Transcript The relationship between genes and traits is often complex

Homework #4 is
due 12/3/07
(only if needed)
Bonus #2 posted
Year End Topics:
•mtDNA
•Mapping
•Probability
•Evolution and the
Origin of Humans
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
Is this all of
your DNA?
Mitochondria have
their own DNA.
Fig 3.18
Both Mitochondria and Chloroplast have DNA
Fig 3.19
Endosymbiotic Theory - proposed origin of
mitochondria and chloroplasts from free-living
bacteria to cellular organelles
Human
Life
Cycle
Combination
of two
individuals
DNA
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
Mitochondrial DNA comparisons
can be used to trace ancestry:
During the Bolshevik revolution, the Tsar’s family
was captured and executed.
Tsar’s Family
There are many stories about what happened to their
youngest daughter Anastasia
Tsar’s Family
Anna Anderson, claimed she was Anastasia
Anna Anderson claimed she was Anastasia, but
tests of her mtDNA and one of Anastasia’s maternal
relatives did not match.
For more info check out:
http://en.wikipedia.org/wiki/Grand_Duchess_Anastasia_Nikolaevna_of_Russia
Or the book “Seven Daughters of Eve” by Bryan Sykes
Next week 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
Linked alleles tend to be inherited together
Fig 4.2
Crossing over produces new allelic combinations
Fig 4.3
Recombinants are produced by crossovers
Fig 4.7
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
For linked
genes,
recombinant
frequencies are
less than 50
percent
Fig 4.8
Homologous
pair of chromosomes
• Does this pedigree show linkage?
Fig 4.23
• Does this pedigree show linkage?
Fig 4.23
The probability of crossing over can be used to
determine the spatial relationship of different genes
Fig 4.9
Homework #4 is
due 12/3/07
(only if needed)
Bonus #2 posted
Year End Topics:
•mtDNA
•Mapping
•Probability
•Evolution and the
Origin of Humans