Genetic TechnologyBiology: Chapter 13

Selective Breeding

Humans have been selecting for certain alleles for thousands of years

Friendly wolves (dogs)

Fat pigs

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 breeding

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)

Hybrids

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 grasses

How does a breeder find the desired organisms?

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 phenotype.

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 Problem-Solving 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

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 year

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

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

Cloning

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

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 (ADD TO YOUR NOTES)

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 genome

In 2001, the genome was published by…

Both of them, at the same time

In 2003, the project was declared completed

Applications of the Human Genome Project

While the Human Genome Project has not yielded the results hoped for, they did give a starting point for much research.

It did help in the research of breast cancer, Alzheimer's disease

Holds promise for much more

Also, it has led to the sequencing of many other organisms, as well as improvements in sequencing technology

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