Biochem Ch 6-7

Question 1

Why are HIV patients at risk for cancers

Answer 1

• with retroviruses, DNA gets randomly incorporated into the genome
• it could be in an oncogene and turn it on; or turn off a Tumor suppressor gene
• However, when gene therapy uses retroviruses, they replace part the retroviral gene with the therapeutic gene, making the retrovirus incapable of self-replication
• retroviruses only invade cells that are dividing

Question 2

Northern Blot

Answer 2

• analyzes RNA
• electrophoresis required
• probe used: 21p-DNA
• used to measure sizes and amounts of specific mRNA molecules to answer questions about gene expression
• typically used to see if genes are being expressed
• ex) pattern of gene expression may give info about disease prognosis and help tailor treatment
  S –D: Southern Blot = DNA
  N–R: Northern Blot = RNA
  O O
  W P: Western Blot = Protein

Question 3

• Retroviruses can invade cells that are ___

- Adenoviruses can invade cells that are ____

Answer 3

• Retroviruses can invade cells that are dividing
• Adenoviruses can invade cells that are not dividing
• however, adenovirus DNA is NOT integrated into the host cell’s chromosome and is eventually lost
• this necessitates repeated treatment with the delivery vector if an adenovirus vector is used

Question 4

Chimeric mice

Answer 4

• contain 2 different sets of stem cells:
• one from the blastocyst donor and one from the original stem cell line
• result is the mouse will have patches of cells (including germ cells) derived from each of the 2 lineages
• composed of 2 distinct cell lines derived from 2 different strains of mice
• can be produced by mixing cells from 2 strains of mice early in embryogenesis, well before the immune system develops
• self-tolerance will allow both types of cells to survive and potentially contribute to the somatic and gremlin tissues of the chimeras
• Chimeras can breed to produce mice that are heterozygous for the transgene and mice that are homozygous for the transgene
• these transgenic mice can transmit the transgene to offspring

Question 5

Southern Blot

Answer 5

• analyzes DNA
• electrophoresis is required
• probe used: 32p-DNA
• used to determine which restriction fragments of DNA are associated with a particular gene
  S –D: Southern Blot = DNA
  N–R: Northern Blot = RNA
  O O
  W P: Western Blot = Protein

Question 6

k

Answer 6

k

Question 7

Dot

Answer 7

• analyzes DNA, RNA or protein
• NO electrophoresis required
• use ASO probes (bind specifically to a single allele of a gene: allele-specific oligonucleotide = ASO)
• used to detect specific DNA, RNA, protein or antibody

Question 8

ampicillin inhibits

Answer 8

peptidoglycan synthesis

Question 9

the DNA sequence recognized by restriction endonuclease EcoRI

Answer 9

• 5’ GAATTC 3’
• pallindrome = an inverted repeat in DNA
  GAATTC
  CTTAAG

Question 10

Western Blot

Answer 10

• AKA immunoblots
• analyzes Protein
• electrophoresis required
• probe used: 125-I or enzyme-linked antibody
• used to measure AMOUNT of antigen (proteins) or antibody
• ex) detect the presence of antibodies to the HIV virus in HIV testing
  S –D: Southern Blot = DNA
  N–R: Northern Blot = RNA
  O O
  W P: Western Blot = Protein

Question 11

uses of PCR

Answer 11

• direct mutation testing
• diagnosing bacterial and viral infections
• HIV testing in situations where antibody tests are uninformative (importantly, infants whose mothers are HIV positive)
• comparing DNA samples in forensic cases (ie paternity testing)
• for PCR to work you need to know the sequence bordering the target region at each of its 3’ ends

Question 12

• STR
• VNTR
• RFLPs
• Genetic fingerprinting

Answer 12

• STR = short tandem repeats
• VNTR = variable number of tandem repeats
• RFLPs = restriction fragment length polymorphisms
• PCR amplification of repetitive sequences such as VNTR
  and STR (short tandem repeat) sequences can be used for genetic fingerprinting
• bc expansion of these repetitive sequences in spacer DNA is highly polymorphic in the population and individual specific

Question 13

cDNA is made from

Answer 13

• mRNA

- only has coding region, no introns

Question 14

measuring viral loads in AIDS patients

Answer 14

• measures the concentration of active circulating virus in the blood of an AIDs patient
• can monitor the status of the infection and the infection’s response to antiviral drugs
  1. a blood sample is treated with reverse transcriptase to produce cDNA from any RNA in the sample
  2. the cDNA is PCR-amplified using primers specific for the end-sequences of the HIV cDNA
• the amplified product is quantitated and related to the original amount of HIV RNA present

Question 15

statins

Answer 15

competitively inhibit HMG-CoA reductase

Question 16

methotrexate

Answer 16

• competitively inhibit DHFR

- depriving deoxythimidine, interferring w DNA synthesis during S phase

Question 17

When looking at a line weaver-burk plot if the lines CROSS you’re looking at a graph of?

Answer 17

competitive inhibition

Question 18

When looking at a line weaver-burk plot, the point where the line crosses the Y-axis represents the

Answer 18

1/Vmax

Question 19

how do you treat methanol poisoning?

Answer 19

• give ethanol
• both are substrates for ADH, but ethanol has a much lower Km.
• this prevents methanol from being converted to formaldehyde (= toxic and not metabolized further)