Reading on sex pp85 88 In many species Review session Th Apr 5 7 9 pm location to be determined midterm M Apr 9 pp109 110 review Analysis of rare mistakes pp516 518 Changes in chrom to Some euploid Table 14 2 p526 pp664 665 RNA splicing helps regulate gene expression pp669 676 except 670 71 Sex determination in Drosophila site of mitotic recombination DNA breaks and improper repair after S phase generate the twin spot of cells homozygous for y and sn y sn y sn m y sn p y sny sn y sn m m mistake p p y sn y sny sn y snGrowth p p y sn y sn m y y yellow patch clone of sn sn singed y sny sn m patch clone of ADULT EXTERIOR m m m m p appearance of an ABNORMAL homozygous yellow patch next to homozygous singed patch would SIGNAL that the female carried a new mutant allele y m sn y m sn y m sn m y m sny m sn p m m mistake p p y m sn m m y m sn m sn p y m sn p m m mm m d e f a b c d e f a b c d e f a b c d e f daughter cells Twin spot Will we see a true twin spot phenotype in this case a b c d e f a b c d e f The inferred abnormal growth behavior of cells in the homozygous yellow patch located next to normal homozygous singed patch would SIGNAL that fact that MOST OF THE CELLS OF THAT F1 FEMALE including her germ cells were heterozygous for a new mutant allele affecting cell growth perhaps even embryonic lethal killing long before adult stage p if a significant fraction of her cells had been homozygous for it zygote F1 female odd patch of y y yellow patch of sn sn singed c and such a female would be fully viable even if the new recessive mutant allele would have been lethal m y b p What if we had induced a NEW recessive MUTATION on a mutagenized y sn chromosome in the father s sperm that affected cell growth parameters y m sn a y m sn y m sn y m sn y m sn odd patch of y y yellow m patch of sn sn singed p m mm p m m ADULT EXTERIOR including germ cells hence avoids complications of pleiotropy lethal either because of a defect in the same function affecting adult cuticle or because of a defect in some other process 1 Problems limit use for genetic screens mitotic recombination infrequent position of exchange not controlled radiation used to induce is damaging tissues in which occurs are not controlled Solution induce using site specific yeast recombination system FRT site y sn y sn m p y sn y sn m m y sn y sn y sny sn p p y sn y sn source of FLPase targeted mistake but only induced when where FLPase induced twin spot yellow FLP recombinase protein that catalyzes recombination at FRTs FRT DNA target 34 bp site for recombinase singed e g eye precursor cells lats lats clone in eye l 3 93B l 3 93B clone in eye of lats adult of l 3 93B adult large tumor suppressor 3rd instar larvae left wildtype right lats lats m m m p p y sn y sn m y sny sn m p p homozygous lats clone on thorax of lats adult fly doomed Xu et al Develop 121 1053 1995 Xu et al Develop 121 1053 1995 Genetic mosaics have zillions of uses besides just facilitating mutant isolation and geneticists have ways of controlling exactly when and where FLPase is generated and hence exactly when and where mitotic recombination is induced Sex education from a genetical perspective 2 Forces in evolution and evolution is what genetics and life is really all about 1 Natural selection reproduction of the fittest human brain peacock tail remember responses to changes in biological environment including parasites are as important as responses to changes in physical environment this term is in your glossary 2 Sexual selection reproduction of the sexiest but a tail with the capacity to change the way life evolves this term is NOT in your glossary runaway sexual selection generally leads to maladaptive sexually selected traits Sex Sexual reproduction vs Asexual reproduction symmetrical sex us Coming together of genetic material from two individuals to form progeny that combine genes from all both parents asymmetrical sex equal genetic contribution from each partner qualitative exceptions mitochondria Y chromosome unequal genetic contribution from each partner bacteria Recall Can there be sex without gender males females Sex Sexual reproduction vs Asexual reproduction Coming together of genetic material from two individuals to form progeny that combine genes from all both parents 3 GAMETES sex cells Sex is ancient and ubiquitous Isogamous sex systems gametes from each parent are of equal size Nevertheless bdelloid rotifers no sex for millions of years Evidence Anisogamous sex systems gametes from each parent are of different sizes Males sperm pollen smaller no meiosis genes are missing unusual distribution of DNA variation suggests no gene mixing for ages Females eggs ovules larger parents have to be separate to qualify 4
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