Genetics Day 2

Questions and Answers

What is pleiotropy in the context of genetics?

The occurrence when a trait is influenced by multiple genes.

The phenomenon where some individuals do not express a phenotype.

The presence of multiple alleles for a single gene.

The ability of a single gene to cause multiple physical traits. (correct)

Which of the following is an example of incomplete penetrance?

Polydactyly (correct)

Marfan syndrome

Albinism

Cystic fibrosis

What does the term 'locus heterogeneity' refer to?

Variation in phenotype expression due to environmental factors.

Dominance of one allele over another.

Multiple genes influencing a single phenotype.

Different mutations at the same gene locus causing similar phenotypes. (correct)

Which statement is true about codominance?

Both alleles are fully expressed in the phenotype. Signup and view all the answers

Maternal inheritance typically concerns which type of traits?

Mitochondrial traits. Signup and view all the answers

What phenomenon describes a phenotype that varies significantly among individuals with the same genotype?

Expressivity Signup and view all the answers

What characterizes dynamic mutations associated with trinucleotide repeat disorders?

They can expand into multiple copies within one generation. Signup and view all the answers

Which of the following disorders is associated with trinucleotide repeat expansions?

Huntington’s Disease Signup and view all the answers

What is a premutation in the context of trinucleotide repeat disorders?

Between 50 and 230 repeats of the trinucleotide sequence. Signup and view all the answers

What phenomenon is described by anticipation in genetic disorders?

The disease displays earlier onset and increased severity in subsequent generations. Signup and view all the answers

What is the main function of mitochondria in a cell?

Production of energy (ATP) and regulation of apoptosis. Signup and view all the answers

What is the typical number of mitochondrial DNA copies per cell?

100 to 1,000 copies per cell. Signup and view all the answers

What characterizes variable expressivity in genetics?

Variability in the expression of a trait due to environmental and genetic factors Signup and view all the answers

How is the AB blood type phenotype in codominant blood group alleles developed?

Both alleles produce molecules leading to a novel phenotype Signup and view all the answers

Which condition is associated with germline mosaicism?

Amelogenesis imperfecta Signup and view all the answers

What is a defining feature of male pattern baldness?

A sex-influenced trait that is dominant in men Signup and view all the answers

What can be said about the inheritance of neurofibromatosis type I?

It is usually inherited as a dominant trait Signup and view all the answers

Which statement is true about multiple blood group alleles?

An individual can carry only two alleles from the three available in the population Signup and view all the answers

How does hemochromatosis affect individuals based on sex?

Women are less affected due to menstruation Signup and view all the answers

What does somatic mosaicism refer to in genetics?

Presence of genetic mutations in somatic cells but not germline Signup and view all the answers

Which trait is known to occur exclusively in females?

Incontinentia pigmenti type 2 Signup and view all the answers

What is NOT a characteristic of single gene inheritance?

Expression is determined by parental origin Signup and view all the answers

Which of the following describes uniparental disomy?

Receiving both homologues from one parent Signup and view all the answers

Which mutation is characterized by a change in a single nucleotide that results in a different amino acid?

Missense mutation Signup and view all the answers

What type of inheritance is characterized by the expression of genes being influenced by the parent of origin?

Non-classical inheritance Signup and view all the answers

Which type of genetic variation refers to the presence of two or more genetically different cell lines within an individual?

Mosaicism Signup and view all the answers

Which of the following is a type of mutation that introduces a premature stop codon?

Nonsense mutation Signup and view all the answers

Which process is related to maternal inheritance patterns?

Mitochondrial inheritance Signup and view all the answers

What principal type of mutation results from the insertion or deletion of nucleotides in a DNA sequence?

Frameshift mutation Signup and view all the answers

Which of these is NOT considered a type of non-classical inheritance?

Autosomal recessive inheritance Signup and view all the answers

Study Notes

Complications in Single Gene Pedigree Analysis

Heterogeneity refers to variations in the genotype-phenotype relationships across different individuals or families.
Pleiotropy describes a single gene affecting multiple physiological or anatomical features, such as Marfan syndrome impacting eyes, skeleton, and cardiovascular systems.
Incomplete dominance allows for a mixed phenotype in heterozygotes, while codominance results in both allele traits being expressed, exemplified by AB blood types.
Multiple alleles can exist within a population for a single trait, although an individual may only possess two.
New mutations can arise, as seen in neurofibromatosis type I, commonly inherited in a dominant manner.
Germline mosaicism involves specific genetic mutations being present only in some gametes, potentially leading to unaffected parents having affected offspring.
Sex-limited traits express differently across genders, with male pattern baldness influenced by autosomal mutations, being dominant in males and recessive in females.

Non-Classical Inheritance

Non-classical inheritance patterns differ from Mendelian ratios, often due to mechanisms like genomic imprinting and uniparental disomy, where both homologous chromosomes come from one parent.
Mosaicism describes the presence of genetically different cell lines within an individual.
Trinucleotide repeat disorders involve unstable DNA sequences, leading to conditions that worsen and appear earlier in subsequent generations, a phenomenon known as anticipation.
Fragile X Syndrome and Huntington's disease are examples of disorders stemming from trinucleotide repeat expansions.

Mitochondrial Genetics

Nuclear DNA is diploid with two genome copies per cell, while mitochondrial DNA (mtDNA) is haploid, circular, and exists in multiple copies per mitochondrion, with a high mutation rate.
Mitochondrial inheritance means transmission is maternal; affected mothers can pass traits to all offspring, while affected fathers cannot.
Heteroplasmy indicates variability in mitochondrial DNA within an individual, affecting disease severity based on the proportion of mutant to normal mtDNA.
Mitochondrial disorders often target high-energy demand tissues, such as the CNS and muscles, with clinical outcomes varying widely based on genetic and environmental factors.
Severe mitochondrial disorders can present as multi-system diseases, while mild forms might be asymptomatic.

Key Terms

Pleiotropy: Single genes affecting multiple traits.
Codominance: Both alleles expressed in heterozygotes.
Mosaicism: Different genetic makeups within one individual.
Anticipation: Conditions worsen across generations.
Heteroplasmy: Variability of mtDNA mutations influencing disease severity.

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