ANNOUNCEMENTS

1
ANNOUNCEMENTS

• No QA session this week. Please come to my
  office hours MWF 9-11 (or call/email for an
  appt.).
• TA Office Hours
• Lindy Jon M 1-3 BRL 013
• Ellen W 9-11 FOR 311A

2
TODAY...

• Practice pedigree analysis
• Goal recognize and predict pedigrees for four
  common patterns of trait inheritance
• Probability and hypothesis testing

3
Pedigree analysis

• Basic patterns of inheritance
• autosomal, recessive
• autosomal, dominant
• X-linked, recessive
• X-linked, dominant (very rare)
• Applying pedigree analysis - practice

4
X-linked dominant pedigrees

• Trait is common in pedigree
• Affected fathers pass to ALL of their daughters
• Males and females are equally likely to be
  affected

5
X-linked dominant diseases

• X-linked dominant diseases are extremely unusual
• Often, they are lethal (before birth) in males
  and only seen in females
• ex. incontinentia pigmenti (skin lesions)
• ex. X-linked rickets (bone lesions)

6
Coat color in a wolf pedigree
Black coat color is a) X-linked, dominant b)
X-linked, recessive c) autosomal, dominant d)
autosomal, recessive e) cant tell with info
provided
7
Strategy for interpreting pedigrees systematical
ly rule out each of the options
8
Based on this pedigree, how is cystic fibrosis
inherited? (a) Autosomal dominant (b) Autosomal
recessive (c) X-linked dominant (d) X-linked
recessive
9
Based on this pedigree, how is cystic fibrosis
inherited? (a) Autosomal dominant (b) Autosomal
recessive (c) X-linked dominant (d) X-linked
recessive
10
Based on this pedigree, how is this trait
inherited? (a) Autosomal dominant (b) Autosomal
recessive (c) X-linked dominant (d) X-linked
recessive (e) Cant tell with info provided.
11
Based on this pedigree, how is this trait
inherited? (a) Autosomal dominant (b) Autosomal
recessive (c) X-linked dominant (d) X-linked
recessive (e) Cant tell with info provided.
12
Based on this pedigree, how is this trait
inherited? (a) Autosomal dominant (b) Autosomal
recessive (c) X-linked dominant (d) X-linked
recessive (e) Cant tell with information
provided.
13
Based on this pedigree, how is this trait
inherited? (a) Autosomal dominant (b) Autosomal
recessive (c) X-linked dominant (d) X-linked
recessive (e) Cant tell with information
provided.
14
Based on this pedigree, how is this trait
inherited? (a) Autosomal dominant (b) Autosomal
recessive (c) X-linked dominant (d) X-linked
recessive (e) Cant tell with information
provided.
15
Based on this pedigree, how is this trait
inherited? (a) Autosomal dominant (b) Autosomal
recessive (c) X-linked dominant (d) X-linked
recessive (e) Cant tell with information
provided.
16
Pedigree Analysis in real life

• Remember
• dominant traits may be rare in population
• recessive traits may be common in population
• alleles may come into the pedigree from 2
  sources
• often traits are more complex
• affected by environment other genes

17
Probability Hypothesis Testing
18

• Goals
• Understanding combining probabilities
• (product and sum rules)
• Understand conditional probabilities
• Understand hypothesis testing
• (chi-square test)

19

• How many unique gametes can an individual of
  genotype AABbCcDdee make?
• 4
• 8
• 16
• 32
• 64

20
A general rule for calculating the number of
possible gametes a given genotype can produce
possible gametes 2n
where n is the number of heterozygous loci
this could be chromosomes or genes
21
The PROBABILITY (P) of an event is the number of
times the event will occur (a) divided by the
total number of possible events (n). P
a/n What is the probability of flipping a
heads? 1 heads
Pheads ------------------------- ½
50 (1 heads 1 tails)
22
Product Rule If events A and B are independent,
then the probability that they both occur is P(A
and B) P(A) x P(B) That is, the probability
of 2 or more independent events occurring
simultaneously is equal to the product of their
individual probabilities.
23
Product Rule P(A and B) P(A) x P(B) What
is the probability of flipping two heads in a
row? P(A) 0.5 P(B) 0.5 P(A and B)
P(A) x P(B) 0.5 x 0.5 0.25 25
24
(No Transcript)
25
Sum Rule The probability of one of two or more
mutually exclusive events occurring is equal to
the sum of their individual probabilities P(A or
B) P(A) P(B)
26
What is the probability of a tall plant from a Tt
x Tt cross?
The probability of a tall plant is ¼ ¼ ¼ ¾.
27
Progressive Retinal Atrophy (PRA) - a common
recessive disease causing blindness in dogs
PP healthy/noncarrier Pp healthy/carrier pp
affected
Is a healthy dog a carrier??
28
Is a healthy dog a carrier (Pp)??
If PP...
PP x pp
all progeny Pp and healthy
We do the cross. We get 5 healthy puppies in a
row. Whats the probability of that outcome if
the test dog is really just a lucky carrier?
29
What is the probability of all 5 puppies being
healthy in a Pp x pp cross? (a) 1/4 (b)
1/8 (c) 1/16 (d) 1/32 (e) 1/64
½ x ½ x ½ x ½ x ½ 3