2.12 DNA Mutagenesis, Repair and Relevant Diseases

Question 1

Any permanent heritable change in the DNA base sequence of an organism

Answer 1

Mutation

Question 2

Has the potential to change the base sequence of mRNA and the amino acid sequence of proteins

Answer 2

Mutation

Question 3

Organisms that are the exact same compy

Answer 3

Clone

Question 4

DNA molecules are cleaved and the fragments are rejoined to give a new combination

Answer 4

Recombination

Question 5

Recombination results to

Answer 5

Generation of new gene/allele combinations
Generating new genes
Integration of a specific DNA or virus
DNA repair

Question 6

Purpose of recombination

Answer 6

For mapping of genes on chromosomes

For making transgenic cells and organisms

Question 7

3 types of mutation

Answer 7

Point Mutation
Frame shift Mutation
Large segment deletion

Question 8

Replacement of a single base with another single base nucleotide

Answer 8

Point mutation

Question 9

2 types of point mutation on the level of the DNA

Answer 9

Type I: Transition

Type 2: Transversion

Question 10

Name the type of point mutation. Cytosine -> Thymine

Answer 10

Transition

Question 11

Name the type of point mutation. Thymine-> Adenine

Answer 11

Transversion

Question 12

Point mutations lead to the following effects in proteins

Answer 12

Silent mutation
Missense mutation
Nonsense mutation

Question 13

New codon codes for the same amino acid

Covered by buffering systems

Answer 13

Silent mutation

Question 14

In silent mutation, there is usually a base change in ____

Answer 14

third position

Question 15

True or false

Silent mutation has no effect on protein.

Answer 15

True

Question 16

New codon codes for a different amino acid

Has variable effects of protein

Answer 16

Missense mutation

Question 17

Missense mutation is called ____ if the new amino acid is similar to the old in terms of chemical structure

Answer 17

Conservative

Question 18

On the other hand, missense mutation is considered ___ when the mutation results in a different amino acid with different properties.

Answer 18

Non-conservative

Question 19

In sicke cell anemia, __ is produced instead of glutamic acid

Answer 19

Valine

Question 20

New codon is stop codon

Answer 20

Nonsense mutation

Question 21

Nonsense mutation results in a ___ and __ protein product

Answer 21

Truncated

Non-functional

Question 22

Deletion or addition of a number of bases not divisible by three

Answer 22

Frame shift mutation

Question 23

Frame shift mutation results in a truncated and usually non-functional protein product, just like in ___ mutation

Answer 23

Nonsense

Question 24

Loss of large areas of chromosomes during unequal crossover in meiosis
Leads to loss of function

Answer 24

Large segment deletion

Question 25

Characterized by intellectual disability, delayed development, small head size, low birth weight and weak muscle tone during infancy Affected individuals ave distinctive facial features, including widely set eyes, low-set ears, small jaw, and a rounded face

Answer 25

Cri-du-chat

Question 26

Cri-du-chat is caused by a deletion of the end of the short arm of chromosome __

Answer 26

5

Question 27

DNA damage is caused by ___ that escaped proofreading.

Answer 27

Mismatched strands

Question 28

DNA repair occurs in ___ of cell cycle

Answer 28

G2

Question 29

Nicks the mismatched strand and the mismatched base is removed

Answer 29

Endonuclease

Question 30

Enzymes that complete the repair after endonuclease nicked the mismatched strand

Answer 30

DNA polymerase I | DNA ligase

Question 31

Also known as Lynch syndrome

Answer 31

Hereditary Non-polyposis colorectal cancer (HNPCC)

Question 32

Familial clustering of cancers at several sites

Answer 32

Hereditary non-polyposis colorectal cancer

Question 33

Hereditary non-polyposis colorectal cancer is due to ___ and ___

Answer 33

Mismatch repair deficiency | Microsatellite instability

Question 34

Caused by gene mutations and epigenetic alterations (activation of oncogenic pathways and inactivation of tumor suppressor genes)

Answer 34

Colorectal cancer

Question 35

Thymine dimers exposed to UV light prevents DNA from replicating the DNA strand beyond the dimers

Answer 35

Xeroderma pigmentosum

Question 36

Damaged DNA due to exposure of UV light by thymine dimers are removed by ___ and the resulting gap is filled by ____

Answer 36

UV-specific endonuclease | DNA polymerase I

Question 37

Remove abnormal nitrogenous bases by hydrolytically cleaving N-glycosidic bond from the deoxyribose-phosphate backbone

Answer 37

Glycosylases

Question 38

Makes a nick at the 5'-site of the AP site

Answer 38

AP endonucleases

Question 39

Types of recombination

Answer 39

Homologous Site specific Transposition

Question 40

Occurs between sequences that are nearly identical

Answer 40

Homologous

Question 41

Occurs between sequences with a limited stretch of similarity

Answer 41

Site specific

Question 42

DNA element moves from one site to another

Answer 42

Transposition

Question 43

Mismatched base pairs that escape the proofreading step are repaired by Mut proteins Mutation to proteins involved in this is associated with Lynch syndrome

Answer 43

Methyl-directed mismatch repair

Question 44

Repair mechanism | UV light exposure causes covalent binding of two adjacent pyrimidies

Answer 44

UV light damage repair

Question 45

Repair mechanism | DNA nitrogen bases altered spontaneously or through deaminating/alkylating compounds

Answer 45

Base excision repair

Question 46

Repair mechanism | Double-strand breaks caused by high-energy radiation or oxidative free radicals

Answer 46

Double strand break repairs