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Questions and Answers
What characterizes monogenic or hereditary diseases?
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?
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?
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?
What percentage of newborns are expected to have genetic abnormalities or defects?
Which of the following diseases correlates with the highest percentage of childhood conditions attributed to genetic defects?
Which of the following diseases correlates with the highest percentage of childhood conditions attributed to genetic defects?
What proportion of childhood hospital admissions are due to genetic diseases or birth defects?
What proportion of childhood hospital admissions are due to genetic diseases or birth defects?
What percentage of the most common cancers have a genetic component?
What percentage of the most common cancers have a genetic component?
Which statement best describes the occurrence of genetic diseases in adulthood?
Which statement best describes the occurrence of genetic diseases in adulthood?
What is the default sexual development in humans?
What is the default sexual development in humans?
Which of the following best explains the relationship between environmental effects and somatic mutations in cancer?
Which of the following best explains the relationship between environmental effects and somatic mutations in cancer?
What significant breakthrough related to human genetics was realized in the year 2007?
What significant breakthrough related to human genetics was realized in the year 2007?
What is considered a serious potential outcome of mutations in germ cells?
What is considered a serious potential outcome of mutations in germ cells?
How can a person sequence their entire genome, as mentioned?
How can a person sequence their entire genome, as mentioned?
What role do mutations play in the evolution of species?
What role do mutations play in the evolution of species?
What is a consequence of mutations accumulated in somatic cells?
What is a consequence of mutations accumulated in somatic cells?
What is the primary difference between mutations and polymorphisms in genetic terms?
What is the primary difference between mutations and polymorphisms in genetic terms?
Which type of genetic variation is the most frequent among humans?
Which type of genetic variation is the most frequent among humans?
What kind of diseases are primarily influenced by genetic polymorphisms?
What kind of diseases are primarily influenced by genetic polymorphisms?
What role do nucleotide excision repair enzymes play in the context of skin cancer and sun exposure?
What role do nucleotide excision repair enzymes play in the context of skin cancer and sun exposure?
At what point in human development can some genetic symptoms manifest?
At what point in human development can some genetic symptoms manifest?
Which statement accurately describes how SNPs contribute to genetic diversity?
Which statement accurately describes how SNPs contribute to genetic diversity?
What kind of genetic condition is Huntington's disease categorized as?
What kind of genetic condition is Huntington's disease categorized as?
Which of the following correctly characterizes large inversions in genetics?
Which of the following correctly characterizes large inversions in genetics?
How does the concept of genetic predisposition relate to polymorphisms?
How does the concept of genetic predisposition relate to polymorphisms?
Which type of genetic variation refers specifically to DNA sequence repetitions?
Which type of genetic variation refers specifically to DNA sequence repetitions?
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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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