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Questions and Answers

What characterizes monogenic or hereditary diseases?

  • They are caused by the combined effects of multiple genes.
  • They only affect adults.
  • They result from a single mutation in one gene. (correct)
  • They always have both genetic and environmental components.

Which statement is true regarding chromosomal diseases?

  • They do not include any genetic components.
  • They arise from environmental factors only.
  • They are exclusively monogenic in nature.
  • They are linked to structural or numerical changes of chromosomes. (correct)

In the context of multifactorial or complex diseases, which factors are involved?

  • They arise independently from both genes and the environment.
  • Only genetic predisposition is involved.
  • Both genetic factors and environmental factors play a role. (correct)
  • Only environmental factors are involved.

What percentage of newborns are expected to have genetic abnormalities or defects?

<p>2% (A)</p> Signup and view all the answers

Which of the following diseases correlates with the highest percentage of childhood conditions attributed to genetic defects?

<p>Childhood blindness (C)</p> Signup and view all the answers

What proportion of childhood hospital admissions are due to genetic diseases or birth defects?

<p>30% (D)</p> Signup and view all the answers

What percentage of the most common cancers have a genetic component?

<p>10% (B)</p> Signup and view all the answers

Which statement best describes the occurrence of genetic diseases in adulthood?

<p>They are rarer in adulthood than in early childhood. (C)</p> Signup and view all the answers

What is the default sexual development in humans?

<p>Female phenotype (A)</p> Signup and view all the answers

Which of the following best explains the relationship between environmental effects and somatic mutations in cancer?

<p>Accumulation of somatic mutations is related to environmental effects. (B)</p> Signup and view all the answers

What significant breakthrough related to human genetics was realized in the year 2007?

<p>Evidence of genome variations across different populations (D)</p> Signup and view all the answers

What is considered a serious potential outcome of mutations in germ cells?

<p>Hereditary genetic diseases (A)</p> Signup and view all the answers

How can a person sequence their entire genome, as mentioned?

<p>Using bodily fluids collected non-invasively (C)</p> Signup and view all the answers

What role do mutations play in the evolution of species?

<p>They create genetic variability necessary for adaptation. (D)</p> Signup and view all the answers

What is a consequence of mutations accumulated in somatic cells?

<p>Development of malignant tumors or complex diseases (D)</p> Signup and view all the answers

What is the primary difference between mutations and polymorphisms in genetic terms?

<p>Mutations occur below a frequency of 1%, whereas polymorphisms occur above that threshold. (B)</p> Signup and view all the answers

Which type of genetic variation is the most frequent among humans?

<p>Single nucleotide polymorphisms (SNPs) (B)</p> Signup and view all the answers

What kind of diseases are primarily influenced by genetic polymorphisms?

<p>Complex multifactorial diseases (C)</p> Signup and view all the answers

What role do nucleotide excision repair enzymes play in the context of skin cancer and sun exposure?

<p>They repair DNA alterations caused by environmental factors. (D)</p> Signup and view all the answers

At what point in human development can some genetic symptoms manifest?

<p>At various life stages including before birth, after birth, or later in life (A)</p> Signup and view all the answers

Which statement accurately describes how SNPs contribute to genetic diversity?

<p>SNPs represent variations that occur frequently and help define alleles within a population. (C)</p> Signup and view all the answers

What kind of genetic condition is Huntington's disease categorized as?

<p>A genetic condition with both juvenile and adult forms of onset (B)</p> Signup and view all the answers

Which of the following correctly characterizes large inversions in genetics?

<p>They can lead to significant phenotypic variation and have evolutionary implications. (C)</p> Signup and view all the answers

How does the concept of genetic predisposition relate to polymorphisms?

<p>Polymorphisms can provide a baseline risk for developing certain complex diseases. (B)</p> Signup and view all the answers

Which type of genetic variation refers specifically to DNA sequence repetitions?

<p>Microsatellites and minisatellites (C)</p> Signup and view all the answers

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Study Notes

Categories of Genetic Diseases

  • Monogenic or Hereditary Diseases: Caused by a single mutation in one gene, with potential modifiers affecting the phenotype subtly.
  • Chromosomal Diseases: Result from structural or numerical alterations of chromosomes.
  • Multifactorial or Complex Diseases: Involve both genetic predispositions (multiple genes) and environmental factors; require interaction between the two for disease manifestation.

Frequency of Genetic Diseases

  • Prevalence in Newborns: 2% of newborns born with genetic abnormalities.
  • Impact on Children: Genetic defects account for 50% of childhood blindness, deafness, and mental retardation; responsible for 30% of pediatric hospital admissions and 50% of pediatric deaths.
  • Cancer Statistics: Approximately 10% of common cancers possess a genetic component, with the remainder linked to somatic mutations influenced by environmental factors.
  • Adult Genetic Diseases: 5% of adults experience diseases where genetic factors play a significant role, though these are rarer than in childhood.

Age of Onset for Genetic Diseases

  • Genetic conditions can manifest at various life stages:
    • Prenatal: Major chromosomal aberrations may cause premature abortion.
    • Postnatal: Congenital malformations can be diagnosed before or shortly after birth.
    • Late Onset: Conditions like diabetes mellitus or Huntington's disease may show symptoms later in life.

Genetic Polymorphisms vs. Mutations

  • Mutations: Rare DNA variations (below 1% frequency) that can cause diseases when pathogenic.
  • Polymorphisms: Common variations (above 1% frequency) that do not significantly affect gene function in the majority of instances.

Single Nucleotide Polymorphisms (SNPs)

  • SNPs are prevalent forms of genetic variation, with 99.9% DNA identity among humans, translating to approximately 3 million differences across the genome.
  • These differences can be benign or contribute to disease predisposition, particularly in multifactorial conditions.

Other Forms of Genetic Variation

  • Indels (Insertions/Deletions): Variations where bases are added or removed from the DNA sequence.
  • Microsatellites and Minisatellites: Repetitive sequences of different lengths in the DNA.
  • Repeated Genes: Individuals may differ in the number of gene copies due to genetic variation.
  • Large Inversions/Deletions: Significant changes in chromosome structure, exemplified by the evolution of the Y chromosome, critical for male sexual development.

Impact of Mutations on Evolution

  • Mutations contribute to genetic variability, essential for adaptation and evolution.
  • Deleterious mutations in germ cells can lead to hereditary diseases; somatic mutations may result in conditions like cancer and cardiovascular diseases.

Advances in Genetic Testing

  • Genome sequencing is accessible, allowing individuals to sequence their DNA from a simple saliva sample, typically costing around $2000.

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