Tuesday, March 11th
QUESTION TO PONDER:
What is meant by the term map unit?
Looking at the chromosome,
how many map units are there on
this fly chromosome?
Today I will:
1. Discuss three sources of genetic variation
within a population.
2. Review phenotype vs. genotype.
3. Differentiate between dominance and
recessiveness.
AP Biology
Random fertilization
 Any 2 parents will produce a zygote
with over 70 trillion (223 x 223) diploid
combinations
AP Biology
Sources of genetic variability
 Genetic variability in sexual reproduction

independent assortment
 homologous chromosomes in Meiosis 1

crossing over
 between homologous chromosomes in
prophase 1

random fertilization
 random ovum fertilized by a random sperm
AP Biology
metaphase1
Genetic Variation
 How do independent assortment and
random fertilization contribute to genetic
variation?
 Orientation of homologous pairs of

chromosomes with regard to each-other is
random (metaphase I)
There is a 50/50 chance that a particular
daughter cell will receive a paternal or
maternal chromosome
AP Biology
Genetic Variation in all organisms
 In asexually reproducing organisms,
mutations are the primary source of
genetic variation
 In sexually reproducing organisms meiosis
accounts for most of the variation.
AP Biology
Genetics
&
The Work of Mendel
Modified from Kim Foglia
AP Biology
Gregor Mendel
 Modern genetics began in the
mid-1800s in an abbey garden,
where a monk named Gregor
Mendel documented inheritance
in peas
used experimental method
 used quantitative analysis

 collected data & counted them

AP Biology
excellent example of scientific
method
Mendel’s work
 Bred pea plants

Pollen transferred from white
flower to stigma of purple flower
P
cross-pollinate
true breeding parents (P)
 P = parental

raised seed & then
observed traits (F1)
 F = filial

allowed offspring
to self-pollinate
& observed next
generation (F2)
AP Biology
anthers
removed
all purple flowers result
F1
self-pollinate
F2
Mendel collected data for 7 pea traits
AP Biology
Looking closer at Mendel’s work
P
true-breeding
true-breeding
X
purple-flower peas
white-flower peas
F1
100%
purple-flower peas
generation
(hybrids)
100%
self-pollinate
F2
generation
AP Biology
75%
purple-flower peas
25%
white-flower peas
3:1
What did Mendel’s findings mean?
 Traits come in alternative versions
purple vs. white flower color
 alleles

 different alleles vary in the sequence of
nucleotides at the specific locus of a gene
 some difference in sequence of A, T, C, G
purple-flower allele &
white-flower allele are two DNA
variations at flower-color locus
different versions of gene at
same location on homologous
chromosomes
AP
Biology
Wednesday, March 12th
Please complete the following:
A homozygous recessive white pea plant is
crossed with a heterozygous purple pea plant.
What are the possible genotypic and phenotypic
ratios of the offspring (F1)?
Today I will…
1. Review how to complete a test cross.
2. State the law of segregation.
3. Describe dominance vs. recessiveness.
AP Biology
Traits are inherited as discrete units
 For each characteristic, an organism
inherits 2 alleles, 1 from each parent

diploid organism
 inherits 2 sets of chromosomes,
1 from each parent
 homologous chromosomes
 like having 2 editions of encyclopedia
 Encyclopedia Britannica
 Encyclopedia Americana
AP Biology
What did Mendel’s findings mean?
 Some traits mask others

purple & white flower colors are
separate traits that do not blend
 purple x white ≠ light purple
 purple masked white

dominant allele
 functional protein
 affects characteristic
 masks other alleles

recessive allele
 no noticeable effect
 allele makes a
AP Biology
malfunctioning protein
allele producing
functional protein
mutant allele
malfunctioning
protein
homologous
chromosomes
Genotype vs. phenotype
 Difference between how an organism
“looks” & its genetics

phenotype
 description of an organism’s trait

genotype
 description of an organism’s genetic
makeup
X
P
Explain Mendel’s results using
…dominant & recessive
…phenotype & genotype
AP Biology
purple
white
F1
all purple
Making crosses
 Can represent alleles as letters
flower color alleles  P or p
 true-breeding purple-flower peas  PP
 true-breeding white-flower peas  pp

PP x pp
X
P
purple
white
F1
AP Biology
all purple
Pp
Looking closer at Mendel’s work
P
true-breeding
true-breeding
X
purple-flower peas
white-flower peas phenotype
PP
pp
100%
purple-flower peas
F1
genotype
100%
generation
(hybrids)
Pp Pp Pp Pp
self-pollinate
F2
75%
purple-flower peas
25%
white-flower peas
generation
AP Biology
?
?
?
?
3:1
Punnett squares
Pp x Pp
F1
generation
(hybrids)
%
genotype
male / sperm
female / eggs
P
p
PP
25%
75%
Pp
P
PP
%
phenotype
50%
Pp
Pp
p
AP Biology
Pp
pp
pp
25% 25%
1:2:1
3:1
Genotypes
 Homozygous = same alleles = PP, pp
 Heterozygous = different alleles = Pp
homozygous
dominant
heterozygous
homozygous
recessive
AP Biology
Phenotype vs. genotype
 2 organisms can have the same
phenotype but have different genotypes
purple
PP
purple
Pp heterozygous
homozygous dominant
How do you determine the
genotype of an individual with
with a dominant phenotype?
AP Biology
Test cross
 Breed the dominant phenotype —
the unknown genotype — with a
homozygous recessive (pp) to
determine the identity of the unknown
allele
x
is it
PP or Pp?
AP Biology
pp
How does a Test cross work?
x
PP
x
pp
Pp
p
p
P
Pp
Pp
P
Pp
Pp
P
Pp
Pp
p
pp
pp
AP Biology
100% purple
p
pp
p
50% purple:50% white or 1:1
Mendel’s 1st law of heredity
PP
 Law of segregation

during meiosis, alleles segregate
P
P
 homologous chromosomes separate

each allele for a trait is packaged into
a separate gamete
p
pp
p
P
Pp
AP Biology
p
Thursday, March 13th
Please do the following:
Take out your Chapter 14 homework. We will
discuss #3 first. So be prepared!
Today I will:
1. Complete a LAB QUIZ over the Meiosis lab.
• Please have your completed labs on your desk.
2. Describe how to apply Chi Square analysis to a
real-world situation.
AP Biology
Lab Quiz: Meiosis
1. Define crossing over. (+2 pt)
2. Describe homologous chromosomes. (+1 pt)
3. Please list the stages of meiosis, including interphase.
(+ 5 pt)
4. What is the purpose or function of the ascus of the
fungus, Sordaria fimicola? (+ 2 pt)
5. Reproduce your data table (Table 3) from the lab.
(+ 4 pt)
6. What is meant by map units? (+ 1 pt)
7. Suppose your are counting ascospores on a slide.
You find that out of 100 asci, 25 show crossing over
and 75 do not. What is the distance from the gene for
spore color to the centromere (map units)? (+ 5 pt)
AP BiologySet up a table like Table 3 to show your results.
Law of Segregation
 Which stage of
meiosis creates the
law of segregation?
Metaphase 1
AP Biology
Chi Square Analysis
Monday, 3/24
 The chi square analysis allows you to use
statistics to determine if your data is
“good” or not.
 In our M & M Activity we are using laws of
probability to determine possible outcomes
for genetic crosses.
 How will we know if our M & M data is
“good”?
AP Biology
 The following formula is used
If your hypothesis is true, then the squared
deviations between the observed and expected
values will most likely be small and so will the
test statistic.
If your hypothesis is false, then the squared
deviations between the observed and expected
values will most likely be large and so will the test
statistic.
AP Biology
 The test statistic is compared to a theoretical



probability distribution
In order to use this distribution properly you
need to determine the degrees of freedom
Degrees of freedom is the number of
phenotypic possibilities in your cross minus
one.
If the level of significance read from the table
is greater than .05 or 5% then your
hypothesis is accepted and the data is useful
AP Biology
 The hypothesis is termed the null
hypothesis which states that there is no
substantial statistical deviation between
observed and expected data.
 Your null hypothesis:
AP Biology
Monohybrid cross
 Some of Mendel’s experiments followed
the inheritance of single characters
flower color
 seed color
 monohybrid crosses

AP Biology
Dihybrid cross
 Other of Mendel’s
experiments followed
the inheritance of 2
different characters
seed color and
seed shape
 dihybrid crosses

AP Biology
Dihybrid cross
P
true-breeding
yellow, round peas
Y = yellow
R = round
true-breeding
green, wrinkled peas
x
YYRR
yyrr
y = green
r = wrinkled
yellow, round peas
F1
100%
generation
(hybrids)
YyRr
self-pollinate
F2
generation
AP Biology
9:3:3:1
9/16
yellow
round
peas
3/16
green
round
peas
3/16
yellow
wrinkled
peas
1/16
green
wrinkled
peas
YyRr
Dihybrid cross
YR Yr
YyRr x YyRr
YR
Yr
yR
yr
YR YYRR YYRr YyRR YyRr
Yr
YyRr
Yyrr
yR YyRR YyRr yyRR
yyRr
yr
AP Biology
YYRr
YyRr
YYrr
Yyrr
yyRr
yyrr
yR
yr
9/16
yellow
round
3/16
green
round
3/16
yellow
wrinkled
1/16
green
wrinkled
Andrea
Grace
Nate
Mandi
Connor
Melanie
Skyler
Brooke
AP Biology
Alex
Taylor W.
Devin
Cierre
Kylee
Sarah
Britynn
Taylor H.
Zach
Blake
Lauren
Dallas
Becca
Breana
Tuesday, March 25th
QUESTION TO PONDER
Suppose you cross a heterozygous purple
flowered/pure-breeding yellow pea plant with a
white flowered/heterozygous yellow pea plant.
List the phenotypic ratios of the possible F1
generation.
Today I will: 1. Perform a dihybrid cross.
2. Use Chi Squared analysis on Indian corn.
AP Biology
Wednesday, March 26th
Please continue working on your Indian Corn
activity. You need to complete your counting
and be ready to start your Chi Square
Analysis.
When finished, you need to pick up the
article off of the front counter.
The Science and Ethics of Cloning (USA Today)
• Please read this over the course of the next
two days.
AP Biology
Thursday, March 27th
Today I will:
• Define cloning.
• Differentiate between various types of
stem cells, embryonic vs. adult.
Please watch The Island. Be sure to follow
the plotline and pay attention to the details.
AP Biology
Friday, March 28th
Please be prepared to continue with
The Island. You will need to pick up the
ESSAY requirement off of the front counter
today.
You must write a one page essay to
answer the prompt at the top of your paper.
This WILL be taken for a grade, and the due
date is MONDAY,
AP Biology
March 31st.
Mendel’s 2nd law of heredity
 Law of independent assortment

different loci (genes) separate into gametes
independently
 non-homologous chromosomes align independently
 classes of gametes produced in equal amounts
 YR = Yr = yR = yr
 only true for genes on separate chromosomes or
on same chromosome but so far apart that crossing
over happens frequently
YyRr
AP Biology
Law of Independent Assortment
 Which stage of meiosis
creates the law of
independent assortment?
Metaphase 1
AP Biology
EXCEPTION
 If genes are on same
chromosome & close together
 will usually be inherited
together
 rarely crossover separately
 “linked”
The
chromosomal
basis of Mendel’s
laws…
Trace the genetic
events through
meiosis, gamete
formation &
fertilization to
offspring
AP Biology
Review: Mendel’s laws of heredity
 Law of segregation

monohybrid cross
 single trait

each allele segregates into separate gametes
 established by Metaphase 1
 Law of independent assortment

dihybrid (or more) cross
 2 or more traits

genes on separate chromosomes
assort into gametes independently
 established by Metaphase 1
AP Biology
EXCEPTION
 linked genes
metaphase1
Mendel chose peas wisely
 Pea plants are good for genetic research

available in many varieties with distinct
heritable features with different variations
 flower color, seed color, seed shape, etc.

Mendel had strict control over
which plants mated with which
 each pea plant has male & female
AP Biology
structures
 pea plants can self-fertilize
 Mendel could also cross-pollinate
plants: moving pollen from one plant
to another
Mendel chose peas luckily
 Pea plants are good for genetic research

relatively simple genetically
 most characters are controlled by a single gene
with each gene having only 2 alleles,
 one completely dominant over
the other
AP Biology