Ch 16: How Genes Work

Question 1

Messenger RNA hypothesis

Answer 1

DNA (info storage)–(transcription)–> mRNA (info carrier)–(translation)–> proteins

Question 2

Central dogma of biology

Answer 2

Particular stretch of DNA (gene) contains info to specify amino sequence of protein

Info in base of DNA = no directly translated into amino sequence

Question 3

Human genome

Answer 3

20,000 genes humans

Potatoe has 39,000

3 bil base pairs

76% of total genome is transcribed into RNA

Question 4

Codon

Answer 4

3 nucleotides code for a single amino acid

Question 5

How do we know it’s 3 nucleotides?

Answer 5

• if each base coded for 1 amino acid= only 4 amino acids
• if pairs of bases codes for amino= max 16
• if triplets= 64 potential amino acids = more than enough

Question 6

Redundancy

Answer 6

Triplets can code for the same amino acid

Question 7

Delete/add 3

Answer 7

Sensible message, reading frame restored, slightly altered but functional protein

Question 8

Francis crick

Answer 8

Making deletions and insertion mutations established code is based on 3 nucleotides for each amino

• triplet code
• reading frame could be resorted if deletions or additions were multiples of 3

Question 9

Marshall Nirenberg

Answer 9

System for synthesizing specific RNA and codons of known sequence and were able to determine which of 64 codes for each 20 amino acids.

Question 10

Korana experiments

Answer 10

Alternating synthetic mRNA

Stretch of alternating amino acids

Question 11

Three stop codons

Answer 11

UAA (U Are Awesome)

UAG (U Are Great)

UGA (U Get As)

Question 12

Start codon

Answer 12

Methionine

AUG (AUGust start school)

Question 13

Valine

Answer 13

GU (U,C,A,G) switched in sickle cell

Question 14

Glutamic acid (Glu)

Answer 14

GAA

GAG

Question 15

Genetic code is redundant

Answer 15

All amino acids Exocet methionine and tryptophan are coded by more than 1 codon

Question 16

Genetic code is unambiguous

Answer 16

A single codon never codes for more than 1 amino acids

Question 17

Genetic code is universal

Answer 17

Few minor exceptions. All codons specify the same amino acids in all organisms

Question 18

Genetic code is conservative

Answer 18

When several codons specify the same amino acid, first two bases are almost always identical

Question 19

Silent mutation

Answer 19

Change in NT that does not change amino acid specidified by codon

Change in genotype but not phenotype

Question 20

Missense mutation

Answer 20

Change in NT changes amino acid specified by codon

Change in primary structure

Question 21

Nonsense mutation

Answer 21

Change in NT that results in early stop codon

Premature termination: polypeptide truncated

Question 22

Frameshift

Answer 22

Addition or deletion of a NT

Reading frame is shifted, massive missense (everything beyond that inserted or deleted mutation is changed)