•Exam #3 W 12/5 at 7-8:30pmin ETC 2.108 for the 9am class and ECJ 1.202 for the noon class

•Review T 12/4 at 5pm in WRW 102

•Homework #4 due 12/3 (if needed)

•Bonus #2 is posted

Grades:

A = 88.5+

B = 77.5

C = 65.5

Exam avg x 0.88 + homework + bonus = grade

Tracking two separate genes, for two separate traits, each with two alleles.

Ratio of 9:3:3:1

Fig 3.4

Crossing-Crossing-overover

Meiosis I

Meiosis II

4 Haploid cells, each unique

Meiosis:In humans, crossing-over and independent assortment lead to over 1 trillion possible unique gametes.(1,000,000,000,000)

Box 2.2

(Ind. Assort.)(Ind. Assort.)

Crossing over produces new allelic combinations

Fig 4.3

Homologouspair of chromosomes

Fig 4.10

Longer regions have more crossovers and thus higher recombinant frequencies

Some crosses do not give the expected results

=25%

8%9%41%42%

These two genes are on the same chromosome

By comparing recombination frequencies, a linkage map can be constructed

= 17 m.u.

Another test

42 recombinants out of 381 offspring =

42/381

11% recombination

Fig 4.9

The probability of crossing over can be used to determine the spatial relationship of different genes

Double recombinants arise from two crossovers

Fig 4.11 Recombinant

Double recombinants can show gene order

Fig4.12

similar to pg 141

What is the relationship between these 3 genes? What order and how far apart?

similar to pg 141

What is the relationship between these 3 genes?What order and how far apart?

Double crossover

similar to pg 141

Which order produces the double crossover?

Which order produces the double crossover?

We have the order.What is the distance?

similar to pg 141

Recombinants between st and ss:

(50+52+5+3)/755=14.6%

similar to pg 141

Recombinants between ss and e:

(43+41+5+3)/755=12.2%

similar to pg 141

st ss e

14.6 m.u.

26.8 m.u.

12.2 m.u.

Put it all together…

Linkage map of Drosophila chromosome 2

Fig 4.13 and 20

Yeast chromosome 3

physical distance linkage

map

Recombination is not completely random.

PhenotypeGenotype

Genes code for proteins (or RNA). These gene products give rise to traits…

It is rarely this simple.

Figs 1.15-17

The relationship between genes and traits is often complex

Complexities include:

• Complex relationships between alleles

• Multiple genes controlling one trait

• One gene controlling multiple traits

• Environmental effects

The colors of peppers are determined by the interaction of several genes

Fig 3.14+.16

Complexity of inheritance leads to genetic diversity.

Eye color: One trait controlled by multiple genes

Fig 6.7

Seven alleles and their interactions in leaf patterning of clover

The relationship between genes and traits is often complex

Complexities include:

• Complex relationships between alleles

• Multiple genes controlling one trait

• One gene controlling multiple traits

• Environmental effects

1 genecontrollingmany traits

Mom = HS Dad = HS

H or S

H or S

HH

HS SS

HS possible offspring75% Normal25% Sickle-cell

Mom

Dad

Sickle-Cell Anemia S=sickle-cell

H=normal

Coincidence of malaria and sickle-cell anemia

Mom = HS Dad = HS

H or S

H or S

HH

HS SS

HS

possible offspringOxygen transport:75% Normal25% Sickle-cell

Malaria resistance:75% resistant25% susceptible

Mom

Dad

Sickle-Cell Anemia S=sickle-cell

H=normal

The relationship between genes and traits is often complex

Complexities include:

• Complex relationships between alleles

• Multiple genes controlling one trait

• One gene controlling multiple traits

• Environmental effects

Next we will look at what DNA can tell us about the origins of Homo sapiens.

•Exam #3 W 12/5 at 7-8:30pmin ETC 2.108 for the 9am class and ECJ 1.202 for the noon class

•Review T 12/4 at 5pm in WRW 102

•Homework #4 due 12/3 (if needed)

•Bonus #2 is posted