3 billion base pairs of dna and about 30,000 genes 97% of human dna is junk, as it does not code...
TRANSCRIPT
3 billion base pairs of DNA and about 30,000 genes
97% of human DNA is junk, as it does not code for protein products
Of this junk, some are regulatory sequences controlling gene expressions, some are introns that interrupt genes and most are repetitive sequences that never get transcribed
Some genetic disorders (Huntington’s disease) are caused by abnormally long stretches of tandem repeats (back-to-back repetitive sequences) within affected genes
These tandem repeats can also make up telomeres
Polymorphic regions of DNA are noncoding and vary from one region to the next
Taking DNA from two sources and combining them
Happens naturally during viral transduction, bacterial transformation and conjugation
Transposons jumping around the genome
Also known as biotechnology
Scientists manipulate and engineer genes in the laboratory
Genetic engineering brings about many medical uses as well as ethical issues
Uses:◦ Produce a protein product, like insulin
◦ Replace a nonfunctioning gene in a person’s cells with a functioning gene by gene therapy, which does not look very promising
◦ Prepare multiple copies of a gene for analysis (more genes copied, the more they can be researched)
◦ Engineer bacteria to clean up the environment (some can eat toxic waste)
Isolate a gene (insulin) Insert gene into a plasmid Insert eh plasmid into a vector, a cell that
will carry the plasmid Clone the gene
◦ as bacteria reproduce through fission, plasmid and selected gene are also cloned
Identify the bacteria that contain the selected gene and harvest it from the culture
Restriction enzymes extracted from bacteria ◦ Help bacteria protect themselves against phages
These enzymes cut DNA at specific recognition sequences, such as GAATTC
Often, these cuts are staggered, leaving single stranded sticky ends to form a temporary unit with other sticky ends
The fragments that result from the cuts made by restriction enzymes are called restriction fragments
Common examples are EcoRI, BamHI and HindIII
Used in gene cloning
Separates large molecules of DNA based on their movement through agarose gel in an electrical field
Smaller molecules of DNA run faster and further through the gel
DNA is negative (phosphate groups) and flows from cathode (-) to anode (+)
Also separates proteins and amino acids
In order to run through a gel, the DNA must be cut by restriction enzymes into small enough pieces to move through the gel
DNA can be sequenced to determine the sequence of bases
Can also be used to compare other DNA samples
http://learn.genetics.utah.edu/content/labs/gel/
Radioactively labeled single strand of nucleic acid molecule used to tag a specific sequence in a DNA sample
The probe bonds to the complementary sequence and enables scientist to detect its location
Used to identify a person who carries an inherited genetic disorder
Cell-free, automated technique by which a piece of DNA can be rapidly copied
Billions of copied DNA fragments can be produced within hours
The DNA piece that is to be copied is placed into a test tube with Taq polymerase (heat-stable form of DNA polymerase extracted from extremophile bacteria)
Along with Taq polymerase, a supply of DNA nucleotides and primers are added to the test tube to promote DNA synthesis
Once DNA is amplified, these copies can be studied or used in comparison with other DNA samples
Information regarding target DNA nucleotide sequence must be known
Size of the piece to be amplified must be very short
CONTAMINATION
Restriction fragment is a segment of DNA that results when DNA is treated with restriction enzymes
When scientists compared junk DNA of a population, they discovered that the restriction fragment pattern is different in every individual
Differences are called RFLPs
Pronounced “riflips”
A RFLP analysis of someone’s DNA gives a human DNA fingerprint that looks like a bar code
Everyone’s RFLP is unique, except for identical twins
Can determine fathers in paternity suits
Can identify perps in rape and murder cases
Introns prevent bacterium from cloning human genes ◦ Introns are long, intervening, noncoding
sequences)
Bacteria cannot delete introns after transcription
In order to clone, scientists must insert a gene without introns
In order to do this, scientists extract fully processed mRNA from cells and then use reverse transcriptase to make DNA transcripts of the RNA
The resulting DNA molecule carries the complete coding sequence of interest without introns
Safety◦ Much of the milk available to consumers has
come from cows that were given bovine growth hormone (BGH)
◦ Vegetables have been genetically engineered to produce special characteristics in the vegetables people eat (size, taste, color)
Privacy◦ DNA probes are being used to create DNA
chips, which are about ½ inch square and can hold personal information about someone’s genetic identity
◦ These chips can scan a person for mutations
◦ The main concern is that the information may not remain private, and insurance companies or possible employers can find out personal information