Exam 1 Part 4 Flashcards Preview

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Flashcards in Exam 1 Part 4 Deck (38)
1

gene silencing

the interplay between DNA methylation and histone acetylation and RNAi to completely shut down expression of genes
More permanent than not

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Methylation

transcriptional machinery is blocked

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CpG island

lots of C followed by Gs

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Methylation can...

sometimes recruit histone deactylases to modify histone tails

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histone tail modification

In response to signals, histone actyl transferases (HATs) bind to histone tails and pull them away from DNA

6

histone actyl transferases

HATs. bind to histone tails and mask their positive charge to pull them away from DNA

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histone deactylases

HDACs recruited by DNA methylation to cause the histone tails to cover DNA

8

RNA interference

regulatory RNAs control target mRNA degration

9

Regulatory RNAs

miRNA
siRNA

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RNAi steps

1. miRNA transcribed
2. miRNA processed to shRNA
3. RISC recognizes shRNA
4. RISC binds to target mRNA
5. RISC cuts mRNA
6. nucleases degrade mRNA

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Loss of function mutation

results in partially or fully nonfuctional gene product

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fully nonfunctional gene product

null allele

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Gain of function mutation

causes the gene product to have more activity

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Mutagensis

creation of mutations

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spontaneous mutations

mistakes during replication
Base can exist in 2 forms (isomers) with different base pairing properties

16

Induced mutations

caused by mutagens

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Mutagens

chemicals, environment (UV, radiation, gamma rays)
base modifying agents
intercalating agents
base analogs

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Classes of mutations

somatic mutation
germ-line mutation

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somatic mutation

not passed on to next generation
ex. moles, tumors

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germ-line mutation

transmitted to future generations
progeny has the mutation in both somatic and germ-line cells

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Mutation types

base pair substitution
base pair insertions/deletions

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base pair substitutions

change one base-pair to another base pair

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base pair insertions /deletions

addition or removal of a base pair
intercalating agents

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Types of base pair substitutions

transition mutations
transversion mutations

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transition mutations

changing from purine-pyrimadine to antoher pur-pyr

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Transversion mutation

change from pur-pyr to pyr-pur and vise versa

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missense mutation

a change in a codon so that a different amino acid is added to the polypeptide
change in function
phenotype change depends on severity of mutation

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nonsense mutation

change from a functional codon that codes an amino acid to a stop codon.

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Silent mutation

change 1 codon for 1 amino acid to a codon that codes for the same amino acid

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neutral mutation

replacing 1 amino acid with a similar amino acid
ex. Lysine -> arginine
mild or no phenotypic effect

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frameshift mutation

insertion or deletion that shifts the reading frame so that missense or stop results

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trinucleotide repeat expansion

areas of the genome hve 3 nucelotides repeated many times in a row
if happens in a coding region, long stretches of an amino acid repeats itself

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forward mutation

change a wild type allele to a mutant allele

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reverse mutation

change to promutation state mutation allele so that the phenotype becomes more like wild type

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suppressor mutations

mutation that masks the phenotype
mutation at a different site than original mutation
2 types

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suppressor mutation types

intragenic suppressors
intergenic suppressors

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intragenic suppressors

within the same gene
deletion farther down the line

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intergenic suppressors

mutation in another gene
mutate tRNA anticodon