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BIO 235 Exam 4 questions and answers.docx
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BIO 235 Exam 4 questions and
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BIO 235 Exam 4 questions and answersHelicase - Unwinds DNA in both directions
Gyrase - topoisomerase that relieves supercoiling ahead of replication fork
Single Stranded Binding proteins do what? - Stabilize single stranded DNA
Primase - Enzyme that makes RNA primers
DNA polymerase cannot? - Reconstruct the 5' end of a DNA strand
this poses problems for linear chromosome integrity
Telomeres - Repetitive DNA sequences TTAGGG
-no protein coding
-binds two types
Two types of proteins that binds in telomeres - -Protective proteins
-telomerase enzyme
Telomerase enzyme - ribonucleoprotein
ribonucleoprotein - composed of RNA and protein
, Binding of telomerase to TTAGGG - Addition of RNA extends ends
-carries its own DNA template as well....to finish DNA strand
Telomerase is key in determining what? - Life-span of cell
Telomerase in immortalized cells - ie germ line, cancer, yeast...
-Telomeres are fully reconstructed with each DNA replication
Telomerase in somatic cells - Virtually absent
-shortened with every cell division
-somatic cells divide 30-50 times then die
in yeast, deletion of telomerase gene leads to what? - Shortening of chromosomes
at each cell division
Telomerase activity in cancer cells? - High activity
Telomerase activity in somatic cells which cancer derives? - low activity or absent
If you can block telomerase activity, you can do what? - STOP CANCER!
Nobel prize in medicine: - Elizabeth Blackburn, Carol Greider, Jack Szostak.
-Protection of chromosomes by the telomerase enzyme
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