Ch 9

Front 1

Two formal terms used to describe categories of mutational nucleotide substitutions in DNA

Back 1

Transversions and transitions

Front 2

An exonuclease enzyme breaks down nucleic acid molecules by Breaking the phosphodiester Bond at the 3 prime or 5 Prime Terminal nucleotides

Back 2

An endonuclease is required for the breaking of internal phosphodiester bonds

Front 3

The XP phenotype is caused by defects in nucleotide excision repair pathways. Mutations in one of several genes can contribute to the XP phenotype. XP patients are extremely sensitive to UV radiation and sunlight. Cells form XP patients are deficient and unscheduled DNA synthesis.

Back 3

Xeroderma pigmentosum

Front 4

These Concepts that affect gene mutations in diploid organisms would apply to haploid organisms such as E. coli

Back 4

Mutations are a source of genetic variation and provide the raw material for natural selection. Mutations have a wide range of effects on organisms depending on the type of base pair alteration, the location of the mutation within the chromosome, and the function of the affected Gene product. Mutations can occur spontaneously as a result of natural biological and chemical processes, or they can be induced by external factors, such as chemicals or radiation. Mutations comprise any change in the base pair sequence of DNA

Front 5

Mutations that occur as a result of natural biological and/or chemical processes are considered what?

Back 5

Spontaneous mutations

Front 6

Why are spontaneous mutations rare?

Back 6

They are relatively rare in comparison to induced mutations that are more directed to the physical or chemical properties of DNA.

Front 7

Why is a random mutation more likely to be deleterious than beneficial?

Back 7

A functional sequence of nucleotides, Eugene, is likely to be the product of perhaps a billion or so years of evolution. Each gene and its product function in an environment that is also involved. A coordinated output of each gene product is required for Life. Deviations from the norm, caused by mutation, are likely to be disruptive because of the complex and interactive environment in which each gene product must function. However, on occasion a beneficial variation occurs

Front 8

Why are most mutations in a diploid organism recessive?

Back 8

In most cases, the amount of product from one gene of each pair is sufficient for production of a normal phenotype.

Front 9

What can change system to uracil and adenine to hypoxanthine by converting an amino group to a keto group?

Back 9

Deaminating agents

Front 10

What will add a methyl or ethyl group to the amino Aikido groups of nucleotides, changing base pair of entities.

Back 10

Alkylating agents

Front 11

What such as 5-bromouracil and 2-amino purine, are incorporated as thymine and adenine, but base pair with guanine and 16 respectively.

Back 11

Base analogs

Front 12

A number of different types of mutation in the hbb gene can cause human B-thalassemia a disease characterized by various levels of anemia. Many of these mutations occur within introns or an upstream non-coding sequences. Why?

Back 12

Mutations and Upstream sequences May disrupt transcriptional factors and or eliminate binding Kama mutations and introns may affect RNA splicing, mutations in introns may affect mRNA stability or translation

Front 13

What genetic defects result in the disorder xeroderma Pigmentosa in humans

Back 13

Defects in the DNA repair system

Front 14

How did these defects in the DNA repair system create the phenotypes associated with xeroderma Pigmentosa

Back 14

By decreasing the rate of DNA mutation repair in skin cells

Front 15

Are human made forms of radiation the major contributors to mutational load in humans

Back 15

Approximately 78% of the radiation exposure to humans comes from natural sources. Although diagnostic x-rays do contribute about 10% of the exposure, other forms of human made forms of radiation contribute only a relatively small amount. Human made radiation exposure is not a major factor

Front 16

Identify the various types of DNA repair mechanisms known to counteract the effects of UV radiation

Back 16

Photo activation repair, excision repair, recombination or repair, SOS repair

Front 17

What is dependent on Photo activated enzyme that Cleaves thymine dimers

Back 17

Photo activation repair

Front 18

What is the process by which an endo nuclease Clips out uv-induced divers, DNA polymerase 3 fills in the Gap, and DNA ligase rejoins the phosphodiester backbone

Back 18

Excision repair

Front 19

What uses the corresponding region of the undamaged parental strand of the same polarity

Back 19

Recombinational repair

Front 20

What is a process in E.coli that induces error-prone DNA replication in an effort to fill gaps by inserting random nucleotides

Back 20

SOS repair

Front 21

What is tautomeric shift

Back 21

Tautomeric shift is an intramolecular proton shift that changes the bonding structure of the molecule

Front 22

Tautomeric shift may lead to a mutation. Why?

Back 22

It allows hydrogen bonding of normally non complementary bases

Front 23

Variation in DNA sequences

Back 23

Allows for phenotypic variability, adaptation to environmental changes, evolution

Front 24

Mutations are

Back 24

Source of new alleles, origin of genetic variation within populations, source of changes that lead to cell death genetic disease and cancer

Front 25

Base analogs

Back 25

Compounds that can substitute for purines and pyrimidines, a compound that mimics the base, incorrect base pairings lead to mutations

Front 26

Alkylating agents

Back 26

Donate alkyl group two amino or keto group two nucleotides, alter base pair of finity, transition mutations result

Front 27

Intercalating agents

Back 27

Flat molecules that wedge between base pairs, cause distortions in base pair which can lead to DNA unwinding causing deletion or insertion

Front 28

Damage reversal

Back 28

Damage type: modified bases, enzyme: multiple specific enzymes methyl guanine DNA methyltransferase, steps: enzyme binds to modified Bass, modification group is removed from base in DNA and covalently added to enzyme permanently inactivates enzymes result: revert to normal base without modification

Front 29

Excision repair

Back 29

Damage type: damage base presence of uracil AP sites, enzymes: DNA glycosylase AP endonuclease DNA polymerase DNA ligase, steps: see slide, results: replacement of damaged base, uracil or repair of AP site