Biology 300 Discussion Quiz 2

What is a Gene?

A sequence of DNA that gives rise to an RNA transcript that can spliced into many different types of regulatory RNAs or mRNAS that can be translated into different polypeptides.

Most genes are pleiotropic?

have more than one function in the body in different cells at different times.

The mutations in a gene can have variable effects on cell functions and result in different observable phenotypes depending on context.

What is a Mutation

A mutation is a change in the sequence of nitrogenous bases in the DNA this results in a variant form that is transmitted to other generations

What are the ways that mutations could occur?

- Spontaneously: mutations caused by DNA polymerase infidelity or exposure to mutagens

What is the background level and the background level mutation rate?

The background level is the rate at which spontaneous mutations accumulate due to unrepaired changes. It is dependent on the efficacy of the repair system

The background level mutation rate = Spontaneous mutation rate - Repair rate

What is a mutation that has an effect on a DNA sequence and what is it called?

Transition: one purine is changed to another purine or one pyridine is changed to another pyrimidine

A -->G

Transversion: A purine is replaced with a pyrimidine or vice versa

G --> C

What is a mutation that has no effect on the protein sequence?

Silent mutation: dna mutation that has no effect on a protein sequence

Missense mutation: DNA mutation that results in an amino acid substitution

What is a mutation that has an effect on DNA length?

Deletion: removal of one or more bases

Insertion: Addition of one or more bases

What is a wild type?

The phenotype that is the most commonly occurring in a population

What is a forward mutation?

A genetic change that alters a wild type gene to a mutant form that leads to a new or altered phenotype

What is a back mutation?

A back mutation introduces another mutation that reverts a mutant back to wild type

What are three ways that a back mutation can occur?

True reversion: Mutation that changes the mutant DNA sequence back to the original wild type

Second site reversion: A second mutation in the same gene that compensates for teh effect of teh firs mutation

Suppressor mutation: A second mutation in a different gene that compensates for the primary mutation.

What are some mutations that contribute to a loss of function?

Amorphic: function is eliminated from the entire polypeptide or a critical domain of the polypeptide

hypomorphic: some activity of the polypeptide is reduced or less gene product is made

What are some mutations that contribute to a gain of function?

Hypermorphic: overactive; too much product is produced

Neomorphic: new activity is acquired due to the mutation

Antimorphic: The newly acquired function is against old activity

What is an allel?

Many variations of a single gene

When a gain of function allele is paired with a wild type which on is out ruling?

gain of function

What is haplosufficency?

Means that in the case of one functional allele and one null allele as long as one functional allele is present the organism will not display a mutant phenotype.

What is haploinsufficency?

The organism needs two completely functional alleles one functional allele is not enough to prevent the organism from displaying a mutant phenotype

When is the only type that the wild type will stay normal when paired with a diff allele?

If it is paired with a null or hypomorphic mutant.

what does it mean when a mutation complements and when a mutation fail to complement?

complement: the mutations are in different genes

fail to complement: mutations are alleles of the same gene

wild type + null

normal

wild type + hypomorphic

normal

wild type + hypermorphic

mutant

hypermorphic + hypomorphic

mutant

wild type + neomorphic

mutant

wild type + antimorphic

mutant

null + antimorphic

mutant

hypomorphic + antimorphic

mutant

wild type + null

mutant