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Genetic Technology
Biology: Chapter 13
Selective Breeding
 Humans have been selecting for certain alleles for thousands of
 Friendly wolves (dogs)
 Fat pigs (a lot of bacon)
 Bananas (didn't exist until humans created them from plantains)
 Horses that are strong enough to ride
 Cows that produce a lot of milk
 So many-Pretty much every food you eat is the result of selective
 Many are the result of inbreeding
 Breeding closely related individuals
 We do this when they have a trait that we want (i.e. Dog breeding)
 Heterozygous organisms
 Can be "better" than their ancestors
 We find organisms with traits that we want, and cross them with
other, related organisms with traits that we want.
 Cereal grains such as wheat, corn, and rice are hybrids of wild
How does a breeder find the desired
 Imagine you are a breeder, and want to find a mate for your
organism. You have a desired trait, and you want to ensure
that all offspring will have that trait. How do you ensure that the
mate will always have offspring that have the trait?
 Homozygous recessive is easy to determine because it is expressed in the
 Homozygous dominant and heterozygous may not be apparent
because they will each express the dominant phenotype
 You will need to perform a test cross
 Crossing the organism with an unknown genotype with one whose
genotype is known.
 Usually, a homozygous recessive organism
Example Test Cross-Complete ProblemSolving Lab 13.1
Genetic Engineering
 A method for increasing the frequency of an allele in a population.
 Fast and reliable
 Done by cutting DNA out of an organism and replacing it with DNA
from another organism
 Can be of the same species, or even from a different species
 Bioluminescent trees?
 A.K.A. Recombinant DNA Technology
 Recombinant=recombined
 Made by connecting fragments from different sources
 An organism that receives DNA from an organism of a different
genus are called Transgenic Organisms
 Think "transplant"
Real-Life Application: Golden Rice
 Problem:
 Vitamin A Deficiency (VAD) kills around 670,000 children under the age of 5 each
 Observation:
 Rice is a staple food in the areas most affected by VAD
 Solution:
 Scientists took genes from organisms able to produce vitamin A, and inserted it into
rice DNA.
 Result:
 The rice produced this way can now supply the Vitamin A needs of these people
 Yay!
 Except…
 People who do not understand science are blocking efforts to supply this rice to the
people who need it, despite repeated tests showing it is as safe as plain rice.
Other instances of Genetic Engineering
 Better insulin for diabetics
 Many medications and vaccines
 An effective test for HIV
 Pest resistant crops
 Hypoallergenic pets
 Many, many more
How it is done
 Molecular scissors (restriction enzymes) cut DNA at the
desired point (between specific bases)
 They do so by breaking attaching to and breaking a specific
nucleotide sequence
 A carrier (vector) carries the new DNA in and inserts it
 It then "recombines" with the DNA of the organism, allowing it to
produce the desired protein
 Creating a genetically identical organism
 Useful during genetic engineering
 After inserting the gene into a vector, it is useful to make many
copies of it
 To clone a gene, this gene is inserted into a bacteria
that reproduces rapidly
 Each time the bacteria reproduces, it makes a copy of the gene
 Cloning of Animals
 Not yet successful (Dolly the sheep lived about 5 years)
 Done by scientists controlling fetal formation
 Usually not perfect, and results in too many mutations for the
organism to survive
Polymerase Chain Reaction (PCR)
 Used to replicate DNA outside of an organism
 The amount of DNA in a sample is small
 More is needed for many tests, and to have backup samples in case of error
 Heat is used to separate the strands of DNA
 An enzyme then replicates the DNA (Recall DNA polymerase? That is the enzyme)
 This process is repeated over and over until many copies have been made.
 Each time, the number of copies of DNA doubles
 Can make millions of copies in a day.
 Used to analyze DNA
 Helped with the Human Genome Project
 Helps in diagnosis of disease
 Also used in criminal investigations for DNA fingerprinting (figuring out who did the crime
by comparing their DNA to DNA found at the crime scene)
Sequencing DNA
 DNA is cloned using PCR
 Strands are put into test tubes containing the nitrogenous bases
(Adenine, Guanine, Cytosine, and Thymine) tagged with
fluorescent dyes.
 This created fluorescent complementary strands of different sizes
 All of the nucleotides will now glow a different color and the strands of DNA
will each be a different size
 The DNA is then placed into a gel
 Electricity is added and attracts the DNA
 The smaller strands move faster through the gel because they have less mass
 The larger strands move more slowly because they have more mass
 Looking at what color winds up where, it is possible to decipher a
nucleotide sequence (see pictures on next page)
 This process is called gel electrophoresis
Gel electrophoresis
DNA fingerprinting
 DNA sequencing by gel electrophoresis is useful in criminal
investigations because DNA from the crime scene will create a
"fingerprint," or pattern that can be compared against suspects
DNA fingerprint.
 Which suspect committed the crime?
The Human Genome
 The Human Genome Project began in 1990
 Several companies, both governmental and private, began a race to discover the
entire sequence of DNA in humans
 Humans have about 35,000-40,000 genes
 The NIH began the project, and stated that it would take 15 years
 Craig Venter's company, Celera Genomics, stated that they could do it faster
 This lead to a race between the government and Celera to be the first to sequence the
 In 2001, the genome was published by…
 Both of them, at the same time
 In 2003, the project was declared completed
 However, this was only the first step (gathering information)
 A lot of new stuff coming from it
Applications of the Human Genome
 While the Human Genome Project has not yielded the
results hoped for, they did give a starting point for much
 It did help in the research of breast cancer, Alzheimer's
 Holds promise for much more
 Also, it has led to the sequencing of many other
organisms, as well as improvements in sequencing
Linkage Maps
Where genes occur on chromosomes
Traditional methods were tedious
It was possible to see which traits were on a
chromosome because they are inherited together
Indirect way of finding linkage
Nowadays, machines can find where genes are
located on chromosomes more accurately and
much easier
Gene Therapy
Promising area of research
Insertion of normal genes into people with
abnormal genes
Used to correct genetic disorders
Still in infancy, but developing
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