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18 Cards in this Set
- Front
- Back
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common causes of congenital malformations
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Certain chemicals, radiation, and viral infections can cause adverse influences during fetal development resulting in congenital malformationsFactors that cause congenital malformations are called teratogens
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abnormalities of sex chromosomes and their manifestations
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Nondisjunction and anaphase lag, which can occur during meiosis, can lead to an abnormal number of chromosomes, termed aneuploidy The process of crossing results in abnormal meiosis, resulting in portions of chromosomes that are lost, attached upside down, or attached to the wrong chromosome Abnormal chromosomal structures result from translocations, inversions, deletions, or duplications |
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Autosomal dominant
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Autosomal dominant traits are expressed in the heterozygous condition, so affected individuals will have at least one affected parent, the trait will generally appear in every generation, two affected parents may have unaffected offspring, and two unaffected parents only have unaffected offspring
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Autosomal recessive
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Autosomal recessive traits are only expressed in the homozygous condition, thus unaffected parents can have affected male and female offspring, whereas two affected parents will result in all of the offspring being affected
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Sex-linked recessive:
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Disorders linked to the Y chromosome are extremely rare, and for that reason the terms sex-linked and X-linked are often used interchangeably oNearly all X-linked disorders are recessive oFemales express the X-linked disease only in the rare instance in which both X chromosomes carry the defective gene oMales however do not have the safety margin of two X chromosomes and express the disease if their one and only X chromosome is abnormal. oAffected individuals are almost always male oAffected fathers transmit the defective gene to none of their sons but to all of their daughters oUnaffected males do not carry the defective gene oA carrier female has a 1 in 2 chance of producing an affected son and a 1 in 2 chance of producing a carrier daughter oFemales are affected only in the rare homozygous state that may occur from the mating of an affected or carrier mother and an affected father |
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methods for diagnosing congenital abnormalities
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Prenatal genetic testing can be performed on samples from amniocentesis, chorion tissue, or umbilical cord blood. Postnatal genetic analysis is usually done on peripheral blood samples of lymphocytes |
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Allele
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Genes that code for a particular trait may come in several forms or alleles
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Phenotype
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Phenotype refers to an individual’s observable attributes
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Genotype
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Genotype refers to the particular set of alleles an individual receives
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Homozygous
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Having two identical alleles for a specific gene product
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Heterozygous
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Having two different alleles for a specific gene product
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Dominant gene
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Dominant genes usually code for functional enzymes and are overtly expressed in the cell’s phenotype
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Recessive gene
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The gene that fails to be expressed in the phenotype when a dominant allele is present; the trait carried in a recessive allele is apparent only when two identical copies are present
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Autosomal inheritance
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A pattern of inheritance in which the transmission of traits depend on the presence or absence of certain alleles on the autosomes
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Sex-linked inheritance
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A pattern of inheritance in which the transmission of traits depends on the chromosomal sex of the individual
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Punnett square
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What Mendel used
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Mutation
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A heritable change in the nucleotide sequence of a chromosome; it is passed on to daughter cells when the cell divides
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Nondisjunction
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The failure of homologous chromosomes to separate normally during meiosis or mitosis, resulting in unequal distribution of chromosomes to daughter cells
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