Mendelian Genetics & Pedigrees
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33 terms
Terms | Definitions |
|---|---|
 Pedigree | Can reveal mode of inheritance & may be used when crosses are not possible |
| Proband | the person whose phenotype first brought attention to the investigation |
| Autosomal Recessive Trait | May skip generations, neither parent may exhibit trait of affected offspring |
| Autosomal Dominant Trait | rarely skips generations, all affected offspring have an affected parent |
| Wild Type | most common allele, not neccessarily dominant |
| Loss of Function Mutation | a mutation that may reduce or eliminate a proteins function |
| Icthyosis | a loss of function mutation in humans |
| Null Allele | mutation causing complete loss of expression |
| Gain of Function mutation | new or enhanced activity on a protein |
| Noonan Syndrome | example of a gain of function mutation in humans |
| Silent mutation | may change teh gene sequence, but not the amino acid that it coes for, usually has no phenotypic effect |
| Incomplete Dominance | neither allele is dominant, produces intermediate phenotype, possible cause:loss of function mutation |
| Tay Sachs disease | incomplete dominance,fatal in homozygous recessive infants, heterozygotes have 1/2 the enzyme activity of homozygous normal individuals |
| Codominance | Both gene alleles produce distinct gene products |
| MN Blood Group | example of codominance |
| Multiple Alleles | no individual has more than 2 alleles but more variants may be possible within a population |
| Lethal allele | recessive, lethal in homozygous, may produce distinct phenotype when heterozygous, example: yellow coat color in mice |
| Huntington Disease | dominant lethal disease, neurodegenerative disorder |
| Epistasis | the effect of one gene masks the effect of another gene |
| Bombay phenotype | genotypically blood type B, but a homozygous recessive at another locus prevents AB antigens from being expressed |
| Complimentary Gene Action | One dominant allele needed at both loci for phenotype to be expressed |
| Pleiotropy | A single gene having multiple effects on an individuals phenotype |
| Marfan Syndrome | example of pleiotropy in humans, hereditary connective tissue disorder |
| Hemizygous | men with only one x chromosome |
| Thomas Morgan | documented x-linkage in white eyed fruit flies |
| Color blindness | example of x-linkage in humans |
| Sex-limited inheritance | phenotype is only presnet in one sex, autosomal gene is responsible |
| Sex-influenced inheritance | present in both sexes, autosomal gene responsible, genotype has different phenotypes in each sex |
| Penetrance | precent expression of a mutant genotype in a population |
| Position Effects | physical location of a gene may affect it's expression |
| Temperature Sensitive Mutation | heat shock genes which protect and repair DNA in elevated temperatures |
| Genomic Imprinting | Some genes are expressed depending on which parent they come from |
| DNA methylation | methyl groups added to DNA during gamete formation silence a gene |
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