Unit 3.4 Studying Human Genetics and Biotechnology.pptx

calendargrumpyBiotechnology

Dec 14, 2012 (4 years and 7 months ago)

152 views

Page 67

Unit 3.4 Studying Human Genetics
and Biotechnology

A.
Problems Studying Human Genetics

1. Ethically irresponsible to conduct
testcrosses on humans.


Testcross:
method to determine the
genotype for a dominant phenotype (AA or
Aa
?), always use homozygous recessive to
compare unknown to.

2. Humans have long life spans and it
requires decades to produce several
generations to study.


Small number of offspring (and long
gestational periods)


Techniques Used to Study Human Genetics

1. Population Sampling
-

determine how often a trait
appears in a small randomly selected group, then
apply to the entire population.


2. Pedigrees
: graphical record of the inheritance of a
single trait over several generations.


Determined based on family/historical documents,
interviews, photographs, and medical records.



C.
Pedigrees


Shapes represent individuals in pedigrees, connecting
lines represent relationships.


Helpful Hints for figuring out pedigrees


If the pedigree is showing a
SEX
-
LINKED

trait:


No male carriers


Trait cannot be passed from father to son


More males will express the trait



If the pedigree is showing an
AUTOSOMAL recessive

trait



Trait can skip a generation


Trait CAN be passed from father to son



Example: The two parents (P1 generation) must have been carriers
(Bb) for a recessive trait. Neither showed the trait, but they had a
child with the trait (bb).

Practice Pedigree


Type O blood is recessive to Type A and B blood. Tom
had type B blood and married Shana who had type A
blood. Together, they had 2 children: Cherith (Type O)
and Bryan (Type AB). Bryan married Ali (Type O) and
they had 2 children: Christian (Type A) and Jon (who
could not donate blood to Christian). Ali had an affair
with Trent, who was homozygous for blood type A. Ali
and Trent had a child with Type A blood.

P 68


D.
Human Genome Project


The Human Genome Project:
is a
collaborative effort among scientists
worldwide to map the genes of humans.

Allowing them to detect gene variations
on the chromosomes which may indicate
a disorder.


Hopes are to develop gene therapy or
genetically based medicines.


http://www.youtube.com/watch?v=XuUpnAz5y1g


E.
Detection of Genetic Disorders


Genetic Counseling:
can help parents
determine the chances of passing a harmful
genetic trait to their child


Sonograms: use of sound waves to produce a
picture of a fetus


Used to evaluate baby’s growth and development


Blood tests: used to screen for proteins


Alpha
-
Feto

protein test (AFP)
-

Levels determine if
baby is at risk for Down’s syndrome, Turner’s , or
spina

bifida.



Amniocentesis:
Removes amniotic
fluid with fetal cells which can be
cultured and produce a
karyotype
.


Karyotype
: a picture of the
chromosomes


Can identify Down’s,
Klinefelters
, and
Turners.






Chorionic
Villi

Sampling:
removes
tissue from the placenta for
karyotyping
.


This can be done earlier in pregnancy and
is more risky.



F.
Prevention/Treatment


Genetic diseases cannot be cured but treated:


Pain medication: to relieve symptoms.


Occupational Therapy:
help people who have conditions
improve their ability to perform everyday tasks


Blood Transfusions: Sickle
-
cell/ Hemophiliacs may require this.


Gene Therapy:
use vectors (viruses) to replace defective genes
with normal ones


Ex. Treating cystic fibrosis and hemophilia


G.
DNA Fingerprint


DNA fingerprint
-

A unique band pattern made
of DNA fragments.



Unique to every individual, unless you have an
identical twin


Uses for DNA Fingerprinting:


Violent Crimes


determines source of DNA left at a
crime scene.


Paternity
-

used to determine the father of a child


Gel Electrophoresis
-

tool used to create a DNA fingerprint, it
separates pieces of DNA based on size (# of base pairs).

Steps in DNA Fingerprinting


Step 1:
Restriction enzyme cleaves the DNA sample at a specific
sequence.


Restriction enzyme:
the enzymes that “cuts” the DNA between the
nitrogen bases


Cleave:
to Cut



Step 2: DNA fragments are loaded into wells on a gel.


Step 3:
Bands are created as electricity forces DNA fragments
through the gel. Small pieces move further than larger pieces.


Step 4: Compare to other DNA samples.



P 79

http://www.youtube.com/watch?v=AEINuCL
-
5wc&feature=related


H.
Genetic Engineering


Genetic Engineering: Modifying DNA or
creating
recombinant DNA.


Transgenic Organism:
an organism which
contains foreign DNA from another species.


Recombinant DNA:
form of artificial DNA
that is created by combining two different
sources of DNA.



Process in creating Transgenic organism:



Step 1: Restriction enzyme is used to
cleave the desired gene
from a DNA sequence (ex. Insulin).


Step 2: The same restriction enzyme is used to cleave the vector.


Vector:
The structure used to carry the foreign DNA, bacterial plasmids
are commonly used.


Plasmid: Circular DNA found in bacteria



Step 3: Foreign DNA and Vector spliced together


Splice:
Combine


Step 4:
The recombinant DNA is inserted into the host (bacteria
cell). Then the host cell will copy and produce the protein.


Insulin can be produced in large quantities by using genetic
engineering and bacteria.



I.
Bioethical Concerns for Genetic Engineering


Should we produce artificial proteins?


Allergic reactions (adding a peanut gene to a corn plant)


Stem cell research


Environmental problems from creating transgenic
organisms:


Super weeds


Antibiotic resistant bacteria


Destruction of beneficial insects like bees by pesticides


Summary

Look at the diagram on page 70. Explain what is happening in
the picture.


Start with the “Donor Cell” to the final “
Protein Product
.”