Transcript Genetics_and_Heredity

Genetics and Heredity
Probability
Probability




The likelihood that a specific event will
occur
Probability = # of 1 times event occurs
number of possible outcomes
Example: What is the
probability that a tossed
coin will be heads?
½ or 50%
Probability

The First Law of Probability:
the results of the first trial
of a chance event do not
affect the results of later
trials of the same event.

In other words, no matter
how many times a flipped
coin lands on tails, every flip
still has a ½ chance of tails.
Probability

Second Law of Probability: The
probability of two or more
independent events occurring
together is the product of their
separate probabilities.

What is the probability that a couple
will have four boys?
50% (1/2 probability each time)
½ x ½ x ½ x ½ = 1/16


Inherited Traits
Are these inherited traits?
Your eye color
Your hair color and texture
Your height
Are these inherited traits?
Your personality
Your musical,
athletic, and
artistic abilities
Think about this….

“My parents have brown eyes, why are
mine blue?”

“My brother is tall. Why am I short?”

“Why does my sister have blonde hair
while mine is brown?”
Gregor Mendel

These are questions that Gregor
Mendel tried to answer..

Born in 1822 in Austria
1843 – Studied
Theology
1846-Studied Science
at the University of
Vienna


Father of Genetics
Johann Mendel
was born in 1822 in
Heinzendorf, Austria, to a
peasant farming family.
Austria
Poland
Italy
Germany
Czech Republic
Austria
During his early years,
Johann did NOT
like agriculture
very much.
He lay around in
his bed “sick” for
weeks, possibly to
avoid farm chores.
Do I LOOK
like
a farmer?
When Johann was 16,
his father had a debilitating farming
accident and Johann was forced to
provide for himself.
When Johann was 18,
he borrowed money from his younger
sister’s dowry to pay for his education
at the university for two years.
When he was 21, one of Johann’s teachers took note of his
exceptionally bright mind and persuaded him to join the
Augustinian monks.
St.Thomas Church,
(now
Brno, Czechoslovakia)
After he arrived at St. Thomas, Johann Mendel changed his name to
Brother Gregory.
The monastery was a center of learning for young men who wanted to
study theology and natural science.
Brother Gregory also spent time
teaching mathematics at a nearby
school.
After one year, in order to become a
teacher, he took the teacher’s
examinations at the University of
Vienna
. . . and failed.
During his early years at the monastery, Mendel began studying and
breeding mice.
The bishop
was not
pleased.
Brother Gregor settled on bees . . .
and peas.
University of Vienna
While at the monastery, Gregor
continued his studies at the
University of Vienna for several
years.
He became a “reserve” teacher for
an ailing professor, teaching science
at a local college while studying
physics at the University of Vienna.
After many years at the
university, Gregor retook the
teacher’s exam,
and failed for the second
time.
In spite of these failures, Mendel
continued to conduct numerous
experiments on plants.
Mendel narrowed his focus to
one particular garden pea,
Pisum sativm.
For 8 years, Mendel experimented with
over 28,000 peas in the large gardens
attached to the monastery.
Rather than study every characteristic of the
garden pea, Mendel narrowed his
observations to 7 traits.
Garden Pea Traits
Observed
Seed shape
smooth
Seed color
yellow
Pod shape
inflated
Pod color
green
Flower color
Flower location
Plant size
purple
axial
tall
wrinkled
green
constricted
yellow
white
terminal
short
In 1866 when Mendel was 44, his experimental results
were published
. . . and ignored long after he died.
In 1900, 3 scientists - Carl Correns, Hugo de
Vries, and Erich von Tschermak - all
independently rediscovered and verified
Mendel's principles, marking the beginning of
modern genetics.
He is now considered the father of genetics.
Mendel’s studies led to:
Concepts in Inheritance


Dominant (H)
Homozygous (HH or hh)
Genotype (HH, Hh or hh)

Purebred (HH or hh)





Recessive (h)
Heterozygous (Hh)
Phenotype (blonde,
brown, red)
Hybrid (Hh)
Theory of Heredity
Inherited allele for
purple P
HOMOZYGOUS
purple flower PP
Inherited allele
for purple P
Theory of Heredity
Inherited allele for
purple flower (P)
HETEROZYGOUS
purple flower (Pp)
Inherited allele for
pink flower (p)
Theory of Heredity
Inherited for pink
flower (p)
HOMOZYGOUS pink
flower (pp)
Inherited for pink
flower (p)
PREDICTING HEREDITY
PUNNETT SQUARES



A Punnett square is a tool used to help
predict the probability of offspring of a
couple.
1. Decide the genes that could be passed
on to the offspring in the gametes from
each parent.
2. Cross the different gene/gamete
possibilities for each possible offspring
combination.
Monohybrid Cross

Monohybrid Cross: a cross that shows the
possible offspring for one trait

Aa x Aa
A: White fur
a: Brown fur


Parent Aa has what
gentotype?
Parent Aa can produce a
gamete with either an “A”
or with an “a”
Monohybrid Cross





Monohybrid Cross: a cross that shows the
possible offspring for one trait A
a
Aa
A:
a:
Aa
x Aa
A
White fur
Brown fur
a
produces gamete “A” or “a”
• Separate the two genes (as though they were
separating into different gametes) and place one
outside the first row on the left and the other under
it outside the second row.
• Separate the other parent genes and place at the
top, one above each column.
Monohybrid Cross




Monohybrid Cross: a cross that shows the
possible offspring for one trait
Aa x Aa
A: White fur
a: Brown fur
• Cross over the
genes to fill in the
boxes of the
square.
A
a
A
AA
Aa
a
Aa
aa
Genotypic Ratios

Genotypic Ratios compare the possible
genotypes (gene combinations in the offspring.
A
a
 Aa x Aa






A: White fur
a: Brown fur
A
AA
Aa
a
Aa
aa
Genotypic ratio:
Number of offspring with homozygous dominant genes AA
Number of offspring with heterozygous/hybrid genes Aa
Number of offspring with homozygous recessive genes aa


Sometimes abbreviated as:
GR = #hom dom (AA) : #hyb (Aa) : hom rec (aa)
GR = 1 : 2 : 1
Phenotypic Ratios

Phenotypic Ratios compare the possible
phenotypes (appearance of the offspring); how
many show the dominant trait or recessive trait.
A
a
 Aa x Aa







A: White fur
a: Brown fur
A
AA
Aa
a
Aa
aa
Phenotypic ratio:
Number of offspring showing the dominant trait (AA & Aa)
Number of offspring showing the recessive trait (aa)
Sometimes abbreviated as:
PR = #show dom (AA & Aa) : #show rec (aa)
PR = 3 : 1
Practice!
Cross a HOMOZYGOUS dominant female with a
HETEROZYGOUS male using the same trait.
What is the
genotypic ratio?
2:2 or 50%
A
A
A
AA
AA
a
Aa
Aa
What is the
phenotypic ratio?
4 white fur
Dihybrid Cross
Dihybrid Cross: shows the possible offspring
for two traits
This shows a
cross between
parents hybrid
for two traits:
BbRr x BbRr
Fur Color:
B: Black
b: White
Coat Texture:
R: Rough
r: Smooth
BR
BbRr x BbRr
Br
bR
br
BR
BBRR
BBRr
BbRR
BbRr
Br
BBRr
BBrr
BbRr
Bbrr
bR
BbRR
BbRr
bbRR
bbRr
br
BbRr
Bbrr
bbRr
bbrr
Dihybrid Crosses
Phenotypic Ratio: # dom/dom : # dom/rec : # rec/dom : # rec/rec
 How
many of the
offspring would have
BR
Br
bR
br
a black, rough coat?
(#dom/dom)
BBRr
BbRR
BbRr
BR BBRR
 How many would
have a black,
Br BBRr
BBrr
BbRr
Bbrr
smooth coat?
(#dom/rec)
 How many would
bbRR
bbRr
bR BbRR BbRr
have a white, rough
coat? (#rec/dom)
Bbrr
bbRr
bbrr
br BbRr
 How many would
have a white,
smooth coat?
Phenotypic Ratio: 9:3:3:1
(#rec/rec)
16
Dihybrid Crosses

If mouse #1 were crossed with mouse #16, what
would their offspring look like?
1
Fur Color:
B: Black
b: White






Coat Texture:
R: Rough
r: Smooth
#1 x #16
BBRR x bbrr
#6 x #10
BBrr x BbRr
#14 x #16
Bbrr x bbrr
BR
Br
bR
br
BR BBRR
BBRr
BbRR
BbRr
Br
BBrr
BbRr
Bbrr
BBRr
16
bR
BbRR
BbRr
bbRR
bbRr
br
BbRr
Bbrr
bbRr
bbrr
More Complex Patterns
of Heredity




Incomplete Dominance
Codominance
Multiple Alleles
Sex-Linked Traits
Incomplete Dominance
R
R
R’
RR’
RR’
R’
RR’
RR’
Red (RR) X white (R’R’)
make pink (RR’)
Incomplete Dominance


Red pigment is produced by the R allele
the non-pigmented R’ allele codes for
enzymes that do not function properly so
it turns white
Dilutes the effect of R causing only partial
expression
Problem: Incomplete
Dominance

Show the cross between a pink and a
white flower.
R
R’
GENOTYPES:
- RR’ (2); R’R’ (2)
- ratio 1:1
R’
RR’
R’R’
PHENOTYPES:
- pink (2); white (2)
- ratio 1:1
R’
RR’
R’R’
Problem: Incomplete
Dominance

Show the cross between a pink (RW) and
a white flower (WW).
GENOTYPES:
- RW (2); WW (2)
- ratio 1:1
W
RW
WW
PHENOTYPES:
- pink (2); white (2)
- ratio 1:1
W
RW
WW
R
W
Polygenic Inheritance
More than one gene controls a trait
 Ex. Skin color, height
Eye color

skin pigmentation
Incomplete Dominance – two
phenotypes create a third
R’R’
WHITE
Hybrid
R’R
RR
PINK
RED
USE PRIMES FOR NON-PIGMENTED ORGASNISM (This
is why you probably won’t see primes in codominance
unless it tells you that it is codominant)!!!
Codominance

Codominance: two dominant alleles are
expressed at the same time
CRCR
CWCW
CRCW
Codominance
** Example: When a red animal is crossed with a white animal, a
roan animal is produced. The phenotypes are:
RR = Red, WW = White, RW = Roan (red and white)
Red
(RR)
White (WW)
Roan (RW)
Hybrid
Occurs in cows too!!!
Codominance – Both Alleles
Expressed at the Same Time
Both the pink and the white alleles
are expressed
May see P = Pink Allele, W = White
Allele making pink and White PW
BUT they will have to state that it
is a codominant trait as primes are
used in other types of inheritance
****Will probably see PW or
IPIW, they show the same thing !
Codominance

Sickle-Cell Anemia is
another codominant
trait.
NA=Normal RBC
NA
National Institute of Health,
http://www.cc.nih.gov/ccc/ccnews/nov99/
Photo attributed to Drs. Noguchi,
Rodgers, and Schechter of NIDDK.
NS=Sickle Cell RBC
NA
NS
NSNA
NSNA
NA
NANA
NANA
Codominance


The heterozygous condition, both
alleles are expressed equally
Sickle Cell Anemia in Humans
NN =
normal cells
SS = sickle cells NS = some of
each
Problem: Codominance

Show the cross between an individual with
sickle-cell anemia and another who is a
carrier but not sick.
N
S
GENOTYPES:
- NS (2) SS (2)
- ratio 1:1
S
NS
SS
PHENOTYPES:
- carrier (2); sick (2)
- ratio 1:1
S
NS
SS
Multiple Alleles


Gene for trait has more than two possible
alleles
Individual only inherits two alleles
Multiple Alleles



There are more than two alleles
for a trait
Blood type in humans
Blood Types?


Type A, Type B, Type AB, Type
O
Blood Alleles?

IA, IB, i
Blood Types
Phenotype
Genotype
A
AA or IAIA or IAi or AO
B
BB or IBIB or IBi or BO
AB
AB or IAIB
O
OO or ii
**Type AB is codominant (both expressed)
**O is recessive, must have BOTH alleles
Rules for Blood Type

A and B are codominant




AA = Type A
BB = Type B
AB = Type AB
A and B are dominant over O



AO = type A
BO = type B
OO = type O
Example of a punnett square of a
Heterozygous Type A father and Type O
mother.
Let’s Make Some Punnett
Squares – Cross the Following:




A homozygous Type A female with a
Type O male
A Type AB male with an O female
A heterozygous Type B male with a
heterozygous A female
A couple that are both type AB
agglutinogen
Type a produces
anti-B antibodies
against type B
called
agglutinins
agglutinogen
Type AB produce NO
antibodies and can
receive any blood
type; attacks nothing
agglutinogen
no agglutinogen
Type B
produces
anti-A
antibodies
against type
A called
agglutinins
Type O Produces
BOTH anti-A and
anti-B antibodies and
attacks both A and B
so Type O folks can
only receive Type O!

http://highered.mcgrawhill.com/sites/0072556781/student_view0
/chapter33/animation_quiz_5.html
Anti-A Anti-B Rh
Type
** Agglutination
(clumping) is a
positive result
** No agglutination
(clumping) is a negative
result
Multiple Alleles




Multiple Alleles: traits with more than 2
alleles
Blood type has 3 alleles: A, B, O
A and B are codominant over O
O is recessive
Phenotype
Genotype
Can Receive
From
Can Donate To
A
I AI A, I Ai
A, O
A, AB
B
IBIB, IBi
B, O
B, AB
AB
I AI B
A, B, AB,O
AB
O
ii
O
A, B, AB, O
Blood Types
Blood Type
Can Donate to:
Can Receive
A+
A+, AB+
A+, A-, O+, O-
A-
A+, A-, AB+, AB-
A-, O-
B+
B+, AB+
B+, B-, O+, O-
B-
B+, B-, AB+, AB-
B-, O-
AB+
AB+
A+, A-, B+, B-, AB+,
AB-, O+, O-
AB-
AB+, AB-
A-, B-, AB-, O-
O+
A+, B+, AB+, O+
O+, O-
O-
A+, A-, B+, B-, AB+,
AB-, O+, O-
O-
+ can ONLY donate to other +’s…-’s can donate to + or –
– Can ONLY receive from – …. + can receive from + or –
How do you know if you carry
deadly genes?
Karyotypes

Karyotypes are a “map” of all 46 (23 pair)
of chromosomes.
Karyotypes
• During mitosis, Metaphase chromosomes are
photographed, enlarged and arranged in pairs by
a computer according to length and location of
the centromere.
Normal Karyotype
How can I tell if I have a genetic disorder?

Karyotypes are a “map” of all 46 (23 pair)
of chromosomes.
What’s wrong with this Karyotype?
Is this a male or a female?
Elbow Partner




Take turns reading “Background
Information” out loud to your elbow
partner – switch every other sentence.
One partner defines the odd numbered
words; one partner defines the even
numbered words
Share definitions
You have 9 minutes, 22 seconds. GO!
Abnormal Number of
Chromosomes
What’s wrong with this Karyotype?
Turner’s Syndrome
What’s wrong with this Karyotype?
Klinefelter’s Syndrome
What’s wrong with this Karyotype?
Down Syndrome
Disorders due to Chromosomal
Numbers
Down’s Syndrome
 Trisomy 21
Trisomy 21 – Down Syndrome

Minor to severe
mental retardation;
a characteristically
large, thick
tongue; shortened
stature; and
almond shaped
eyes
Trisomy 21 – Down Syndrome
Trisomy 13 – Patau Syndrome
Trisomy 13 - Patau Syndrome
Symptoms:








Cleft lip or palate
Clenched hands (with outer fingers on top of the
inner fingers)
Decreased muscle tone
Extra fingers or toes (polydactyl)
Hernias
Low-set ears
Mental retardation, severe
Seizures
Abnormal Numbers of Sex
Chromosomes
Males are XY
Females are XX




Turner’s Syndrome
XO-female
Short and stocky
Don’t develop adult female characteristics
Sterile
Beth at 13 (in middle)
and at 31
Turner’s Syndrome - XO
Monosomy -only 1 X
chromosome
Klinefelter’s Syndrome




XXY- male
Don’t develop adult male characteristics
Low intelligence
Sterile
Klinefelter XXY
•
•
•
•
Relatively high-pitched voices,
feminine body contours and breast
little facial and body hair
sterile
Diagnosing Disorders
Amniocentesis
 Amniotic fluid removed by needle
 Karyotyped
Chorionic Villus Sampling


Sample of placenta removed
karyotyped
Karyotype Practice



Look on back of Study Guide
Follow Directions to complete table using
the attached pictures
Work individually; raise your hand if you
have questions
Tracing Family Traits
A pedigree is a series of symbols
that charts several generations of a
families genetic history.
Females are represented by
circles and males by squares.
A line connecting them is a marriage.
This family has two children, one girl and
one boy.
If someone in the family has a
certain disease, such as cystic
fibrosis, the square will be colored
in. Sometimes carriers are
represented by a half colored in
shape.
Carries gene
Has disease
Other pedigree symbols:
GENDER UNKNOWN
?
MISCARIGE
MULTIPLE INDIVIDUALS
TWINS
6
GENERATIONS are represented by
Roman numerals. The individuals
are numbered in each generation.
In the next slide, who is the mother
of individual #4?
DOMINANT GENETIC
DISEASES
I.
1
2
2
3
II.
1
4
III.
1
2
EXAMPLES:
1. HUNTINGTON’S
DISEASE
2. POLYDACTYLY
3. DWARFISM
RECESSIVE GENETIC
DISEASE
I.
1
2
4
5
II.
3
6
III.
7
8
RECESSIVE DISEASES:
1. CYSTIC FIBROSIS
2. PKU
3. TAY-SACHS
4. SICKLE CELL ANEMIA
SEX-LINKED GENETIC
DISEASE
I.
1
2
2
3
II.
1
4
III.
1
2
SEX-LINKED DISEASES
1. HEMOPHILIA
2. COLOR BLINDNESS
3. DUCHENE MUSCULAR
DISTROPHY
4. MALE PATTERN
BALDNESS
Sex-Linked Traits
Sex-Linked Traits – Traits
X or Y chromosome
** Y chromosome has
between 70 and 200 genes,
most code for what makes a
dude a dude!
** X chromosome has between
900 and 1500 genes and contains
more than just make me a gal
genes !
What are Sex-Linked Traits?
Traits that are located on one of the
sex chromosomes (XY or XX)
1) Hemophilia: Failure
of blood to clot
Alix and Nicholas II
2) Muscular Dystrophy:
wasting away of
muscles
Can I inherit a sex-linked disease?
Fathers (XY) can
only pass
disorders to
daughters (XX)
Mothers (XX) can
pass disorders to
both sons (XY) and
daughters (XX)
Most disorders are carried on
the X chromosome, so males
are more likely to inherit them.
Colorblindness Is Recessive and On
the X Chromosome
Pedigree for Colorblindness
Pedigree of Tongue Rollers (Dominant)
Rr
rr
Rr
rr
rr
rr
Rr
Rr
rr
rr
rr
rr
Rr
rr
rr
Rr
rr
Rr
rr
Royal Hemophilia Pedigree
http://www.sciencecases.org/hemo/hemo.asp