Bio400 Exam 4 Rated A+ Solution guide (Verified)

Bio400 Exam 4 Rated A+ Solution guide (Verified) genetic Code - Answer- The nucleotide triplets of DNA and RNA molecules that carry genetic information in living cells. UAA, UAG, UGA - Answer- stop codons nonsynonymous mutation - Answer- a nucleotide mutation that alters the amino acid sequence of a protein Nonsense mutation - Answer- A mutation that changes an amino acid codon to one of the three stop codons results in a nonfunctional protein. synonymous mutation - Answer- A mutation that does not result in a different amino acid Frameshift mutation - Answer- involves the insertion or deletion of a nucleotide in the DNA sequence not divisible by 3 reading frame - Answer- Reading mRNA nucleotides in the correct groupings. DNA Replication Fidelity - Answer- Accuracy of DNA replication process. DNA Polymerase III - Answer- synthesizes new DNA only in the 5' to 3' direction 5'-3' polymerization domain 3'- exonuclease domain DNA damage - Answer- abnormal chemical structure in DNA DNA mutations - Answer- Changes in the sequence of base pairs Point mutation - Answer- Changes in one or few nucleotides Substitution - Answer- A mutation in which a nucleotide or a codon in DNA is replaced with a different nucleotide transition - Answer- A-G(purines), C-T(pyrimidines) Transversions - Answer- a purine and a pyrimidine are interchanged Indel - Answer- Insertion or deletion of nucleotides chromosome abnormalities - Answer- Changes in the number and structure of entire chromosomes AUG - Answer- start codon How many codons - Answer- 64 What is the proofreading function of DNA polymerase? - Answer- DNA polymerases can identify a mismatched nucleotide and remove it from the daughter strand. What activity does DNA polymerase use to remove mismatched nucleotides? - Answer- The enzyme uses a 3' to 5' exonuclease activity. In which direction does DNA synthesis resume after proofreading? - Answer- DNA synthesis resumes in the 5' to 3' direction. mismatch repair (MMR) - Answer- An enzymatic system for repairing base mismatches (non-Watson-Crick pairs) in DNA. mismatch repair (MMR) steps - Answer- recognition; removal; resynthesis and ligation mismatch repair (MMR) Disease - Answer- Hereditary non-polyposis colon cancer (HNPCC) Prevalence: 1 in 280 Americans define Depurination - Answer- hydrolytic cleavage of the glycosidc bonds in DNA Depurination leads to - Answer- the formation of apurinic site (AP, or abasic site) and results in an alteration of the structure Define deamination - Answer- removal of an amino group from a molecule Deamination leads to - Answer- Spontaneous deamination of cytosine is the hydrolysis reaction of cytosine into uracil, releasing ammonia in the process Deamination by nitrous acid - Answer- sodium nitrate (common food preservative) converted to nitrous acid in the stomach, which is a mutagen Define Alkylation of DNA - Answer- The transfer of an alkyl group to specific bases and DNA backbone Alkylation of DNA may result - Answer- in adducts that are mutagenic and toxic base excision repair (BER) - Answer- DNA repair that first excises modified bases and then replaces the entire nucleotide base excision repair (BER) steps - Answer- 1. Recognition by glycosylase 2. Removal of base from sugar creates an apyrimidinic or apurinic site (abasic) 3. APE endonuclease nick on phosphodiester bond 4. Phosphodiesterase removes the deoxyribose sugar 5. DNA pol beta adds the new nucleotide 6. Last phosphodiester bond made by ligase Photolesion Produced by UV radiation - Answer- Thymine Dimer Thymine Dimer Repair: Photoreactivation - Answer- Direct removal • DNA photolyase • FADH • Present in bacteria, fungi, plants and animals (with the exception of placental mammals) Nucleotide Excision Repair (NER) - Answer- a DNA repair system in which several nucleotides in the damaged strand are removed from the DNA and the undamaged strand is used as a template to resynthesize a normal strand. Nucleotide Excision Repair (NER) Steps - Answer- (1) DNA-damage recognition, (2) incision on both sides of the DNA lesion and removal of the damaged DNA fragment, (3) gap-filling DNA synthesis, and (4) ligation of open DNA ends. Transcription-Coupled Repair (TCR) - Answer- A nucleotide excision repair pathway in eukaryotes that is triggered when RNA polymerase encounters a lesion in the DNA and stalls. Nucleotide Excision Repair (NER) Disease - Answer- Xeroderma Pigmentosum (XP) Xeroderma pigmentosum (XP) - Answer- is a hereditary condition characterized by extreme sun sensitivity, leading to a very high risk of skin cancer and other medical problems Translesion synthesis (TLS) - Answer- the synthesis of DNA over a template strand that harbors some type of DNA damage. This occurs via lesion-replicating polymerases. DNA Replication by TLS polymerase Repair is error-prone DNA Double-Strand Break Repair (DSB) - Answer- double-strand break repair model refers to the various models of pathways that cells undertake to repair double strand-breaks ( DNA Double-Strand Break sources - Answer- Exogenous • Ionizing radiation • UV radiation • Mutagens Endogenous • Free radials • Meiosis • Lesion at replication fork