Download genetic engineering

Chapter 5
Heredity
Define heredity.
The passing of traits from parent to
offspring.
The different forms of a trait that
a gene may have are called____.
Alleles
As a result of meiosis, every sex cell has
_____ allele for each trait. During
fertilization, each parent donates _____
chromosome. This results in the _____
alleles for the trait in the new individual.
One
One
Two
The study of how traits are
inherited through the interaction
of alleles is _____________.
Genetics
Who was the Austrian monk known as
the “father of genetics” because of his
experiments with pea plants?
Gregor Mendel
Mendel was the first scientist to study
how ________ are passed from one
generation to the next, and he was first to
use the mathematics of __________ to
explain heredity.
Traits
Probability
One of the things that made Mendel’s
results so accurate is that he used large
numbers of plants. He studied almost
__________ pea plants over a period of
_____ years.
30,000
8 years
When Mendel crossed two homozygous
plants with different expressions of a trait, for
example, GGXgg (homozygous green pea
pods X homozygous yellow pea pods, he
found that the pea pods all looked like one of
the parents. These new plants were called
__________.
hybrids
Gg
Distinguish between alleles that are
dominant and alleles that are recessive.
Dominant: A trait that covers over,
or dominates, another form of that
trait. (R)
Recessive: A trait that is covered
over, or dominated, by another form
of that trait. (r )
Explain the use of a Punnett square.
A Punnett Square is a tool that can be used to
predict the probability of certain traits in
offspring. It shows the different ways the traits
can combine.
In a Punnett square, ________ are used
to represent the alleles. An upper case
letter stands for a ________ allele. A
lower case letter stands for a_________
allele.
Letters
Dominant (T)
Recessive (t)
From the letters on a Punnett square, one can
determine the genotype and phenotype of an
organism. Contrast genotype and phenotype.
Genotype
The genetic makeup of an organism.
(RR)
Phenotype
The way an organism looks and
behaves as a result of its genotype.
(Round seeds)
Most cells in your body have two alleles
for every trait, one allele from the male
parent and one allele from the female
parent. These alleles are located on
__________ within the nucleus of cells.
Chromosomes
An organism with two alleles that
are the same can be described as
__________.
Homozygous
(BB)
An organism that has two different
alleles for a trait can be described as
__________.
Heterozygous
(Bb)
When making a Punnett square, explain
where the letter representing the alleles for
each parent are written.
The two letters for one parent are written along
the top of the grid, one letter per box.
The two letter for the second parent are written
down the side of the grid, one letter per box.
Law of Segregation
When chromosomes separate during
meiosis, alleles separate so that
offspring receive one allele from each
parent.
Law of Independent Assortment
When chromosome pairs separate during meiosis,
they separate independently of other chromosome
pairs.
Law of Dominance
Traits are controlled by alleles, and alleles can
be either dominant or recessive.
When purebred red four o’clocks were bred with
purebred white four o’clocks, the offspring were
pink. When offspring of two homozygous parents
show and intermediate phenotype, this inheritance
is called _____________________.
Incomplete Dominance
Define multiple alleles, and give one
example of a multiple allele in
humans.
A trait that is controlled by more than
two alleles.
Example: human blood type
How many alleles for blood types
are there? Identify them.
Three
A, O, B
Identify the blood type that is an
example of codominance.
AB
Explain how a parent with type A
blood and a parent with type B blood
could have a child with type O blood.
Both parents must be heterozygous and carry the
recessive allele for type O blood.
AO, BO
Define polygenic inheritance and
name three examples of polygenic
inheritance.
When a group of gene pairs act together to
produce a trait.
Examples: eye color, hair color, skin color,
height
Your ___________ plays a role in how some of your
genes are expressed or whether they are expressed at
all. For example, a person who is at risk for skin
cancer might limit his or her exposure to the sun.
environment
When a gene undergoes a change that results
in a trait being expressed differently or when
an error occurs when the DNA is copied
inside the cell, such changes and errors are
called __________________.
mutation
Identify one example of a chromosome
disorder, and briefly explain characteristics
of this disorder.
Down’s Syndrome: Occurs when three copies of
chromosome 21 are produced. Individuals with
this disorder can be short, exhibit learning
disabilities, and have heart problems.
Explain how an individual would get a
recessive genetic disorder.
Both parents would have the recessive allele
responsible for the disorder, and each parent
would pass the allele for the disorder to the
child.
Identify two examples of recessive
genetic disorders.
Cystic Fibrosis
Sickle Cell Anemia
Scientists identified one pair of genes that determine
the sex of an organism. They labeled the pair
_______ in females and _____ in males. The
__________ always determines the sex of the
offspring because he can contribute either an _____ or
a _____ during fertilization.
XX
XY
Male
X
Y
An allele inherited on a sex
chromosome is called a
________________.
sex-linked gene
Color blindness is an example of a
_________________ because this trait
is a recessive allele carried on the _____
chromosome.
Sex-linked disorder
X
Explain why males are more often color
blind than females.
Males only have one X chromosome so
a male with this allele on his X
chromosome is colorblind.
A __________ can be used to trace a trait
through several generations.
Pedigree
Define genetic engineering.
Biological and chemical methods to change
the arrangement of a gene’s DNA to
improve crop production, produce large
volumes of medicine, and change how cells
perform their normal functions.
Which type of genetic engineering involves
inserting a useful section of DNA into a
bacterium?
Recombinant DNA
__________ can be used to produce insulin
for diabetic patients, to produce growth
hormone for dwarfism, and to produce
chemicals to treat cancer.
Recombinant DNA
___________ is a type of genetic
engineering in which a normal allele is
placed in a virus. The virus then delivers
the normal allele to a target cell. The
normal allele replaces the defective one.
Gene Therapy
Gene therapy has been used to control
________________ and some kinds of
_________.
Cystic Fibrosis
Cancer
Explain why stores usually label foods
that have been genetically engineered.
Consumers should have a choice whether or not
they buy genetically engineered foods. The
long-term effects of consuming genetically
engineered foods are not known.
One flower is heterozygous red (Rr), and it is
crossed with a homozygous white flowwer (rr).
What is the probability of one of their offspring
being white?
R
r
Rr
r
rr
50%
r
Rr
rr
In a certain species of plant, purple (P) is
dominant to white (p). If a homozygous
purple plant (PP) is crossed with a
homozygous white (pp), what percentage of
the offspring will be purple?
p
P
P
Pp
Pp
100%
p
Pp
Pp
In a certain species of pine trees,short needles (S) are
dominant to long needles (s). If a heterozygous short
needled pine tree is crossed with another
heterozygous short needled pine tree, what is the
probability that a long needled pine would be an
offspring?
S
S
s
SS
Ss
25%
s
Ss
ss
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