Unit 7: Heredity and Biotechnology

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Oct 23, 2013 (4 years and 21 days ago)

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1

Unit 7: Heredity and Biotechnology



Name: ___________
___________________ Hr______


I
.
H
eredit
y



The passing of traits
from

parents and offspring.


A.

Genetics



________________________
_
____________________


B.

Gene

-

________________
______
_________
__________________



__________________
_______________________________


_________________________________________________

C.

Allele


A
lternate versions of a trait (straight v. curly hair, widow’s peak or not)

D.

Parental Gene
ration (P
1
)



The
parents to be mated or bred
.


E.

Filial Generation (F
1
)



The
offspring of parental generation
.


F.

Pure/true breeding


When

offspring (
F
1
) always show same trait as parents
(P
1
)
.


G.

Hybrid



The
offspring of
2
pure parents
that have

differen
t traits

(
r
ed flower parent X white flower parent)
.


II
.
Mendel’s Experiments and Results

(Gregor Mendel performed genetic studies on pea plants from the 1830
’s
-

1850’
s
)




Mendel crossed two
different
pure traits and saw that only one of the traits appeare
d in the F
1

generation
. Then the
other trait

reappeared

in the F
2

generation.




Mendel concluded that something inside the plant controlled which of the two traits appeared, he called it a
factor.




What Mendel called a factor, we
now
call a





and know t
hat they are coded for in DNA
.




Mendel concluded that since there were two forms of every trait/characteristic
that
he studied (height, color, seed
texture, etc.) that there were two factors/genes controlling each trait

(1 from each parent
)
.

View pea trai
ts below.
























Mendel’s Principles

(based on observational evidence
without

the help of microscopes,
chemistry
, etc...)


1.

Dominance & Recessiveness



When 2 different
genes

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
” or

“turn off”
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)


2

2.

Segregation



Sin
ce all organisms have 2
genes for each trait

(one on each homologous chromosome)
, then during the



making of sex cells

(meiosis)

there

must be a separation of
genes
, one to each new sex cell
(
this



separation/segregation occurs
during

anaphase).






*

refers to alleles of same trait













3.

Independent Assortment



Genes

for different traits are not connected, they are sent to sex c
ells independent of



each other
(just because the plant was tall it need not have round seeds)
.

By luck, the
traits


Mendel studied were located on s
eparate chromosomes.




Q:
What could cause the Principle of Independent Assortment to be incorrect?
_______________________



________________________________________________________________________________________





Linked ge
nes do n
ot assort independently.


The
more
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
from
each



ot
her on a chromosome
may

assort independently.


This information has helped scientists build


chromosome maps

such as the one
shown at



right for
Drosophila

melanogaster


(the fruit fly)
.






Q:
What can disrupt linkage?

____
______________________________________________________________



Q: What causes Genetic Variation?

(a) __________________________________________________________



(b) _____________________________
_________
, (c) ______________________
__________________
_____



Q:
Why were pea plants (or zebra fish
, yeast, bacteria,

and fruit flies today) good organisms to study?



1. _________________________________________________
5.

___________________________________



2. _________________________________________
________
6.

___________________________________



3. _________________________________________________
7.

___________________________________



4. _________________________________________________
8.
___________________________________



Q:

Why

is Gregor Mendel called the “Father of Genetics”?

_________________________________________



_________________________________________________________________________________________



____________________________________________________________
_____________________________


3

III
.

Genetic

Cross

Vocabulary

Dominant alleles will be symbolized with a capital letter (T

-

Tall
);

recessive alleles with a lower case letter of the dominant allele (t

-

short
).

A.

Genotype



The actual genes an organism posses
ses (TT, Tt, tt)
-

one from each parent
.


B.

Phenotype



The
expression of the genotype (result of specific genes being turned on)

-

TT =
Tall
, Tt =
Tall
, tt =
short
.


C.

Homozygous

















D.

Heterozygous

















E.

Carrier



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)
.


F.

Multiple Allele Trait



When more than

two alleles
determine the phe
notype (Example: Blood = A, B, O)
.


G.

Probability



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
ha
nce of flipping heads once?


What
is the chance of flipping heads three times

in a row?



_________________________________ ______________________________________________



IV
.
Predicting the Outc
omes of Genetic Crosses



Punnett Square



A tool used to predict the genotypes and phenotypes of genetic crosses.



How to set up a Punnett square:


1)

Identify and abbreviate all known alleles (T = tall, t = short)


2)

Write the genotype of the parents to

be crossed (Tt x tt)


3)

Draw a Punnett square and put one parent across the top and the other
down the side.


4)

Complete the Punnett square. Place the parental alleles in the empty
b
oxes of their corresponding row or
column.


5)

List all genotypes and phenoty
pes in probability form.


Offspring Genotypes:

T
t

= 50%


Offspring Phenotypes:

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.


Alleles =


Pare
ntal Genotypes:



Offspring Genotypes:




Offspring Phenotypes:



T

t

t

T
t

t
t

t

T
t

t
t













4

Codominance



When
both

forms of a trait are dominant. The resulting phenotype for a heterozygous offspring
displays



both traits equally.

Since neither one is
recessive, neither one can “cover up” the other.


Example: White x Red = red + white speckles (
Roan
)


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
horse.


Alleles =


Parental Genot
ype =


Offspring Genotype =



Offspring Phenotype =






Incomplete Dominance



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)
.


Example:
w
hite x
r
ed =
p
ink

Neither red (r) nor white (w) is dominant. In incomplete dominance, r & w together would look pink. Cross two pink flowers.



Alleles =


Parental Genotypes =


O
ffspring Genotypes =



Offspring Phenotypes =






Multiple Allele
s

-

For

m
any genes
there are

more than 2 alleles
in a population. T
his
does
not

mean that an
individual




has more than 2
alleles for 1 gene; an individual s
till inherits just
1

allele for each trait from each parent.


Alleles = A, B, O (A and B are both dominant, while O is recessive)


Blood Phenotype

Type A

Type B

Type AB

Type O

Genotypes

AA or AO

BB or BO

AB

OO


Cross a heterozygous Type A x homozygous T
ype B


Parental Genotypes:


Offspring Genotypes:



Offspring Phenotypes:



































5

V
.
Genetic Patterns




A.

Sex Determination






1.

Sex Chromosomes



Those chromosomes that determine the gender of an or
ganism (XX = female, XY = male)


2.

Autosomes



All “no
n
-
sex” chromosomes
(22 pair
s

in human body cells).


B.

Human
somatic
cells
-

2 sex chromosomes (either XX or XY)
+

44 autosomes = 46 chromosomes per

somatic

cell


C.

Sex
-
linked traits
(those carried on the X chromosome, such as colorblindness or male pattern ba
ldness):


N = Normal Vision, n = colorblind


Possible female genotypes: X
N

X
N

= Normal Vision, X
N

X
n

= Normal Vision (carrier), X
n

X
n

= Colorblind


Possible male genotypes: X
N

Y = Normal Vision, X
n

Y = Colorblind


Q: What does “carrier” mean?
Why ca
n’t
males be carriers for sex
-
linked traits?

___________________________



______________________________________________________________________________________________



____________________________________________________________________________
__________________



Cross a normal vision male with a carrier female.



Parental Genotypes:



Offspring Genotypes:




Offspring Phenotypes:





*
Polygenic Traits

-

Traits controlled by 2 or more genes

(skin, hair & eye color in humans are determined by

several genes).



VI
.

Mutation



A

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














1.
Gene or Point Mutation



M
utation

that only affects
one gene
.



THE CAT ATE THE RAT





a)
Addition or
Insertion

-

___________________________________________

THE
FAT

CAT ATE THE



b)
Subtraction or Deletion



________________________________________

THE
ATE THE RAT







c)
Substitution or Missense



______________________________________

THE C
O
T ATE THE RAT












6






2.
Chromosomal Mutation



M
utation

that affects
many genes

on one or more chromosomes.



a)
Deletion



________________________________
_
___
_



Diagrams of Chromosomal Mutations





_____________________________________________














b)
Duplication



______________________________
_
____



______________________________________________



c)
Inversi
on



_________________________________
_
___



______________________________________________



d)
Translocation


__________________________
_
_______



______________________________________________










e)
Nondisjuncti
on



__________________________
_
_____

Draw Nondisjunction in the space below:



______________________________________________


M
utation
s

can lead to a genetic disorder. A

few

examples
of the

thousands

of genetic diseases
are
described on the next page
.

VI
I
.
Genetic Disorders
:
Some diseases can be inherited from our parents through alleles that they pass down to us.

A. Chromosomal abnormalities

1.
Down Syndrome:

Caused by a trisomy
(3) of

chromosome 21; produces mild to severe
mental retardation
.

2.

Turner’s Syndrome:

Caused by a missing X chromosome (genotype XO). Women with Turner’s syndrome



are sterile because their sex organs do not develop during puberty.


3.
Klinefelter’s Syndrome
:
Caused by an extra
sex
chromosome (genotype XXY). Men with this disorder have



underdeveloped sex organs
,
abnormally long legs
and arms, and large hands.


B. Dominant Allele

1.
Achondroplasia:

The most commo
n form of

dwarfism.

2.
Huntington's disease:
S
ymptoms develop in people’s 30's when the nervous system begins breaking down.


C. Codominant Allele

1.
Sickle cell disease
:
S
ickle
-
shaped blood cells develop that can cause blockage in blood vessels
.

D.

Recessive

Allele

1.
Tay
-
Sachs disease
:
R
esults in nervous system breakdown and death in the early years.

2.
Cystic Fibrosis:

Excess mucus is present in the lungs, the digestive tract, and the liver. People with CF are



more suscept
ible to infections
, respiratory and digestive problems.



E. Sex
-
linked Disorder


1.

Hemophilia:
M
issing
a

protein necessary for bloo
d clotting
. People with this disease can die from a minor cut.

Q:

Not

all

mut
ations lead to genetic disorders, explain ho
w.




a)
____________________________________________________________________________________________




____________________________________________________________________________________________




b)
____________________________
________________________________________________________________


7

VII
I
.
Human Heredity

Pedigree



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







Pedigree Problem

Cystic Fibrosis is an autosomal (
not

s
ex
-
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
ur
bodies
.
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

CF
, 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
can
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.

























Pedigree Key

Male (no disease)


Male (diseased)


Male (carrier)


Female (no disease)


Female (diseased)


Female (carrier)


Mates


Death


Offspring


Siblings



8

II
.
Biotechnology and
Genetic Engineering



A
.
Genetic Engineering



transfer

of DNA/genes from one organism to
another.




1. It is also called
recombinant DNA technology

or
gene splicing
.


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).


Q:

Why is it possible to transfer genes between
different
species and still
have the gene function properly?

______________
__________________
_____________________________________________________________
_____________________________________________________________


B
.
Steps of Genetic Engineering



1. Scientists
collect a sample of the gene they want to transfer
.

DNA extraction is the
remov
al of DNA

from cells by lysing
the membrane

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.



2.
Restriction enzymes
, also known as
end
o
nucleases
,

a
re added to the sample of DNA.


a.

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













3
.
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
RFLP’s
(
R
estriction

F
ragment
L
ength
P
olymorphisms).




a
. A mixture of DNA fragments is placed at one end of a porous gel.



b
.
The gel is placed in a box of fluid and connected to a power source that will send electric
ity through the gel.



c
. The negatively charged DNA molecules move toward the positive end of the gel
.



d
. The smaller fragments move faster through the gel
toward

the positive end than the larger fragments.



e. Once the fragments are spread
out enough on the gel, a pattern of bands is revealed.










Wel
l


9

Results

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
, just
like fingerprints are patterns that are unique to each human
. This pattern of DNA fragments is called a
DNA
fingerprint

(much like bar codes used for scanning merchandise)
, but cannot be determined by a person’s actua
l fingerprint.


B.
DNA Fingerprinting



the identification of organisms
using sequences of DNA that vary widely
between organisms.

An organisms DNA is cut
using restriction enzymes. The RFLP’s are then
separated by electrophoresis. The pattern
created
may be unique for each individual, if the
proper region of DNA is chosen.




Example Problem:




Is Jack the father of Payle?
_____________




How do you know?

___________________



___________________________________



Example Problem:

Scient
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,
and
D
. 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
(
s
)

has the smallest fragment of DNA? _________________________


2. Which Plant Specie
(
s
)

has the largest fragment of DNA? _________________________


3. Which Plant Spe
cie
(
s
)

is most closely related to the unknown plant? _________________________


4. Which Plant Specie
(
s
)

is least closely related to the unknown plant? _________________________


Q: Identify and explain uses for DNA fingerprinting.



1) ______________
______________________________________________________________________________


2) ____________________________________________________________________________________________


3) ____________________________________________________________________
________________________


4) ____________________________________________________________________________________________


5) ____________________________________________________________________________________________



6) ____________________
________________________________________________________________________



+


+



Well

Q:
What
determines

how far a fragment
will move in the gel?


= RFLP


10

III
.
Genome Sequencing



P
rocess of locating determining the nucleotide or base sequence for
a DNA segment/strand
.


A.

Define
Genome
: ______________________________________________
______________________________
.


B.

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 ( __________________).


C.

Human Gen
ome Project



A
n international

(share cost & benefits)
effort to map and sequence the human genome.




-

The project began in 1990 under
the
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.

Q:

What are some uses for the information
gained
f
rom

the Human Genome Project

(and from sequencing other
organisms’ genomes)
?

_________________________________________________________________________


_
_____________________________________________________________________________________________



IV
.
Gene Therapy



A

therapy used to cure a diseased individual
by correcting or replacing a mutated

gene.




1. A normal gene is cut out using restriction en
zymes and copied by PCR

(Polymerase Chain Reaction)
.



2.
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).

Stem
cells are classified by their
plasticity
, 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:


1.
Totipotent



The most pl
astic or versatile stem cell. When a sperm cell and egg cell unite during fertilization, the result is
a one
-
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.


2.
Pluripotent



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.


3.
Multipotent

-

These cells are less plastic. They will become one of a few types of cells within a particular tiss
ue. For
example, multipotent blood cells can become red blood cells, white blood cells, or platelets.


4.
Adult



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.