Chapter 6: Genetic and Pediatric Diseases Flashcards
How many genes are in the human genome?
25,000 protein-coding genes
This is an organism’s genetic material.
Genome
This is a discrete set of nucleotides. It is a section of DNA that instructs protein synthesis and is a unit of inheritance.
Gene
This is a single genetic locus and an alternative form of a gene.
Allele
These are permanent changes in DNA.
Mutations
- Germ line (hereditary): all cells
- Somatic (acquired): some cells
This term refers to conditions transmitted to offspring.
Hereditary disorders
This term refers to all of the last trimester and one month after.
Perinatal
This term refers to the newborn (first four weeks).
Neonate
This term refers to the child after the first year.
Infant
This type of mutation is when a nucleotide base is replaced by another, codes for alternative amino acid.
Point mutations (missense)
This type of mutation is characterized by the insertion/deletion of 1 or 2 nucleotides, which alters the “reading frame”.
Frameshift mutation
This type of mutation is characterized by an amplification of a sequence of 3 nucleotides.
Trinucleotide repeat
This category of genetic disorders is also known as Mendelian disorders. They are rare and hereditary (Autosomal dominant, autosomal recessive, or X-linked recessive)
Single-gene mutations (of large effect)
How are single-gene mutations (of large effect) screened for?
Amniocentesis and ultrasonography
What are the categories of genetic disorders?
- Disorders of single-gene mutations of large effect
- Disorders of multifactorial inheritance
- Disorders of chromosomal abnormalities
- Disorders of atypical inheritance
This term refers to single mutations which may have a variety of phenotypic effects.
Pleiotropy
This term refers to multiple mutations being expressed as the same trait.
Genetic heterogeneity
In this single gene mutation one parent is typically affected. Offspring have a 50% chance of having the disease and the most common form of expression is the heterozygous form. They are more likely to affect structural proteins and membrane receptors.
Autosomal dominant disorders
What are some factors associated with autosomal dominant disorders?
- Reduced penetrance (have the mutation, but are phenotypically normal)
- Variable expressivity (same mutation is expressed differently within different individuals
In this single gene mutation the parents are unlikely to be affected. Offspring have a 25% chance of expressing the disease and the most common form of expression is the homozygous expression. They most commonly disrupt enzymes.
Autosomal recessive disorders
In this single gene mutation heterozygous females are the ones to transmit them. Male offspring have a 50% chance of expressing the disease while female offspring are protected.
X-linked disorders (sex-linked)
This condition is autosomal dominant and characterized by a fibrillin (structural protein) gene mutation. Some characteristics include arachnodactyly, bilateral lens subluxation, ruptured aorta, and basilar invagination.
Marfan syndrome
This condition is a group of single-gene disorders (autosomal dominant or recessive) caused by defective collagen synthesis. It is characterized by hyperextensible skin and hypermobile joints.
Ehlers-Danlos syndrome
This is the most common Mendelian disorder (autosomal dominant). It is caused by a mutated LDLR gene and characterized by impaired LDL transport and catabolism.
Familial hypercholesterolemia
These are cholesterol deposits on tendons.
Xanthomas
Which familial hypercholesterolemia is more severe? Heterozygous or Homozygous.
Homozygous
This condition is autosomal recessive and caused by a mutation in the CFTR gene. This results in decreased chloride ion transport resulting in viscous secretions (lungs and pancreas) and increased salt in sweat.
Cystic fibrosis
This is the most common condition caused of death due to cystic fibrosis?
Cor pulmonale
This condition is autosomal recessive and individuals who have this can’t metabolize phenylalanine into tyrosine. This due to a mutated phenylanalanine hydroxylase.
Phenylketonuria (PKU)
This condition is autosomal recessive, which results in an abnormal galactose metabolism metabolism (mutated GALT gene). It can lead to CNS, liver, and kidney damage.
Galactosemia
This is a group of rare autosomal recessive conditions characterized by a lack of lysosomal enzymes and an accumulation of metabolites. It can lead to CNS damage, hepatosplenomegaly, and cellular dysfunction.
Lysosomal storage diseases
Tay-Sachs disease, Niemann-Pick disease (Type A, B, C), Gaucher disease, and Mucopolysaccharidosis are examples of what type of disease?
Lysosomal storage diseases
This condition is characterized by an inability to metabolize Gm2 gangliosides due to a mutated hexosaminidase A enzyme. It can result in destruction of CNS, PNS, and ANS tissue leading to mental retardation, blindness, and motor weakness.
Tay-Sachs disease (Gm2 gangliosidosis)
What feature is characteristic of Tay-Sachs disease?
A cherry-red central macula (retina)
This condition in general is characterized by an accumulation of sphingomyelin due to a deficiency in acid sphingomyelinase
Niemann-Pick disease
This type of Niemann-Pick disease is the most severe and results in visceromegaly and neurological damage. It is lethal by age 3.
Type A
This type of Niemann-Pick disease results in visceromegaly and no neurological damage. It is most commonly limited to hepatosplenomegaly.
Type B
This is the most common type of Niemann-Pick disease. It is a non-enzymatic deficiency characterized by defective lipid transport (mutated NPC1 or NPC2) and results in ataxia, dystonia, dysarthria, or psychomotor regression.
Type C
This condition is due to a mutated glucocerebrosidase gene resulting in the accumulation of glucocerebroside, which results in enlarged phagocytes, severe hepatosplenomegaly, osteolysis, osteonecrosis, and pancytopenia.
Gaucher disease