8 Color Blindness Xb = No color blindness XB = color blindness Determine the crosses (both phenotype and genotype) for the following crossesColor blind father x normal mother yields one color blind son.Normal father, carrier mother.Normal father, color blind mother.What cross will yield a color blind daughter?
9 Sex Linked Traits Called hemizygous Do occur in females but males have a higher probability of inheriting the traitDuchenne muscular dystrophy, hemophilia, color blindness
10 X Inactivation in Females Having two X chromosomes is a lot of genes!One X chromosome will be turned offBarr body: X chromosome condenses and will be near the nuclear envelopeOvaries – Barr body will be duplicated for viable egg cellsIn development, different X chromosomes could be turned offAbout ½ of the cells display the mother’s traits and half display the father’s
12 Linked GenesGenes on the same chromosome that tend to be inherited togetherMorgan believed body color and wing shape were inherited together
13 Genetic Recombination Recombinant: Offspring show combinations of traits not found in the parentsHow does this happen?
14 Recombinants Mendel’s peas YyRr x yyrr Complete the punnett square for the above cross.Which genotype and phenotypes are recombinants? Which are parental types?
15 Crossing Over During Meiosis I (Prophase I) Homologous chromosome pairs come together forming a tetradCrossing overEach chromosome will cross with the other in the pairParts of the chromosome will be exchanged
16 Recombination Frequency How likely is it that the two genes will be linked?Based on how close they are on the chromosomeCloser they are, more likely they will be linkedLinkage map: genetic map based on recombination frequency
17 Linkage Mapping Problem Mating: AaBb x aabb A = Long antennaea = Short antennaeB = Green eyebrows, andb = Blue eyebrows.Say you make this mating, and your actual results look like this: Long Green - 850Long Blue - 150Short Green - 150Short Blue - 850
18 Calculate Linkage Map Distance One linkage map unit (LMU) is 1% recombination. Thus, the linkage map distance between two genes is the percentage recombination between those genes.In this case, we have a total of 300 recombinant offspring, out of 2000 total offspring. Map distance is calculated as (# Recombinants)/(Total offspring) X 100.What is the LMU of the two genes?
19 Linkage Map Summary How can you recognize when genes are linked? How do you calculate linkage map distance?What does the linkage map distance tell you?How does a linkage map relate to independent assortment of genes?
21 Dihybrid CrossIn summer squash, white fruit color (W) is dominant over yellow fruit color (w) and disk-shaped fruit (D) is dominant over sphere-shaped fruit (d). If a squash plant true-breeding for white, disk-shaped fruit is crossed with a plant true-breeding for yellow, sphere-shaped fruit, what will the phenotypic and genotypic ratios be for the F1 generation and the F2 generation?
24 Summary of Dihybrid Cross White color (W) is dominant over yellow fruit color (w) and disk-shaped fruit (D) is dominant over sphere-shaped fruit (d)
25 Chi Square (X2) TestDetermines statistical significance of a set of dataUse in genetics: if genes sort INDEPENDENTLY they will follow the expected ratios of domintant : recessiveIf not, they will not follow expected ratios and we would reject the null hypothesis
26 Chi Square Set Up Phenotype Genotype #observed #expected (o-e)(o-e)2(o-e)2 / e
27 Exit TicketBaby chicks are pecking at grains of cracked corn of different colors. A researcher is attempting to determine if they have a preference for one color over another. He counts the number of grains chosen in an arena that has equal numbers of red, blue, green and yellow corn chunks. Here are his results:red: 250blue: 220green 230yellow 240Perform a Chi Square analysis on these results. Can he reject the null hypothesis of no preference? Explain your answer.
28 Monohybrid Cross Practice Problem A student makes a monohybrid cross with Drosophila. She crosses two heterozygotes for the white eye. Ww x Ww. She expects to see a 3:1 phenotypic ratio of Red eyes (WW and Ww) to white eyes (ww), her null hypothesis. She rears the next generation through to adult flies and counts the following numbers:White eyes 210Wild type 680What change occurs in the allelic frequencies between generations 1 and 2? Perform a chi square analysis on these results and find out if it is close enough to 3:1 to fail to reject her null hypothesis. Make sure to show all work and explain your conclusions.
29 Dihybrid Chi Square Problem In the garden pea, yellow cotyledon color is dominant to green, and inflated pod shape is dominant to the constricted form. Considering both of these traits jointly in self-fertilized dihybrids, the progeny appeared in the following numbers:193 green, inflated184 yellow constricted556 yellow, inflated61 green, constrictedDo these genes assort independently? Support your answer using Chi-square analysis.
30 15.4 Alterations of chromosome number or structure cause some genetic disorders
31 Abnormal Chromosome Number Nondisjunction: chromosomes do not separate correctlyMeiosis I or II
32 AneuploidyGamete with abnormal number of chromosomes unites with a normal gameteOffspring will have abnormal number of chromosomesMonosomic (2n – 1); Trisomic (2n + 1)Change in number of copies of chromosomes – only changes the chromosome number by 1Polyploidy: triploidy (3n), tetraploidy (4n)Extra copies of COMPLETE sets of chromosomesWill cause chromosome numbers to be doubled or halved
33 Chromosomal Mutations Involve changes in the number or structure of chromosomes4 types:DeletionDuplicationInversionTranslocation
34 Deletion and Duplication Loss of all or part of a chromosomeDuplication:Produce extra copies of the chromosome
35 Inversion and Translocation Reverse direction of parts of the chromosomeTranslocation:Part of one chromosome breaks off and attaches to another chromosome
36 Human Disorders caused by Chromosomal Alterations Turner SyndromeDown syndromeCri du chatPrader-Willi SyndromeHuntington’s DiseaseAngelman Syndrome
37 Inheritance PatternsNot all fall into set patterns of equal inheritanceGenomic ImprintingEffect of the allele for a certain trait depends on which parent passed on the traitCould be expressed in different strengths
38 Organelle Genes Extranuclear genes (found in cytoplasm) Mitochondrial genesChloroplast genesNOT distributed to the offspring in the Mendelian fashionCome from mother – why?
39 Mitochondrial Genes Most make up the ETC and ATP synthase Defects in these genes will affect energy productionMost severely nervous system and muscular system
40 Review Topics Genetics and probability Alleles and allele frequency Observes and expected phenotypesSex linked traits (hemizygous) / Linked genesRecombination (frequency of recombination = probability of recombination)Chi square analysisTypes of chromosomal mutationsGenomic Imprinting (1)
41 Kleinfelter Syndrome 47 chromosomes XXY Male sex organs - small testes, sterileFeminine body characteristicsTaller than averageNo mental disability