Chapter 12 - Gene Mutation

Rank the different steps that occur during the formation of collagen in a sequential order. Place the first step at the top. -Enzymes snip off the ragged ends of the polypeptides, forming mature collagen. -The collagen fibrils continue to associate with each other outside the cell, building networks that hold it together. -The three procollagen chains coil into a very regular triple helix, with glycine in the middle.

1. The three procollagen chains coil into a very regular triple helix, with glycine in the middle. 2. Enzymes snip off the ragged ends of the polypeptides, forming mature collagen. 3. The collagen fibrils continue to associate with each other outside the cell, building networks that hold it together.

An expanding triplet repeat number of fewer than _____ copies is stably transmitted to the next generation and does not produce symptoms.

40

Which of the following is a true statement about minisatellites?

A minisatellite size in a child that does not match the size of either parent indicates that a mutation occurred in a parent's gamete.

Insertion

A mutation that adds DNA bases.

What happens if, by chance, an unstable tautomeric base is inserted into newly forming DNA?

A spontaneous mutation, because the error is perpetuated when that strand replicates

Which of the following would be characterized as a point mutation?

Addition or deletion of a single DNA base and Change in a single DNA base

Different disease phenotypes caused by mutations in the same gene are termed ______ ______.

Allelic Disorders or Diseases

Synonymous codons specify the same ______ ______.

Amino Acid

A mutagen is ________.

An agent that causes a mutation

Mutagen

An agent that causes mutation.

In expanding repeat disorders, the number of repeats may increase from generation to generation as they are transmitted, leading to earlier and more severe clinical manifestations. This phenomenon is called ______.

Anticipation

Mutations ______.

Can affect any part of the genome

Adding or deleting a number of bases that is not a multiple of three creates a ______ mutation.

Frameshift

Both homozygotes for hemoglobin S and homozygotes for hemoglobin C are resistant to the disease ______ because the unusual hemoglobin alters the red blood cells in ways that keep out the parasite that causes the infection.

Malaria

Polymorphism

A DNA base or sequence at a certain chromosomal locus that varies in a small percentage of individuals in a population.

Short Tandem Repeat (STR)

A DNA sequence of 2 to 10 bases that repeats at a specific site in a genome. Used in forensics to distinguish individuals.

Somatic Mosaicism

A condition in which a somatic mutation causes a phenotype to affect parts of the body descended from the original cell in which the mutation occurred.

Allelic Diseases

Different diseases caused by mutations in the same gene.

Triplet repeat diseases typically cause a ______.

Dominant toxic gain-of-function

A(n) _____ is a type of copy number variant.

Duplication

Gonadal Mosaicism

Having two or more genetically distinct cell populations in an ovary or testis.

Both hemoglobin S and hemoglobin C result from mutations that change the sixth amino acid in the beta globin polypeptide. What are the outcomes of these mutations?

Homozygotes for hemoglobin C have borderline or mild anemia while homozygotes for hemoglobin S have severe anemia.

A new recessive mutation would not be obvious until two heterozygotes produced a(n) _____ recessive offspring with a noticeable phenotype.

Homozygous

Most of the potentially mutagenic radiation individuals are exposed to is _____, which means that it has sufficient energy to remove electrons from atoms.

Ionizing

What feature of the genetic code protects against mutations to an extent?

Synonymous codons

One cause of spontaneous mutation stems from the tendency of free DNA bases to exist in two slightly different chemical structures, called _____.

Tautomers

In gonadal mosaicism, a mutation would be found in ______.

Testis or ovary cells in the parent and Gametes

Both sickle cell disease and ______ result from abnormalities in the beta globin protein.

Thalassemia

Which of the following changes does NOT alter a gene's reading frame?

The addition of six bases

A mutation changes the DNA sequence from CCT GAG GAG AAG to CCT GGG GAG AAG. Identify the type of mutation that has occurred.

Transition

A(n) _____ is a point mutation where a purine replaces a purine or a pyrimidine replaces a pyrimidine.

Transition

Males who inherit the Fragile X chromosomal abnormality but show no symptoms are called ______ males because they pass the affected chromosome to all of their daughters.

Transmitting

A mutation changes the DNA sequence from CAC CTG ACT CCT to CAC CTG TCT CCT. Identify the type of mutation that has occurred.

Transversion

A(n) _____ is a point mutation where a purine replaces a pyrimidine or vice versa.

Transversion

Collagen consists of a ______ helix of ______ polypeptides.

Triple; Procollagen

True or false: In the context of splice-site mutations, retaining an intron is unusual because most introns have stop codons in all reading frames.

True

The tiny mutation responsible for sickle cell disease is a substitution of the amino acid _____ in the beta globin polypeptide chain.

Valine for glutamic acid

Tandem Duplication

A copy of a DNA sequence next to the original sequence.

Somatic Mutation

A genetic change in a non-sex cell.

Conditional Mutation

A genotype that is expressed only under certain environmental conditions.

Germline Mutation

A mutation that is in every cell in an individual because it was present in the fertilized ovum.

Deletion

A mutation that removes part of a DNA sequence or part of a chromosome.

Splice-Site Mutation

A point mutation at a site in a gene that controls intron removal, resulting in extra or absent amino acids in the protein product.

Nonsense Mutation

A point mutation that changes an amino-acid-coding codon into a stop codon, prematurely terminating synthesis of the encoded protein.

Transition

A point mutation that replaces a purine with a purine or a pyrimidine with a pyrimidine.

Transversion

A point mutation that replaces a purine with a pyrimidine or vice versa.

Exon Skipping

A protein that is missing contiguous amino acids because a missense mutation creates an intron splice site.

Nonsense-Mediated Decay

A response that destroys mRNAs in which nonsense mutations encode shortened proteins that could have toxic effects on the cell.

Expanding Repeat

A short DNA sequence of usually three or four nucleotides that is present in a certain range of copy numbers in wild type individual but, when expanded, causes a disease.

Missense Mutation

A single-base change (point mutation) that alters a codon so that it specifies a different amino acid.

Point Mutation

A single-base change in DNA.

_____, a DNA repair mechanism in humans, replaces one to five nucleotides at a time, but specifically corrects errors that result from oxidative damage.

Base excision repair

Humans have two types of excision repair: ______ excision repair and ______ excision repair.

Base; Nucleotide

Examples of mutational "hot spots" include which of the following?

Both short repetitive sequences and palindromes

The mode of action of ionizing radiation is that it _____.

Breaks the DNA sugar-phosphate backbone

How are estimates of the spontaneous mutation rate for a particular gene usually derived?

By using observations of new dominant mutations which are detectable simply by observing the phenotype

Mismatch Repair

Checking DNA for misalignment of short, repeated segments.

The DNA sequences that differ in number from person to person are called _____.

Copy number variants

Somatic mutations occur as errors during ______ ______ at about every 300 mitotic cell divisions.

DNA Replication

Mutate refers to the process of altering a(n) ______ sequence.

DNA, Base, Gene, Chromosome, or Nucleotide

Excision Repair

Enzyme-catalyzed removal of pyrimidine dimers in DNA.

Which of the following mechanisms repairs DNA damaged by UV light by removing and replacing the pyrimidine dimer and a few surrounding bases?

Excision repair

In a type of mutation called a(n) _____, a gene actually grows as a small part of the DNA sequence is copied and added.

Expanding repeat

Anticipation is a hallmark of which of the following types of diseases?

Expanding triplet diseases

True or false: All DNA sequences are equally likely to mutate.

False

True or false: In the context of expanding triplet repeats, larger repeats are stable, growing with each generation and causing symptoms that are less severe.

False

______ ______ syndrome is the most common inherited form of intellectual disability. Males with the condition have inherited an unusual chromosome, with a terminal segment connected by a thin thread, from their mothers.

Fragile X

Which condition is characterized by an X chromosome prone to breakage?

Fragile X Syndrome

In a _____ mutation, the change occurs during the DNA replication that precedes meiosis.

Germline

_____ mutations are transmitted to the next generation of individuals.

Germline

Thalassemia and sickle cell disease are both associated with mutations in the ______ gene.

Globin

A parent could have a mutation in some sperm or oocytes because a spontaneous mutation occurred in the developing testis or ovary and was transmitted only to the cells descended from the original cell bearing the mutation. This condition is called ______ ______.

Gonadal Mosaicism

The family of Martin Fugate and Elizabeth Smith had some individuals who were slightly bluish and others with a bluer appearance. Those that appeared bluer were ______ for the mutation causing the "blue person disease".

Homozygous

In some genes, mutations are more likely to occur in regions called ______ ______ where sequences are repetitive.

Hot Spots

Fragile X syndrome shows ______ ______ as demonstrated by the observation that one-fifth of males who inherit the chromosomal abnormality have no symptoms.

Incomplete Penetrance

Mutations that are the result of exposure to chemical agents or radiation are called ______ mutations.

Induced

______ mutations are those caused by the intentional use of mutagens.

Induced

A characteristic of a pseudogene is that _____.

It is a DNA sequence that is not translated into protein

In hot spots, when DNA strands locally unwind to replicate in symmetrical or repeated sequences, bases located on the same strand may pair. This creates a ______ that interferes with ______.

Loop; DNA replication

Researchers tracked mutation rates after accidental exposures to mutagens by comparing the lengths of _____ sequences.

Minisatellite

An agent that causes a mutation is called a(n) ______

Mutagen

A(n) ______ is a change in a DNA sequence.

Mutation

Identify the different kinds of mutations that lead to allelic diseases.

Mutations in different parts of a gene and Mutations that are localized (single-base change) or catastrophic (a missing gene) and Mutations altering the protein in ways that affect its interactions with other proteins

Which of the following is an example of an expanding repeated disease?

Myotonic dystrophy

Identify the events that can cause exposures to mutagens.

Natural disasters that damage radiation-emitting equipment and Industrial accidents and Medical treatments such as chemotherapy and radiation

_____, a DNA repair mechanism in humans replaces up to 30 nucleotides and removes errors that result from several types of insults, including exposure to chemical carcinogens, UVB in sunlight, and oxidative damage.

Nucleotide excision repair

For the family with "blue person disease", members with ______ mutation(s) were slightly bluish while those inheriting ______ mutation(s) had a bluer appearance.

One or 1; Two or 2

A change in a single DNA base is known as a(n) ______ mutation.

Point

Several triplet repeat diseases are called ______ diseases because they are caused by repeats of the mRNA codon CAG, which encodes that particular amino acid.

Polyglutamine

A crossover between a working gene and its ______ results in a fusion gene. Some cases of ______ can result from this type of mutation.

Pseudogene; Gaucher disease

Hot spots are ______.

Regions of a gene that are more likely to undergo mutations

When DNA is damaged, the cell may ______ the error or signal a process called ______ to initiate cell death.

Repair; Apoptosis

In which two ways do cells respond if DNA is damaged?

Repairing the error and Dying by apoptosis

Base Excision Repair

Replacement of one to five contiguous DNA nucleotides to correct oxidative damage.

Nucleotide Excision Repair

Replacement of up to thirty nucleotides to correct DNA damage of several types.

Somatic mutations are generated as a result of errors in which process?

Replication of DNA

The first genetic illness understood at the molecular level was _____.

Sickle cell disease

In which of the following cells are somatic mutations most likely to occur?

Skin cells and Blood cells

A _____ mutation happens during DNA replication before a mitotic cell division, and is transmitted to the next generation of cells, not individuals.

Somatic

A(n) _____ mutation is a point mutation that can greatly affect a gene's product if it alters a site where introns are normally removed from the mRNA.

Splice-site