1. A Mendelian Worldview

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

4. 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

6. 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)

7. 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

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

13. What happens if two character traits are followed simultaneously?
Results of all Mendel's crosses in which parents differed for one character
Parental phenotype F F F2 ratio
1 . Round X wrinkled seeds All round round; 1850 wrinkled 2.96:1
2. Yellow X green seeds All yellow yellow; 2001 green 3.01:1
3. Purple X white petals All purple purple; 224 white 3.15:1
4. Inflated X pinched pods All inflated inflated; 299 pinched 2.95:1
5. Green X yellow pods All green green; 152 yellow 2.82:1
6. Axial X terminal flowers All axial axial; 207 terminal 3.14: 1
7. Long X short stems All long long; 277 short 2.84: 1
What happens if two character traits are followed simultaneously?

14. Fig

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.

17. 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.

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

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

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

21. telophase, cytokinesis Meiosis I product cellsB 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

22. 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

23. Fig

24. 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

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

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

27. 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 !!!!!!!

28. 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

29. Barbara McClintock

30. Chiasmata are the sites of crossing over
Figure 4-4

31. Chiasmata visible in
Locusta migratoria
spermatogenesis
A synaptonemal complex

32. 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

33. double recombination
ct+

34. 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 . ct % NR
v .. cv . ct % v,cv ; cv,ct
v+ . cv+ . ct 40 3% v,cv ; cv,ct
v .. cv . ct % v,cv ; v,ct
v+ . cv+ . ct % v,cv ; v,ct
v ..cv+ . ct % v,ct ; cv,ct
v+ . cv . ct % v,ct ; cv,ct

35. Phenotype # of progeny(T=1448) % of progeny recombinant
v ..cv+ . ct ~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: = 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%)
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.)?

36. phenotype # of progeny % of progeny recombinant
v ..cv+ . ct ~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: (3+5) = 284 = 19.6%
v,ct recombinants: = 191 = 13.2%
ct,cv recombinants: = 93 = 6.4%
v ct cv
13.2 m.u.
6.4 m.u.
Hmmm…What is the expected # of double recombinants?
A: * = .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

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

38. 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.

40.  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)

41. 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

42. Pseudoachondroplasia phenotype
Figure 2-30