Ch. 15

Question 1

Archibald Garrod- 1902

Answer 1

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

Question 2

Beadle and Tatum 1941

Answer 2

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

Question 3

Beadle and Tatum studied neurospora crassa

Answer 3

• used X rays to damage DNA

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

Question 4

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

Answer 4

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

Question 5

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

Answer 5

Modified to one-gene/one-polypeptide hypothesis

Question 6

Central dogma

Answer 6

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

Question 7

Transcription=

Answer 7

DNA to RNA

Question 8

Translation=

Answer 8

RNA to protein

Question 9

Retroviruses violate this order using

Answer 9

Reverse transcriptase to convert their RNA genome into DNA

Question 10

Transcription

Answer 10

• 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

Question 11

Translation

Answer 11

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

Question 12

RNA

Answer 12

• 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)

Question 13

Genetic code

Answer 13

• 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

Question 14

Codon

Answer 14

Block of 3 DNA nucleotides corresponding to an amino acid

Question 15

Spaced codon

Answer 15

Codon sequence in a gene punctuated

Question 16

Unspaced codon

Answer 16

Codons adjacent to each other

Question 17

Stop codons

Answer 17

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

Question 18

Start codon

Answer 18

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

Question 19

Code is degenerate, meaning that

Answer 19

Some amino acids are specified by more than one codon

Question 20

Mitochondria and chloroplasts have

Answer 20

Some differences in “stop” signals

Question 21

Prokaryotic transcription

Answer 21

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

Question 22

Promoter

Answer 22

• 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

Question 23

Elongation

Answer 23

• 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

Question 24

Termination

Answer 24

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

Question 25

Prokaryotic transcription is coupled to translation

Answer 25

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

Question 26

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

Answer 26

- RNA polymerase I transcribes rRNA - RNA polymerase II transcribes mRNA and some snRNA - RNA polymerase III transcribes tRNA and some other small RNAs

Question 27

Initiation of transcription: requires a series a transcription factors

Answer 27

- 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

Question 28

Termination

Answer 28

Termination sites not as well defined

Question 29

mRNA modifications

Answer 29

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

Question 30

mRNA modifications: addition of a 5’ cap

Answer 30

Protects from degradation; involved in translation initiation

Question 31

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

Answer 31

Created by poly-A polymerase; protection from degradation

Question 32

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

Answer 32

Pre-mRNA splicing done by spliceosome