A Mendelian Worldview

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

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

Data of Mendel (1866) pea plant from green seed pea plant from yellow seed X All seeds yellow - Grow into plants and self fertilize First filial generation (F1) second filial generation (F2) Count # of green and yellow seeds: 8023 total seeds 6022 yellow 2001 green – grown into plants: self fertilization yields all green seeds 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)

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

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

What happens if two character traits are followed simultaneously? 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 wrinkled 2.96:1 2. Yellow X green seeds All yellow 6022 yellow; 2001 green 3.01:1 3. Purple X white petals All purple 705 purple; 224 white 3.15:1 4. Inflated X pinched pods All inflated 882 inflated; 299 pinched 2.95:1 5. Green X yellow pods All green 428 green; 152 yellow 2.82:1 6. Axial X terminal flowers All axial 651 axial; 207 terminal 3.14: 1 7. Long X short stems All long 787 long; 277 short 2.84: 1 What happens if two character traits are followed simultaneously?

Fig. 13.16

Second Law=The Law of Independent Assortment: 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.

Each trait is governed by 2 particles*, one inherited from each 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). 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). Mendel’s 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.

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

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

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

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

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

Fig. 13.16

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

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

Eye Color Is a Sex-Linked Trait in Drosophila female male female male Figures\Chapter10\High-Res\life7e-fig-10-23-0.jpg females males females males

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

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

Barbara McClintock

Chiasmata are the sites of crossing over Figure 4-4

Chiasmata visible in Locusta migratoria spermatogenesis A synaptonemal complex

crossveinless defines a new family of Twisted-gastrulation-like modulators of bone morphogenetic protein signalling Peter Vilmos, Rui Sousa-Neves, Tamas Lukacsovich & J Lawrence Marsh

double recombination ct+

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+ 580 40% NR v+ . cv . ct 592 41% NR v .. cv . ct+ 45 3% v,cv ; cv,ct v+ . cv+ . ct 40 3% v,cv ; cv,ct v .. cv . ct 89 6% v,cv ; v,ct v+ . cv+ . ct+ 94 6% v,cv ; v,ct v ..cv+ . ct 3 0.2% v,ct ; cv,ct v+ . cv . ct+ 5 0.3% v,ct ; cv,ct

Phenotype # of progeny(T=1448) % of progeny recombinant v ..cv+ . ct+ 580 ~40% NR v+ . cv . ct 592 ~41% NR v .. cv . ct+ 45 ~3% v,cv ; cv,ct v+ . cv+ . ct 40 ~3% v,cv ; cv,ct v .. cv . ct 89 ~6% v,cv ; v,ct v+ . cv+ . ct+ 94 ~6% v,cv ; v,ct v ..cv+ . ct 3 ~0.2% v,ct ; cv,ct v+ . cv . ct+ 5 ~0.3% v,ct ; cv,ct v,cv recombinants: 45 + 40 + 89 + 94 = 268 = 18.5% v,ct recombinants: 89 + 94 + 3 + 5 = 191 = 13.2% ct,cv recombinants: 45 + 40 + 3 + 5 = 93 = 6.4% Aha! The genes must all be on the same chromosome! (RF’s < 50%) v ct cv 13.2 m.u. 6.4 m.u. 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.)?

phenotype # of progeny % of progeny recombinant v ..cv+ . ct+ 580 ~40% NR v+ . cv . ct 592 ~41% NR v .. cv . ct+ 45 ~3% v,cv ; cv,ct v+ . cv+ . ct 40 ~3% v,cv ; cv,ct v .. cv . ct 89 ~6% v,cv ; v,ct v+ . cv+ . ct+ 94 ~6% v,cv ; v,ct v ..cv+ . ct 3 ~0.2% v,ct ; cv,ct ; v,cv !! v+ . cv . ct+ 5 ~0.3% v,ct ; cv,ct ; v,cv !! Aha! – we now realize the smallest classes of recombinants as doubles! v,cv recombinants: 45 + 40 + 89 + 94 + 2(3+5) = 284 = 19.6% v,ct recombinants: 89 + 94 + 3 + 5 = 191 = 13.2% ct,cv recombinants: 45 + 40 + 3 + 5 = 93 = 6.4% v ct cv 13.2 m.u. 6.4 m.u. Hmmm…What is the expected # of double recombinants? A: 0.132 * 0.064 = .0084 .0084 * 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

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

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.

 New Genes Identified on the Human Y Chromosome  Testis Determining Factor (SRY) Channel Flipping (FLP) Catching and Throwing (BLZ-1) Self Confidence (BLZ-2) - (note: unlinked to ability) Preadolescent fascination with Arachinida and Reptilia (MOM-4U) Addiction to Death and Destruction Films (T2) 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)

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

Pseudoachondroplasia phenotype Figure 2-30