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What are three diseases that involve DNA repair
- Xeroderma pigmantosa --> Pyrimadine dimer problems
- Ataxia telangiectosia --> ATM problems
- HNPCC (Lynch Syndrome)
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What are the parts of Interphase?
G1, S, and G2
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Name two Tumor Suppressor Genes
p53 and RB
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Which phase involved the condensing of chromosomes?
prophase
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Which chromosomes are Acrocentric?
13, 14, 15, 21, and 22 are the acrocentric chromosomes. These chromosomes give rise to ribosomal RNA
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When does crossing over occur?
Prophase of meiosis I
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What is the consequence of nondisjunction?
anueploidy – The chromosomes pair and don’t split
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How many copies of mtDNA are there per mitochondrion?
between 2 and 10
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What does mtDNA code for?
13 protein coding genes (for proteins involved with ATP synthesis), 2 genes for ribosomal RNA, and 22 tRNA genes
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Where did your mitochondria come from?
all from mother, and do not follow Mendelian inheritance patterns
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Which has greater gene density, E. coli or Humans?
E. Coli, by about 100X
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List the types of DNA and their prevalence
repetitive (50%), heterochromatin (8%), regulatory (17%), Intronic (23.5%), Coding (1.5%)
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What allows for the start of the origin of replication
DNaA, which melts the DNA at the origin of replication, allowing for polymerases to gain access
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What do the 3' and 5' mean?
3' = hydroxyl group, 5' = phosphate group
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what stabalizes unwound ssDNA?
ssDNABP (single strand DNA binding proteins)stick the the unwound strands
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What unwinds DNA?
DNA Helicase
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What are the types of topoisomerases and what do they accomplish?
- Type I DNA Topoisomerases- cut one DNA strand to relax supercoils then seal the nick
- Type 2 DNA Topoisomerases- cut Both strands, allow the supercoil to relax, then seal the nick
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What are two drugs that target topoisomerases?
- Etopside is an anticancer agent that targets human topoisomerase II
- Quinolones target bacterial DNA gyrase, which is a type II topoisomerase
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What removes RNA primers in Prokaryotes and in Eukaryotes
- Prokaryotes - DNA polymerase I
- Eukaryotes - RNaseH and FEN1
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What are the key eukaryotic DNA polymerases?
- Pol alpha - primase activity that adds a short piece of DNA to RNA primer
- Pol delta - elongates strand and has 3' to 5' exonuclease activity
- Pol epsilon - fills in the gap after the primer is removed
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What is a way to block DNA elongation?
Nucleoside anologs with modified sugars are used for anti-cancer (cytarabine) or antiviral (zidovudine -AZT) treatment because they block DNA elongation.
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Four functions of telomeres
- 1) Ensure that Genes are fully replicated
- 2) Protect the end of chromosomes by having repetitive AGGGTT
- 3) Shorten with Age (when gene replication is compromised, cell stops dividing
- 4) Do not shorten in cancer cells or stem cells because these cells express telomerase
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What is telomerase
- an enzyme comprised of protein and a short piece of RNA (thus a ribonucleotide)
- has reverse transcriptase activity
- maintains telomere length
- expression of telomerase in primary cell lines results in their imortalization
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What are the 5 classes of histones?
H2A, H2B, H3 and H4 form the nucleosome core, while H1 binds DNA between nucleosome beads (the linker histone)
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How do histones impact gene expression?
the histones can be modified, (acetylated, methylated, and phosphorylated) especially on N-terminal tails which alters gene expression
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How is DNA packed into a chromosomal structure?
It is first wound around histones, forming nucleosome beads, then packed more tightly into a 30nm fiber, and eventually into the final chromosomal structure
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which direction does DNA polymerase read the parental strand and synthesize new DNA?
- Reads parental strand from 3' to 5'
- synthesized new DNA from 5' to 3'
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What does DNA polymerase III accomplish?
- catalyzes chain elongation (5' to 3' polymerase activity)
- proofreading (3' to 5' exonuclease activity)
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What does DNA polymerase I do?
- looks for nick between 3' end of new DNA and 5' end of RNA primer
- Removes RNA primer (5' to 3' exonuclease)
- fills in gaps accurately (5' to 3' polymerase, 3' to 5' exonuclease)
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