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genetics > Lecture 11 > Flashcards

Lecture 11 Flashcards

1
Q

23S rRNA

A
  • catalytic RNA

- caalyzes peptide bond formation between amino acid on tRNA at A site and growing peptide chain bond to rRNA in P site

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2
Q

peptidyl transferase

A

cataltic activity of 23S rRNA

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3
Q

structure domains of ribosomal RNA

A

-50S (23S and 5S) of 70S prokaryotes

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4
Q

functional domains of proteins

A
  • sequences with 50-300 amino acids
  • fold into stable, unique conformation
  • LDL receptor protein domains
  • exon shuffling
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5
Q

chromosome mutations

A
  • change in total number of chromosomes
  • depletion or duplication of genes/segments of chromosomes
  • rearrangements of genetic material within or among chromosomes
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6
Q

deletions and duplications in the alterations of chromosomes

A

-total amount of genetic info in chromosome changes

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7
Q

inversions and translocations in alternations of chromosomes

A

-genetic material remains the same but rearranged

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8
Q

what is a mutation?

A
  • an alteration in DNA sequence in DNA sequence
  • any base-pair change in sequence
  • singe base-pair substitution
  • deletion or insertion of base pairs
  • major alteration in chromosomal structure
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9
Q

where may chromosomal mutations occur?

A
  • somatic or germ cells

- coding or noncoding regions

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10
Q

point mutation (base substitution)

A

-change from one base pair to another

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11
Q

missense mutation

A

results in new triplet code for different amino acid

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12
Q

nonsense mutation

A

results in triplet code for for stop codon (translation terminated prematurely)

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13
Q

silent mutation

A

A mutation that changes a single nucleotide, but does not change the amino acid created.

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14
Q

frameshift mutation

A
  • results from insertations or deletions of base pair
  • loss or addition of nucleotide causes shift in reading frame
  • frame of triplet reading during translation is altered
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15
Q

loss of function mutation

A

reduces/eliminates function of gene product

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16
Q

null mutation

A

results in complete loss of function

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17
Q

dominant mutation

A

results in mutant phenotype in diploid organism

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18
Q

dominant gain of function mutation

A

results in gene with enhanced, negative or new function

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19
Q

lethal mutations

A

interrupt essential process and result in death (highly conserved genes; natural selection does not tolerate alterations)

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20
Q

lethal conditional mutations

A

dependent on organism’s enviroment

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21
Q

neutral mutation

A

majority of mutations occur in a noncoding region, effect on genetic fitness of organism is neither beneficial nor detrimental

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22
Q

spontaneous mutation

A
  • changes in nucleotide sequence that occur naturally

- arise from normal biological or chemical processes that alter nitrogen bases

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23
Q

induced mutation

A

result from influence of extraneous factors, either natural or artificial

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24
Q

what do mutations arise from?

A
  • replication
  • replication is imperfect
  • DNA polymerase occasionally persists after proofreading
  • errors due to mispairing predominantly lead to point mutations
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25
Q

replication slippage

A
  • if loop occurs in template strand during replication, DNA polymerase musses lopped out nucleotides, and small insertion and deletion occur
  • more common in repeat sequences
  • hot spots for DNA mutations
  • contribute to hereditary diseases
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26
Q

DNA repair system

A

maintains the integrity of genetic material; repairs systems, counteracts genetic damage that can result in genetic disease and cancer

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27
Q

DNA polymerase

A

proofreads, removes, and replaces incorrectly inserted nucleotides

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28
Q

mismatch repair

A
  • activated when proofreading fails
  • mismatches are detected, cut, and removed (by endonuclease and exonuclease) and the correct nucleotide is inserted by DNA polymerase
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29
Q

strand discrimination

A
  • adenine methylase recognizes DNA sequences and adds methyl group to adenine residues on old strand
  • newly synthesized strand of replication remians unmethylated
  • mismatch repair recognizes unmethylated strand and repair
30
Q

postreplication repair

A
  • responds after damaged DNA has escaped repair and has failed complete replication
  • RecA protein directs recombination exchange with corresponding region on undamaged parental strand
31
Q

excision repair

A
  • light independent DNA repair
  • exonuclease recognizes and cuts distortion/error
  • DNA polymerase inserts complementary nucleotides in missing gap
  • DNA ligase seals final nick
32
Q

inducible enzymes

A

bacteria adapt to environment by producing inducible enzymes only when specific substrates are present

33
Q

constitutive enzymes

A

enzymes are continuously produced regardless of chemical makeup of environment

34
Q

repressible system

A
  • presence of specific molecule inhibit gene expression

- abundance of end product in environment represses gene expression

35
Q

negative control

A

genetic expression occurs unless shut off by regulator molecule

36
Q

positive control

A

transcription occurs only when regulator molecules directly stimulates RNA production

37
Q

lactose

A

galactose and glucose containing disaccharide; lactose is an inducer
-gene activity is repressed when lactose is absent and induced when available

38
Q

where are gene responsible for coding for enzymes located?

A
  • organized into clusters
  • regulatory regions are located upstream of gene cluster they control
  • on the same strand; cis-acting
39
Q

cis and trans acting sites

A
  • regulatory site events determine if genes are transcribed into mRNA
  • binding of trans-acting element at cis-acting site regulates gene cluster negatively or positively
40
Q

lac Z

A

encodes beta-galaosidase, an enzyme that converts disaccharide lactose to monosaccharides glucose and galactose; conversion is necessary for lactose to serve as primary energy source in glycolysis

41
Q

Lac Y

A

specifies primary structure of permease, an enzyme that facilitates entry of lactose into bacterial cell

42
Q

Lac A

A

encodes enzyme transacetylase, which may be involved in removal of toxic by products of lactose digestion from the cell

43
Q

Lac I

A

located close to but not part of lac operon structural genes. produces repressor molecule, which regulates transcription of structural genes

44
Q

lac operon structural genes

A
  • lacZ, lacY, and lacA
  • all three are transcribed as a single unit
  • results in polycistronic mRNA
45
Q

constitutive mutations

A

genes with these mutations produce enzymes regardless of lactose presence/absense

46
Q

operon

A

group of genes is regulated and expressed together as a unit

47
Q

lac operon: negative control

A

-operon subject to negative control
-transcription occurs only when repressor fails to bind operator region
-repressor normally binds DNA sequence in operator region
-inhibits RNA polymerase
-represses transcription of
structural genes

48
Q

summary of the operon

A
  • invoked series of molecular interactions between proteins and DNA
  • no lactose, enzyme are not needed and expression of genes encoding enzymes are repressed
  • lactose present, indirectly induces activation of genes by binding repressor
49
Q

I- mutation

A

the repressor protein is altered or absent and cannot bind to the operator region
-structural genes are always turned on

50
Q

Oc mutant

A

the nucleotide sequence of the operator DNA is altered and will not bind with a normal repressor molecule
-the structural genes are always turned on

51
Q

how is gene regulation more complex in eukaryotes?

A
  • Greater amount of D N A that is associated with histones and other proteins
  • mRNA s must be spliced, capped, and polyadenylated prior to transport from nucleus
  • Genes on numerous chromosomes are enclosed in a double membrane nucleus
  • mRNAs have a wide half life range
52
Q

cis-acting DNA sequences

A
  • located on same chromosomes as gene that it regulates; required for accurate regulated transcription of genes
  • promoters, enhancers, and silencers
53
Q

promoters (core and proximal)

A

nucleotide sequences that serve as recognition sites for transcription machinery

  • located immediately adjacent to regulatory genes
  • critical for transcription initiation
54
Q

core promoter

A

-determines accurate initiation of transcription

55
Q

proximal-promoter elements

A

modulate efficiency of basal levels of transcription

56
Q

focused promoters

A

specific transcription initiation at start sire; major type of initiation for lower eukaryotes

57
Q

dispersed promoters

A

direct initiation from several weak transcriptional start sites

58
Q

promoter structure DNA sequence is made up of?

A
  • initiator
  • TATA box
  • TFIIB recognition element
  • downstream promoter element
  • motif ten element - loss of transcriptional activity upon mutation of a TATA-box or DPE can be compensated by the addition of an MTE
59
Q

enhancers

A
  • regulate transcription of eukaryotic genes, cis-acting transcription of regulatory elements
  • located on either side of gene, some distance from gene, or even within gene, important in reaching maximum level of transcription
60
Q

insulators

A

found between an enhancer and a promoter for a nontarget gene; allow some enhancer-promoter interactions and block others

61
Q

silencers

A
  • regulate transcription

- repress the level of transcription initiation

62
Q

transcription factors

A
  • transcription regulatory proteins
  • target cis-acting sites of genes regulating expression
  • multiple transcription factors bind to several different enhancers and promoter elements and fine-tune the level of transcription initiation
63
Q

activators

A

-increase transcription initiation

64
Q

repressors

A

-decrease transcription initiation

65
Q

DNA-binding domain

A
  • transcription factor functional domain

- binds to specific DNA sequences in the cis-acting regulatory site

66
Q

trans-activating domain

A
  • transcription factor functional domain

- activates or represses transcription by binding to other transcription factors or RNA polymerase

67
Q

helix-turn-helix (HTH)

A
  • characteristic domains of DNA binding proteins

- present in both eukaryotic and prokaryotic transcription factors

68
Q

zinc-finger

A
  • found in wide range of transcription factors that regulate gene expression
  • DNA binding proteins
69
Q

basic leucine zipper

A
  • allows for protein-protein dimerization

- DNA binding proteins

70
Q

general transcription factors (GTF)

A
  • required at promoter to initiate basal or enhanced levels of transcription
  • assembly of proteins in specific order forms pre-initiation complex
  • PIC provides platform for RNAP2 to recognize transcription start sites
71
Q

coactivators

A
  • interact with proteins and enable activators to make contact with promoter-bound factors
  • coactivators form complex enhanceosome
72
Q

enhanceosome

A
  • interacts with transcription complex

- repressors proteins at silencer elements decrease rate of PIC assembly and RNAP2 release

genetics (11 decks)

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