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Molecular Biology. 2 Genetics = Information Flow Transmission Genetics = Classical Genetics = information flow between generations Molecular Biology =

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Presentation on theme: "Molecular Biology. 2 Genetics = Information Flow Transmission Genetics = Classical Genetics = information flow between generations Molecular Biology ="— Presentation transcript:

1 Molecular Biology

2 2 Genetics = Information Flow Transmission Genetics = Classical Genetics = information flow between generations Molecular Biology = Molecular Genetics = information flow within cells/organisms DNA RNA Protein = THE CENTRAL DOGMA

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4 pea plant from green seed Data of Goss (1824) X pea plant from yellow seed All seeds yellow – grow and self fertilize Some pods with all yellow seeds – grow into plants and self fertilize Some pods with all seeds yellow, some with green and yellow seeds Some pods with all green seeds Many pods with both yellow and green seeds Self fertilization of plants grown from green All progeny plants Have pods with green seeds only

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6 6 Data of Mendel (1866) pea plant from green seed X pea plant from yellow seed All seeds yellow - Grow into plants and self fertilize (F1) First filial generation Count # of green and yellow seeds: total seeds yellow green – grown into plants: self fertilization yields all green seeds (F2)second filial generation Take 519 yellow seeds – grown into plants: self fertilization Of these 519 plants, 166 bred true (all yellow seeds), 353 did not (mixed yellow and green seeds)

7 7 Mendel s model True breeding yellow AA True breeding green aa egg cells pollen cells x fertilize Aa (yellow seeds) – grow into plants and self fertilize F1 F2 AAAa aAaa (pollen) (eggs) A A a a 3:1 yellow:green __________________ ¼ true breeding yellow ½ impure yellow ¼ true breeding green a A

8 8 Mendel s First Law Each trait is governed by 2 particles*, one inherited from each parent. These two particles do not influence each other in any way within an individual, but separate, uncontaminated in any way, into gametes at the time of reproductive cell Formation. (an unstated corollary is that any pollen cell can fertilize any egg cell = random fertilization). Testing the law: - the test cross (Aa x aa) predicts new ratios - other traits tested *Introduce modern terms: dominant, recessive, alleles, phenotype, genotype, heterozygote, homozygote

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13 13 Results of all Mendel's crosses in which parents differed for one character Parental phenotype F1 F2 F2 ratio 1. Round X wrinkled seeds All round 5474 round; 1850 wrinkled2.96:1 2. Yellow X green seeds All yellow 6022 yellow; 2001 green 3.01:1 3. Purple X white petals All purple 705 purple; 224 white3.15:1 4. Inflated X pinched pods All inflated 882 inflated; 299 pinched2.95:1 5. Green X yellow pods All green 428 green; 152 yellow2.82:1 6. Axial X terminal flowers All axial 651 axial; 207 terminal3.14: 1 7. Long X short stems All long 787 long; 277 short2.84: 1 What happens if two character traits are followed simultaneously?

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16 16 Mendel s Second Law Second Law=The Law of Independent Assortment: During the formation of gametes, the segregation of alleles at one locus is independent of that of the segregation of alleles at any other.

17 17 Mendels Second Law The Law of Independent Assortment: During the formation of gametes, the segregation of alleles at one locus is independent of that of the segregation of alleles at any other. Each trait is governed by 2 particles*, one inherited from each parent. These two particles do not influence each other in any way within an individual, but separate, uncontaminated in any way, into gametes at the time of reproductive cell Formation. (an unstated corollary is that any pollen cell can fertilize any egg cell = random fertilization). Each trait is governed by 2 particles*, one inherited from each parent. These two particles do not influence each other in any way within an individual, but separate, uncontaminated in any way, into gametes at the time of reproductive cell Formation. (an unstated corollary is that any pollen cell can fertilize any egg cell = random fertilization). Mendels First Law

18 18 Genes (alleles) eye view of meiosis and mitosis A / a

19 A a A a A a chromosome (DNA) replication during S phase prior to mitosis

20 A a A a A a A a A a mitotic metaphase anaphase, telophase, cytokinesis

21 A a A a A a b b B B B b a a b b A A B B genotype: Aa; Bb Meiosis I metaphase Meiosis I product cells replication Meiosis I anaphase, telophase, cytokinesis

22 a a b b A AB B Meiosis I product cells A B A B a b a b Meiosis II product cells Meiosis II anaphase, telophase, cytokinesis Meiosis II metaphase AB ab

23 a a b b A A B B Meiosis I product cells A B A a a b Meiosis II products cells Meiosis II anaphase, telophase, cytokinesis Meiosis II metaphase b B Ab aB

24 Figure 2-30 Pseudoachondroplasia phenotype

25 Figure 2-26 Red-eyed and white-eyed Drosophila

26 26 Eye Color Is a Sex-Linked Trait in Drosophila female male female male females males females males

27 white-eyed, normal-winged female x red-eyed, miniature winged male (wild type) w + mw m + w + m wild type females w m + white-eyed, normal-winged males x w m + ½ red-eyed, miniature winged for male progeny, EXPECT: w + m ½ white-eyed, normal-winged 64% of males fell into above classes, but 36% were either wild type Or doubly mutant !!!!!!!

28 w m + w + m wild type females genetic recombination = chromosomal crossing over 36% of chromosomes in meiosis I: w m + white-eyed, normal-winged males x w + m + w m 36% of males are either doubly mutant or wild type :

29 Figure 4-4 Chiasmata are the sites of crossing over

30 Chiasmata visible in Locusta migratoria spermatogenesis A synaptonemal complex

31 Chapter 4 Opener A recombination-based map of one of the chromosomes of Drosophila

32 vermillion (v + = red eyes, v = vermillion eyes) crossveinless (cv + = normal wing veins, cv = missing crossveins) cut (c + = normal wing margins, c = snipped wing margins) v +. cv. ct x v. cv +. ct + v + /v. cv/cv +. ct/ct + x v/v. cv/cv. ct/ct (three point testcross) phenotype# of progeny% of progeny recombinant v.. cv +. ct %NR v +. cv. ct59241%NR v.. cv. ct + 453%v,cv ; cv,ct v +. cv +. ct403%v,cv ; cv,ct v.. cv. ct896%v,cv ; v,ct v +. cv +. ct + 946%v,cv ; v,ct v.. cv +. ct30.2%v,ct ; cv,ct v +. cv. ct %v,ct ; cv,ct

33 Phenotype # of progeny(T=1448)% of progeny recombinant v.. cv +. ct + 580~40%NR v +. cv. ct592~41%NR v.. cv. ct + 45~3%v,cv ; cv,ct v +. cv +. ct40~3%v,cv ; cv,ct v.. cv. ct89~6%v,cv ; v,ct v +. cv +. ct + 94~6%v,cv ; v,ct v.. cv +. ct3~0.2%v,ct ; cv,ct v +. cv. ct + 5~0.3%v,ct ; cv,ct v,cv recombinants: = 268 = 18.5% v,ct recombinants: = 191 = 13.2% ct,cv recombinants: = 93 = 6.4% Aha! The genes must all be on the same chromosome! (RF s < 50%) Hmmm…why is the measured distance between v,cv (18.5m.u.) less than the sum of the measured v,ct (13.2 m.u.) and ct,cv (6.4 m.u) distances(=19.6 m.u.)? vctcv 13.2 m.u.6.4 m.u.

34 double recombination

35 Hmmm…What is the expected # of double recombinants? A: * = * 1448 = 12 expected double recombinants But… we got only 8 (3+5) Why? A: Interference! I = 1 - coefficient of coincidence (coc = o/e) = 0.33 vctcv 13.2 m.u.6.4 m.u. phenotype# of progeny% of progeny recombinant v.. cv +. ct + 580~40%NR v +. cv. ct592~41%NR v.. cv. ct + 45~3%v,cv ; cv,ct v +. cv +. ct40~3%v,cv ; cv,ct v.. cv. ct89~6%v,cv ; v,ct v +. cv +. ct + 94~6%v,cv ; v,ct v.. cv +. ct3~0.2%v,ct ; cv,ct ; v,cv !! v +. cv. ct + 5~0.3%v,ct ; cv,ct ; v,cv !! v,cv recombinants: (3+5) = 284 = 19.6% v,ct recombinants: = 191 = 13.2% ct,cv recombinants: = 93 = 6.4% Aha! – we now realize the smallest classes of recombinants as doubles!

36 36 Genetic Mapping Mapping genes in humans involves determining the recombination frequency between a gene and an anonymous marker Anonymous markers such as single nucleotide polymorphisms (SNPs) can be detected by molecular techniques.

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38 Testis Determining Factor (SRY) Channel Flipping (FLP) Catching and Throwing (BLZ-1) Self Confidence (BLZ-2) - (note: unlinked to ability) Addiction to Death and Destruction Films (T2) Preadolescent fascination with Arachinida and Reptilia (MOM-4U) Sitting on John Reading (SIT) Selective Hearing Loss (HUH?) Lack of Recall for Important Dates (OOPS) Inability to Express Affection Over the Phone (ME-2) Spitting (P2E) New Genes Identified on the Human Y Chromosome

39 39 effects of recombination on chromosomes within a family siblings inherit different chromosome regions from their parents grandson inherits chromosome regions from all four of his grandparents chromosomes

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