charactersg. Dihybrid Cross- examining 2 traitsi. Cross between F1 dihybrids, determines whether two genes are transmitted to offspring as a package (linked) or independentlyii. Linked- on same chromosomeh. Predictionsi. Dependent (linked, inherited together)- F1 will only produce YR and yr1. Phenotypic ratio of 3:1ii. Independent (inherited separately)- F1 will produce YR, Yr, yR, yr1. Phenotypic ratio of 9:3:3:12. Genes are packaged into gametes in all possible combinations- as long as each