L20: Genetic Mutation, Diseases, & Treatment

Question 1

What is a mutation?

Answer 1

A mutation is a change in DNA nucleotide sequence.

Question 2

Which normal biological process causes mutations?

Answer 2

occur mostly during DNA replication processes

Question 3

Mutations are typically random. What is significant about this fact?

Answer 3

enables adaptation and evolution

Question 4

Can mutations be passed to offspring and, if so, how?

Answer 4

Mutations within germ cells/gametes can be transmitted
to a zygote (offspring). If it lives, it is now a source of a new allele for the gene locus that mutated

Question 5

What role does mutation have in adaptation and evolution?

Answer 5

new genetic variation (alleles) allows for biota to adapt and evolve

Question 6

What can a maladaptive mutation cause?

Answer 6

disease
ex: cancer

Question 7

Be able to discern among the following types of mutation: silent substitution, missense substitution, nonsense substitution, triplet deletion/insertion, missense frameshift, and nonsense frameshift.

Answer 7

ok

Question 8

Which kinds of mutation can be transmitted to offspring?

Answer 8

adaptive and maladaptive

Question 9

How do adaptive an maladaptive mutations differ?

Answer 9

adaptive benefit the biota, maladaptive cause harm

Question 10

Do mutations occur spontaneously?

Answer 10

yes

Spontaneous mutation occurs as random errors in
replicating genetic material

Question 11

During which cellular process do mutations occur?

Answer 11

DNA replication

Question 12

During which cellular process are mutations manifested into physical traits?

Answer 12

Cells make errors during replication. Most are fixed by
repair enzymes but those that are not exist as mutations.

Question 13

What is a mutagen?

Answer 13

Mutagens are agents that cause DNA mutation

Question 14

What impact do mutagens have on mutation?

Answer 14

The rate of mutation and severity increases as cells are exposed to mutagens

Question 15

What are examples of mutagens?

Answer 15

*Ionizing radiation
- radioactive decay
- UV energy
*Various chemical agents (Arsenic, Benzene, etc.)
*Biological agents (certain viruses like HPV)

Question 16

What is point mutation?

Answer 16

changes in DNA base pairs

Question 17

What is a substitution mutation?

Answer 17

Substitution mutations occur when a single bp is replaced by another bp in a DNA sequence.

Question 18

What is a deletion or insertion mutation?

Answer 18

Deletion/Insertion mutations occur when one or more
bp are deleted/inserted into a DNA sequence.

Question 19

What is a frame-shift mutation?

Answer 19

Deletion/Insertion mutations cause a frameshift.

Question 20

What is a silent mutation?

Answer 20

(one bp subbed for another) a type of substitution

Most substitutions are silent: because they occur in introns
or as 3rd position mutations.

Question 21

Why is a silent mutation considered silent?

Answer 21

Silent mutations do not alter protein/phenotype/phenon.

Question 22

Even though silent mutations are not expressed they can be exploited for what practical purpose?

Answer 22

identification

Silent mutations in non-coding DNA used to prepare a genetic fingerprint for ID

Question 23

What is a nonsense mutation?

Answer 23

(one bp subbed for another) a type of substitution

Nonsense mutations stop protein synthesis because of a premature stop codon.

Question 24

Which types of alleles are likely nonsensical?

Answer 24

Recessive alleles (i, r) in which
you fail to make a protein (e.g., O–) are likely nonsensical

Question 25

What is missense mutation?

Answer 25

(one bp subbed for another) a type of substitution

Missense mutations alter protein but impact varies; depends on which a.a. changes occur where.

Question 26

Which types of alleles are likely missensical?

Answer 26

Co-dominant alleles (IA, IB) and incomplete dominant alleles (HbB, HbS) are likely missensical.

Question 27

How are nonsensical and missensical mutations similar and different?

Answer 27

They’re both a form of substitution mutations. nonsensical creates a premature stop in aa sequence & missensical change an aa in the sequence

Question 28

Which kind of mutation is hemophilia A? Which gene is mutated? On which chromosome is this gene locus found?

Answer 28

Most cases of Hemophilia A result from nonsense
mutations of the F8 gene on the X sex chromosome

Question 29

What is FVIII and what role does it play in the body?

Answer 29

FVIII is a blood clotting factor. Persons who lack it have no/poor clotting.

Question 30

Which cells normally express FVIII (factor 8)?

Answer 30

FVIII is expressed from F8 gene by cells in the liver, blood vessels, etc

Question 31

What is the basic treatment for hemophilia A? Is there a cure for hemophilia A?

Answer 31

Treatment: acute and prophylactic injections of FVIII.
Cure: Not yet; gene therapy in mice and dogs is promising

Question 32

Which kind of mutation is causes sickle-cell anemia. Which gene is mutated? On which chromosome is this gene locus found?

Answer 32

Most Sickle-cell Anemia results from missense mutation in Hbβ-globin gene on homologue

Question 33

What is β-globin and what larger molecule does it help make? What role does this larger molecule play in the body?

Answer 33

Two β-globin subunits (blue) + 2 α-globin (yellow)
= hemoglobin (Hb). He transports O2 in blood.

Question 34

Which cells normally express B-globin?

Answer 34

Each is expressed from Hbβ gene by RBCs.

Question 35

What is the difference between B-globin and S-globin?

Answer 35

B-globin make round RBC and S-globin makes RBC into a long sickle shaped

Question 36

What happens to a RBC that makes S-globin? How does this impact a person?

Answer 36

RBC are sickled shape which cause them to not circulate well through small blood vessels and your immune system i gonna try to attack them

Question 37

What is the basic treatment for sickle-cell anemia? Is there a cure for sickle cell anemia?

Answer 37

Treatment: limit exertion, manage pain and inflammation.
Cure: sometimes bone marrow transplant; (gene therapy?).

Question 38

What is a deletion mutation?

Answer 38

decrease the number of a.a in a protein

Question 39

What happens to the length of a gene that has undergone a deletion mutation?

Answer 39

decrease

Question 40

What happens to the number of amino acids in its protein product? (deletion)

Answer 40

decrease

Question 41

What is an insertion mutation?

Answer 41

increase in the number of a.a in a protein

Question 42

What happens to the length of a gene that has undergone an insertion mutation?

Answer 42

increase

Question 43

What happens to the number of amino acids in its protein product? (insertion)

Answer 43

increase

Question 44

What is a frame-shift mutation?

Answer 44

insertion/ deletion cause a frame shift. Frame shift mutations alter all a.a. downstream of mutation changing protein structure and function.

Question 45

Which factor determines the severity of frame-shift mutation?

Answer 45

Severity depends on where frame shift occurs in gene.

Question 46

Which disease was given as an example of a deletion/frame-shift mutation?

Answer 46

Deletion of 3 nucleotides in a gene that codes a protein
that regulates the movement of ions in and out of cells
results in the Cystic fibrosis mutant allele.

Question 47

What has prevented cures for genetic diseases?

Answer 47

Most genetic disease are not curable because the mutator allele occurs in all cells

Question 48

What is genetic therapy and how might it overcome the longstanding barrier to cures for genetic diseases?

Answer 48

replaces a faulty gene or adds a new gene in an attempt to cure disease or improve your body’s ability to fight disease

Question 49

Which kinds of cell lines might be cured in this way? Why are such cells candidates for genetic therapy?

Answer 49

To cure the disease (and not merely treat it) requires
that a ‘healthy’ allele be introduced to be expressed.

This kind of genetic therapy is only viable in cell lines still
participating in the cell cycle.

Question 50

What hurdles remain to be addressed?

Answer 50

ensuring gene is expressed during correct time/amount; unintended side effect; etc

Question 51

What role does a virus serve in genetic therapy?

Answer 51

introduce a new allele. Viruses are naturally good at infecting cells and insertion genetic material into cells

Question 52

Are all mutations harmful?

Answer 52

Mutation not only causes diseases (maladaptive phenons),
but results in beneficial phenons that underly the capacity
for adaptation of populations and evolution of species.

Question 53

What role does the environment have in determining whether a given allele is good or bad?

Answer 53

The environmental context helps decide if a particular
allele is deleterious (harmful) or advantageous.

Alleles are selected by the environment: it influences how
alleles will ↓ or ↑ in frequency in a population.

Question 54

In which geographic regions does this allele increase in frequency in populations? Why does HbS increase in these areas?

Answer 54

In malaria-prone regions, sickle-cell heterozygotes (BS) may
have greater survival than homozygotes who may die of SCA
(SS) or malaria (BB).

Question 55

What role does mutation serve in the processes of adaptation and evolution?

Answer 55

Mutation is the ultimate source of variation in biota.

Mutation not only causes diseases (maladaptive phenons),
but results in beneficial phenons that underly the capacity
for adaptation of populations and evolution of species.