1. 14. What is a microarray? What can be learned from it? (12.9)
Glass slide with thousands of single-stranded DNA fragments arranged in a grid – each strand from one gene
One array contains DNA from thousands of genes, allowing the researcher to determine which genes are turned on or off in the sample of cells
Can contribute to a better understanding of certain diseases

2. 15. What is gel electrophoresis
15. What is gel electrophoresis? Why do the DNA fragments move through the gel? Why do the smaller fragments move farther? (12.10)
Gel electrophoresis acts as a molecular sieve that separates nucleic acids or proteins on the basis of charge and size
Fragments move because they are attracted to the positive pole (DNA is negatively charged due to phosphate groups)
Larger molecules get slowed down by fibers in the gel…have a harder time trying to navigate through the thick gel…smaller molecules make it further towards the + pole

3. 16. What are RFLPs? What two methods are used to do analysis of restriction fragments? (12.11)
RFLP (Restriction Fragment Length Polymorphism) – when DNA is cut with restriction enzymes, size differences in homologous DNA sequences are reflected in the restriction fragments produced (depends on number of recognition sites)
(1) Gel Electrophoresis (separates strands based on length) and (2) DNA Probes (focus in on bands coming from sequences of interest)

4. 17. Why are RFLPs useful in criminal cases? (12.12)
Because everyone’s DNA is different, different fragment lengths will be produced for different people
Comparison of the gel electrophoresis from samples from the crime scene with samples from suspects can effectively rule people out or provide strong evidence of guilt

5. 18. What is a DNA fingerprint? (12.12)
DNA Fingerprint – a specific pattern of bands resulting from gel electrophoresis of RFLPs
Highly unlikely that two people will have the same fingerprint, HOWEVER, related individuals will share more banding patterns than unrelated individuals
Can be used to determine paternity or in criminal cases

6. 19. What is gene therapy? What are some technical and ethical issues surrounding gene therapy? (12.13)
Gene Therapy – manipulation of DNA to alter an affected individual’s genes
TECHNICAL ISSUES
For a permanent cure, new genes must be transferred to cells which multiply in order to give rise to NEW (fixed) cells
Interference with necessary cell function?
How to assure they will turn on and off correctly?
ETHICAL ISSUES
Who will have access? Will it be restricted to the wealthy?
What kinds of “diseases” should and should not be considered for gene therapy?
Somatic Cell Gene therapy – harder but only affects one individual VS. Germ Line Gene Therapy – easier but affects gene pool and subsequent generations

7. 20. What is PCR? What advantage does this technique have over gene cloning? (12.14)
PCR (Polymerase Chain Reaction) – the amplification (large scale copying) of a segment of DNA; up to 100 billion copies in a few hours
BENEFITS
Faster than gene cloning
Only requires a small sample
DNA can be partially degraded

8. Briefly describe the process of PCR. ( 12.14)
DNA sample is mixed with heat-stable DNA polymerase (taq polymerase), nucleotide monomers, and other ingredients
Exposure to heat denatures the DNA molecules
Primers hybridize target DNA
DNA polymerase attaches complimentary nucletoides
DNA is cooled to reanneal
Process repeats

9. 22. What is repetitive DNA. Where are the short repeats usually found
22. What is repetitive DNA? Where are the short repeats usually found? What function do scientists think these serve? (12.16)
Repetitive DNA – nucleotide sequences present in many copies throughout the genome
Examples include the TATA sequence
Placement at centromeres and at ends of chromosomes (telomeres) suggests that these sequences play a role in chromosome structure & protection
About 97% of DNA in our cells is non-coding

10. Significant loss of telomere DNA  cell death!
23. What are telomeres? What is the relationship between telomeres and cell death? Telomeres and cancer? (12.16)
Telomeres – repetitive sequences at chromosomal ends, possible involvement in protection of chromosomes
Significant loss of telomere DNA  cell death!
Stress has been proven to cause significant telomere shortening!!
“Too Much Stress May Give Genes Gray Hair”
Significant lengthening of the telomere can also lead to immortal cells (such as cancer) which evade normal cell aging

11. 24. What are transposons? What do scientists think they are responsible for? (12.16)
Transposons – “jumping genes,” DNA with long (100s of nucleotides) repeating segments that can move or be copied from one location to another on a single chromosome (or between chromosomes)
Along with disruption of gene function, believed to be responsible for the proliferation of dispersed repetitive DNA in the human genome