Transcript 11/27 - link

Homework #4 is
due 12/4/07
(only if needed)
Bonus #2 posted
Year End Topics:
•mtDNA
•Mapping
•Probability
•Evolution and the
Origin of Humans
Grades:
A = 88.5+
B = 77.5
C = 65.5
Exam avg x 0.88
+ homework +
bonus = grade
Final time?
Genotype
Phenotype
Dominant
Recessive
Genotype
Phenotype
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
Only the egg provides mitochondria to the offspring.
mitochondria
Pg 112
Human
Life
Cycle
In females
Mom provides
50.000275%
and Dad
provides
49.999825%
of DNA to
offspring.
… because
Mom provides
100% of
mitochondrial
DNA
A few diseases are caused by mutations in mtDNA
Fig 3.24
Pedigree of a mitochondrial disease:
Which shape represents females?
Fig 3.25
Pedigree of a mitochondrial disease:
Males and females may be affected by a
disease coded on mtDNA, but only
females pass it on.
Fig 3.25
For our final lecture of the semester, we will
look at what DNA can tell us about the origins
of Homo sapiens.
Variation in Peas
Fig 3.2
Phenotype
Genotype
Fig 3.3
Tracking two
separate
genes, for
two separate
traits, each
with two
alleles.
Ratio of
9:3:3:1
Fig 3.4
Approximate position of seed color and shape genes
in peas
Y
y
Gene for seed color
r
Chrom. 1/7
R
Chrom. 7/7
Gene for
seed shape
Recombinants are
meiotic output
different from
meiotic input
Fig 3.11
Box 2.2
Crossingover
Meiosis:
In humans,
crossing-over and (Ind. Assort.)
independent
assortment lead to
over 1 trillion
possible unique
gametes.
(1,000,000,000,000)
Meiosis I
Meiosis II
4 Haploid cells, each unique
Linked alleles tend to be inherited together
Fig 4.2
Crossing over produces new allelic combinations
Fig 4.3
Recombinants are produced by crossing over
Fig 4.7
For linked
genes,
recombinant
frequencies are
less than 50
percent
Fig 4.8
Homologous
pair of chromosomes
Does this pedigree show recombination or linkage?
Fig 4.23
Does this pedigree show recombination or linkage?
Fig 4.23
Longer regions
have more
crossovers and
thus higher
recombinant
frequencies
Fig 4.10
Some crosses
do not give
the expected
results
=25%
42% 41%
9%
8%
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
The probability of crossing over can be used to
determine the spatial relationship of different genes
Fig 4.9
Double recombinants arise from two crossovers
Fig 4.11
Recombinant
Double recombinants can show gene order
Fig
4.12
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?
similar to pg 141
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
Put it all together…
26.8 m.u.
st
ss
14.6 m.u.
e
12.2 m.u.
Linkage map of
Drosophila
chromosome 2
Recombination is not
completely random.
physical
distance
Yeast chromosome 3
Fig 4.13 and 20
linkage
map
Alignment of physical and recombination maps
Fig 4.25
Genotype
Phenotype
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
Homework #4 is
due 12/4/07
(only if needed)
Bonus #2 posted
Year End Topics:
•mtDNA
•Mapping
•Probability
•Evolution and the
Origin of Humans