Download Slide 1

Mendel and the Gene Idea CH11
Bio Seminar today! Biology in South India!
© 2014 Pearson Education, Inc.
Why was Mendel able to deduce this particulate
pattern while others were struggling with how
inheritance worked….?
Imagine you are interested in
inheritance…….What measurements could you
make on the people in this class?
© 2014 Pearson Education, Inc.
Forget what you know!
What is blending inheritance??
Imagine balls are individuals filled with paint and you mimic
mating by randomly pulling them out of a bucket two by
two….
© 2014 Pearson Education, Inc.
Fig. 1. Difference between the outcomes from blending and from particulate inheritance. In postMendelian terms, we assume a single diallelic locus, and hence three diploid genotypes (AA, blue; Aa,
green; aa, yellow). Under particulate inheritance, the population's variability is preserved from
generation to generation. In contrast, the conventional wisdom of Darwin's day saw offspring inherit a
blend of parents' characteristics, here represented as the average of the two parental shadings. The
result
is Education,
that theInc.
variability diminishes in successive generations (the variance is halved each generation
© 2014
Pearson
He was successful because he chose ….
•flower color is purple or white
•flower position is axil or terminal
•stem length is long or short
•seed shape is round or wrinkled
•seed color is yellow or green
•pod shape is inflated or constricted
•pod color is yellow or green
He did not choose traits like
•number of seeds per pod
•pod length
•pod width
•seeds per plant
•seed weight
© 2014 Pearson Education, Inc.
Figure 11.2
Technique
1
Why are peas so
great to work with?
2
Parental
generation
(P)
3
Stamens
Carpel
4
Results
5
First filial
generation
offspring
(F1)
© 2014 Pearson Education, Inc.
Figure 11.4
Review of terms….
What is a locus? What are alleles?
Allele for purple flowers
Locus for flower-color gene
Pair of
homologous
chromosomes
Allele for white flowers
•Is this individual with these chromosomes in their cells
homozygous or heterozygous?
•What is the genotype?
•If purple flower allele is dominant, what is the phenotype?
© 2014 Pearson Education, Inc.
P
P
X
Homozygous Purple
What will gametes look like?
What will their genotype be?
© 2014 Pearson Education, Inc.
Homozygous White
P
P
X
What will gametes look like?
© 2014 Pearson Education, Inc.
All heterozygotes!
They are called the F1 generation (results of first cross)
What color will they be if P is dominant?
© 2014 Pearson Education, Inc.
Figure 11.3-3
Experiment
P Generation
(true-breeding
parents)
Purple flowers
White flowers
F1 Generation
(hybrids)
All plants had purple flowers
Self- or cross-pollination
Whatpurple F1 together (do a Pp x
So all F1 are Pp-lets breed these
Pp cross)!
F2 Generation
What are the genotypes of the gametes of these Pp plants?
How would we do a Punnet square showing this cross?
705 purple-flowered 224 white-flowered
plants
plants
© 2014 Pearson Education, Inc.
Figure 11.5-3
P Generationare P and p
So gametes
and we are going
Purple flowers
Appearance:
to mate
two
of thesePP
Genetic
makeup:
P
F1 Gametes:
White flowers
pp
p
F1 Generation
Appearance:
Genetic makeup:
Gametes:
Purple flowers
Pp
½ p
½ P
Sperm from
F1 (Pp) plant
F2 Generation
P
p
PP
Pp
Pp
pp
P
Eggs from
F1 (Pp) plant
p
3
© 2014 Pearson Education, Inc.
:1
Figure 11.6
3
Phenotype
Genotype
Purple
PP
(homozygous)
Purple
Pp
(heterozygous)
1
2
1
© 2014 Pearson Education, Inc.
Purple
Pp
(heterozygous)
White
pp
(homozygous)
Ratio 3:1
Ratio 1:2:1
1
Figure 11.3-3
Experiment
P Generation
(true-breeding
parents)
Purple flowers
White flowers
F1 Generation
(hybrids)
All plants had purple flowers
Self- or cross-pollination
F2 Generation
705 purple-flowered 224 white-flowered
plants
plants
© 2014 Pearson Education, Inc.
Probability!
Rr vs Rr cross
Gametes or Sperm for Rr individual will be…..
Gametes or Eggs for Rr individual will be….
What proportion of gametes in bucket will be R? r?
What is probability of an
RR individual in next
generation?
An Rr individual?
An rr individual?
© 2014 Pearson Education, Inc.
Figure 11.9

Rr
Segregation of
alleles into eggs
Rr
Segregation of
alleles into sperm
Sperm
R
½
R
R
½
¼
¼
r
r
r
R
r
¼
© 2014 Pearson Education, Inc.
r
R
R
Eggs
½
r
½
¼
Imagine crossing a pea heterozygous at the loci for flower color
(white versus purple) and seed color (yellow versus green) with a
second pea homozygous for flower color (white) and seed color
(yellow). What types of gametes will the first pea produce?
•
•
•
two gamete types: white/white and purple/purple
two gamete types: white/yellow and purple/green
four gamete types: white/yellow, white/green, purple/yellow,
and purple/green
• four gamete types: white/purple, yellow/green, white/white,
and purple/purple
• one gamete type: white/purple/yellow/green
For this cross assume white is dominant and yellow is
dominant…. What different offspring will you get????
© 2014 Pearson Education, Inc.
Figure 11.8
Experiment
YYRR
P Generation
yyrr
y
Gametes YR
y
yr
r
Y Y
F1 Generation
R
YyRr
R
Hypothesis of
dependent assortment
Predictions
Hypothesis of
independent assortment
Sperm
or
Predicted
offspring in
F2 generation
¼ YR ¼ Yr ¼ yR ¼ yr
Sperm
½ YR ½ yr
¼ YR
½ YR
Eggs
½ yr
YYRR YyRr
YyRr
¾
yyrr
¼ Yr
Eggs
¼ yR
YyRR YyRr
YYRr
YYrr
YyRr
Yyrr
YyRR YyRr
yyRR
yyRr
YyRr
yyRr
yyrr
¼
Phenotypic ratio 3:1
¼ yr
9
16
3
16
Yyrr
3
16
1
16
Phenotypic ratio 9:3:3:1
Results
315
© 2014 Pearson Education, Inc.
YYRR YYRr
108
101
32
Phenotypic ratio approximately 9:3:3:1
r
Figure 11.8
Experiment
YYRR
P Generation
yyrr
Gametes YR
yr
F1 Generation
YyRr
Hypothesis of
dependent assortment
Predictions
Hypothesis of
independent assortment
Sperm
or
Predicted
offspring in
F2 generation
¼ YR ¼ Yr ¼ yR ¼ yr
Sperm
½ YR ½ yr
¼ YR
½ YR
Eggs
½ yr
YYRR YyRr
YyRr
¾
yyrr
¼ Yr
Eggs
¼ yR
YyRR YyRr
YYRr
YYrr
YyRr
Yyrr
YyRR YyRr
yyRR
yyRr
YyRr
yyRr
yyrr
¼
Phenotypic ratio 3:1
¼ yr
9
16
3
16
Yyrr
3
16
1
16
Phenotypic ratio 9:3:3:1
Results
315
© 2014 Pearson Education, Inc.
YYRR YYRr
108
101
32
Phenotypic ratio approximately 9:3:3:1
Figure 11.8
Experiment
YYRR
P Generation
yyrr
Gametes YR
y
r
yr
Y Y
F1 Generation
R
YyRr
R
Hypothesis of
dependent assortment
Predictions
F1?
Hypothesis of
independent assortment
Sperm
or
Predicted
offspring in
F2 generation
¼ YR ¼ Yr ¼ yR ¼ yr
Sperm
½ YR ½ yr
¼ YR
all YyRr
½ YR
Eggs
½ yr
But F2?
YYRR YyRr
YyRr
¾
YyRr x YyRr?
yyrr
¼
Phenotypic ratio 3:1
¼ Yr
Eggs
¼ yR
Y¼
9
Results
gametes YR and yr only!
315
© 2014 Pearson Education, Inc.
y
r
108
101
32
R
yr
YYRR YYRr
YyRR YyRr
YYRr
YYrr
YyRr
Yyrr
YyRR YyRr
yyRR
yyRr
Y
yyRr
yyrr
y
YyRr
3
16
16
Yyrr
3
x
16
1
16
Phenotypic ratio 9:3:3:1
r
R
y
r
Phenotypic ratio approximately 9:3:3:1
Figure 11.8
Experiment
YYRR
P Generation
yyrr
Gametes YR
y
r
yr
Y Y
F1 Generation
R
YyRr
R
Hypothesis of
dependent assortment
Predictions
F1?
Hypothesis of
independent assortment
Sperm
or
Predicted
offspring in
F2 generation
¼ YR ¼ Yr ¼ yR ¼ yr
Sperm
½ YR ½ yr
¼ YR
all YyRr
½ YR
Eggs
½ yr
But F2?
YYRR YyRr
YyRr
¾
YyRr x YyRr?
yyrr
¼
Phenotypic ratio 3:1
¼ Yr
Eggs
¼ yR
Y¼
9
Results
gametes YR and yr only!
315
© 2014 Pearson Education, Inc.
y
r
108
101
32
R
yr
YYRR YYRr
YyRR YyRr
YYRr
YYrr
YyRr
Yyrr
YyRR YyRr
yyRR
yyRr
Y
yyRr
yyrr
y
YyRr
3
16
16
Yyrr
3
x
16
1
16
Phenotypic ratio 9:3:3:1
r
R
y
r
Phenotypic ratio approximately 9:3:3:1
Figure 11.8
Experiment
YyRr x YyRr?
Gametes YR
gametes
YR and yr only!
F Generation
Y
1
Hypothesis of
dependent assortment
Predictions
yr
y
Y
y
Hypothesis of
independent assortment
r
YyRr
x
R
R
r
Sperm
or
Predicted
offspring in
F2 generation
¼ YR ¼ Yr ¼ yR ¼ yr
Sperm
½ YR ½ yr
YR
Next generation (combine gametes¼ randomly)?
YYRR YYRr YyRR
½ YR
Eggs
YYRR YyRr
Gamete YR plus gamete
YR =
½ yr
YyRr yyrr
Gamete YR plus gamete yr =
¾
Gamete yr plus gamete
yr¼ =
Phenotypic ratio 3:1
YYRR
YyRr
yyrr
© 2014 Pearson Education, Inc.
108
101
¼ yR
¼ yr
9
16
YYRr
YYrr
YyRr
Yyrr
YyRR YyRr
yyRR
yyRr
YyRr
yyRr
yyrr
3
16
Yyrr
3
16
1
16
Phenotypic ratio 9:3:3:1
Results
315
¼ Yr
Eggs
YyRr
32
Phenotypic ratio approximately 9:3:3:1
Figure 11.8
Experiment
YYRR
P Generation
yyrr
Gametes YR
yr
F1 Generation
YyRr
Hypothesis of
dependent assortment
Predictions
Hypothesis of
independent assortment
Sperm
or
Predicted
offspring in
F2 generation
¼ YR ¼ Yr ¼ yR ¼ yr
Sperm
½ YR ½ yr
¼ YR
½ YR
Eggs
½ yr
YYRR YyRr
YyRr
¾
yyrr
¼ Yr
Eggs
¼ yR
YyRR YyRr
YYRr
YYrr
YyRr
Yyrr
YyRR YyRr
yyRR
yyRr
YyRr
yyRr
yyrr
¼
Phenotypic ratio 3:1
¼ yr
9
16
3
16
Yyrr
3
16
1
16
Phenotypic ratio 9:3:3:1
Results
315
© 2014 Pearson Education, Inc.
YYRR YYRr
108
101
32
Phenotypic ratio approximately 9:3:3:1
Figure 11.8
Experiment
YYRR
P Generation
yyrr
Gametes YR
yr
F1 Generation
YyRr
Hypothesis of
dependent assortment
Predictions
Hypothesis of
independent assortment
Sperm
or
Predicted
offspring in
F2 generation
¼ YR ¼ Yr ¼ yR ¼ yr
Sperm
½ YR ½ yr
¼ YR
½ YR
Eggs
½ yr
YYRR YyRr
YyRr
¾
yyrr
¼ Yr
Eggs
¼ yR
YyRR YyRr
YYRr
YYrr
YyRr
Yyrr
YyRR YyRr
yyRR
yyRr
YyRr
yyRr
yyrr
¼
Phenotypic ratio 3:1
¼ yr
9
16
3
16
Yyrr
3
16
1
16
Phenotypic ratio 9:3:3:1
Results
315
© 2014 Pearson Education, Inc.
YYRR YYRr
108
101
32
Phenotypic ratio approximately 9:3:3:1
1. What were the three examples they went over?
© 2014 Pearson Education, Inc.
2. Why are twins raised in different households considered so
valuable to biologists?
3. What is heritability? (they talk about height in this article)
© 2014 Pearson Education, Inc.
4. Draw a graph.
Label the y-axis “Average height of offspring”
Label the x-axis put “Average height of parent”
What would a line on this graph look like if height is highly
heritable!
© 2014 Pearson Education, Inc.
FYI these graphs are not a result of twin analyses but are a
result of studying inheritance through regression statistics.
5. Which graphs show hi, medium and low heritability?
6. What might a graph with the actual heritability of height look
like? Draw one!
© 2014 Pearson Education, Inc.
© 2014 Pearson Education, Inc.
7. If heritability is high like .8 does that mean the environment
is not important?
8. Why do we freak out when we learn the heritability of IQ is
something like .75? Historical connections?
9. What are we learning from situations where identical twins
differ in specific substantial ways despite being raised in the
same household? (autism example)
10. So what is epigenetics?
11. There are several analogies towards the end of the articlewhat were they?
© 2014 Pearson Education, Inc.
Round allele (R) is dominant to the wrinkled allele (r). Yellow allele (Y) is dominant to
the green allele (y).
For this cross what are
genotype and phenotype
frequencies for these F1
© 2014 Pearson Education, Inc.
Figure 11.8
Experiment
YYRR
P Generation
yyrr
Gametes YR
yr
F1 Generation
YyRr
Hypothesis of
dependent assortment
Predictions
Hypothesis of
independent assortment
Sperm
or
Predicted
offspring in
F2 generation
¼ YR ¼ Yr ¼ yR ¼ yr
Sperm
½ YR ½ yr
¼ YR
½ YR
Eggs
½ yr
YYRR YyRr
YyRr
¾
yyrr
¼ Yr
Eggs
¼ yR
YyRR YyRr
YYRr
YYrr
YyRr
Yyrr
YyRR YyRr
yyRR
yyRr
YyRr
yyRr
yyrr
¼
Phenotypic ratio 3:1
¼ yr
9
16
3
16
Yyrr
3
16
1
16
Phenotypic ratio 9:3:3:1
Results
315
© 2014 Pearson Education, Inc.
YYRR YYRr
108
101
32
Phenotypic ratio approximately 9:3:3:1
For this cross what are genotype and phenotype
frequencies for these F1
© 2014 Pearson Education, Inc.
Heritability of a trait is the extent to which differences within
a population can be explained by differences in their
genetics.
Ex here is height heritability=.80 so this means that 80% of
the differences among people within a population are due to
differences in their genes.
© 2014 Pearson Education, Inc.
http://erinjenne.blogspot.com/2011_02_01_archive.html
© 2014 Pearson Education, Inc.
Figure 11.10-2
P Generation
Red
CRCR
Gametes
White
CWCW
CR
CW
Pink
CRCW
F1 Generation
Gametes ½ CR ½ CW
Today…..What is this called?
Is this blending inheritance???
© 2014 Pearson Education, Inc.
Albinism in humans occurs when both alleles at a
locus produce defective enzymes in the biochemical
pathway leading to melanin. Given that
heterozygotes are normally pigmented, which of the
following statements is/are correct?
•
•
•
•
•
One normal allele produces as much melanin as two normal
alleles.
Each defective allele produces a little bit of melanin.
Two normal alleles are needed for normal melanin
production.
The two alleles are codominant.
The amount of sunlight will not affect skin color of
heterozygotes.
© 2014 Pearson Education, Inc.
Imagine a locus with four different alleles for fur color in an
animal. The alleles are named Da, Db, Dc, and Dd. If you
crossed two heterozygotes, DaDb and DcDd, what genotype
proportions would you expect in the offspring?
•
•
•
•
•
25% DaDc, 25% DaDd, 25% DbDc, 25% DbDd
50% DaDb, 50% DcDd
25% DaDa, 25% DbDb, 25% DcDc, 25% DdDdDcDd
50% DaDc, 50% DbDd
25% DaDb, 25% DcDd, 25% DcDc, 25% DdDd
© 2014 Pearson Education, Inc.
When a disease is said to have a multifactorial basis,
it means that
• both genetic and environmental factors contribute
to the disease.
• it is caused by a gene with a large number of
alleles.
• it affects a large number of people.
• it has many different symptoms.
• it tends to skip a generation.
Come up with an example of a multifactorial
disease!
© 2014 Pearson Education, Inc.
Figure 11.12
What is this
called????
BbEe
BbEe
Sperm
What is going
Eggs
on????
¼ BE
¼ bE
¼ BE
¼ Be
¼ be
BBEE
BbEE
BBEe
BbEe
BbEE
bbEE
BbEe
bbEe
BBEe
BbEe
BBee
Bbee
BbEe
bbEe
Bbee
bbee
¼ bE
¼ Be
¼ be
9
© 2014 Pearson Education, Inc.
:
3
: 4
Figure 11.13
AaBbCc
AaBbCc
Sperm
1
1
1
1
1
Eggs
1
1
1
1
8
1
8
1
1
8
8
1
8
1
1
8
8
8
8
8
8
8
8
8
8
Phenotypes:
Number of
dark-skin alleles:
© 2014 Pearson Education, Inc.
1
8
1
64
0
6
64
1
15
64
2
20
64
3
15
64
4
6
64
5
1
64
6
1
64