Genetic Testing

mutation

a variation in the sequence of nucleotides which can alter the structure of a protein

Point Mutation (Substitution)

A mutation that exchanges one base for another (T for A, C for G)

What are the three affects of Point mutation?

Nonsense, Missense, Silent

Nonsense

ends in a stop

Missense

changes one amino acid

Silent

doesn’t change the amino acid

Frameshift

Changes all subsequent amino acids

Insertion

the addition of a nucleotide

Deletion

the deletion of a nucleotide

Which is worse point or frameshift?

Frameshift

How do mutations affect your phenotype?

they alter the 3D shape of proteins (folding pattern depends on side group)

What causes mutations?

1. Spontaneous mistakes during replication! ERRORS!

2. Mutagens: chem or physical agents

Are Mutations Harmful or Beneficial?

Depends on protein involved

• physical traits may give species an advantage

• chem traits may cause disease

Myostatin gene

Inhibits muscle growth

Genetic Testing

• looks at the genetic makeup of an induvial to determine what type of allele or gene markers they carry.

• some tests are definitive while others indicate the RISK someone has for a possible trait.

Why do Genetic Testing?

• family history of one specific disease - carrier identification or late-onset disorders

• newborn symptoms of genetic disorder

• they are concerned about passing on a genetic problem to their children prenatal

How is Genetic Testing done?

• blood tests

• saliva

• karyotype - chromosomes

What are some concerns of Genetic Testing?

How is info used? by who? are tests definitive? if you have the gene, are you going to develop the trait?

Sickle Cell Disease

• caused by point mutation in the gene that codes for hemoglobin

• causes a change in one amino acid

  • goes from a polar to non-polar amino acid

  • (Glutamic acid -→valine)

What does change in amino acids do?

causes the RBC’s to become stiff, sticky, and sickle shaped

Symptoms if SCD

• blood clotting

• strokes

• kidney damage

• RBCs can rupture

  • number of RBCs decreases

  • less oxygen can be carried

  • fatigue

What appears to be the inheritance of the disease?

H^AH^A = normal RBCs

H^SH^S = develop sickle cell anemia

H^AH^S = have both normal and abnormal hemoglobin. Normally healthy individuals

DNA Fingerprint

• image that identifies an individual based on unique sequences in their genome

• Obtained with use of restriction enzymes, PCR, and gel electrophoresis

Step 1: Polymerase Chain Reaction (PCR)

• used to rapidly make millions to billions of copies of specific DNA sample

1. DNA is heated to separate strands

2. The mixture is cooled, and primers bind to the strands

3. DNA polymerase adds nucleotides to strands, producing two complementary strands

4. Process repeats, and the section of DNA is copied again. Each cycle doubles the amount of DNA.

Step 2: Restriction Enzymes

• Recognize a specific sequence of bases in a DNA molecule

• cleaves (cuts) the DNA at that sequence

• Each persons DNA segments will be different sizes

Where do restriction enzymes come from?

• naturally occur in bacteria

• help protect bacteria against viral infection by cutting virus DNA into nonfunctioning pieces

Step 3: Gel Electrophoresis

• Separates DNA fragments by using an electric field to force them to migrate through a gel

• Separates DNA by size and charge

Electrophoresis Steps

1. DNA is negatively charged so will be attracted to positive charge

2. The positive charge is created by an electrical field

3. The gel acts as a sieve, smaller pieces through more easily than larger pieces