Concept 14.4: Many human traits follow Mendelian patterns of inheritance

Flashcards from Concept 14.4 of Pearson's Campbell Biology, Twelfth Edition.

Human genetics

Based around basic Mendelian genetics even with the limitations of human subjects for genetic research

Pedigree

A family tree that describes the inheritance of a trait across generations

• Used to analyze the results of human matings that have already occurred to make future offspring predictions

Recessive disorders

Disorders that range from relatively mild to life-threatening that only show up with individuals homozygous for the allele

• Always born to carrier or affected parents

Carriers

Heterozygous individuals who carry the recessive allele but are phenotypically normal

• Rarity reduces likelihood of meeting and mating

Albinism

A recessive condition characterized by a lack of pigmentation in skin and hair

Consanguineous matings

Matings between close relatives that increase the chance that both parents of a child carry the same rare allele

• Often outlawed or taboo in many societies and cultures

Cystric fibrosis

The most common lethal genetic disease in the United States

• Results in defective chloride transport ions in plasma membranes, leading to a buildup of chloride ions outside the cell

• Mucus buildup and abnormal nutrient absorption in the small intestine are common symptoms

• Can cause death by the age of 5; requires antibiotics and physical therapies to prolong life usually up to 40s

Sickle-cell disease

A disease that affects 1 out of 400 African-Americans

• Caused by the substitution of a single amino acid in the hemoglobin protein in red blood cells, leading to abnormally shaped cells in homozygotes

• However, heterozygote carriers are typically healthy and are less susceptible to the malaria parasite

• Symptoms include physical weakness, pain, organ damage, and even paralysis

Dominant disorders

Disorders that are caused by dominant alleles

• Those that cause lethal diseases are rare and arise by mutation

Achondroplasia

A form of dwarfism caused by a rare dominant allele

Huntington’s disease

A degenerative disease of the nervous system with no obvious phenotypic effects until the individual is about 35 to 40 years of age

• Nervous system deterioration, when started, is irreversible and fatal

• Can be tested for within an individual’s genome, up to personal choice

Lifestyle

A major factor on an individual’s phenotype regardless of the genotype

Genetic counselors

Professionals that provide information to prospective parents concerned about a family history for a specific disease

• Help determine the risk of a child with a specific disease for decisions about having children

• Fetal and newborn testing can also reveal genetic disorders

Amniocentesis

Sampling the liquid that bathes the fetus for the removal and testing of genetic disorders

Chorionic villus sampling (CVS)

Using a sample of the placenta for the removal and testing of genetic disorders

Phenylketonuria (PKU)

A recessively inherited disorder that occurs in 1 of every 10,000 to 15,000 births in the United States

• Routinely tested for at birth in most American hospitals alongside several other conditions