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Flashcards in Ch. 15 Deck (32)
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1
Q

Archibald Garrod- 1902

A
  • recognizes that alkaptonuria is inherited via a recessive allele
  • proposed that patients with the disease lacked a particular enzyme
2
Q

Beadle and Tatum 1941

A

Deliberately set out to create mutations in chromosomes and verify that they behaved in a Mendelian fashion in crosses

3
Q

Beadle and Tatum studied neurospora crassa

A
  • used X rays to damage DNA

- looked for nutritional mutations. Had to have minimal media supplemented to grow

4
Q

Beadle and Tatum looked for fungal cell’s lacking specific enzymes

A
  • the enzymes were required for the biochemical pathway producing the amino acid arginine
  • they identified mutants deficient in each enzyme of the pathway
5
Q

Beadle and Tatum- one gene/one-enzyme hypothesis has been

A

Modified to one-gene/one-polypeptide hypothesis

6
Q

Central dogma

A

First described by Francis Crick. DNA to RNA to protein.

7
Q

Transcription=

A

DNA to RNA

8
Q

Translation=

A

RNA to protein

9
Q

Retroviruses violate this order using

A

Reverse transcriptase to convert their RNA genome into DNA

10
Q

Transcription

A
  • DNA directed synthesis of RNA
  • Only template strand of DNA used
  • U (Uracil) in DNA replaced by T (Thymine) in RNA
  • mRNA used to direct synthesis of polypeptides
11
Q

Translation

A
  • synthesis of polypeptides
  • takes place at ribosome
  • requires several kinds of RNA
12
Q

RNA

A
  • all synthesized from DNA template by transcription
  • mRNA
  • ribosomal RNA (rRNA)
  • transfer rna (tRNA)
  • small nuclear RNA (snRNA)
  • signal recognition particle RNA (SRP RNA)
  • micro-rna (miRNA)
13
Q

Genetic code

A
  • Francia Crick and sydney vrenner determined how the order of Nucleotides in DNA encoded amino acid order
  • codon
  • introduced single nucleotide insertions or deletions and looked for mutations- frameshift mutations
  • indicates importance of reading frame
14
Q

Codon

A

Block of 3 DNA nucleotides corresponding to an amino acid

15
Q

Spaced codon

A

Codon sequence in a gene punctuated

16
Q

Unspaced codon

A

Codons adjacent to each other

17
Q

Stop codons

A
  • 3 codons (UUA, UGA, UAG) used to terminate translation
18
Q

Start codon

A
  • codon (AUG) used to signify the start of translation
19
Q

Code is degenerate, meaning that

A

Some amino acids are specified by more than one codon

20
Q

Mitochondria and chloroplasts have

A

Some differences in “stop” signals

21
Q

Prokaryotic transcription

A
  • single RNA polymerase
  • Initiation of mRNA synthesis does not require a primer
  • requires promotor, start site, termination site. (Transcription unit)
22
Q

Promoter

A
  • forms a recognition and binding site for the RNA polymerase
  • found upstream of the start site
  • not transcribed
  • asymmetrical: indicate site of initiation and direction of transcription
23
Q

Elongation

A
  • grows in 5’-to-3’ direction as ribonucleotides are added
  • transcription bubble: contains RNA polymerase, DNA template, and growing RNA transcript
  • after the transcription bubble passes, the now-transcribed DNA is rewound as it leaves the bubble
24
Q

Termination

A

Marked by sequence that signals “stop” to polymerase

  • causes the formation of phosphodiester bonds to cease
  • RNA-DNA hybrid within the transcription bubble dissociates
  • RNA polymerase releases the DNA
  • DNA rewinds
25
Q

Prokaryotic transcription is coupled to translation

A
  • mRNA begins to be translated before transcription is finished
  • operon: grouping of functionally related genes. Multiple enzymes for a pathway. Can be regulated together
26
Q

Eukaryotic transcription: 3 different RNA polymerases. Each RNA polymerase recognizes its own promoter

A
  • RNA polymerase I transcribes rRNA
  • RNA polymerase II transcribes mRNA and some snRNA
  • RNA polymerase III transcribes tRNA and some other small RNAs
27
Q

Initiation of transcription: requires a series a transcription factors

A
  • necessary to get the RNA polymerase II enzyme to a promoter and to initiate gene expression
  • interact with RNA polymerase to form initiation complex at promoter
28
Q

Termination

A

Termination sites not as well defined

29
Q

mRNA modifications

A

In eukaryotes, the primary transcript must be modified to become mature mRNA

30
Q

mRNA modifications: addition of a 5’ cap

A

Protects from degradation; involved in translation initiation

31
Q

mRNA modifications: addition of a 3’ poly-A tail

A

Created by poly-A polymerase; protection from degradation

32
Q

mRNA modifications: removal of non-coding sequences (introns)

A

Pre-mRNA splicing done by spliceosome