MI unit 2

Single-Gene Disorder

Mutation in one gene, causes one protein to be made incorrectly

Multifactorial Disorder

Caused by a variety of mutations in several genes and introns as well as environmental factors. They are often the cause of several chronic disorders.

Chromosomal Disorders

Normal: 44 (22 pairs) autosomal chromosomes and 2 (1 pair) sex chromosomes.

Whole/partial missing/extra chromosome

Diagnosed with karyotypes (picture of the chromosomes)

Mitochondrial Disorders

Caused by mutations in mitochondrial DNA (not in the nucleus). Mitochondrial DNA is only passed down by the mother (only one copy of the gene). Deals with energy and metabolism. It usually affects all cells in the body, but not always.

Preimplantation Genetic Diagnosis

Used following in vitro fertilization. Babies are tested for genetic defects and only healthy babies are inserted into the mother.

Amniocentesis

Done during the second trimester of pregnancy. Takes a sample of the amniotic fluid for genetic testing (requires use of an ultrasound)

Polymerase Chain Reaction

Melt: Highest temperature to separate strands

Anneal: Lowest temperature to allow primers to bind

Extend: Middle temperature to allow Taq polymerase to copy DNA

Final Extension: 10 minutes of extend to allow all DNA to copy.

Done in a thermocycler

Genotype

Genetic code for a gene

Phenotype

Expression of gene (Ex. Blue eyes, brown hair)

How much of their genetic code do all humans share?

99.9%

Single Nucleotide Polymorphisms

SNPs, Single nucleotide differences in the human genome that separate each individuals

Gene Therapy

Replacing abnormal genes with healthy ones to cure/treat genetic disorders

Moral issues: Playing God, safety, abuse, going to far

Vectors

Delivery System for genes, frequently viruses, can be RNA

Retrovirus

Carries DNA as RNA, can hold up to 8,000 base pairs. It is possible to target specific cell types and new DNA will duplicate with the cell. However, it may cause an immune response.

Adenovirus

Carries DNA as double stranded DNA and can hold up to 7,500 base pairs. It affects dividing and non-dividing cells and can target specific cells.

Adeno-Associated Virus

Carries DNA as single-stranded DNA and can hold up to 5,000 base pairs. It does not make humans ill, infects dividing and non-dividing cells, can target specific cells, will integrate with the DNA of the host cell, and inserts into a specific region that does not harm humans 95% of the time. However, it requires a helper virus to replicate and fewer base pairs are transferred.

Herpes Simplex Virus

Carries DNA as double stranded DNA and can hold up to 20,000 base pairs. It does not disrupt the host cell's genes, and it lasts a long time, including through replication, as a circular piece of DNA. However, it only targets the nervous system, does not integrate into the host cell's DNA, and may cause an immune response.

Liposome

Carries DNA as a circular piece of double stranded DNA (plasmids) and has no limit on the number of base pairs. It can be engineered to integrate with the host cell's DNA. It cannot target specific cells, and it does not enter the cell wall as effectively as viruses. They are not very effective at integrating with the host cell's DNA even if they are engineered to do so, and some are toxic.

Naked DNA

Carries DNA as a circular piece of double stranded DNA (plasmids) and has no limit on the number of base pairs. It can be engineered to integrate with the host cell's DNA, is generally not toxic, and does not generate and immune response.

Genetic Testing Lab Steps

1. DNA (in cells) extracted from mouth with saline solution.

2. Spin in centrifuge to put DNA in pellet inside cells.

3. Re-suspend the cells in the liquid.

4. Add liquid to cells (opens cell membranes).

5. Centrifuge (DNA in supernatant, cell debris in pellet)

6. Do PCR

7. Two tubes, one digested and one undigested. Add HaeIII to digested.

8. Do PCR again.

9. Gel electrophoresis.

Denaturation

In DNA, the separation of the two strands of the double helix.

(Melt)

Anneal

To be capable of combining with complementary nucleic acid by a process of heating and cooling

Gene

A discrete unit of hereditary information consisting of a specific nucleotide sequence of DNA.

Genetic Counseling

A process of communication that deals with the occurrence or risk that a genetic disorder will occur in a family

Genetic Testing

The use of methods to determine if someone has a genetic disorder, will develop one, or is a carrier.

Restriction Enzyme

A degradative enzyme that recognizes specific nucleotide sequences and cuts up DNA.

Supernatant

The (usually) clear liquid left behind after a precipitate has been spun down to the bottom of a vessel by centrifugation

Thermal Cycler

An instrument that automatically cycles through different temperatures used to complete PCR reactions

Gene therapy

The alteration of the genes of a person afflicted with a genetic disease

Preimplantation Genetic Diagnosis (PGD)

In assisted reproductive technology, the determination of genetic abnormalities in the embryo before it is transferred to the uterus

Vector

An agent (as a plasmid or virus) that contains or carries modified genetic material and can be used to introduce extra genes into the genome of an organism

Genetic counseling

A process of communication that deals with the occurrence or risk that a genetic disorder will occur in a family

Genetic testing

The use of methods to determine if someone has a genetic disorder, will develop one, or is a carrier

Karyotype

A display of the chromosome pairs of a cell arranged by size and shape

Polymerase chain reaction (PCR)

A technique that involves copying short pieces of DNA and then making millions of copies in a short period of time

Primer

A short piece of DNA or RNA that is complementary to a section of template strand and acts as an attachment and starting point for the synthesis strand during DNA replication

Restriction enzyme

A degradative enzyme that recognizes specific nucleotide sequences and cuts up DNA.

Single nucleotide polymorphism (SNP)

One base-pair variation in the genome sequence

Taq polymerase

A DNA synthesis enzyme that can withstand the high temperatures of PCR

Thermal cycler

An instrument that automatically cycles through different temperatures used to complete PCR reactions