1 --Biology 321 Spring 2013 Assignment Set #2 Sex Linkage, Sex Determination & Probability  Required Readings Assignments (on web site) Parthenogenesis in Komodo dragons: should males and females be kept together to avoid triggering virgin birth in these endangered reptiles? Nature 444: 1021-1022 Dec 21, 2006 This interesting paper reflects a number of key concepts & themes that we have already covered or will explore in upcoming lectures: • Basic Mendel and independently assorting gene loci: calculating genotype probabilities (in this case probability of homozygosity at all loci if progeny were produced by sexual reproduction • How to restore diploidy in the products of meiosis in the absence of a fertilization event • Variations on chromosomal sex determination: Z & W sex chromosomes • Using molecular techniques (DNA fingerprinting) to determine parentage of offspring in question – the microsatellite sites on the DNA that are examined behave in proper Mendelian fashion • Phenotypic plasticity and the role of genes and the environment in determining phenotype Required Reading and Problem Assignments in 10th edition of text Chapter 2 Read carefully pgs 50-65: Section 2.6 on Human Pedigree analysis Work Chapter 2 problems 10, 47, 57, 60, 61, 66, 77 (Note: pedigree problems will be assigned in Set 3) Chapter 3 Work problems 30 & 31 Required Reading and Problem Assignments in 9th edition of text http://fire.biol.wwu.edu/trent/trent/assignmentset2.9.pdf2 Set 2 Problems sorted by analytical and/or content type Using and understanding genetic terminology Text Chapters 2 & 3: most questions This problem set: most questions Assigning appropriate allele symbols Text Chapter 3: 30, 31 This problem set: 2, 5, 7, 8, & 10 Figuring out whether a trait is X-linked (standard XY) or autosomal: Text Chapter 2: 57 Text Chapter 3: 30, 31 This problem set: 1A, 4, 7 & 8 Figuring out dominance & interpreting crosses when sex determination mechanism is KNOWN (ie XX & XY vs ZZ & ZW): Text Chapter 2: 77 Text Chapter 3: 30, 31 This problem set: 1A, 1B, 2, 4, 7 , 8, 9 (Komodo dragon part C), Figuring out dominance & interpreting crosses when sex determination mechanism is UNKNOWN (ie XX & XY vs ZZ & ZW): This problem set: 3, 5 Using Mendel & Morgan (sex linked traits) to deduce parental (and progeny) genotypes from progeny phenotypic ratios  data set large so ratios more or less match predicted probabilities for each phenotypic/genotypic class Text Chapter 3: solved problem 1; 30, 31 This problem set: 1A, 3, 4, 7 & 8 Using Mendel & Morgan (sex linked traits) to predict progeny genotypes/phenotypes and ratios from parental genotypes/phenotypes Text Chapter 2: 60, 61, 66, 77 This problem set: 9 (Komodo dragon problem) Sorting through the complexities of real data or ambiguous data Text Chapter 2: 57, This problem set: 9 (Komodo dragon problem) Basic Probability Product and Sum rules Text Chapter 2: 47 (uses both rules), 66 This problem set: 6, 9 (Komodo dragon problem) Conditional probability (limiting the possible outcomes) This problem set: 63 This Table summarizes Chromosomal Sex-determining Mechanisms DON’T MEMORIZE IT. IF YOU NEED THIS INFORMATION FOR AN EXAM QUESTION I WILL GIVE IT TO YOU. I will assume though that you know the sex determination mechanism for mammals and fruitflies! Shaded cells = diploid animals Organism Female Male Comments • Mammals • Some amphibians and reptiles • Many insects such as the fruitfly Drosophila • Some plants with male and female sexes XX XY Males produce two different types of sperm: 50% carry an X chromosome and 50% a Y chromosome • Some insects (including spiders) • Some roundworms (such as Caenorhabditis elegans) XX XO Y chromosome is absent. Males have a single X chromosome and produce two different types of sperm: 50% bearing an X chromosome and 50% with no sex chromosome Pattern of sex linkage same as XX, XY species • Birds • Some insects (such as moths and butterflies) • Some amphibians and reptiles including the KOMODO dragon ZW ZZ By convention, Z and W are used to indicate the sex chromosomes in these species. The Z chromosome is equivalent to the X chromosome. Females produce two different types of eggs: 50% carry the Z chromosome and 50% carry the W chromosome. Bee, wasps and ants diploid haploid Males usually develop from unfertilized eggs; females from fertilized eggs There are no sex chromosomes per se4  Problem 1A Two phenotypically wild-type Drosophila (with long wings and red eyes) are crossed, and two mutant phenotypes (curved wings and lozenge eyes) are seen to segregate among the progeny as follows: Females Males 600 long-wing, red eyes 300 long wing, red eyes 200 curved wing, red eyes 300 long wing, lozenge eyes 100 curved wing, red eyes 100 curved wing, lozenge eyes (i). The curved wing mutation is: a. autosomal recessive b. autosomal dominant c. sex-linked recessive d. sex-linked dominant (ii). The lozenge eye mutation is: a. autosomal recessive b. autosomal dominant c. sex-linked recessive d. sex-linked dominant (iii). The female parent is: a. heterozygous for both genes b. heterozygous for the wing gene and homozygous for the eye gene c. homozygous for the wing gene and heterozygous for the eye gene d. none of the above (iv). The male parent is: a. hemizygous for both genes b. hemizygous for the wing gene and heterozygous for the eye gene c. heterozygous for both genes d. heterozygous for the wing gene and hemizygous for the dominant allele of the eye gene e. heterozygous for the wing gene and hemizygous for the recessive allele of the eye gene. Consult the notes on sex determination while you are working on these problems.  Problem 1B a. A female wasp of genotype aabb mates with a male wasp of genotype AB (where genes A and B are on different chromosomes). Predict the phenotype & genotypes of the male and female offspring. Useful info: • males produce sperm by cell division process that resembles mitosis (why?) • a mated female usually lays fertilized and unfertilized eggs in an unpredictable ratio b. Predict the outcome of the reciprocal cross (of that shown in part a) assuming the parents were from true-breeding strains. c. An AaBb female mates with a male wasp of