CHAPTER 11 Flashcards
What are mutations?
Heritable changes in DNA that can be passed to future generations
What is difference between mutations in somatic cells vs germ cells?
In somatic cells, they’re passed on by cell division to daughter cells and not transmitted to future generations. In germ cells, they’re passed onto future generations.
What are mutation rates affected by?
Gene Zoe, presence of specific nucleotide repeats, spontaneous or environmentally induced chemical changes
What is mutation rate?
The number of mutated alleles per gene in each generations
What leads to a spontaneous mutation?
Results from errors in normal cellular processes such as DNA replication. It can also be causes by natural changes in the molecular structure of bases in DNA
What causes induced mutations?
Caused by mutagens, such as radiation and chemicals, that affect DNA and cellular processes
How can small chemical changes in bases cause spontaneous mutations?
Tautomeric shifts: small atomic shifts that change the structure of nucleotide bases
How is radiation a source of mutation?
Ionization and free radicals can both cause DNA mutations
What are base analogs ?
Mutagenic chemicals that resemble nucleotides and are incorporated into DNA or RNA during synthesis
How can bases in DNA be modified by chemical mutagens?
Nitrous acid changes cytosine to uracil
What is nucleotide substitution ?
Replacement of one or more nucleotide in DNA molecule with other nucleotides
What is a silent mutation
Nucleotide substitution that does not change the amino acid
What is Missense mutation
Single amino acid substitution
What is Nonsense substitution
Changes an amino acid to a termination codon
What’s a silent mutation?
DNA: TTC —> TTT
mRNA: AAG —> AAA
What is a nonsense mutation?
DNA: TTC —> ATC
mRNA: AAG —> UAG
What is a missense mutation?
DNA: TTC —> TGC
mRNA: AAG —> ACG
What is a frame shift mutation?
Frameshift mutations alter the reading frame, changing the amino acids in the protein
How does proofreading during DNA replication works?
Sometimes can add incorrect nucleotides. Synthesizes new strands and proofreads. Will correct mistake if identified.
In addition to DNA polymerase, what is another check?
Repair enzymes. It recognizes distortions caused by the insertion of the wrong base during DNA replication.
what causes sickle cell anemia?
a specific single nucleotide substitution
what causes cystic fibrosis?
associated with many different mutations in a single gene. over 1900 mutations have been identified in this single gene. therefore it has a wide range of symptoms
what is epigenetic?
chemical modifications to DNA and alters gene expression (increase or decrease) but doesn’t change DNA sequence
How does his tone modification work?
DNA winds around a histone complex to form a nucleosome. Promoters that are wound tightly in a nucleosome are unavailable for RNA polymerase and not expressed
epigenetic modification
specific to cell type and can help control human development.
