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Yellow dots mark the locus of a specific gene on a homologous pair of human chromosomes The chromosomal basis for Mendel’s Laws Sex-linked inheritance Evidence for linked genes in Drosophila Page 9 #3 P: EETTBB X eettbb etb ETB EeTtBb F1 cross EeTtBb X EeTtBb F1p%: 100% Long ears, brown tails, and brown eyes F2p%: 56.25% Long, brown, brown 18.75% Long, brown, blue 18.75% short, cotton, brown 6.25% short, cotton, blue ETB ETb etB etb ETB EETTBB EETTBb EeTtBB EeTtBb ETb EETTBb EETTbb EeTtBb EeTtbb etB EeTtBB EeTtBb eettBB eettBb etb EeTtBb EeTtbb eettBb eettbb Page 9 #4 P: EEttbb X eeTT BB eTB Etb EeTtBb F1 cross EeTtBb X EeTtBb F1p%: 100% Long ears, brown tails, and brown eyes EtB Etb eTB eTb EtB EEttBB EEttBb EeTtBB EeTtBb F2p%: Etb 18.75% Long, cotton, brown eTB 37.5% Long, brown, brown 6.25% Long, cotton, blue eTb 12.5% Long, brown, blue 18.75% short, brown, brown 6.25% short brown, blue EEttBb EEttbb EeTtBb EeTtbb EeTtBB EeTtBb eeTTBB eeTTBb EeTtBb EeTtbb eeTTBb eeTTbb Production of recombinant gametes by a dihybrid female page 10 #1 636 Gray body, normal wings 253 Black body, vestigial wings 50 Gray body, vestigial wings 61 black body, normal wings Phenotypes %’s If linked Actual %’s Gray, normal 75% 63.6% 56.25% Gray, vestigial 5.0% 18.75% Black, normal 6.1% 18.75% 25.3% 6.25% Black, vestigial 25% Yes, 11.1 map units %’s If Not linked page 10 #2 364 Long ears, brown fur 122 short ears, white fur 6 Long ears, white fur 8 short ears, brown fur Phenotypes %’s If linked Actual %’s %’s If Not linked Long, brown 75% 72.8% 56.25% Long, white 1.2% 18.75% Short, brown 1.6% 18.75% 24.4% 6.25% Short, white 25% Yes, 2.8 map units Page 11 #4 P BBNN X bbnn F1 cross BbNn X BbNn bn BN BbNn F1p%: 100% brown eyes, normal wings F2p%: 75%-6%= 69% 4% 4% 25%-2%= 23% .75 x.08 0.06 .25 x.08 0.02 BN bn BN BBNN BbNn bn BbNn bbnn Brown eyes, normal wings Brown eyes, vestigial wings Red eyes, normal wings Red eyes, vestigial wings Page 11 #5 P llgg X LLGG F1 cross LlGg X LlGg LG lg LlGg F1p%: 100% Long proboscis, clear wings LG lg LG LLGG LlGg lg LlGg llgg F2p%: 75%-13.5%= 61.5% Long proboscis, clear wings 9% Long proboscis, gray wings 9 % Short proboscis, clear wings 25%-4.5%= 20.5% Short proboscis, gray wings .75 .25 x.18 x.18 0.135 0.045 Recombination frequencies can be used to construct a genetic map. A partial genetic map of a Drosophila chromosome Chromosomal systems of sex determination. In human males the SRY gene codes a protein that regulates genes that triggers the development of testes and many other maleness genes. The transmission of sex-linked recessive traits Sex-linked traits in humans include red-green color blindness hemophilia, and Duchenne muscular dystrophy X inactivation and the tortoiseshell cat. The tortoiseshell gene is on the X chromosome and the phenotype requires the present of both alleles (one on each X chromosome) The XIST gene on one X chromosome is active and codes RNA which coats that X chromosome which initiates the methylation of that X and causes it to condense and form a Barr body Meiotic nondisjunction Nondisjunction results in aneuploidy XO-Turner Syndrome only human monosomy that survives no Barr bodies/cell XXY-Klinefelter Syndrome one Barr body/cell XYY – Super male greater chance of violence XXX & XXXX – Super female greater chance of violence 2 or 3 Barr bodies/cell Trisomy 21-Down syndrome-can also be caused by translocation of part of chromosome 21 cri du chat-deletion of part of chromosome 5 CML-translocation of part of 22 to the tip of 9 A tetraploid mammal?? Prader-Willi syndrome when inherited from male Angelman syndrome when inherited from female Genomic Imprinting is accomplished by methylation of genes to turn them off “silence them” or areas near them to turn them on. Male imprinting is designed to produce a larger, stronger, fetus and female imprinting is designed to produce a smaller fetus. Genomic imprinting is an attempt by the male to produce larger, stronger offspring; the female imprints are an attempt to produce smaller less energy draining offspring fragile X syndrome-one section of the X hangs by a thin thread of noncoiled DNA which is composed of long sets of triplet repeats – CGG genomic imprinting by the mother is more likely to cause the syndrome Variegated leaves caused by extranuclear genes that are inherited from the ovum. Where did all your mitochondria come from?