Lecture 11 notes

Question 1

how are codons read?

Answer 1

amino acids have to be ‘activated’ before incorporation in a protein
the activated form of the amino acid is attached to small RNA (tRNA)

Question 2

transfer RNA

Answer 2

(tRNA) small RNA

• adaptors between codons and amino acids
• two ‘readings’: addition of correct amino acid to tRNA and antiparallel base pairing between codon in mRNA and anticodon in tRNa
• each tRNA can recognize multiple codons
• made from genes
• a mutation in a tRNA gene can alter the anticodon

Question 3

aminoacyl-tRNA synthetastes

Answer 3

• attach amino acids to tRNAs
• reaction: aa + ATP + tRNA -> aminoacylated tRNA
• each amino acid has its own tRNA synthetase

Question 4

wobble phenomenon

Answer 4

• base pairing rules are relaxes at 5’ position of anticodon
• contributions of relaxed rules: RNA structure and modified nucleotides in tRNA
• 5’ base of anticodon is modified
• I can pair with U, C or A

Question 5

is it possible to have mutant tRNAs that suppress missense mutations?

Answer 5

yes but these are very unhealthy since many proteins will have incorrect amino acids from ‘misreading’ of the code

Question 6

silent mutation

Answer 6

change in base pair that codes for the same amino acid

Question 7

missense mutation

Answer 7

change in base pair codes for a different amino acid

Question 8

nonsense mutation

Answer 8

change in base pair codes for stop codon

Question 9

frameshift mutation

Answer 9

insertion/deletion of base pair causes next amino acids to change

Question 10

genetic approach to understanding gene function

Answer 10

• mutate gene
• observe mutant phenptype
• infer wildtype function

Question 11

loss of function alleles

Answer 11

• usually recessive to wild type
  amorph: null allele
  hypomorph: weak allele

Question 12

gain of function alleles

Answer 12

*usually dominant to wild type
hyper morph: overactive
anti morph: dominant negative
neomorph: new function

Question 13

amorph

Answer 13

no gene product, or no functional gene product

Question 14

hypomorph

Answer 14

less of wild type gene product, or mutant gene product with less activity than normal gene product

Question 15

a nonsense mutant would most likely be a:

a. hypomorph
b. amorph

Answer 15

amorph

Question 16

hypermorphs

Answer 16

• excess wildtype gene product
• mutant gene product with increased activity
• mutations can be in the coding region or regulatory regions

Question 17

antimorph

Answer 17

• mutant gene product that prevents the wildtype gene product working
• antimorphic mutations are usually in the ORF

Question 18

neomorph

Answer 18

• mutant gene product
• wildtype gene product in new context
• neomorphic mutations can be in the ORF or in a regulatory region

Question 19

deletion of a gene would probably be which type of mutant?

a. hypomorph
b. amorph
c. hypermorph
d. anti morph
e. neomorph

Answer 19

amorph