Transcript Genetics

Do Now:
True or False?

1. Certain acquired characteristics, such as mechanical or
mathematical skill may be inherited.

2. Color blindness is more common in males than in females

3. A person may transmit characteristics to offspring which he/she does
not show.

4. Certain inherited traits may be altered by the stars, planets or
moon early in development.

5. The total number of male births exceeds female births each year.

6. There is such a thing called “Werewolf syndrome” that could be
linked to genes.
Hypertrichosis
(“werewolf syndrome”)
Stephen Bibrowski as
“Lionel the Lion-faced
Man”
Patterns of Heredity
Genetics
Chapter 4
Objectives:

To distinguish between
heredity and inheritance

To describe Mendel’s
experiments in heredity

To compare heterozygous
vs. homozygous and
dominant vs. recessive.
Genetics = the study of heredity by which traits are
passed from parents to offspring

The passing of genes/traits
from parents to offspring.
Many of your traits, including
eye color, shape of your eyes,
texture of your hair, height,
weight, resemble those of you
parents!
Inheritance -passing of traits by heredity
segment of DNA on a chromosome that codes
for a particular protein

genes occur in
pairs
Thanks Mom and Dad!

We inherit genes from
our parents

Those genes code for
the traits we express

Most traits are coded by
more than 1 gene!
Recall….


A pair of
chromosomes are
called homologous
(homo meaning
same)
Homologous
chromosomes have
the same size,
structure, and
genetic information.
What are alleles?
Alternative forms of a
gene.
Dominant
capital letter (shields
recessive trait)
Recessive
Lowercase letter
(usually hidden)
T = tall
t = short
Do Now

What is genetics?

What are alleles? Provide examples!

Who is the father of genetics!?
The history of Gregor Mendel- 1866

Austrian Monk – Czech

Father of Genetics!

Bred different varieties of
garden pea plants.

First to develop rules that
accurately predict patterns
of heredity.
•
Discovered how traits were
inherited in a population
– 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
1.
Several traits exist in two clear different forms.
Ex: Flower color was either purple OR white
2.
The male and female reproductive parts are enclosed within
the same flower. It is easy to control mating by allowing a
flower to fertilize itself (self fertilization), or you can transfer
pollen to another flower (cross pollination).
3.
The garden peas are:
-
Small
-
Grow easily
-
Mature quickly
-
Produce many offspring.
**Results can be obtained quickly with many offspring.
Steps in Mendel’s research…
1.
Allowed each garden pea to self-pollinate for several
generations to ensure “true-breeding” for that particular
trait.
P Generation = parental generation
2.
Mendel then cross-pollinated two P generation plants that
had different forms of the trait (purple and white flower).
The offspring from that were called the F1 generation.
F1 generation- Filial Generation
3.
Allowed the F1 generation to self-pollinate and those
offspring are called the F2 generation.
F2 Generation - Filial Generation
Mendel’s Crosses with Pea Plants
P1
parental
generation
Pure tall
plants
X
Cross
F1
first filial
generation
F
Pollination
All Tall plants
Self
second filial
2 generation
Pure short
plants
Pollination
787 tall plants, 277 short plants
3 to 1 ratio
Mendel’s 3 Laws of Inheritance
1. Law of Dominance-Each trait is controlled
by 2 factors, one factor (dominant ) may
mask the other factor (recessive ) preventing
it from having an effect.
Mendel’s 3 Laws of Inheritance
 2. Law of Segregation-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
Ww
W
w
Mendel’s 3 Laws of Inheritance
3. Law of Independent Assortment- Gene
pairs (homologous) will separate randomly
into gametes (metaphase I of meiosis)
(Why? Random orientation of homologous pairs at the
metaphase plate)
Mendel Video

https://www.youtube.com/watch?v=GTiO
ETaZg4w
Phenotype vs. Genotype
Genotype: Genetic makeup of an organism (genes).
(internal information. Ex: BB, Bb, bb)
Phenotype: the physical characteristics of an organism.
(Ex. Blue Eyes, or Brown Eyes)
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
Recessive: Need two
recessive alleles in order to
express it. (bb)
Dominant: The expressed
form of the trait when
present (even if it is just 1
allele) (Bb or BB)
In dogs, black fur is dominant
over white fur color.
B = black fur
b = white fur
BB or Bb
bb
If Joseph Gordon-Levitt is heterozygous for black hair…
(H=Black, h=blonde)
 1. What is JGL’s genotype?
 2. What is JGL’s phenotype?
Beyonce is BB. (B= brown eyes, b=blue eyes)
 1. What is her genotype?
 2. What is her phenotype?
 3. Is her heterozygous or homozygous?
Explain.
Punnett Square

A diagram that predicts the outcome of a
genetic cross by considering all possible
combinations of gametes in the cross.

Probability calculations can predict the results of genetic
crosses. It is the likelihood that a specific event will
occur.
= number of one kind of possible outcome
Total number of all possible outcomes
Example: If you flip a coin, you will have 1
outcome, but two possible outcomes.
Your answer would be ½.
Question 1
 A jar
contains 3 red marbles, 7 green
marbles, and 10 white marbles. If a
marble is drawn at random, what is
the probability that this marble is
white?
Question 2
 Suppose
you toss a coin and roll a
dice. What is the probability that you
toss heads and roll a four?
Question 3
 Two
dice are rolled, find the
probability that the sum is equal
to 5.

When flipping a coin and it lands on tails  ½ or 1:2
Genotypic ratio: What is genetically written
 Phenotypic ratio: what physical traits you would see

3:1
3 Black : 1 White
Assign symbols
2. Determine parents genotype
3. Draw punnett square
4. Place gametes on left + top of square
5. Fill in punnett square
6. Analyze + answer questions
1.
T: Tall plants
t: Short plants
1.
2.
Phenotypic Ratio and %:
Genotypic Ratio :
Monohybrid Cross
R= Can roll your tongue
 r= Can’t roll your tongue

R

Genotype Ratio:

Phenotype Ratio:
R
r
r
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
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.
Test cross – an individual with unknown genotype is
crossed with a homozygous recessive individual
Used to determine the genotype of any
individual whose phenotype is
dominant
 Ex: A yellow pea is yellow, but can be YY
or Yy.
 To find out if the yellow pea is
homozygous or heterozygous, you cross
it with a recessive pea and the outcome
will tell you depending on the ratio.
Lets Try a Test Cross
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?
And Another…

In fruit flies, red eyes are dominant over sepia eyes. While
working in your lab late one night, a red eyed fruit fly came in
for a crash landing on your apple. Wanting to know more
about your new friend, you decide to run a test cross on your
little buddy.
 If all of the offspring turn out to be red-eyed ( all 347 of them!!) what
would be the genotypes of the flies used in your test cross? (Use R and
r)
 __________x __________
 Genotypic Ratio:
 Phenotypic Ratio:
Just one more….

You are a mink farmer. In minks, black fur is dominant over
white fur. The market for black mink fur cots is higher than
white fur. You decide only to raise black mink. However, the
guy you bought your minks from seems a little strange. You
want to make sure these minks are true breeds so you run a
test cross.
 Give the phenotypes of the minks in your test cross:
○ _________x________
 In the first run, 30 out of 60 offspring are black, and the test are white!
What are the actual genotypes of the minks in your test cross?
○ ________x_________
 Was the black furred mink a pure breed? What is his genotype?
What is a dihybrid Cross?

A dihybrid cross allows us to predict
possible outcomes of offspring that will
have 2 traits simultaneously.
 Ex: what would you get if you crossed a
Brown-haired brown-eyed male with a
blonde-haired 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
1. Determine parent genotypes
2. Determine alleles to be passed down
3. Set up punnet square
4. Determine outcome
 Phenotype Ratio
 Genotype Ratio
Dihybrid Crosses

Looking at two different traits
 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
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.)
10.3 Gene Linkage and Polyploidy
Several genes on a chromosome
 Gene Linkage:

 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
because they are so close together on a
chromosome.
Drosophila (Fruit Flies)
First organism with linked genes
 Linked genes typically travel together
during crossing over

Chromosome Map
Crossing over occurs more frequently
between genes that are far apart
 Map of genes on a chromosomes and
frequency of crossing over

Polyploidy


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.
Inheritance of Traits

Pedigree – a family history that shows how
a trait is inherited over several generations.

You can see how a genetic disorder runs in
a family.

Carriers are individuals who are
heterozygous for an inherited disorder but
do not show symptoms.

Carriers can pass the allele for the disorder
to their offspring
DO NOW
Fill in the genotypes for the following
pedigree
 B=brown eyes
 b = blue eyes

Do Now

Please hand in your labs in the bin up
front.

Then answer:
 What do you think incomplete dominance
means?
11.2 Incomplete Dominance:
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
Lets Practice!
In snapdragons, flower color is controlled by
incomplete dominance. The allele for Red is R and
the allele for white is W.
1. Knowing this trait is incompletely dominant, what
would be the phenotype for the heterozygous
condition (RW)?_______________
2. For each phenotype below: Identify the
genotype.
Red____________
White ____________
A pink flowered snap dragon is crossed with a
white flowered snapdragon.
Make a Punnett Square and:
1. Give the expected probabilities for each
genotype and phenotype
2. Give the ratios for the genotypes and
phenotypes.
Codominance


Neither trait is dominant instead, both traits are
expressed (No Blending)
Ex) Roan Cows.
 white hair (HW) is codominant with red hair (HR)
 horses with genotype (HRHW) have coats with a mixture of
red and white hairs (roan)
Sickle Cell Disease

Affects red blood cells and ability to transport oxygen.

Homozygous recessive alleles=

Heterozygous=

Homozygous dominant alleles=
Sickle Cell and Malaria
People who are
heterozygous for sickle cell,
have a higher resistance to
malaria.
Multiple alleles – 3 or more alleles that
control a trait
 Example
– blood type (IA,IB,io)
GENOTYPES
IAIA
IAio
RESULTING PHENOTYPES
Type A
Type A
I BI B
IBio
Type B
Type B
I AI B
ioio
Type AB
Type O
Universal Donor?
Sample Problem

Determine the possible offspring of the
following crosses
1. AB and O
 2. AA and BO
 3. AB and AB

More Practice

A father is heterozygous for his type B
blood and the mother has type O blood.
 What are the possible blood types of the
babies born from this couple?
Just one More…..

A father is heterozygous for his type A
blood and his mother is heterozygous
for her type B blood.
 What percentages of their offspring would
you expect to have….
 Type A Blood______%
 Type B Blood______%
 Type AB Blood______%
 Type O Blood______%
Coat Color of Rabbits
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

cc x Ccch
 Genotype and phenotype ratios
Do Now- What do you see?
What do you see?

http://enchroma.com/test/instructions/
Autosomal vs. Sex-Linked

Autosomal – it will appear in both sexes equally
trait whose allele is located on the X or Y
chromosome. Most are recessive.
 X linked: gene is located on the X chromosomes
 Y linked: gene is located on the Y chromosome
Because males carry only one X chromosome, a male who carries a
recessive allele on the X or Y will exhibit the sex linked condition.
A female who carries a recessive allele on one X chromosome will not
exhibit the condition if there is a dominant allele on her other X
chromosome. Needs 2 recessive X to show condition!
What are the chances of having a girl?

How would you go about solving it?
Sex Chromosomes
We have 23 pairs of chromosomes
 1 pair are known as the sex chromosomes, which
determines the sex of the offspring

Males = XY
 Females = XX

Sex-Linked Traits

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 – Interaction of multiple
pairs of genes
A wide range of variability! Genes can be located on
different chromosomes
Traits can be influenced by the
environment!
Hydranga Flowers:
When in acidic soil, they bloom blue flowers
When in basic soil, they will bloom pink flowers
Arctic Fox – Enzymes will make pigments during a
certain time of the year.
Treating Genetic Disorders
Most genetic disorders cannot be cured,
although progress is being made.
 Families who have a history of genetic
disorders are recommended to undergo
counseling before having a child. They can find
out how it could affect their offspring.
 Some genetic disorders can be treated if
diagnosed early enough, such as PKU (lacking
a certain enzyme).

 If known, that child can be put on a certain diet and
medicine routine.
Treating Genetic Disorders

Most genetic disorders cannot be cured, although
progress is being made.

Families who have a history of genetic disorders
are recommended to undergo counseling before
having a child. They can find out how it could
affect their offspring.

Some genetic disorders can be treated if
diagnosed early enough, such as PKU (lacking a
certain enzyme).
 If known, that child can be put on a certain diet and
medicine routine.
What is genetic mapping?


Genetic mapping - also called linkage mapping can offer firm evidence that a disease transmitted
from parent to child is linked to one or more
genes. It also provides clues about which
chromosome contains the gene and precisely
where it lies on that chromosome.
Genetic maps have been used successfully to find
the single gene responsible for relatively rare
inherited disorders, like cystic fibrosis and
muscular dystrophy. Maps have also become
useful in guiding scientists to the many genes that
are believed to interact to bring about more
common disorders, such as asthma, heart disease,
diabetes, cancer and psychiatric conditions.
Gene Therapy

May soon allow scientists to correct certain recessive genetic
disorders by replacing defective genes with copies of a healthy
one.

First step of gene therapy is to isolate a copy of the gene.

Scientists are trying to input that gene into the cell by attaching it
to a cold virus. Attempts in humans have not been successful.

However, the outlook is promising.
Genetic Disorders
Sickle Cell Anemia
 Cystic Fibrosis (CF)
 Hemophilia
 Tay- Sachs Disease
 Huntington’s Disease (HD)
 Hypercholesterolemia

 In Groups, you will research a specific
disease and present it to the class.
TWINS