GENE 320 Exam 3 Key

Dideoxynucleotide chain-termination sequencing, commonly known as Sanger sequencing, also revolutionized the field of genetics, as it provided a way to determine the sequence of DNA. The process relies on a small amount of dideoxynucleotides that is added to the reaction. The dideoxynucleotides contain a unique fluorescent label corresponding to each nucleotide. The dideoxynucleotides also have a hydrogen at the 3' carbon instead of a hydroxyl group. During DNA synthesis, this modification causes the polymerase reaction to

terminate

Genomic disorders such as deletions and duplications are primarily caused by ____ during meiosis

unequal crossing over

Long terminal repeat (LTR) retrotransposons are often suppressed in the genome. In some instances, they can retrotranspose to different sites in the genome, including genes. Based on your understanding of genetics, what do you think would happen if a LTR inserted into an intron of a gene?

The LTR could prematurely terminate transcription of the gene

A reciprocal translocation involves

An exchange of segments of DNA between 2 non-homologous chromosomes

To be considered a copy number variant (CNV), the rearrangement must span an entire gene

False

In the pedigree below, a disease-causing mutation is detected in the Male probing, but the mutation is not present in either parent or any of the siblings. What type of mutation would explain the disease in the probing?

De novo mutation

PCR revolutionized the field of genetics. It created a rapid way of cloning a specific fragment of DNA by eliminating the need to use host cells for cloning. What are the three steps of the PCR process in the order in which they are performed?

Denaturation, Hybridization/ annealing, and extension

Locus heterogeneity refers to:

Mutation in different genes that results in the same disease

Gene duplication is though to have played an important role during evolution. How might gene duplication give rise to different traits among different species of animals?

New variants within duplicated gene could give rise to a different function of the protein

In the pedigree below, a heterozygous mutation in the BIMZ gene is believed to be responsible for causing a disease in the male probing. The mutation, however, is present in the mother, grandfather, and great grandfather. What type of inheritance pattern or phenomenon would permit this mutation to be penetrant in the male probing but not his mother, grandfather, or great grandfather?

Genomic imprinting

Complementary DNA libraries contain complementary DNA copies made from mRNAs isolated from cultured cells or tissues. cDNA libraries are constructed by isolating mRNA from cells and then synthesizing a complementary DNA molecules using a ___ enzyme

Reverse transcriptase

Fragile X syndrome is caused by expanded CGG repeats in the promoter of the FMR1 gene. It is a unique disorder, because the repeats are in the promoter region and not in the coding region. How do the expanded repeats in the promoter region cause Fragile X syndrome?

The repeats cause the cell to methylate the promoter, thus silencing expression of the FMR1 gene

Penetrance is a term used to describe whether a trait caused by a genetic variant is seen or not, whereas expressitivity describes

The spectrum of range of a trait caused by a genetic variant

The mutagen that causes thymine dimers is

UV light

In the pedigree, the male probing is affected with a severe neurodevelopment disorder. Genetic testing shows that the site, mother, and grandmother are carriers of the mutation but unaffected. What type of inheritance pattern likely caused the disorder in the proband?

Y linked

Based on our understanding of meiosis and Mendelian genetics, independent assortment of chromosomes and alleles leads to ____

an extensive amount of genetic diversity

Gregor Mendel's postulates have become the principles of transmission genetics. His success is attributed to examining one or a few pairs of contrasting traits, his accurate quantitative records, and ___

choice of a suitable organism

An inversion that occurs on a chromosomes prior to gamete formation can lead to major rearrangements in the gametes, such as

deletions, inversions, and duplications

Allelic heterogeneity refers to:

different mutant alleles of a gene that are capable of causing the same disease

In the schematic below, the IacZ gene in the Multiple Cloning Site of the vector is used to

distinguish between bacterial cells containing the recombinant and nonrecombinant DNA

Down syndrome is caused by trisomy 21. Almost all cases of Down syndrome are caused because of ____ during meiosis

non-disjunction

Recombinant DNA technology refers to the joining of DNA molecules, usually from different biological sources, that are not found in nature. The basic procedure for producing recombinant DNA involves generating specific DNA fragments using ___

restriction enzymes

In the schematic below, a DNA molecules can be cloned into the vector using the Multiple Cloning Site, which has

several restriction sites, which can be used to linearize the vector to insert the recombinant DNA molecules

What is the term used to describe a trait in which a single autosomal gene causes a phenotype in both males and females, but the phenotype is more pronounced in males than it is in females

sex-influenced

Huntington disease is an autosomal dominant disorder, affecting motor coordination and cognitive function. Trinucleotide expansion of CAG repeats in the HD gene causes Huntington disease. Often the symptoms associated with the disease arise earlier in life and become more severe in affected individuals as the mutation is inherited is passed on from one generation to the next. This phenomenon is known as

Anticipation

In pedigree below, the female is affected with a. neurological disorder that was not penetrant until later in life; however, the symptoms appeared at an earlier age than the symptoms did in her father. What type of inheritance pattern likely caused the disorder the the proband?

Autosomal dominant

In the pedigree below, the probing is homozygous for a disease-causing mutation. Genetic testing shows that both parents are carriers for the mutation. What type of inheritance pattern likely caused the disease in the proband?

Autosomal recessive

____ is an inheritance pattern in which the 2 alleles of a single gene produce 2 gene products that can be seen simultaneously (that is, they are neither dominant nor recessive)

Codominance

Cystic fibrosis is a common genetic disease, affecting approximately 1 in 2,500 individuals. Individuals with CF inherit the mutation from both parents, but in some instances the mutant alleles causing CF are different from each other. This is referred to as a :

Complex heterozygote

____ is an inheritance pattern in which a cross between parents with contrasting traits results in offspring with an intermediate phenotype?

Incomplete dominance

In recombinant DNA technology vectors are engineered with antibiotic resistance genes. What is the function of an antibiotic resistance gene in a vector?

It is used as a selectable marker to distinguish bacteria that has been transformed with the vector up from those that have not

For some X-linked disorders, only females are affected and not males. How can this be?

The mutation is lethal in males

The UBE3A gene is imprinted with maternal-specific expression in the brain. LOF mutations on the maternal UBE3A allele cause Angelman syndrome, a severe neurological disorder. What effect does genomic imprinting have on the penetrance of mutations in UBE3A

The mutation will be 100% penetrant when it is located on the maternal allele

Cancer is a complex disease usually resulting from an accumulation of both genetic and epigenetic changes. In some cancers, there are genetic mutations affecting one allele but not the other allele, yet neither allele is functional. How can this be?

The other allele is silenced by hypermethylation

Genetic diseases are often caused by:

a single base mutation or small insertion/deletion that affects the function of a particular gene

In the pedigree below, is the probing a fraternal twin or identical twin

fraternal twin

Genomic imprinting is an epigenetic phenomenon that results in the ___

parent of origin dependent differential allelic expression of a gene

Inversions are a unique class of structural variation as

they do not lead to a loss of genetic information