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

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

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)

RFLP animation

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

Fingerprint (12E) activity

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

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

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

21. Briefly describe the process of PCR. ( 12.14)

1. DNA sample is mixed with heat-stable DNA polymerase (taq polymerase), nucleotide monomers, and other ingredients

2. Exposure to heat denatures the DNA molecules

3. Primers hybridize target DNA

4. DNA polymerase attaches complimentary nucletoides

5. DNA is cooled to reanneal

6. Process repeats

PCR animation

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

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

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