Chapter 3 Flashcards
Variation
In alleles of genes, it occurs both within and among populations. Genetic variation is important because it provides the genetic material for natural selection.
Mutation
A change in the nucleotide sequence of the genome of an organism, virus, or extrachromosomal genetic element. Mutations result from unprepared damage to DNA or to RNA genomes (typically caused by radiation or chemical mutagens), errors in the process of replication, or from the insertion or deflection of segments of DNA by mobile genetic elements.
Single Nucleotide Polymorphism (SNP)
A DNA sequence variation occurring when a single nucleotide in the genome differs between members of a biological species or paired chromosomes.
Transversion
The substitution of a purine for a pyrimidine, or vice versa.
DNA polymerase
A cellular or viral enzyme that synthesizes DNA molecules from their nucleotide building blocks, distinguishing from RNA polymerase or other polymerase.
INDELs
The insertion or deletion of bases in the DNA of an organism.
Hydrolysis
The cleavage of chemical bonds by the addition of water.
Heteroduplex
A double-stranded (duplex) molecule of nucleic acid originated through the genetic recombination of single complementary strands derived from different sources, such as from different homologous chromosomes, or even from different organisms.
Lesion
Any abnormality in the tissue of an organism, usually caused by disease or trauma.
CpG (sites)
Regions of DNA where a cytosine nucleotide occurs next to a guanine nucleotide in the linear sequence of bases along its length. “CpG” is shorthand for “—C—phosphate—G—”, that is, cytosine and guanine separated by only one phosphate.
Dinucleotide
A nucleotide consisting of two units each composed of a phosphate, a pentose, and a purine or pyrimidine base.
Methylation
The addition of a methyl group to a substrate or the substitution of an atom or group by a methyl group. It is a form of alkylation with a methyl group, rather than a larger carbon chain, replacing a hydrogen atom. In biological systems, methylation is catalyzed by enzymes; such methylation can be involved in modification of heavy metals, regulation of gene expression, regulation of protein function, and RNA processing.
Open Reading Frame (ORF)
The part of a reading frame that contains no stop codons. The transcription termination pause site is located after the ORF, beyond the translation stop codon, because if transcription were to cease before the stop codon, an incomplete protein would be made during translation.
Promoter
A region of DNA that initiates transcription of a particular gene. Tey are located near the transcription start sites of genes, on the same strand and upstream on the DNA.
Enhancer
A short (50-1500 bp) region of DNA that can be bound with proteins to activate transcription of a gene or genes.
Polydenylation
The addition of a poly(A) tail to a primary transcript RNA. The poly(A) tail consists of multiple adenosine monophosphates; in other words, it is a stretch of RNA that has only adenine bases. In eukaryotes, it is part of the process that produces mature messenger RNA for translation, making it important for gene expression.
MicroRNA (miRNA)
A small, non-coding RNA molecule found in plants, animals, and some viruses, which functions in transcriptional and post-transcriptional regulate of gene expression.
Gene Conversion
The process by which one DNA sequence replaces a homologous sequence such at the sequences become identical after the conversion event.
Gene Duplication
A major mechanism through which new genetic material is generated during molecular evolution. It can be defined as any duplication of a region of DNA that contains a gene. They can arise as products of several types of errors in DNA replication and repair machinery as well as through fortuitous capture by selfish genetic elements.
Variable Number Tandem Repeat (VNTR)
A location in a genome where a short nucleotide sequence is organized as a tandem repeat. These can be found on many chromosomes, and often show variations in length between individuals. Each variant acts as an inherited allele, allowing them to be used for personal or parental identification.
