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PCOL 838 EXAM 1 Questions And Answers Well Illustrated.

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PCOL 838

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Course PCOL 838

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PCOL 838 EXAM 1 Questions And Answers
Well Illustrated.

What are the purines and pyrimidines? - correct answer. purines: adenine, guanine
pyrimidines: cytosine, uracil, thymine

What are some examples of the cause of mutations in DNA? - correct answer. cellular
metabolism, UV light exposure, ionizing radiation, chemical exposure, replication errors

What happens when the DNA is damaged/a mutation occurs? - correct answer. cell
cycle checkpoint activation, transcriptional program activation, DNA repair, apoptosis

What is the definition of a gene? - correct answer. A segment of DNA encodes a
product responsible for a measurable trait.

What are the coding and noncoding regions of DNA? - correct answer. exons: coding
regions
introns: spliced out

What are the different types of mutations? - correct answer. • Single nucleotde change
/ Substitution --> single nucleotide polymorphism (SNP)
• Insertion and deletion (INDELS)
Chromosomal rearrangement:
• Aneuploidy
• Inversion
• Translocation

What is the difference between nonsense, silent, and missense mutations? - correct
answer. • Nonsense mutations are often deleterious.
• Silent mutations and some missense mutation maybe
hereditable, and become an allele in the population -->
variation
• Missense mutation: Amorphic, neomorphic, hypermorphic,
hypomorphic, Antimorphic

What gives rise to alleles? - correct answer. single nucleotide polymorphism (SNP)
and insertion deletions (INDELS) give rise to different versions of a same gene, known
as alleles.

,What are Metacentric, Submetacentric, Acrocentric, Telocentric chromosomes? -
correct answer. Metacentric: p and q arm are the same
Submetacentric: p arm is slightly shorter than the q arm
acrocentric: very little p-arm, normal q arm
telocentric: no p arm, q arm still present

What is Klinefelter syndrome? - correct answer. most common type of primary
hypogonadism (defect is at gonadal level)
XXY genotype
Male phenotype at birth but failure to mature sexually
at puberty
At puberty, testes become fibrotic and seminiferous tubules
are largely destroyed
Low to low-normal circulating testosterone levels
High estrogen:androgen ratio can lead to feminization
Treated with androgen replacemen

What is aneuploidy? What is a condition that is an example of this? - correct answer.
the presence of an abnormal number of chromosomes in a cell
Klinefelter Syndrome

What is a robertsonian translocation? - correct answer. the most common form of
chromosomal rearrangement where the participating chromosomes break at their
centromeres and the long arms fuse to form a single, large chromosome with a single
centromere

What is the difference between paracentric and pericentric inversions? - correct answer.
Paracentric inversions do not include the centromere and both breaks occur in one arm
of the chromosome.

Pericentric inversions include the centromere and there is a break point in each arm

What are isochromosomes? - correct answer. two identical arms joining together
resulting in loss of genetic material

What is a common place to see gene amplification? - correct answer. Gene
amplification often seen in cancer cells where an oncogene is amplified hundreds of
time --> higher expression of oncogene
--> malignant transformation

Which type of mutations are heritable? Germline or somatic? - correct answer.
Germline mutation
• Mutation to the germinal cells (sperm / ovum).
• Germ line mutations can be passed down to the next generation.
• Can cause hereditary diseases.

,What is mosaicism? - correct answer. some mutations may arise during early
embryogenesis, in which case tissues of the affected individual contain a mixture, or
mosaic, of mutant and nonmutant cells. Depending on the time of embryogenesis and
cell type in which a new mutation arises, an individual may carry the mutation in some
but not all of their germ cells (germline mosaicism), some but not all of their somatic
cells (somatic mosaicism), or both.

What is chimerism? - correct answer. People that have two different sets of DNA are
called human chimeras

How often does a mutation cause a disease? - correct answer. Overall frequency of
disease attributable to defect in a single gene (a.k.a Mendelian disorder) is ~1%.
-Most mutations are either asymtomatic or embryonic lethal

Why are medelian disorders so rare? - correct answer. The rarity of Mendelian
disorder could be attribute to:
• Symptoms of some mutations are not apparent.
• Mutation is lethal during development.
• Mutations to several genes (multifactorial) are
required for phenotypic development.
• Mosaicism

What is the difference between autosomal and X-linked inheritance? - correct answer.
• Autosomal can be recessive or dominant (Mendelian inheritance pattern)
• X-linked - mostly manifest in men because of hemizygosity

What is autosomal recessive inheritance? - correct answer. • Autosomal
• Classical Mendelian inheritance.
• Only one allele is working.
• This often gives rise to 50% protein level.
• 50% protein level is typically enough for normal function.
• Need both alleles to manifest disease phenotype --> recessive inheritance.

What is autosomal dominant inheritance? - correct answer. • If 50% protein level is not
enough for normal function -->dominance inheritance.
• Most are actually semidominant, where individual inherited with both loss-of-function
alleles manifest more severe phenotype.
• True dominant with loss-of-function mutation can occur when loss-of-heterozygosity
causes a different problem. For example: hereditary cancer syndromes such as Von
Hippel Lindau (VHL) disease, Cowden syndrome, Hereditary leiomyomatosis and renal
cell cancer (HLRCC)

What is an example of an X-linked dominant disease? - correct answer. fragile X
syndrome

, What is an example of an x-linked recessive disease? - correct answer. hemophilia

What is an example of codominance? - correct answer. Blood type

What is an example of a mitochondrial disease? - correct answer. Leber hereditary
optic neuropathy

What is Leber hereditary optic neuropathy (LHON)? - correct answer. mitochondrial
disease
-CNS imaging studies may reveal abnormalities of the basal ganglia and corpus
striatum
• Lead to optic cell death and progressive vision loss.
• Incomplete penetrance: 50% of male and 85% of female never experience any vision
loss of related health problems.
• Affected individuals are typically homoplasmy, heteroplasmy individual will eventually
become homoplasmy

What is heteroplasmy vs. homoplasmy? - correct answer. heteroplasmy: A cell can
have some mitochondria that have a mutation in the mtDNA and some that do not.

homoplasmy: a cell that has a uniform collection of mtDNA: either completely normal
mtDNA or completely mutant mtDNA

What is penetrance and incomplete penetrance? - correct answer. Manifestation of
disease phenotype under a set of predefine criteria.
Incomplete penetrance of dominantly inherited diseases is one of the reasons why
deleterious allele persist in the population.
Same mutation can affect different tissues --> different phenotype -->variable
expressivity.

What is the genetic cause of Hereditary leiomyomatosis and renal cell cancer
(HLRCC)? - correct answer. • FH gene encode fumarate hydratase, a TCA cycle
enzyme.
• autosomal dominance
• Disease arise when the normal allele is lost (LOH - loss-of-heterozygocity).

What are the two different diseases caused by the FH loss-of -function mutation? -
correct answer. Hereditary leiomyomatosis and renal cell cancer (HLRCC) -
Autosomal dominant with incomplete penetrance

Fumarate hydratase deficiency - Autosomal recessive.

What are different causes of loss of heterozygosity (LOH)? - correct answer. mitotic
nondisjunction, mitotic recombination, and gene conversion

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