INHERITANCE Chapter 6 Early Idea of Heredity Blending Theory of Inheritance Parents traits mixed in offspring Gregor Mendel Called the father of genetics Pea plant study Tall vs. short Gregor Mendels Bio https://www.youtube.com/watch?v=QmSJ GhPTB5Ehttps://www.youtube.com/watch?v=QmSJ GhPTB5E Mendel & Geneticss/notes_mendel.htmlhttp://www.biologycorner.com/bio2/genetic s/notes_mendel.html Ppt of Mendel and his pea experiments (This is where the Mendel rap is.) Mendels Results Mated tall plant with short plant Produced only tall plants Mendel Tries Again Self-fertilized the offspring Tall and Short plants produced Mendel Figures it Out! Parents pass on alleles that remain separate No blending! Particulate Theory of Inheritance Mendels Peaspea-plants-helped-us-understand- genetics-hortensia-jimenez-diaz Genes vs. Alleles Gene Height Allele: different forms of a gene Tall Short Types of Alleles Dominant Allele: capital letter Dominant Trait: phenotype with at least one dominant allele (TT or Tt) Recessive Allele: lowercase letter Recessive Trait: phenotype with both recessive alleles (tt) Genotype Genetic makeup Represented by letters (alleles) 2 alleles = Genotype of one trait (one allele from each parent) Ex: TT, Tt, tt Homozygous: genotype if alleles are the same TT, tt BB,bb Heterozygous: genotype if alleles are different Tt Bb Phenotype Appearance Determined by genotype Ex: tall, short brown eyes, blue eyes Practice Questions 1.If having a widows peak is dominant, what will be the phenotype of a person with the genotype Dd? 2.If not having a cleft chin is dominant, what is the phenotype of a person with genotype aa? 3.Curly hair is dominant. What could be the following persons genotype? HH Hh Principle of Segregation Alleles separate during meiosis when homologous chromosomes are divided among gametes Probability in Genetics Probability: predicts chances that certain events will occur Used to predict offspring traits Inheritance of Alleles Monohybrid Cross: cross organisms that differ in one trait Punnett Squares TT x tt TT t t 100% Tt = tall Tt Tt x Tt 25% TT = Tall 50% Tt = Tall 25% tt = Short 75% Tall, 25% Short Tt T t TTTt ttTt Monohybrid Cross Problem #1 A yellow flowered plant (Yy) is crossed with a white flowered plant (yy). What are the genotypes and phenotypes of the offspring? Yy y y Yy yy Yyyy 50% Yy 50% yy 50% yellow 50% white Monohybrid Cross and Punnett Squares https://www.youtube.com/watch?v=i-0rSv6oxSY&safe=active Dihybrid Cross Cross between two traits Pea shape and pea color Dihybrid Cross RRYY x rryy Step 1: Find all gamete combinations Parent 1 gametes: RY, RY, RY, RY Parent 2 gametes: ry, ry, ry, ry R=round and Y=yellow Dihybrid Cross RY ry RrYy Phenotypes 16 Round and yellow RrYy x RrYy Parent 1 (RrYy) RY, Ry, rY, ry Parent 2 (RrYy) RY, Ry, rY, ry R=round r= wrinkled Y=yellow y=green Dihybrid Cross RYRyrYry RY Ry rY ry RRYYRRYyRrYYRrYy RRYyRRyyRrYyRryy RrYYRrYyrrYY rrYy RrYyRryyrrYy rryy Phenotypes 9 round and yellow 3 round and green 3 wrinkled and yellow 1 wrinkled and green Dihybrid Cross Practice Questions What are the gamete combinations for the genotype RrTT? RT,RT,rT,rT What are the gamete combinations for the genotype rrTt? rT,rt,rT,rt What are the gamete combinations for the genotype RrTt? RT,Rt,rT,rt https://www.youtube.com/watch?v=qIGXTJLrLf8 Dihybrid Cross Principle of Independent Assortment The principle of independent assortment states that genes for different traits can segregate independently during the formation of gametes During meiosis, alleles divide independently of alleles for other characteristics Sex Determination Sex chromosomes: X and Y Females = XX Eggs all have X Males = XY Half of sperm have X, half have Y Polygenic Traits Traits determined by more than one gene Height Skin Color Hair Color Eye Color EYE COLOR https://www.youtube.com/watch?v=MjBZa ed9yzM Multiple Alleles Genes with more than 2 alleles Ex: Blood type I= makes enzyme that adds A/B to blood cell i= does not make enzyme I A I A or I A i = type A I B I B or I B i = type B I A I B = type AB ii= type O Practice Problem If a man with the genotype ii marries a woman who is I A i, what are the genotypes and phenotypes of their offspring? Codominance Both alleles are fully expressed Ex: Blood Type I A I B = AB blood Incomplete Dominance No dominant or recessive alleles Both alleles are partially expressed Incomplete dominance Red flowered snapdragon crossed with White flowered snapdragon produces Pink flowers Incomplete Dominance Problem Among certain flowers the allele for red flowers (R) is incompletely dominant to the allele for white flowers (r). What would be the genotypes and phenotypes of the offspring between two pink flowers? X-Linked Traits Trait whose gene is carried only on X chromosome Expressed in males more often Nondisjunction Nondisjunction: Failure of paired chromosomes to separate (to disjoin) during cell division, so that both chromosomes go to one daughter cell and none go to the other. Nondisjunction causes errors in chromosome number, such as trisomy 21 (Down syndrome) and monosomy X (Turner syndrome). It is also a common cause of early spontaneous abortions. Turners Syndrome XO Klinefelters Syndrome Detection of Disorders: Pedigree Pedigrees Family tree showing genetic traits Shows genotypes and phenotypes of each family member Squares = males Circles = females Solid colored = have trait Horizontal lines = marriage Vertical lines = offspring Sample Pedigree #1 Autosomal recessive (not X-linked) aa Aa aa Aa Aa/ AA Sample Pedigree #2 X-linked recessive XcYXcY XcYXcY XY XcXXcX XX X c X XcXXcX Great review PPTs for you!