Transcript PowerPoint

Do Now:
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1. Certain acquired characteristics, such as
mechanical or mathematical skill may be inherited.
2. Certain thoughts or experiences of a mother
mark or alter the hereditary makeup of an unborn
child.
3. Color blindness is more common in males than in
females.
4. A person may transmit characteristics to offspring
which he/she does not show.
5. Certain inherited traits may be altered by the
stars, planets or moon early in development.
6. The total number of male births exceeds female
births each year.
Objectives:
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To distinguish between
heredity and inheritance
To describe Mendel’s
experiments in heredity
To compare
heterozygous vs.
homozygous and
dominant vs. recessive.
Genetics
Chapter 10.2, 10.3, 11.1, and
11.2
Basic Genetics
The
Father
of
Genetics
Gregor Mendel
1866- Gregor Mendel
•Austrian Monk
•Worked with Pea Plants
•Pure breeds
•Self-fertilization
•Discovered how traits were inherited in a
population
Heredity – transmission of
traits from parents to their
offspring
Inheritance
passing of
traits by
heredity
Mendel’s experiments
used pea plants
Pollination – transfer of pollen from
anthers to stigma in flowers
1) self pollination
occurs within the
same flower or
same plant
2) cross pollination
occurs between
different plants
Mendel’s Crosses with Pea Plants
P
parental
1 generation
Pure tall
plants
X
Cross
F1
F2
first filial
generation
Pollination
All Tall plants
Self
second filial
generation
Pure short
plants
Pollination
787 tall plants, 277 short plants
3 to 1 ratio
Definitions
Genetics – study of heredity
Gene – segment of DNA on a
chromosome that codes for a
particular protein
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genes
occur in
pairs
Allele – alternative form of a gene
T = tall
t = short
Recessive
Lowercase
letter (usually
hidden)
Dominant
capital
letter (shields
recessive trait)
G = green
pods
g = yellow
pods
Phenotype –
physical
characteristics
of an organism
(Ex: Blue eyes or Brown Eyes)
Genotype – genetic makeup
of an organism (genes)
(internal information
Ex: BB, Bb, bb)
Where do Phenotypes come from?
Example of Genotype and
Phenotype
TT
genotype
Tall
phenotype
Homozygous – when both alleles
of a pair are the
same
homozygous
dominant
homozygous
recessive
TT
tt
Heterozygous – when both alleles
of a pair are not
the same
heterozygous
(tall)
Tt
In rabbits, black fur color is
dominant over brown fur color
B = black fur
b = brown fur
bb
BB or Bb
Think – Pair - Share
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If Fred Flintstone is heterozygous for black hair.
(B=Black, b=blonde)
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What is Fred’s genotype?
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What is Fred’s phenotype?
Tweety bird is YY. (Y= yellow feathers, y=brown
feathers)
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1. What is his genotype?
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2. What is his phenotype?
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3. Is he heterozygous or homozygous? Explain.
Homework
Worksheet on
homozygous/heterozygous and
dominant and recessive.
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Due Tomorrow (or next time I see
you!)
Do Now:
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Provide an example of the
following terms:
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Heterozygous
Homozygous
Genotype
Phenotype
Dominant
Recessive
Allele
Gene
Objective:
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To describe Mendel’s 3 laws
of inheritance
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Complete a Monohybrid
cross
**Take Out your Homework!!!
1) Law of Dominance
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Each trait is controlled by 2
factors, one factor (dominant ) may
mask the other factor (recessive )
preventing it from having an effect.
P1
F1
F2
2) Law of Segregation
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Each allele a
person has
separates into
different gametes
Ex. Ww – one W
goes in one sperm
and the other w
goes into another
sperm
w W
w
W
Sperm
3) Law of Independent
Assortment
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Gene pairs
(homologous)
will separate
randomly into
gametes
(metaphase I
of meiosis)
Monohybrid Cross
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R= Can roll your tongue
r= Can’t roll your tongue
R
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Genotype Ratio:
R
r
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Phenotype Ratio:
r
Genotypic vs. Phenotypic
Ratios
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Phenotype Ratio:
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Ratio of different physical traits
Ex) Brown eyes ¼ or 25%
Genotype Ratio:
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Ratio of the different possible alleles
Ex) Tt = ¼ or 25%
Test cross – an individual with
unknown genotype is crossed
with a homozygous recessive
individual
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used to determine
the genotype of
any individual
whose
phenotype is
dominant
Lets Try a Test Cross
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Spongebob squarepants doesn’t know
whether or not he is Homozygous
Dominant or Heterozygous for his yellow
color. The recessive trait is a white
sponge. Let’s say that we perform a “test
cross” on spongebob (spongebob + a
white female sponge) and all of the baby
sponges are yellow. What would
spongebob’s genotype be?
Lets Try a Monohybrid together!
1) Daffy Duck is heterozygous for black feathers.
Daisy Duck is homozygous for yellow feathers. Set
up a punnett square and determine probabilities of
their potential offspring. (Both genotype and
phenotype ratios!)
2) B = Black
b = yellow
Practice!
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Get with a partner and work on the
sample problems!
DO NOW:
Sleeping Beauty has freckles. Her
prince charming is heterozygous
for no freckles. What are the
chances of her children having
freckles? Please show your work.
Objectives:
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To set up and complete a
dihybrid cross.
What is a dihybrid Cross?
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A dihybrid cross allows us to predict
possible outcomes of offspring that will
have 2 traits simultaneously.
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Ex: what would you get if you crossed a
Brown-haired brown-eyed male with a blondehaired blue-eyed female? How many of the
children would have brown hair and brown
eyes? Brown hair and blue eyes? Blonde hair
and brown eyes? Blonde hair and blue eyes?
Example
Setting up Dihybrid Crosses
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1. Determine parent genotypes
2. Determine alleles to be passed down
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The FOIL method
3. Set up punnet square
4. Determine outcome
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Phenotype Ratio
Genotype Ratio
Dihybrid Crosses
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Looking at two different traits
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Ex. Hair color and eye color
B=brown eyes
b=blue eyes
R=Brown hair
r=blonde hair
Mother is heterozygous for both traits
Father is heterozygous for eye color and homozygous
dominant for hair color
What could the phenotypes and
genotypes be of their children?
More Practice
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Mickey Mouse is heterozygous for Round
ears and homozygous for Black eyes.
Minnie Mouse also is homozygous for
Floppy ears and heterozygous for Black
eyes. Determine genotype and phenotype
ratios. (B=black, b=brown, R=round, r=
floppy.)
Practice!
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It’s Harry Potter time!! Get with a partner
and work on the sample problems
involving some of my favorite fictional
characters!
DO NOW
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Take out your Harry Potter Homework!
What is the phenotypic ratio for a dihybrid
cross where each parent is heterozygous
for both traits?
Objectives:
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To define gene
linkage and
polypoidy.
To understand
pedigrees and figure
out how to use one.
10.3 Gene Linkage and
Polyploidy
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Several genes on a chromosome
Gene Linkage:
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When two genes are close to each other on
the same chromosome
Gene Linkage
 Linked genes on a chromosome results in
an exception to Mendel’s law of
independent assortment
 Linked genes usually do not segregate
independently
Drosophila (Fruit Flies)
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First organism with linked genes
Linked genes typically travel together
during crossing over
Chromosome Map
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Crossing over occurs more frequently
between genes that are far apart
Map of genes on a chromosomes and
frequency of crossing over
Polyploidy
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Occurrence of one or more extra sets of
all chromosomes in an organism.
Ex. A triploid organism (3n) - means that
it has three complete sets of
chromosomes.
True or False – Correct false
statements
_______ 1. Crossing over occurs more frequently
between genes that are close together on a
chromosome.
_______ 2. Gene linkage was first studied by
using garden peas.
_______ 3. Scientists call a drawing like the one
shown below a chromosome map.
_______ 4. Chromosome map percentages
represent actual chromosome distances.
Matching
Pedigree
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Shows history of a trait in a family
Allows researchers to analyze traits within
a family
Symbols for Pedigree
Lets try to figure out their
genotypes!
Dominant or Recessive
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Pedigrees can depict both dominant and
recessive traits…
Homework
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Pedigree worksheet! Due next class! –
worth 5 points!!
Do Now
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Take out pedigree homework!
Fill in the genotypes for the following
pedigree
B=brown eyes
b = blue eyes
Do Now
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Ariel and Prince Eric are curious to see
what their babies will look like! Eric is
heterozygous for black hair and Ariel has
the recessive trait of red hair. Both are
recessive for blue eyes. If they have 32
children, how many can we EXPECT to
have red hair and blue eyes?
Objectives
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To understand incomplete dominance and
be able to do incomplete dominance
monohybrid crosses.
To explain codominance, multiple alleles,
sex-linked traits, and polygenic
inheritence.
Test Cross
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When the genotype of an individual is
unknown, cross the individual with a
homozygous recessive
The outcome of the cross determines the
genotype of the unknown
11.2 Incomplete Dominance:
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Heterozygous phenotype is an
intermediate phenotype between the two
homozygous phenotypes.
Two alleles are blended
Ex) Four O’clock Flowers
Red + White = Pink
Incomplete Dominance
Codominance
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Neither trait is dominant instead, both
traits are shown (No Blending)
Ex) Roan Cows
Red + White = RED AND WHITE
Sickle Cell Disease
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Affects red blood cells and ability to
transport oxygen.
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Homozygous recessive alleles=
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Heterozygous=
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Homozygous dominant alleles=
Sickle Cell and Malaria
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People who are
heterozygous for sickle
cell, have a higher
resistance to malaria.
Multiple alleles – 3 or more alleles
that control a trait
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Example – blood type (IA,IB,io)
GENOTYPES
IA IA
IAio
IB IB
IBio
IAIB
ioio
RESULTING PHENOTYPES
Type A
Type A
Type
Type
Type
Type
B
B
AB
O
Universal Donor?
Sample Problem
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Determine the possible offspring of the
following crosses
1. AB and O
2. AA and BO
3. AB and AB
Coat Color of Rabbits
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Rabbits have a hierarchy of coat color
4 alleles (C, cch, ch, and c)
Dominant C > cch> ch > c
Recessive
C Full color
cch Chinchilla
ch Himalayan
c albino
Coat Color of Rabbits
Chinchilla
Albino
Full Color
Himalayan
Let’s try a sample problem
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cc x Ccch
 Genotype and phenotype ratios
What do you see?
What do you see?
Sex Linked Traits
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Traits located on the sex chromosomes
(X or Y)
X linked: gene is located on the X
chromosomes
Y linked: gene is located on the Y
chromosome
What are the chances of having a
girl?
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How would you go about solving it?
Sex-Linked Traits
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A man who is color blind marries a woman
that is heterozygous for color blindness.
What is the chance of having a color blind
boy?
Polygenic Traits
 Polygenic traits arise from the interaction
of multiple pairs of genes.
Objectives:
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To define test cross
To define incomplete
dominance
To define codominance
Codominance – condition in which
both alleles of a gene are expressed
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example – roan coat in horses
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white hair (HW) is codominant with red
hair (HR)
horses with genotype (HRHW) have
coats with a mixture of red and white
hairs (roan)
Roan Coat
Objectives:
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To predict the results of
dihybrid crosses by using
a Punnett square
dihybrid cross – cross between
individuals that involves two pair of
contrasting traits