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Human Heredity
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Karyotypes
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Genome= the full set of genetic information that an organism
carries in its DNA

To see human chromosome, biologists photograph cells in
mitosis (when chromosomes are fully condensed). They then
cut them out and arrange them in a karyotype
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a karyotype shows the complete diploid set of chromosomes
grouped in pairs and arranged in order of decreasing size
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Sex Chromosomes
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First 44 chromosomes = autosomes
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2 of 46 chromosomes- sex chromosomes
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Females: XX
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Males: XY
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X chromosome contains more than 1200 genes
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Y chromosome contains about 140
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Most are associated with male sex
determination and sperm development
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Dominant and Recessive Alleles
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MC1R helps determine skin and hair color
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some of MC1R’s recessive alleles produce red hair
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An individual with red hair usually has two of these recessive
alleles (one from each parent)
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Dominant alleles produce darker hair colors
Rh blood group- Rh+ and Rh
Rh+ is dominant
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Codominant and Multiple Alleles
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ABO blood group determined by a gene with three alleles: IA,
IB, and i
 IA
and IB are codominant—individuals with both alleles produce
both antigens and therefore have the blood type AB
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Homozygous recessive individuals (ii) produce no antigens and
have blood type O
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Sex Linked Inheritance
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Hemophilia
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Colorblindness
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X- Chromosome Inactivation
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In female cells, most of the genes in one of the X
chromosomes are randomly switched off forming a dense
region in the nucleus called a Barr body
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Cats: the color of spots on their fur is controlled by a gene on
the X chromosome. Spots are either orange or black
depending on which X chromosome is inactivated in
different patches of their skin.
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Male cats can have spots of only one color
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Tricolor  must be female
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Human Pedigrees
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A chart used to trace traits over several generations
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Can be used for any species
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Shows the presence or absence of a trait according to the
relationships between parents, siblings, and offspring
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More pedigree symbols…
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1
1
2
2
3
1
4
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1
1
2
2
3
1
4
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When describing a person
you write the generation #
a dash (-) then the
individual number
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Example: II-2 shows the
trait
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Example: II-1 is the oldest
child of the original
parents
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1
1
This pedigree shows
the occurrence of
attached earlobes
(shaded in).
2
2
3
1
Earlobes
E = Free earlobes
e = attached earlobes
4

What is the genotype of I-2?
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What is the genotype of I-1?
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Can II-1 be homozygous
dominant?
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Human Genetic Disorders to know:
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Sickle Cell Disease
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Huntington’s Disease- caused by a dominant allele for a protein
found in brain cells
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symptoms: mental deterioration, uncontrollable movements
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Appear in middle age
Cystic fibrosis (CF)
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Most common in people of European ancestry
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Deletion of 3 bases in the gene for a protein called CFTR removes
phenylalanine from CFTR protein, causing protein to fold improperly
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Cell membranes are unable to transport Cl- ions
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CF allele is recessive
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Children with CF have serious digestive problems and produce thick,
heavy mucus that clogs their lungs and breathing passages
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Genetic Disorders to know…
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Tay-Sachs disease
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Deadly disease of the nervous system
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Autosomal recessive disorder
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Common among Ashkenazi Jewish population
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Symptoms appear between 3-6 months; child usually dies by age
4 or 5
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Symptoms:
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Deafness, blindness
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Loss of muscle strength, loss of motor skills
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Increased startle reaction
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seizures
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Studying the Human Genome
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For a long time, reading the DNA sequences in the human
genome seemed impossible (the smallest chromosome
contains nearly 50 million base pairs!)
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1960’s- scientists found that they could use natural enzymes
in DNA analysis
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By using tools that cut, separate, and then replicate DNA base
by base, scientists can now read the base sequences in DNA
from any cell
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Cutting DNA
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DNA is much too large to analyzed, so it must first be cut into
pieces
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Restriction enzymes= high specific substances produced
by bacteria that can cut even the largest DNA molecule into
precise pieces that are several hundred bases long
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called restriction fragments
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Hundreds of known restriction enzymes
A restriction enzyme is like a key that fits only one lock
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Cutting DNA
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The EcoRI restriction enzyme only recognizes the base
sequence GAATTC.
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Cuts each strand between G and A, leaving single-stranded
overhangs with the sequence AATT
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Overhangs called “sticky ends” because they can bond, or “stick”
to a DNA fragment with the complementary base sequence
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Separating DNA
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Gel electrophoresis= a technique used to separate
and analyze DNA fragments
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DNA fragments are put into wells on a gel that is similar
to a slice of gelatin
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Electric voltage moves them across the gel (gel is
positively charged on the end; fragments are negatively
charged)
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Shorter fragments move faster than longer fragments
Within an hour or two, the fragments separate, each
appearing as a band on the gel
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Reading DNA
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After the DNA fragments have been separated, they are
placed in a test tube containing DNA polymerase, along with
all four nucleotide bases
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DNA polymerase makes new strands of DNA using the
templates
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The researchers also add a small number of bases that have a
chemical dye attached
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Each time a dye-labeled nucleotide is added, DNA
replication stops
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The result is a series of color-coded DNA fragments of
different lengths
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Researchers can then separate these fragments, often by gel
electrophoresis
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The order of the colored bands on the gel tells the exact
sequences of bases in the DNA
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The entire process can be automated and controlled by
computers so that thousands of bases can be read in a matter
of seconds.
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Genetic Engineering
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Selective Breeding
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Humans use selective breeding, which takes advantage of
naturally occurring genetic variation, to pass wanted traits on
to the next generation of organisms.
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New varieties of plants (teosinte  corn!!!)
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Over 150 dog breeds
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Horses, cats, and cows
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Hybridization
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Two common methods of selective breeding:
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Hybridization
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Inbreeding
Hybridization- crossing dissimilar individuals to bring
together the best of both organisms
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Hybrids- individuals produced by such crosses; tend to be
hardier
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Luther Burbank- developed over 800 varieties of plants
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Combined disease resistance with food-producing capacity
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Inbreeding
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Inbreeding= the continued breeding of individuals with
similar characteristics
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Maintains desirable characteristics
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Dogs
Can be risky—most of the members of the breed are
genetically similar
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Increases the chance that a cross between two individuals will
bring together two recessive alleles for a genetic defect
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Human example: Amish (Pennsylvania Dutch)—high incidence of
genetic disorders since almost all descend from about 200 18th
century founders
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Increasing Variation
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Breeders can increase genetic variation in a population by
introducing mutations, which are the ultimate source of
biological diversity.
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Biotechnology= the application of a technological process,
invention or method to living organisms
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
Manipulating the genetic makeup of an organism
Can increase mutations by exposure to radiation or
chemicals
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Can produce a few mutants w/ useful characteristics
+  Bacterial mutations
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Millions of bacteria can be treated at one time increases
chances of being successful
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Allowed scientists to produce hundreds of useful bacterial strains
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Oil-digesting bacteria for cleaning oil spills
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Working on bacteria that can clean up radioactive substances
and metal pollution
Polyploid plants
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Use drugs that prevent that separation of chromosomes
Plant
Probable
Ancestral
Haploid #
Chromosome
Number
Ploidy Level
Domestic oat
7
42
6N
peanut
10
40
4N
Sugar cane
10
80
8N
Banana
11
22, 33
2N, 3N
Cotton
13
52
4N
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Copying DNA
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Extracting DNA- easy.
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Finding a specific gene among millions of fragments- not so
easy.
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Southern blot analysis= a technique for finding specific
DNA sequences, among dozens
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Polymerase chain reaction (PCR)= a technique that allows
biologists to make copies of a specific gene once it is found
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PCR
1.
2.
3.
4.
5.
A short piece of DNA that complements a portion of the
sequence is added (called a primer)
DNA is heated to separate strands
As the DNA cools, primers bind to the single strands
DNA polymerase starts copying the region between the
primers
These copies can sere as templates to make more copies
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PCR
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Recombinant DNA
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A DNA sequence can be synthesized and incorporated into
the DNA of an organism using DNA ligase or other enzymes
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A gene from one organism can also be attached to the DNA
of another organism…called recombinant DNA
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Transgenic Organisms
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Contain genes from other species
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Produced by the insertion of recombinant DNA into the
genome of a host organism
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Can be done in plants and animals
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Cloning
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Genetically Modified (GM)
organisms
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GM crops- resistance to insects, herbicides, viral infections
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Rot and spoilage???
GM animals- 30% of milk in US comes from cows that have
been injected with hormones that increase milk production
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Pigs—more lean meat, high levels of omega-3 acids
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Salmon– growth hormones
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Spider genes in lactating goats—silk
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Antibacterial goat milk
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Recombinant DNA technology in
health and medicine
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Preventing disease
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Medical research- simulate human disease in studies
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Treating disease
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HGH
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Insulin
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Blood clotting factors
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Cancer fighting molecules (interleukin-2 and interferon)
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Gene therapy
The process of changing a gene to treat
a medical disease or disorder
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An absent or faulty gene is replaced by a normal, working
gene
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Engineer a virus that cannot reproduce or cause harmful
effects (just delivers the gene to the target cells)
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Very high risk (Jessie Gelsinger)
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