Chapter 15: How Genes Work

Question 1

What are knock out mutants?

Answer 1

alleles that do not function

Question 2

What does the one gene-one enzyme hypothesis (by Tatum and Beatle) state?

Answer 2

that each gene contains the info required to make an enzyme

Question 3

What do genes do?

Answer 3

they contain the information needed to make proteins

Question 4

Why can’t info from DNA be directly converted into proteins?

Answer 4

• DNA is enclosed in a nucleus

- ribosome, where protein synthesis takes place, are outside the nucleus

Question 5

What did Jacob and Monod suggest in regards to the fact that DNA can’t be directly used to make proteins?

Answer 5

that mRNA is responsible for carrying info from DNA (inside nucleus) to the site of protein synthesis (cytoplasm)

Question 6

RNA polymerase

Answer 6

synthesizes RNA molecules according to the base sequence of DNA

Question 7

Does RNA polymerase need a primer in order to produce RNA?

Answer 7

No.

Question 8

What does the central dogma (proposed by Francis Crick) state?

Answer 8

that DNA codes for RNA, which codes for proteins

Question 9

Through what process is DNA coded for RNA?

Answer 9

Transcription

Question 10

Through what process is mRNA coded for proteins?

Answer 10

Translation

Question 11

What some exceptions to the central dogma?

Answer 11

• some genes can code for RNA molecules that do not function as mRNA
• information can even transferred from RNA to DNA

Question 12

How does the sequence of bases in a strand of mRNA code for the sequence of amino acids in a protein?

Answer 12

George Garnow hypothesized each 3 base code=an amino acid

Question 13

genetic code

Answer 13

the rules that specify the relationship between a sequence of nucleotides in DNA/RNA and the sequence of amino acids in a protein

Question 14

A group of 3 bases that code for an amino acid is called:

Answer 14

codon

Question 15

Why is the triplet code the best for reading mRNA?

Answer 15

-could code for up to 64 amino acids (only have 20, so way more than enough)

Question 16

What happens when 3 base pairs were deleted from the mRNA?

Answer 16

altered, but no loss, in function of the protein

Question 17

What happens when 1 or 2 base pairs were deleted from the mRNA?

Answer 17

loss in function of protein

Question 18

reading frame

Answer 18

sequence of DNA/RNA into a particular series of 3 nucleotide codons

Question 19

What is the start codon?

Answer 19

AUG

Question 20

What is the start amino acid?

Answer 20

MET (methionine)

Question 21

What are the properties of the genetic code?

Answer 21

1) Rebundant (more than one codon for each amino acid)
2) Unambiguous: single codon NEVER codes for more than one
3) nearly universal:all codons specify the same AA in all organisms
4) Conservative: when several codons specify the same amino acids, the first 2 bases are almost always identical

Question 22

What are some outcomes of a mutation?

Answer 22

• change in genotype, new alleles
• change in genotype=change in mRNA transcribed and amino acids translated
• change in primary structure of proteins and phenotypes

Question 23

point mutation

Answer 23

a single base change in the DNA sequence

Question 24

silent mutation

Answer 24

change in nucleotide that doesn’t change the amino acid

Question 25

missense (replacement) mutation

Answer 25

change in nucleotide that change amino acid (ie. sickle cell disease)

Question 26

nonsense mutation

Answer 26

change in nucleotide that results in an early STOP codon

Question 27

frameshift mutation

Answer 27

addition or deletion of nucleotides

Question 28

What is the consequence of a silent mutation?

Answer 28

change in genotype, but not phenotype

Question 29

Consequence of missense mutations?

Answer 29

change in primary structure of protein (amino acid sequence)

Question 30

Consequence of nonsense mutations?

Answer 30

premature termination

Question 31

Consequence of frameshift mutation?

Answer 31

reading frame is shifted….massive missense

Question 32

The mRNA codons GUU, GUC and GUA code for valine. A mutation occurred in the codon, but didn’t change the amino acid. What kind of mutation would this be?

Answer 32

silent

Question 33

Where in the codon would this mutation occur?

Answer 33

in the 3rd position

Question 34

beneficial mutation

Answer 34

increase fitness in certain environments (ie. increased ability to survive and reproduce)

Question 35

neutral mutation

Answer 35

has no effect on organism’s fitness (ie. silent mutations)

Question 36

deleterious mutation

Answer 36

decrease fitness in certain environments (ie. decreased ability to survive and reproduce)