Unit 7: Heredity and Biotechnology
The passing of traits
parents and offspring.
lternate versions of a trait (straight v. curly hair, widow’s peak or not)
parents to be mated or bred
Filial Generation (F
offspring of parental generation
) always show same trait as parents
ed flower parent X white flower parent)
Mendel’s Experiments and Results
(Gregor Mendel performed genetic studies on pea plants from the 1830
Mendel crossed two
pure traits and saw that only one of the traits appeare
d in the F
. Then the
in the F
Mendel concluded that something inside the plant controlled which of the two traits appeared, he called it a
What Mendel called a factor, we
and know t
hat they are coded for in DNA
Mendel concluded that since there were two forms of every trait/characteristic
he studied (height, color, seed
texture, etc.) that there were two factors/genes controlling each trait
(1 from each parent
View pea trai
(based on observational evidence
the help of microscopes,
Dominance & Recessiveness
When 2 different
for the same trait app
ear in an organi
sm, 1 gene will
dominate or be exp
ressed, the other
gene will not be
expressed (a dominant
gene will “cover up
the recessive gene)
refers to alleles
of same trait
Example: tall pea plant X short pea plant = tall pea plant
(Tall is dominant to short in pea plants)
ce all organisms have 2
genes for each trait
(one on each homologous chromosome)
, then during the
making of sex cells
must be a separation of
, one to each new sex cell
refers to alleles of same trait
for different traits are not connected, they are sent to sex c
ells independent of
(just because the plant was tall it need not have round seeds)
By luck, the
Mendel studied were located on s
What could cause the Principle of Independent Assortment to be incorrect?
nes do n
ot assort independently.
closely located two genes are on
a chromosome, the more likely they are to
be inherited together.
Genes that are found
on separate chromosomes or are far
her on a chromosome
This information has helped scientists build
such as the one
(the fruit fly)
What can disrupt linkage?
Q: What causes Genetic Variation?
, (c) ______________________
Why were pea plants (or zebra fish
, yeast, bacteria,
and fruit flies today) good organisms to study?
is Gregor Mendel called the “Father of Genetics”?
Dominant alleles will be symbolized with a capital letter (T
recessive alleles with a lower case letter of the dominant allele (t
The actual genes an organism posses
ses (TT, Tt, tt)
one from each parent
expression of the genotype (result of specific genes being turned on)
, Tt =
, tt =
Describes the genotype of
an individual that has a copy of, or carries, the recessive trait, which is not
expressed in the phenotype of the organism
(being heterozygous for a trait)
Multiple Allele Trait
When more than
determine the phe
notype (Example: Blood = A, B, O)
The likelihood that a specific event will occur. It can be expressed as a decimal, percentage,
fraction, or a ratio.
Example: Flipping a coin.
What is the c
nce of flipping heads once?
is the chance of flipping heads three times
in a row?
Predicting the Outc
omes of Genetic Crosses
A tool used to predict the genotypes and phenotypes of genetic crosses.
How to set up a Punnett square:
Identify and abbreviate all known alleles (T = tall, t = short)
Write the genotype of the parents to
be crossed (Tt x tt)
Draw a Punnett square and put one parent across the top and the other
down the side.
Complete the Punnett square. Place the parental alleles in the empty
oxes of their corresponding row or
List all genotypes and phenoty
pes in probability form.
Tall = 50%
tt = 50%
Short = 50%
Tall height is dominant to short height in pea plants. Cross two parents who are both heterozygous for height.
forms of a trait are dominant. The resulting phenotype for a heterozygous offspring
both traits equally.
Since neither one is
recessive, neither one can “cover up” the other.
Example: White x Red = red + white speckles (
Both Red (R) and White (W) are dominant. RW would be both red and white and look roan. Cross a red horse with a white
Offspring Genotype =
Offspring Phenotype =
When neither form of a trait is dominant. The resulting phenotype for a heterozygous offspring
is usually a mix
or blending of th
e two traits (tall + short = medium or black + white = grey)
Neither red (r) nor white (w) is dominant. In incomplete dominance, r & w together would look pink. Cross two pink flowers.
Parental Genotypes =
ffspring Genotypes =
Offspring Phenotypes =
more than 2 alleles
in a population. T
mean that an
has more than 2
alleles for 1 gene; an individual s
till inherits just
allele for each trait from each parent.
Alleles = A, B, O (A and B are both dominant, while O is recessive)
AA or AO
BB or BO
Cross a heterozygous Type A x homozygous T
Those chromosomes that determine the gender of an or
ganism (XX = female, XY = male)
in human body cells).
2 sex chromosomes (either XX or XY)
44 autosomes = 46 chromosomes per
(those carried on the X chromosome, such as colorblindness or male pattern ba
N = Normal Vision, n = colorblind
Possible female genotypes: X
= Normal Vision, X
= Normal Vision (carrier), X
Possible male genotypes: X
Y = Normal Vision, X
Y = Colorblind
Q: What does “carrier” mean?
males be carriers for sex
Cross a normal vision male with a carrier female.
Traits controlled by 2 or more genes
(skin, hair & eye color in humans are determined by
change in the sequence of DNA that affects the genetic information; caused by mutagens.
Examples of mutagens:
germ/sex cell mutation
somatic cell mutation
Types of Mutations
Normal Codon Sequence
Gene or Point Mutation
that only affects
THE CAT ATE THE RAT
CAT ATE THE
Subtraction or Deletion
ATE THE RAT
Substitution or Missense
T ATE THE RAT
on one or more chromosomes.
Diagrams of Chromosomal Mutations
Draw Nondisjunction in the space below:
can lead to a genetic disorder. A
of genetic diseases
described on the next page
Some diseases can be inherited from our parents through alleles that they pass down to us.
A. Chromosomal abnormalities
Caused by a trisomy
chromosome 21; produces mild to severe
Caused by a missing X chromosome (genotype XO). Women with Turner’s syndrome
are sterile because their sex organs do not develop during puberty.
Caused by an extra
chromosome (genotype XXY). Men with this disorder have
underdeveloped sex organs
abnormally long legs
and arms, and large hands.
B. Dominant Allele
The most commo
n form of
ymptoms develop in people’s 30's when the nervous system begins breaking down.
C. Codominant Allele
Sickle cell disease
shaped blood cells develop that can cause blockage in blood vessels
esults in nervous system breakdown and death in the early years.
Excess mucus is present in the lungs, the digestive tract, and the liver. People with CF are
ible to infections
, respiratory and digestive problems.
protein necessary for bloo
. People with this disease can die from a minor cut.
ations lead to genetic disorders, explain ho
A family record that shows how a trait is inherited over several generations. It is useful in helping
determine the risk of having a chil
d with a family disease
Cystic Fibrosis is an autosomal (
linked) recessive disorder caused by a defect in the CFTR gene. This gene codes
for a transport protein called a chloride ion channel that is important for producing sweat, digestive juices, and mucus in o
Defective CFTR proteins cause the bo
dy to produce
unusually thick, sticky mucus that 1) clogs the lungs and leads
to life threatening lung infections; and 2) obstructs the pancreas and stops digestive enzymes from helping your body break
down and absorb food.
A man (III
3) comes from a fami
ly that has a history of
cystic fibrosis in
some offspring. In trying to determine whether or not
he carries an allele for
, he constructed a pedigree of his family’s history in relationship to the condition
Complete the pedigree below. In the spa
ces below each symbol, write as much of the genotype of each
individual as you
from the information provided. Heterozygotes do not show symptoms, so you must determine who is heterozygous and
divide their symbol to indicate that they carry one allele.
Male (no disease)
Female (no disease)
of DNA/genes from one organism to
1. It is also called
recombinant DNA technology
2. Genetic engineering can take place
within a species (e.g. transferring
genes between humans) or between species (e.g. transferring genes
between humans and bacteria).
Why is it possible to transfer genes between
species and still
have the gene function properly?
Steps of Genetic Engineering
collect a sample of the gene they want to transfer
DNA extraction is the
al of DNA
from cells by lysing
and separating the DNA from other cell parts.
Because a gene (1000’s per human chromosome) is so
small, scientists use enzymes to cut out the gene they want to move. In bacteria there
are special enzymes that cut up
DNA that is foreign to that cell. In bacteria these “restriction enzymes” are a defense mechanism against smaller bacteria
and viruses that infect may infect them.
, also known as
re added to the sample of DNA.
Each enzyme identifies its own recognition sequence where it will cut DNA.
b. Researchers choose restriction enzymes that will cut before and after the gene they want to transfer.
c. The restri
ction enzyme cuts the DNA at the specific sequence.
Examples of Restriction Enzymes and their Recognition Sequences
The DNA fragment for the desired gene must then be separated from the rest of the DNA by gel electrophoresis.
The pieces of DNA are called
. A mixture of DNA fragments is placed at one end of a porous gel.
The gel is placed in a box of fluid and connected to a power source that will send electric
ity through the gel.
. The negatively charged DNA molecules move toward the positive end of the gel
. The smaller fragments move faster through the gel
the positive end than the larger fragments.
e. Once the fragments are spread
out enough on the gel, a pattern of bands is revealed.
of Gel Electrophoresis
: Since each organism or individual has a unique DNA sequence, the RFLPs that
result from cutting the DNA with restriction enzymes makes a pattern on the gel th
at is unique to that individual
like fingerprints are patterns that are unique to each human
. This pattern of DNA fragments is called a
(much like bar codes used for scanning merchandise)
, but cannot be determined by a person’s actua
the identification of organisms
using sequences of DNA that vary widely
An organisms DNA is cut
using restriction enzymes. The RFLP’s are then
separated by electrophoresis. The pattern
may be unique for each individual, if the
proper region of DNA is chosen.
Is Jack the father of Payle?
How do you know?
ists found members of a plant species they did not recognize. They wanted to determine if the unknown species was
related to one or more of four known species,
A, B, C,
. The relationship between species can be determined most
accurately by comparin
g the results of gel electrophoresis of the DNA from different species. The chart below represents the
results of gel electrophoresis of the DNA from the unknown plant species and the four known species.
1. Which Plant Specie
has the smallest fragment of DNA? _________________________
2. Which Plant Specie
has the largest fragment of DNA? _________________________
3. Which Plant Spe
is most closely related to the unknown plant? _________________________
4. Which Plant Specie
is least closely related to the unknown plant? _________________________
Q: Identify and explain uses for DNA fingerprinting.
how far a fragment
will move in the gel?
rocess of locating determining the nucleotide or base sequence for
a DNA segment/strand
Hundreds of genomes have been sequenced. The list includes members of all 6 kingdoms (Archaebacteria,
Eubacteria, Protists, Fungi, Plants, & Animals), viruses, and even cellular organelles ( __________________).
(share cost & benefits)
effort to map and sequence the human genome.
The project began in 1990 under
leadership of James Watson, of DNA fa
me, at a cost of $3,000,000,000
A draft sequence was completed in 200
0, and a final sequence was announced in 2003.
What are some uses for the information
the Human Genome Project
(and from sequencing other
therapy used to cure a diseased individual
by correcting or replacing a mutated
1. A normal gene is cut out using restriction en
zymes and copied by PCR
(Polymerase Chain Reaction)
The copies are introduced into the diseased individual.
3. Methods for introducing the gene include
a. using non
harmful viruses (vector) to deliver gene to a cell’s DNA
b. intravenous (IV)
injections into the bloodstream
c. direct insertion into affected cells
Gene Therapy for Sickle Cell Disease
IV. Stem Cells
Unspecialized cells that can produce daughter cells that are specialized (have specific functions).
cells are classified by their
, or ability to become other, specific cells. Adult humans are made
up of over 200 different specialized cells (skin, liver, heart, blood, etc.)
Stem cell categories include:
The most pl
astic or versatile stem cell. When a sperm cell and egg cell unite during fertilization, the result is
celled zygote. The zygote is totipotent because it can give rise to any cell type, including an entire organism. The
zygote will eventually beco
me every cell of an organism including other stem cells. The first few cell divisions make more
totipotent cells, after 4 days the divisions produce pluripotent cells.
Pluripotent cells, like totipotent cells can give rise to any type o
f cell. Unlike totipotent cells, pluripotent cells
cannot create an entire organism. Pluripotent cells give rise to multipotent cells.
These cells are less plastic. They will become one of a few types of cells within a particular tiss
example, multipotent blood cells can become red blood cells, white blood cells, or platelets.
An adult stem cell is a multipotent stem cell in adult humans that is used to replace cells that have been
damaged, infected, or died. Adul
t stem cells are unspecialized cells in specialized tissue.