Warm Up: For these Guinea pigs, tan hair is dominant over black.

1
Warm Up For these Guinea pigs, tan hair is
dominant over black.

• 1. What are the genotypes for each individual?
• 2. Who is homozygous and who is heterozygous?
• -----------------------------

Mom
Dad
tt
Tt
tt

• What are the alleles?
• What are the genotypes/phenotypes?
• Where did the ALL alleles come from?
• Predict the likelihood that this genotype/
  phenotype would result.

Baby
2
Key Ideas

• How can a Punnett square be used in genetics?
• How can mathematical probability be used in
  genetics?

3
Objectives Using Mendelian Genetics

• Describe how a Punnett square is used in
  genetics.
• List ways to express mathematical probability in
  genetics.

4
Vocabulary

• Punnett square
• Probability
• Pedigree
• Genetic disorder

5
What You Should Recall.
Were looking at this

• You know that Mendel gave us two important laws.
• Independent assortment Speaks to the fact that
  genes separate independent of one another
• Segregation Speaks to the fact that alleles of
  the same gene have equal probability of
  segregating into gametes.
• Once the gametes are formed, Mendelian genetics
  also gives us an outline on how to figure out
  what the likelihood, the probability, of an
  offspring has to show particular traits, based
  upon dominant recessive alleles.
• Today you will learn how to figure out the
  probability of certain traits being inherited and
  shown, using Punnett Squares.

6
Using Punnett Squares

• How can you predict the chances an offspring will
  have a certain genotype, therefore phenotype?
• A Punnett square is a model that predicts the
  probability of likely outcomes of a genetic
  cross.
• Remember that a cross is to mate or breed two
  individuals.
• A Punnett square shows all of the genotypes that
  could result from a given hybrid cross.
• The important thing to remember is that this
  shows what could happennot necessarily what
  always happens.
• The simplest Punnett square consists of a square
  divided into four boxes.
• This is a monohybrid cross
• The combination of letters in each box represents
  one possible genotype in the offspring.

7
Meiosis
EVERY CHILD BORN WOULD HAVE THE SAME CHANCES TO
INHERIT ANY OF THE COMBINATIONS OF ALLELES!
This isnt necessarily one child this represents
the probability one child will have a certain
genotype genotype determines phenotype
Fertilization
Meiosis
Probable zygotes that can be produced by one
fertilization
8
Using Punnett Squares

• Constructing a Simple Punnett square for
  Monohybrid Crosses
• Draw a 2 x 2 chart.
• Conclude what the genotype of the parents
  gametes are based upon the description given.
• Write the GENOTYPE of the parents gametes on the
  top and sides of the chart. There is one letter
  per column row.
• This represents the allele being donated by a
  gamete during fertilization.
• Fill in the columns and rows corresponding with
  the heading allele.

Y Y
y Yy Yy
y Yy Yy
These are the possible allele combinations for
the offspring
9
Ratios and Punnett Squares

• A Punnett square basically predicts ..
• all the possible combinations for alleles for
  each trait examined.
• This can be use to predict the likelihood of
  traits of an offspring the probability of things
  happening.
• It also reveals the ratio of one type of
  offspring compared to the other types offspring.
• The ratio can help compare genotypes to other
  genotypes or phenotypes to other phenotypes.
• It ultimately shows how the possible offspring
  compare to the other offspring.

10
Ratio Review

• What is a ratio?
• A ratio is an expression, of at least two
  numbers, that is used to compare values.
• It is written separated by a colon.
• Ex. If there are (normally) 5 fingers for every
  hand would be written as 51 ratio of fingers to
  hands.
• It would be said as a ratio of 5 fingers to one
  hand
• A ratio shows how many events happen compared to
  the events of others.

11
Ratios of Fingers to Hands

• There is a ratio of five fingers to every one
  hand.
• Written 51

3
2
4
1
5
1
12
Using Punnett Squares

• Punnett squares give us genotypes probabilities
  to determine phenotypes.
• In a monohybrid homozygous dominant cross, all of
  the offspring will be homozygous.
• The ratio of the genotypes will be 1 YY0
  others, meaning all the offspring will be the
  same genotype for the alleles.
• This is called the genotypic ratio.
• The phenotypic ratio describes the comparison of
  all the traits displayed.
• The phenotypic ratio here is all the dominant
  form all dominant.

Y Y
Y YY YY
Y YY YY
13
Using Punnett Squares

• In a monohybrid cross between a homozygous
  dominant and a homozygous recessive all the
  offspring will be heterozygous (ex. Yy).
• What are the genotypic phenotypic ratios here?
• The genotypic ratio would again be
• 1Yy0 others.
• Because there is no other alternative, there is
  no other thing to compare to.
• Since theres only 1 genotype, there can be only
  1 phenotype.
• As such, the phenotypes would be all the dominant
  form.

Y Y
y Yy Yy
y Yy Yy
14
Using Punnett Squares

• In a monohybrid heterozygous cross the genotypic
  ratio will be 1 YY 2 Yy 1 yy.
• This is what Mendel observed in his F2
  generations!
• What is the phenotypic ratio?

Y y
Y YY Yy
y Yy yy

• 3 yellow (dominant) 1 green (recessive)

15
Using Punnett Squares

• Phenotypes
• Remember, genotype determines phenotype, but the
  ratio is not always the same between the two.
• You need to think about the trait that will be
  shown depending upon the allele combination.
• In a monohybrid cross between homozygotes all the
  offspring will be the same, therefore all the
  offspring will express the same trait.

• However, in a monohybrid heterozygote cross,
  where the genotypic ratio is 1 2 1,
• the phenotypic ratio will be 3 1.

16
Punnett Squares
17
Dihybrid Crosses
Mendel noticed that alleles for one gene do not
affect the inheritance of the alleles for another
gene. independent assortment

• This makes predicting the probability of
  inheriting a combination of two non-linked genes
  more challenging but entirely possible.
• What does non-linked mean?

18
Dihybrid Crosses.

• In order to accomplish this you must consider all
  possible gametes for an individual, then perform
  the cross.
• Lets try crossing two heterozygotes for pea
  color and flower color.
• PpYy x PpYy
• Take a minute and figure out the possible gametes.

19
Dihybrid Crosses.

• In order to accomplish this you must consider all
  possible gametes for an individual, then perform
  the cross.
• Lets try crossing two heterozygotes for pea
  color and flower color.
• PpYy x PpYy
• Take a minute and figure out the possible gametes.

PY
20
Dihybrid Crosses.

• In order to accomplish this you must consider all
  possible gametes for an individual, then perform
  the cross.
• Lets try crossing two heterozygotes for pea
  color and flower color.
• PpYy x PpYy
• Take a minute and figure out the possible gametes.

pY
PY
21
Dihybrid Crosses.

• In order to accomplish this you must consider all
  possible gametes for an individual, then perform
  the cross.
• Lets try crossing two heterozygotes for pea
  color and flower color.
• PpYy x PpYy
• Take a minute and figure out the possible gametes.

pY
Py
PY
22
Dihybrid Crosses.

• In order to accomplish this you must consider all
  possible gametes for an individual, then perform
  the cross.
• Lets try crossing two heterozygotes for pea
  color and flower color.
• PpYy x PpYy
• Take a minute and figure out the possible gametes.

pY
Py
py
PY
23
Dihybrid Crosses.

• In order to accomplish this you must consider all
  possible gametes for an individual, then perform
  the cross.
• Lets try crossing two heterozygotes for pea
  color and flower color.
• PpYy x PpYy Conduct the cross, calculate
  probabilities.

PY
pY
Py
py





PY
pY
Py
py
24
CW/HW

• Complete both sides of the worksheet by next
  class (25pts). We will develop this and work on
  trihybrid crosses tomorrow.
• Questions on HW.
• Answers, then trihybrid.

25
Trihybrid Crosses

• We have over 30,000 genes.
• Not all of them are Mendelian but many are.
• How would you predict the chances an individual
  inherited this combination of Mendelian traits
  from two heterozygotes
• Cleft chin (d)
• No dimples (r)
• A widows peak (d)
• Attached ear lobes (r)
• Hitchhikers thumbs (r)
• freckles? (d)
• The more variables you consider the higher the
  degree of difficulty is inherent.
• Well stop at three different, non-linked genes
  but considering these will help you appreciate
  just how unique you are!
• The probabilities of another person inheriting
  the exact same combination of alleles you did is
  nearly impossible.

.75 .75x.25 .75x.25x.75 .75x.25x.75x.25 .75x.25x.7
5x.25x.25 .75x.25x.75x.25x.25x.75 0.66 (7 out
of 1000)
26
Trihybrid Crosses

• Consider crossing heterozygotes for flower color,
  pea color, pea shape.
• PpYyRr x PpYyRr
• What should you do?
• First identify all the gametes that could form
  from each parent (independent assortment
  segregation assumed).
• PYR PYr PyR Pyr pYR pYr pyR pyr
• Then set up your 8 x 8 grid and distribute the
  gametes.

27
2nd Distribute gametes
PYR PYr PyR Pyr pYR pYr pyR pyr
PYR PYr PyR Pyr pYR pYr pyR pyr
PYR
PYr
PyR
Pyr
pYR
pYr
pyR
pyr
28

• Combine gametes and analyze.
• What is the
• Genotypic ratio? Phenotypic ratio?

PYR PYr PyR Pyr pYR pYr pyR pyr
PYR PPYYRR PPYYRr PPYyRR PPYyRr PpYYRR PpYYRr PpYyRR PpYyRr
PYr PPYYRr PPYYrr PPYyRr PPYyrr PpYYRr PpYYrr PpYyRr PpYyrr
PyR PPYyRR PPYyRr PPyyRR PPyyRr PpYyRR PpYyRr PpyyRR PpyyRr
Pyr PPYyRr PPYyrr PPyyRr PPyyrr PpYyRr PpYyrr PpyyRr Ppyyrr
pYR PpYYRR PpYYRr PpYyRR PpYyRr ppYYRR ppYYRr ppYyRR ppYyRr
pYr PpYYRr PpYYrr PpYyRr PpYyrr ppYYRr ppYYrr ppYyRr ppYyrr
pyR PpYyRR PpYyRr PpyyRR PpyyRr ppYyRR ppYyRr ppyyRR ppyyRr
pyr PpYyRr PpYyrr PpyyRr Ppyyrr ppYyRr ppYyrr ppyyRr ppyyrr
29

• What is the
• Genotypic ratio? Phenotypic ratio?

GR1PPYYRR2PPYYRr2PPYyRR1PPYYrr4PPYyRr2PPYyrr
1PPyyRR2PPyyRr1PPyyrr 2PpYYRR4PpYYRr2PpYYr
r4PpYyRR8PpYyRr4PpYyrr2PpyyRR4PpyyRr2Ppyyrr
1ppYYRR 2ppYYRr 1ppYYrr2ppYyRR4ppYyRr2ppYyrr
1ppyyRR2ppyyRr1ppyyrr PR27PYR9PYw9PgR3Pgw9
wYR3wgR3wYw1wgw
PYR PYr PyR Pyr pYR pYr pyR pyr
PYR PPYYRR PPYYRr PPYyRR PPYyRr PpYYRR PpYYRr PpYyRR PpYyRr
PYr PPYYRr PPYYrr PPYyRr PPYyrr PpYYRr PpYYrr PpYyRr PpYyrr
PyR PPYyRR PPYyRr PPyyRR PPyyRr PpYyRR PpYyRr PpyyRR PpyyRr
Pyr PPYyRr PPYyrr PPyyRr PPyyrr PpYyRr PpYyrr PpyyRr Ppyyrr
pYR PpYYRR PpYYRr PpYyRR PpYyRr ppYYRR ppYYRr ppYyRR ppYyRr
pYr PpYYRr PpYYrr PpYyRr PpYyrr ppYYRr ppYYrr ppYyRr ppYyrr
pyR PpYyRR PpYyRr PpyyRR PpyyRr ppYyRR ppYyRr ppyyRR ppyyRr
pyr PpYyRr PpYyrr PpyyRr Ppyyrr ppYyRr ppYyrr ppyyRr ppyyrr
30

• What is the
• Genotypic ratio?
• Phenotypic ratio?

• How many (out of 64) will be
• Purple flowers, Yellow peas, Round peas?
• white flowers, green peas, wrinkled peas?
• Purple flowers, green peas, Round peas?
• white flowers, Yellow peas, Round peas?
• Purple flowers, green peas, wrinkled peas?
• Heterozygous for all three traits?

27 of 64
1PPYYRR2PPYYRr2PPYyRR1PPYYrr4PPYyRr2PPYyrr1P
PyyRR2PPyyRr1PPyyrr2PpYYRR4PpYYRr2PpYYrr4PpY
yRR8PpYyRr 4PpYyrr2PpyyRR4PpyyRr2Ppyyrr1ppYY
RR2ppYYRr 1ppYYrr2ppYyRR4ppYyRr2ppYyrr1ppyyR
R2ppyyRr1ppyyrr 27PYR9PYw9PgR3Pgw9wYR3wgR
3wYw1wgw
PYR PYr PyR Pyr pYR pYr pyR pyr
PYR PPYYRR PPYYRr PPYyRR PPYyRr PpYYRR PpYYRr PpYyRR PpYyRr
PYr PPYYRr PPYYrr PPYyRr PPYyrr PpYYRr PpYYrr PpYyRr PpYyrr
PyR PPYyRR PPYyRr PPyyRR PPyyRr PpYyRR PpYyRr PpyyRR PpyyRr
Pyr PPYyRr PPYyrr PPyyRr PPyyrr PpYyRr PpYyrr PpyyRr Ppyyrr
pYR PpYYRR PpYYRr PpYyRR PpYyRr ppYYRR ppYYRr ppYyRR ppYyRr
pYr PpYYRr PpYYrr PpYyRr PpYyrr ppYYRr ppYYrr ppYyRr ppYyrr
pyR PpYyRR PpYyRr PpyyRR PpyyRr ppYyRR ppYyRr ppyyRR ppyyRr
pyr PpYyRr PpYyrr PpyyRr Ppyyrr ppYyRr ppYyrr ppyyRr ppyyrr
31

• What is the
• Genotypic ratio?
• Phenotypic ratio?

• How many (out of 64) will be
• Purple flowers, Yellow peas, Round peas?
• white flowers, green peas, wrinkled peas?
• Purple flowers, green peas, Round peas?
• white flowers, Yellow peas, Round peas?
• Purple flowers, green peas, wrinkled peas?
• Heterozygous for all three traits?

1 of 64
1PPYYRR2PPYYRr2PPYyRR1PPYYrr4PPYyRr2PPYyrr1P
PyyRR2PPyyRr1PPyyrr2PpYYRR4PpYYRr2PpYYrr4PpY
yRR8PpYyRr 4PpYyrr2PpyyRR4PpyyRr2Ppyyrr1ppYY
RR2ppYYRr 1ppYYrr2ppYyRR4ppYyRr2ppYyrr1ppyyR
R2ppyyRr1ppyyrr 27PYR9PYw9PgR3Pgw9wYR3wgR
3wYw1wgw
PYR PYr PyR Pyr pYR pYr pyR pyr
PYR PPYYRR PPYYRr PPYyRR PPYyRr PpYYRR PpYYRr PpYyRR PpYyRr
PYr PPYYRr PPYYrr PPYyRr PPYyrr PpYYRr PpYYrr PpYyRr PpYyrr
PyR PPYyRR PPYyRr PPyyRR PPyyRr PpYyRR PpYyRr PpyyRR PpyyRr
Pyr PPYyRr PPYyrr PPyyRr PPyyrr PpYyRr PpYyrr PpyyRr Ppyyrr
pYR PpYYRR PpYYRr PpYyRR PpYyRr ppYYRR ppYYRr ppYyRR ppYyRr
pYr PpYYRr PpYYrr PpYyRr PpYyrr ppYYRr ppYYrr ppYyRr ppYyrr
pyR PpYyRR PpYyRr PpyyRR PpyyRr ppYyRR ppYyRr ppyyRR ppyyRr
pyr PpYyRr PpYyrr PpyyRr Ppyyrr ppYyRr ppYyrr ppyyRr ppyyrr
32

• What is the
• Genotypic ratio?
• Phenotypic ratio?

• How many (out of 64) will be
• Purple flowers, Yellow peas, Round peas?
• white flowers, green peas, wrinkled peas?
• Purple flowers, green peas, Round peas?
• white flowers, Yellow peas, Round peas?
• Purple flowers, green peas, wrinkled peas?
• Heterozygous for all three traits?

9 of 64
1PPYYRR2PPYYRr2PPYyRR1PPYYrr4PPYyRr2PPYyrr1P
PyyRR2PPyyRr1PPyyrr2PpYYRR4PpYYRr2PpYYrr4PpY
yRR8PpYyRr 4PpYyrr2PpyyRR4PpyyRr2Ppyyrr1ppYY
RR2ppYYRr 1ppYYrr2ppYyRR4ppYyRr2ppYyrr1ppyyR
R2ppyyRr1ppyyrr 27PYR9PYw9PgR3Pgw9wYR3wgR
3wYw1wgw
PYR PYr PyR Pyr pYR pYr pyR pyr
PYR PPYYRR PPYYRr PPYyRR PPYyRr PpYYRR PpYYRr PpYyRR PpYyRr
PYr PPYYRr PPYYrr PPYyRr PPYyrr PpYYRr PpYYrr PpYyRr PpYyrr
PyR PPYyRR PPYyRr PPyyRR PPyyRr PpYyRR PpYyRr PpyyRR PpyyRr
Pyr PPYyRr PPYyrr PPyyRr PPyyrr PpYyRr PpYyrr PpyyRr Ppyyrr
pYR PpYYRR PpYYRr PpYyRR PpYyRr ppYYRR ppYYRr ppYyRR ppYyRr
pYr PpYYRr PpYYrr PpYyRr PpYyrr ppYYRr ppYYrr ppYyRr ppYyrr
pyR PpYyRR PpYyRr PpyyRR PpyyRr ppYyRR ppYyRr ppyyRR ppyyRr
pyr PpYyRr PpYyrr PpyyRr Ppyyrr ppYyRr ppYyrr ppyyRr ppyyrr
33

• What is the
• Genotypic ratio?
• Phenotypic ratio?

• How many (out of 64) will be
• Purple flowers, Yellow peas, Round peas?
• white flowers, green peas, wrinkled peas?
• Purple flowers, green peas, Round peas?
• white flowers, Yellow peas, Round peas?
• Purple flowers, green peas, wrinkled peas?
• Heterozygous for all three traits?

9 of 64
1PPYYRR2PPYYRr2PPYyRR1PPYYrr4PPYyRr2PPYyrr1P
PyyRR2PPyyRr1PPyyrr2PpYYRR4PpYYRr2PpYYrr4PpY
yRR8PpYyRr 4PpYyrr2PpyyRR4PpyyRr2Ppyyrr1ppYY
RR2ppYYRr 1ppYYrr2ppYyRR4ppYyRr2ppYyrr1ppyyR
R2ppyyRr1ppyyrr 27PYR9PYw9PgR3Pgw9wYR3wgR
3wYw1wgw
PYR PYr PyR Pyr pYR pYr pyR pyr
PYR PPYYRR PPYYRr PPYyRR PPYyRr PpYYRR PpYYRr PpYyRR PpYyRr
PYr PPYYRr PPYYrr PPYyRr PPYyrr PpYYRr PpYYrr PpYyRr PpYyrr
PyR PPYyRR PPYyRr PPyyRR PPyyRr PpYyRR PpYyRr PpyyRR PpyyRr
Pyr PPYyRr PPYyrr PPyyRr PPyyrr PpYyRr PpYyrr PpyyRr Ppyyrr
pYR PpYYRR PpYYRr PpYyRR PpYyRr ppYYRR ppYYRr ppYyRR ppYyRr
pYr PpYYRr PpYYrr PpYyRr PpYyrr ppYYRr ppYYrr ppYyRr ppYyrr
pyR PpYyRR PpYyRr PpyyRR PpyyRr ppYyRR ppYyRr ppyyRR ppyyRr
pyr PpYyRr PpYyrr PpyyRr Ppyyrr ppYyRr ppYyrr ppyyRr ppyyrr
34

• What is the
• Genotypic ratio?
• Phenotypic ratio?

• How many (out of 64) will be
• Purple flowers, Yellow peas, Round peas?
• white flowers, green peas, wrinkled peas?
• Purple flowers, green peas, Round peas?
• white flowers, Yellow peas, Round peas?
• Purple flowers, green peas, wrinkled peas?
• Heterozygous for all three traits?

3 of 64
1PPYYRR2PPYYRr2PPYyRR1PPYYrr4PPYyRr2PPYyrr1P
PyyRR2PPyyRr1PPyyrr2PpYYRR4PpYYRr2PpYYrr4PpY
yRR8PpYyRr 4PpYyrr2PpyyRR4PpyyRr2Ppyyrr1ppYY
RR2ppYYRr 1ppYYrr2ppYyRR4ppYyRr2ppYyrr1ppyyR
R2ppyyRr1ppyyrr 27PYR9PYw9PgR3Pgw9wYR3wgR
3wYw1wgw
PYR PYr PyR Pyr pYR pYr pyR pyr
PYR PPYYRR PPYYRr PPYyRR PPYyRr PpYYRR PpYYRr PpYyRR PpYyRr
PYr PPYYRr PPYYrr PPYyRr PPYyrr PpYYRr PpYYrr PpYyRr PpYyrr
PyR PPYyRR PPYyRr PPyyRR PPyyRr PpYyRR PpYyRr PpyyRR PpyyRr
Pyr PPYyRr PPYyrr PPyyRr PPyyrr PpYyRr PpYyrr PpyyRr Ppyyrr
pYR PpYYRR PpYYRr PpYyRR PpYyRr ppYYRR ppYYRr ppYyRR ppYyRr
pYr PpYYRr PpYYrr PpYyRr PpYyrr ppYYRr ppYYrr ppYyRr ppYyrr
pyR PpYyRR PpYyRr PpyyRR PpyyRr ppYyRR ppYyRr ppyyRR ppyyRr
pyr PpYyRr PpYyrr PpyyRr Ppyyrr ppYyRr ppYyrr ppyyRr ppyyrr
35

• What is the
• Genotypic ratio?
• Phenotypic ratio?

• How many (out of 64) will be
• Purple flowers, Yellow peas, Round peas?
• white flowers, green peas, wrinkled peas?
• Purple flowers, green peas, Round peas?
• white flowers, Yellow peas, Round peas?
• Purple flowers, green peas, wrinkled peas?
• Heterozygous for all three traits?

8 of 64
1PPYYRR2PPYYRr2PPYyRR1PPYYrr4PPYyRr2PPYyrr1P
PyyRR2PPyyRr1PPyyrr2PpYYRR4PpYYRr2PpYYrr4PpY
yRR8PpYyRr 4PpYyrr2PpyyRR4PpyyRr2Ppyyrr1ppYY
RR2ppYYRr 1ppYYrr2ppYyRR4ppYyRr2ppYyrr1ppyyR
R2ppyyRr1ppyyrr 27PYR9PYw9PgR3Pgw9wYR3wgR
3wYw1wgw
PYR PYr PyR Pyr pYR pYr pyR pyr
PYR PPYYRR PPYYRr PPYyRR PPYyRr PpYYRR PpYYRr PpYyRR PpYyRr
PYr PPYYRr PPYYrr PPYyRr PPYyrr PpYYRr PpYYrr PpYyRr PpYyrr
PyR PPYyRR PPYyRr PPyyRR PPyyRr PpYyRR PpYyRr PpyyRR PpyyRr
Pyr PPYyRr PPYyrr PPyyRr PPyyrr PpYyRr PpYyrr PpyyRr Ppyyrr
pYR PpYYRR PpYYRr PpYyRR PpYyRr ppYYRR ppYYRr ppYyRR ppYyRr
pYr PpYYRr PpYYrr PpYyRr PpYyrr ppYYRr ppYYrr ppYyRr ppYyrr
pyR PpYyRR PpYyRr PpyyRR PpyyRr ppYyRR ppYyRr ppyyRR ppyyRr
pyr PpYyRr PpYyrr PpyyRr Ppyyrr ppYyRr ppYyrr ppyyRr ppyyrr
36
Punnett Square Practice/Homework

• Complete the worksheet.
• Check the website for the answers.
• Ask questions if you dont understand.
• Pay attention to the process so you can get it
  right.

37
Wednesday February 6, 2013Copy onto your
Quizzie paper the following question. Answer it
and save it to turn in. If you dont know an
answer, get a book and find it or review with a
friend. Blanks will count against you and wrong
answers dont help you.

• Quizzie
• Q1 If a mom thats homozygous recessive for hair
  color (shes blonde) and a dad is heterozygous
  for hair color (he has black hair), what will be
  the possible genotypes of any children they have?
  Show this with a Punnett Square.
• Q2 What chance do the children have to get
  blonde hair?
• Q3 What are the ratios for the genotypes and
  phenotypes?
• -----------------------------
• Agenda
• Check Punnett Squares
• Discussion Test Crosses.
• QL Test Crosses

b b 50 chance of getting blonde hair
B Bb Bb GR 11
b bb bb PR 11
38
Punnett Squares Answers
1 P P
P PP PP
P PP PP
Genotypic Ratio 1PP0 (all) 100PP Phenotypic Ratio 1Purple0(all)100Purple Genotypic Ratio 1PP0 (all) 100PP Phenotypic Ratio 1Purple0(all)100Purple Genotypic Ratio 1PP0 (all) 100PP Phenotypic Ratio 1Purple0(all)100Purple
3 Y Y
y Yy Yy
y Yy Yy
GR 1Yy0 100 Yy PR 1Yellow0 100yellow GR 1Yy0 100 Yy PR 1Yellow0 100yellow GR 1Yy0 100 Yy PR 1Yellow0 100yellow
2 G g
g Gg gg
g Gg gg
GR 1Gg1gg 50Gg, 50gg PR 1green 1yellow 50green, 50yellow GR 1Gg1gg 50Gg, 50gg PR 1green 1yellow 50green, 50yellow GR 1Gg1gg 50Gg, 50gg PR 1green 1yellow 50green, 50yellow
4 P p
P PP Pp
p Pp pp
GR 1PP2Pp1pp 25PP, 50 Pp, 25pp PR 3purple 1white 75purple, 25white GR 1PP2Pp1pp 25PP, 50 Pp, 25pp PR 3purple 1white 75purple, 25white GR 1PP2Pp1pp 25PP, 50 Pp, 25pp PR 3purple 1white 75purple, 25white
39
Thursday February 7, 2013Copy onto your
Quizzie paper the following question. Answer it
and save it to turn in. If you dont know an
answer, get a book and find it or review with a
friend. Blanks will count against you and wrong
answers dont help you.

• Quizzie 3 Imagine you are a farmer and wanted
  to start selling green sweet peas (what Mendel
  produced and studied). You buy a pea plant that
  is sold to you as a true-breeding green pea plant
  for nice round peas. You are skeptical because
  the guy who sold it to you seemed shady. You are
  intending to plant several acres with this
  plants seeds and have a lucrative business.
• Q1 What specific technique could you perform to
  find out exactly what the genotype of your plant
  is?
• Q2 What phenotype would you want all the
  offspring from this technique to be?
• Q3 If the offspring of a test cross all have the
  dominant trait, is the genotype of the individual
  being tested heterozygous or homozygous?
• --------------------
• Agenda
• Discussion Probabilities
• Penny Genetics Lab
• Hand in Testcross MiniLab

40
Using Probability

• A Punnett square shows the possible outcomes of a
  cross, but it also is used to calculate the
  probability of each outcome.
• Probability is the likelihood that a specific
  event will occur out of the total number of
  events.
• Probability can be calculated and expressed in
  many ways.
• Probability can be expressed in words, as a
  decimal, as a percentage, or as a fraction.

41
Using Probability, continued

• Probability formulas can be used to predict the
  probabilities that specific alleles will be
  passed on to offspring.
• Probabilities are usually expressed as decimals
  or as percentages although fractions are okay.
• 2/4 ½ 0.5 50
• ¼ 0.25 25
• ¾ 0.75 75
• The possible results of a heterozygous cross
  (which is trying to predict the genotypes of
  offspring from the mating of two heterozygotes)
  are similar to those of flipping two coins at
  once.
• This is where we will begin our testing.

42
Using Probability

• Punnet Squares are nice tools to use but the real
  question remains
• How can you be sure that the Punnet squares
  accurately show how genetics really works?
• The solution will hopefully be revealed in the
  next exercise
• Penny Genetics

43
Penny Genetics LabTesting the validity of
Punnett Squares.

• Get into groups of two (max). Get one packet per
  pair.
• In groups of two you will perform an
  investigation into whether Punnett Squares can be
  used to predict randomness of nature.
• For the next 5 minutes Completely read the lab
  intro skim the rest. Ill answer questions
  then.
• A Punnett Square makes a prediction but does it
  match the randomness in nature? Perform a Punnett
  Square and then flip coins to see if they match.
• Part I
• First Figure out the PHENOTYPES based upon the
  description.
• Second Predict if the PUNNETT SQUARE will match
  the COIN FLIPS
• Third Complete the PUNNETT SQUARE (this is the
  prediction)
• Fourth Flip the COINS 100x.
• Fifth COMPARE the two.
• You may write on the lab, but dont lose it or
  youll have to hand write it or print it off the
  website.
• Your objective is to get through all of Part I
  Part II if everything goes good so work
  diligently! Complete everything today to save
  yourself homework.
• This Lab is worth 125 points. Due Friday.

44
Monday February 11, 2013Copy onto your Quizzie
paper the following question. Answer it and save
it to turn in. If you dont know an answer, get a
book and find it or review with a friend. Blanks
will count against you and wrong answers dont
help you.

• Quizzie 4
• In pea plants, tallness (T) is dominant to
  shortness (t). Crosses between plants with these
  traits can be analyzed using a Punnett square
  similar to the one shown below.
• Q1 Complete this Punnett Square.
• Q2 Box 2 and box ____________________ in the
  Punnett square represent plants that would be
  heterozygous for the trait for tallness.
• Q3 The phenotype of the plant that would be
  represented in box 4 of the Punnett square would
  be ____________________.
• --------------------------------------------------
  --------------------------------------------------
  ----------------------------
• Agenda
• Discussion Pedigrees
• In-class/ HW Activity Pedigree Analysis
• Penny Genetics DUE. Turn these in to the inbox.

T t
T 1 2
t 3 4
45
Applications of Mendelian Genetics

• Families can sometimes be surprised when
  recessive traits pop up out of seemingly
  nowhere.
• Not knowing how genetics works can stress people
  out unnecessarily.
• If a child expresses, shows, a recessive trait
  but the parents express the dominant trait what
  are the genotypes of the parents how can you
  figure this out?

46
The point of using a Punnett Square

• Punnett squares are useful when predicting the
  ratios of offspring.
• For example, is you want to know the probability
  of how many siblings in your family can have the
  phenotype of black hair your can calculate that
  if you know the genotypes of your parents.
• But what if you dont know their genotypes?
• The 1st option is using a test cross.

47
Test Cross Mini Lab

• If you arent sure what the genotype of a
  parent showing a dominant trait is you
  perform a test cross.
• In a test cross, you always cross the unknown
  with a homozygous recessive individual.
• The difference is in the ? allele.
• What does it mean if half of the offspring show
  the recessive trait?

B ?
b
b
Bb b?
Bb b?
48
Test Cross

• The test-cross mating can have two possible
  phenotype outcomes.
• All dominant offspring
• What would the ? have to be?

B ?
b
b
Bb b?
Bb b?
49
Test Cross

• The test-cross mating can have two possible
  phenotype outcomes.
• Half recessive offspring.
• What would the ? have to be?

B ?
b
b
Bb b?
Bb b?
50
Genes Linked Within Chromosomes

• Many traits do not follow Mendels laws because
  he studied the simplest kinds of heredity where
  characters are determined by independent genes.
• Genes that are close together, as well as the
  traits they determine, are said to be linked.
• During meiosis, genes that are linked (close
  together) on the same chromosome are less likely
  to be separated than genes that are far apart.
• We discussed this in Punnett Squares when we
  challenged independent assortment.
• Linked genes tend to be inherited together.
• Sex-linked genes are those genes inherited
  together based upon gender chromosomes.

51
Linked v Non-linked
Linked
Linked
Not-Linked
Not-Linked
52
What is Sex-Linked? How does it happen?
STANDARD GENDER DISTRIBUTION PROBABILITY 50
MALE - 50 FEMALE
X Y
X XX XY
X XX XY
XC Y
XC XCXC XCY
Xc XCXc XcY
STANDARD GENDER DISTRIBUTION PROBABILITY 50/50
BUT ADD INTO THE MIX COLOR-BLINDNESS, WHICH IS
ONLY FOUND ON THE X CHROMOSOME
53
A Sex-Linked TraitRed-Green Color Blindness

• Can you see the numbers?

Trace from x to x theres a line there.
X
X
54
Sex-Linked Gene Inheritance
Notice the distribution of the alleles. In this
case you must take two things into account. Sex
the allele.
XC Xc
XC XC XCXC
Y XC XcY
55
Test Crosses Linkage Exercises

• Complete the worksheet for homework.

56
Show the cross of a man who has hemophilia with a
woman who is a carrier along with the
genotypic/phenotypic ratios for the possible
offspring.
GR 1XHXh1XhXh1XHY1XhY PR 2 F Norm 1 M Norm
1 M Hemophilia
XH Xh
Xh XHXh XhXh
Y XHY XhY
57
The Royal Disease

• European Royalty in the 19th 20th centuries
  came with a price.
• Although many were spared the horrible tragedy of
  bleeding to death, some were not so lucky due to
  the pervasive recessive X-linked trait hemophilia.

58
Hemophilia in History Study in pedigree.The
most famous example.
Men who died of Hemophilia in Order of Death Men who died of Hemophilia in Order of Death Men who died of Hemophilia in Order of Death
Name Death Relation to Queen Victoria
Prince Friedrich of Hesse and by Rhine 29-May-1873 grandson
The Prince Leopold, Duke of Albany 28-Mar-1884 son
Prince Heinrich Friedrich of Prussia 26-Feb-1904 great grandson
Lord Leopold Mountbatten 23-Apr-1922 grandson
Prince Rupert of Teck 15-Apr-1928 great grandson
Infante Gonzalo of Spain 13-Aug-1934 great grandson
Alfonso, Prince of Asturias 6-Sep-1938 great grandson
Prince Waldemar of Prussia 2-May-1945 great grandson
59
Pedigrees. Genetics Tool

• Now
• Karyotyping Detect obvious chromosome
  abnormalities
• Genetic testing Detect hidden mutations in DNA
• Some disabilities arent fatal
• Red-green color blindness
• Albinism
• But others are
• Hemophilia
• Duchene muscular dystrophy
• Do you think its important to study these
  diseases and how they are passed through
  families?

60
Pedigrees

• Other than determining the probabilities of
  Mendelian traits being inherited and displayed in
  a monohybrid cross (aka Punnett Square),
  geneticists use another tool, called a pedigree,
  to identify patterns of inheritance in multiple
  generations.

http//www.youtube.com/watch?v W7x1ETPkZsk
61
Using a Pedigree

• Mendel observed several generations of pea plants
  to help identify some trends in heredity.
• His observation of inheritance is a good example
  of performing an isolated family history study to
  see how a trait is inherited.
• A pedigree is a similar study, except over many
  generations.
• A pedigree is a diagram that shows several
  generations of a family and the occurrence of
  certain genetic characteristics.
• A primary reason a pedigree is used is to help a
  family understand a genetic disorder and how its
  passed on.
• A genetic disorder is a disease or disorder that
  can be inherited.

62
Using a Pedigree

• A pedigree can help answer questions about three
  aspects of inheritance
• Sex linkage
• - To identify which deleterious genes are located
  on the X chromosome (deleterious BAD)
• Dominance
• - Identify the dominant or recessive alleles
• Heterozygosity (aka a Carriers for a disease)
• - Help determine the genotype of parents.

63
Using a Pedigree Sex Linked Genes
Hemophilia High blood pressure DMD Congenital
night blindness

• The sex chromosomes, X and Y, carry genes for
  many characters other than gender.
• A sex-linked gene is located on either an X or a
  Y chromosome.
• Traits that are not expressed equally in both
  sexes are commonly sex-linked traits.
• Examples
• Colorblindness a sex-linked trait that is
  expressed more in males than in females.
• Baldness expressed more in males
• Any other ones?...

64
Using a Pedigree Dominance, Carriers

• Dominance If a person has a trait that is
  autosomal (meaning what?) and dominant and has
  even one dominant allele, he or she will show the
  trait.
• Dominant traits have a tendency to show up more
  often than not.
• They do follow Mendelian probabilities though.
• Heterozygosity If a person is either
  heterozygous or homozygous dominant for an
  autosomal gene, his or her phenotype will show
  the dominant trait.
• If a person heterozygous for a recessive trait he
  or she will not show the trait but can and may
  pass it on.
• Why would the trait not be passed on?
• There is a 50/50 chance of passing it on.
• Persons carrying the recessive allele but not
  displaying the trait are called carriers.

65
Pedigree Basic Symbols
Horizontal lines show relationships that produced
offspring
Vertical lines show offspring from the pair
Siblings
66
Group Questions. Using alleles A, a, you have 5
minutes to discuss with your group and answer.

1. What is the sex of individual 3?
2. Who shows the trait?
3. Is this trait dominant or recessive? Why?
4. What is the genotype of individual 3?
5. What are the genotypes of Mom Dad?
6. Who can you not determine the genotype for?
7. BONUS Is this trait sex-linked? How do you know?

1. Female
2. Female 3
3. Recessive or mom dad would have it.
4. aa
5. Aa, Aa
6. Siblings 1, 2, 4
7. No, otherwise dad would have the trait too. One
   of the Xs for 3 would have to come from dad.

67
Using a Pedigree Strategy

• Remember
• If a person is homozygous recessive, his or her
  phenotype will show the recessive trait.
• A recessive trait in a child shows that both
  parents were heterozygous carriers of that
  recessive allele.
• Dominant traits show up more often than
  recessive.
• Look for the people displaying the trait! Using
  logic you can determine the parents genotypes ?
  then the siblings.
• Pedigree Analysis Practice. (CW/HW 25pts)
• Example 1 has 2 unknowns, not 9.
• Pedigree Mini-Lab exercise. (HW)
• You may work in groups of two and you can write
  on the worksheet.
• Problems should be worked out today and this is
  due tomorrow.
• It is worth 25 pts (1/4 lab).

68
Summary

• A Punnett square shows all of the genotypes that
  could result from a given cross.
• Probability formulas can be used to predict the
  probabilities that specific alleles will be
  passed on to offspring.
• A pedigree can help answer questions about three
  aspects of inheritance sex linkage, dominance,
  and heterozygosity.

69
Genotypes Allele combo
F
F
F
F
f
Phenotypes Trait
f
F
f
f
70

71
Section 12.1-12.3 Quiz

• The quiz says 12. 12.2 but its for sections
  12.1-12.3.
• Write all answers on a separate sheet of paper.
• Do not write on the quiz.
• If you write on the quiz you will get a zero.
• You may use books.
• Correct answers are worth 1 pt. ea.
• You do not need to write complete sentences.
• Double check your work before you turn them in.
• Turn in your answers to the test/quiz tray in the
  back.

72
(No Transcript)