Important piece of information for Monday:

1. Important piece of information for Monday: Testing site: Last names beginning A-L: 101 Barker Last names beginning M-Z: 240 Mulford

2. (1) Deletion mapping of genes (Benzer) using the segregational test for allelism: Can you recover a wildtype allele from the mutant hybrid? (a recombination test) If youcan, the point mutant is outside the region deleted. (2) Deletion mapping of genes (Bridges) using the functional test for allelism: Is the mutant hybrid phenotype wildtype? (a complementation test) If itis, the point mutant is outside the region deleted.

3. w- rst- fa- Df(1)256-45) phenotype Bulge in the synapsed polytene chromosomes shows what is deleted. Fig. 14.8 Deletion mapping based on a complementation test = w- (mutant) phenotype (failure to complement) hence white is within region deleted.

4. Inversion breakpoints bw+In(3R)bw- Inversionsalso have helped locate genes on theDrosophila polytene chromosome map viacomplementation tests …cause loss of ability to complement bw- may knock out bw+ In(3R)bw-/bw- = brown eye phenotype

5. The complementation test as an operational definition of the gene is not quite as straightforward as it may sound. genes can have very complex complementation patterns because of all the various kinds of information they contain that work only in cis (and all the various ways in which that information can be changed by mutation)

6. p227 Heading: “rII regon has two genes” From your text: Is this statement compatible with the statement that complementation groups are what we want to call genes? (starting bottom of p291): A gene is not simply the DNA that is transcribed into the mRNA codons specifying the amino acids of a particular polypeptide. Rather, a gene is all the DNA sequences needed (IN CIS) for expression of the gene into a polypeptide product.A gene therefore includes the promoter sequences that govern where transcription begins and, at the opposite end, signals for the termination of transcription. A gene also includes sequences dictating where translation starts and stops. In addition to all these features, eukaryotic genes contain introns that are spliced out of the primary transcript to make the mature mRNA. Because of introns, most eukaryotic genes are much larger than prokaryotic genes. So promoters are part of genes. Are promoter mutations part of complementation groups? How about intron mutations?

7. A bacterial promoter (cis-acting information for transcription start) 51 bp transcript---> Fig. 8.12

8. the fine-structure map of rIIA & rIIB generated by recombination between mutants in the same genes (as complementation groups)? 1,612 INDEPENDENT mutants mapped for Fig. 7.21 (and ultimately >3000) B -- A

9. There are 12 bp between rIIA & rIIB “genes” (T4 has 168,903 total bp) …hence no room for a standard promoter

10. rII makes a polycistronic mRNA rII-A rII-B P

11. classic example of polycistronic mRNA Figure 17.5: The Lactose Operon in E. coli

12. 7 23 rIIA&B mutants in the promotor for a polycistronic mRNA rII “complementation map” of point mutants (a very different kind of “map”) rII-B 2 65 87 99 rII-A 3 5 66 71 three complementation groups? No, one complex complementation group (one “gene”) provided 7 and 23 don't meiotically map as large deletions

13. Alternative pre-mRNA splicing is what allows Drosophila DSCAM gene to make 30,000 different proteins 6 vs. 7-8 alternative exons introns exons Fig. 8.18 Eukaryotic genes are even messier: …and the regulatory regions (non-protein-coding) can extend enormous distances on both sides

14. (NATURE 184:1927-29, 1959)

15. largest class (r+encodes a single polypeptide with three sequential enzymatic activities required for purine biosynthesis)

16. These are the mutants that argue for one gene with a complex complementation pattern (14/31)

17. This “map” of rudamentary alleles does not imply anything about where the various mutations might lie on a meiotic map. It is simply a schematic representation of a collection of data from a series of complementation tests designed to determine functional allelism

18. did they complement (Y or N)? a -/b -: Let’s consider three r mutant alleles: Yes they don’t overlap on the map …and the hybrid fly looked: wildtype

19. did they complement (Y or N)? a -/h -: No they do overlap on the map

20. z3 / a z3 / h z3 / i Consider a new r mutant allele, rz3 Which heteroallelic combination (hybrid) is mostlikely to have a mutant phenotype? z3 / i Which heteroallelic combination is most likely to generate a wildtype allele during meiosis? ? no basis for a determination

21. …and i is the most frequent class This “map” tells us next to nothing about the possible molecular basis for the complex complementation pattern …but so long as we have reason to believe that group i contains at least some point mutants, all the mutants on this “map” are likely to be in the same(thing that we want to call a)gene.

22. Central Dogma: information flow N.A. Protein Mutations (changes in DNA): the lifeblood of genetic analysis (1) What kinds can we make? (categories) (2) How do we make them? (mutagenesis) (3) How do we find them? (mutant screens & selections) (4) Why bother? ?

23. the return of the fly An older Benzer: (1967-2007) fruit fly (D.melanogaster) as his genetic workhorse The young S. Benzer: (1950s) phage T4 as his genetic workhorse (while fly work was in its "eclipse period") • founded many of the most • interesting areas of modern • behavioral genetics • (clocks & learning, etc.) • set up the experimental system most • effective for studying fly development: • the compound eye Benzer's question for the fly: how do genes encode complex nervous systems?

24. Can mutations affecting the fly eye tell us anything about our eyes? Fig. 20.10

25. hypomorphic or null mutations of the Pax-6 gen In a fetal mouse hypomorphic or null mutations of the eyeless gene in an adult fruit fly (homozygote would have died as an embryo) (humananiridia dominant “genetic disease”) Fig. 20.4

26. Induced “ectopic” expression of mouse Pax-6 gene product Fig. 20.10

27. Fig. 8.31, panel d: A neomorphicdominantmutation in the fly Antennapedia gene causes ectopic expression of a leg-determining gene in structures than normally produce antennae (actually its wildtype function is to force cells that would otherwise make an antenna to make a leg instead)

28. andabx Fig. 20.23 …but the most informative mutations may not be compatable with survival to the adult stage (a somewhat revolutionary idea, remarkably enough)

29. (ftz+) ftz amorph (null mutant) homozygote a fruit fly 9h after fertilization Fig. 20.2 tail head wildtype (it’s recessive lethal)

30. something Thomas Hunt Morgan never guessed (among other things): you can get a huge amount of phenotypic information out of the skin of a dead maggot by 16h after fertilization, even if doomed denticle belt pattern on the larval cuticle (cuticle: “skin,” tho. actually “skeleton”) (denticles: maggot tire treads) reveals where fly cells think they are in space Wieschaus and Nüsslein-Volhard, Nobel Prize 1995

31. Fig. 20.19 maximally informative mutant phenotypes for understanding metazoan pattern formation hunchback knirps Krüppel (ftz is in the “pair rule” family, not the “gap” family of mutant phenotypes) wildtype