Ch 2 - Definitions

allele

allele

alternative forms of a gene at a given locus

autosome

any chromosome other than the sex chromosomes or the mitochondrial DNA

chromatid

the two parallel identical strands, connected at the centromere, of a doubled chromosome after chromosomal replication but before anaphase

chromosome

organized structures that carry DNA; humans have 22 pairs of non-sex ___ and 1 pair of sex ___

codon

a sequence of three nucleotides which together form a unit of genetic code in a DNA or RNA molecule

copy number variant polymorphisms

a polymorphism that occurs when a segment of genome (such as an entire gene) is doubled during the crossing-over process in meiosis

exon

sequence found in pre-mRNA that codes for the peptide

genetic code

set of rules that define how information in the DNA or RNA is used to create chains of amino acids (proteins)

genome

the total genetic material contained within the chromosomes of an organism; in humans, it is made up of 26 chromosomes, and almost all cells contain an entire copy of it

genome-wide association study (GWAS)

a survey of several genetic variants in different individuals to study if there is an association with traits such as disease susceptibility or how individuals respond to certain drugs

genotype

genetic constitution of an organism used to refer to the set of two alleles inherited for a particular gene or locus; an individual’s genetic makeup or sum total of genes

haplotype

a set of alleles or polymorphisms of a chromosome often inherited together

heterozygote

an individual who has two different alleles at a given locus on a pair of homologous chromosomes

histones

proteins that organize DNA into units termed nucleosomes

homozygote

an individual possessing a pair of identical alleles at a given locus on a pair of homologous chromosomes

insertion/deletion polymorphisms

polymorphisms that result from addition or deletion of nucleotide(s) or base pair(s) from the DNA sequence of a gene

intron

sequence found in pre-mRNA that is a noncoding region

linkage disequilibrium

non-random association of alleles at different sites

messenger ribonucleic acid (mRNA)

large family of RNA molecules that convey genetic information from DNA to the ribosome

nonhomologous

not pertaining to a pair of chromosomes

nonsynonymous SNP

single nucleotide changed in the coding regions of DNA resulting in a codon that codes for a different amino acid

nucleotide

a compound consisting of a nucleoside linked to a phosphate group; form the basic structural unit of nucleic acids such as DNA

phenotype

physical manifestation of a genetic trait or a general constitutional manifestation of health or disease in an individual

ribonucleic acid (RNA)

a nucleic acid present in all living cells

short tandem repeat (STR) polymorphism

short sequence of DNA (2-5 base pairs), which are repeated multiple times in a sequence; also called “microsatellites”

single nucleotide polymorphism (SNP)

a DNA sequence variation occurring when a single nucleotide in the genome differs between paired chromosomes in an individual

synonymous SNP

single nucleotide changes in the coding regions of DNA that does not result in a change in the protein sequence

wild type

phenotype or gene of the typical form found in natural conditions; “normal”

RNA polymerase (RNAP)

enzyme responsible for copying a DNA sequence into an RNA sequence during transcription

pharmacogenomics

study of how genetic variations influence an individual’s response to drugs

phenome

refers to all phenotypes expressed by an organism

genetic association

when one or more genotypes are associated with a genetic trait beyond what would be expected by chance

genetic association studies

conducted to identify relationships between patterns of polymorphisms and traits

pharmacogenomic association studies

compare frequencies of genotypes and alleles for a drug response phenotype

crossover/recombination

when homologous chromosomes that are paired together exchange genetic materials; more likely with alleles close to each other on a chromosome

hotspot

short genomic region where recombination events are more likely to occur