Genetic Stuff Flashcards
Gene definition
Sequences of DNA that contain the instructions for making a protein
Allele definition
Alternate form of a gene due to a change, deletion or insertion of nucleotides.
Two alleles of each autosomal gene are found in each cell. They are either dominant or recessive.
Homozygous
Two identical alleles for a gene
Heterozygous
Two different alleles for a gene
Hemizygous
Only one allele for a gene
Phenotype
Characteristic or trait that can be measured or observed and is based on genotype
The physical characteristics
Locus
The location of a gene on the chromosome
Multifactorial inheritance explained
Most diseases are complex and involve an interplay between genes and environment
Epistasis
Interaction between two or more genes (Example- one gene can increase or decrease the expression of a second gene)
Genetic homogeneity
Only a single SNP causes the mutation
SNP-Single nucleotide polymorphism
Genetic heterogeneity
Different mutations cause identical or similar phenotype
What are the two types of genetic heterogeneity?
Allelic heterogeneity- Different mutations at the same location
Locus heterogeneity- Mutations at different loci producing the same phenotype
Karyotype
Organization of the pairs of chromosomes from a metaphase cell based on their size
Mosaicism
When two or more cells of an individual have distinct karyotype
This results from chromosomal changes due to mitotic errors that occur after conception
Lyonization
The process where almost all genes on one X chromosome are inactivated in females
What does an Xi dark spot indicate?
Barr body
Expressivity
Spectrum of phenotypic expression with the same genetic mutation
Variable organ involvement, severity, and onset of disease
Penetrance
Likelihood that individuals with a mutant genotype express the phenotype
Genetic imprinting
Gene inactivation occurs on chromosome regions of autosomes leading to expression of only one parental allele
Aneuploidy
Loss or gain of one or more chromosomes
Results from failure of a chromosome pair to separate
Polyploidy
Many multiples of the entire set of chromosomes
What are the four types of chromosomal breakages?
Deletion, duplication, inversion, translocation
Trinucleotide repeat disorders
Due to expansion of a repetitive sequence of nucleotides in a gene
Genetic anticipation
Worsening of the disorder with subsequent generations due to the number of repeats of nucleotides increasing as the mutation goes from generation to the next
