Unit 3.4 Studying Human Genetics
Problems Studying Human Genetics
1. Ethically irresponsible to conduct
testcrosses on humans.
method to determine the
genotype for a dominant phenotype (AA or
?), 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
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.
: graphical record of the inheritance of a
single trait over several generations.
Determined based on family/historical documents,
interviews, photographs, and medical records.
Shapes represent individuals in pedigrees, connecting
lines represent relationships.
Helpful Hints for figuring out pedigrees
If the pedigree is showing a
No male carriers
Trait cannot be passed from father to son
More males will express the trait
If the pedigree is showing an
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).
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.
Human Genome Project
The Human Genome Project:
collaborative effort among scientists
worldwide to map the genes of humans.
Allowing them to detect gene variations
on the chromosomes which may indicate
Hopes are to develop gene therapy or
genetically based medicines.
Detection of Genetic Disorders
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
protein test (AFP)
Levels determine if
baby is at risk for Down’s syndrome, Turner’s , or
fluid with fetal cells which can be
cultured and produce a
: a picture of the
Can identify Down’s,
tissue from the placenta for
This can be done earlier in pregnancy and
is more risky.
Genetic diseases cannot be cured but treated:
Pain medication: to relieve symptoms.
help people who have conditions
improve their ability to perform everyday tasks
Blood Transfusions: Sickle
cell/ Hemophiliacs may require this.
use vectors (viruses) to replace defective genes
with normal ones
Ex. Treating cystic fibrosis and hemophilia
A unique band pattern made
of DNA fragments.
Unique to every individual, unless you have an
Uses for DNA Fingerprinting:
determines source of DNA left at a
used to determine the father of a child
tool used to create a DNA fingerprint, it
separates pieces of DNA based on size (# of base pairs).
Steps in DNA Fingerprinting
Restriction enzyme cleaves the DNA sample at a specific
the enzymes that “cuts” the DNA between the
Step 2: DNA fragments are loaded into wells on a gel.
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.
Genetic Engineering: Modifying DNA or
an organism which
contains foreign DNA from another species.
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.
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
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.
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
Antibiotic resistant bacteria
Destruction of beneficial insects like bees by pesticides
Look at the diagram on page 70. Explain what is happening in
Start with the “Donor Cell” to the final “