LECTURE 19

Question 1

Proofreading

Answer 1

Corrects errors during DNA replication

• DNA pol lll detects and removes mismatches

Question 2

Exoculease

Answer 2

An enzyme that removes nucleotides from the end of the polymer

Question 3

Mismatch repair

Answer 3

Fixes mispaired bases, and small insertions or deletions that happens during DNA synthesis.

Question 4

Steps to mismatch repair

Answer 4

1) mismatch detected, involves many different proteins.
2) endonuclease cuts new DNA on both sides,
3) DNA pol lll fills the gap
4) DNA ligase seals the hole in the backbone

Question 5

A methylation of the parent DNA strand happens

Answer 5

Before replication

Question 6

The methylation is delayed for several mins after replication, giving time for the

Answer 6

repair system to fix the mismatch

Question 7

Nucleotide excisions repair

Answer 7

Used to remove pyrimidine diners formed by UV damage

Question 8

Thymine diner

Answer 8

Covalent bonds forms between adjacent thymine bases, caused by damage form UV light

Question 9

Damage caused by UV light occurs

Answer 9

Throughout the cell cycle

Question 10

Steps to nucleotide excision repair

Answer 10

1) many different enzymes involved in detecting the distortion
2) an endonuclease enzyme cuts the DNA and removes all bases between cuts
3) DNA pol l replaces mussing nucleotides
4) DNA ligase seals the free end

Question 11

Methods of repairing DNA

Answer 11

1) proofreading
2) mismatch repair
3) nucleotide excision repair

Question 12

Xeroderma pigmentosum

Answer 12

Skin disease caused by a defect in the endonucleases that remove UV damage.

Question 13

Fibroblasts isolates form individual XP individuals are very

Answer 13

Sensitive to UV light

Question 14

All polypeptides are proteins, but not all proteins are

Answer 14

Made up of a single polypeptide

Question 15

DNA ________ cells characteristics

Answer 15

Defines

Question 16

Proteins ________ cells characteristics

Answer 16

Determines

Question 17

Alkapeonuria

Answer 17

Causes a build up of amino acids phenylanine and tyrosine, produces dark urine

Question 18

Alkapeonuria caused by

Answer 18

Absence of an enzyme required for a metabolic pathway

Question 19

Why do X rays cause mutations ?

Answer 19

They have short wavelengths and therefore very strong

Question 20

Beagle and Tatum experiment

Answer 20

Minimum medium: only given for wats needed, required to make their own amino acids

Complete medium: each culture is started form one cell that sure uses X rays.

Minimal medium: strain C cannot grow when all amino acids are removed, next tests which amino acids it cannot make

Question 21

Meadow and Tatum showed that each

Answer 21

Mutant was deficient in a single enzyme that catalyzes a specific step in the production of amino acids

“ one gene, one enzyme”

Question 22

Central dogma

Answer 22

Information stored in DNA —> information transmission mRNA m—> information use (protein)

Question 23

Transcription

Answer 23

• synthesis of RNA using info in DNA
• making a copy of the info in a similar language going form DNA to RNA
• mRNA is used to make a protein

Question 24

Translation

Answer 24

• synthesis of polypeptide using info in mRNA
• the mRNA language is translated into polypeptide language
• required ribosomes

Question 25

In prokaryotes, translation and transcription

Answer 25

Both occur in the same place. -translation of mRNA DNA even start before transcription has finished

Question 26

In eukaryotic cells, transcription occurs in the

Answer 26

Nuclear envelope and translation occurs outside the nuclear envelope.