SCT III Flashcards
Comparative genomics
The field of science that studies the similarities between the genome structure and function of different species.
Pseudogene
Shows a high degree of sequence homology to a non-allelic functional gene, but which is itself nonfunctional.
i.e. a section of DNA that is similar to a functional gene, but it does not produce a functional protein.
Hominins
Extinct species that are more closely related to humans than other great apes.
Ideogram
A schematic representation of chromosomes; a standardized, species-specific set of chromosomes with G-banding used to show the relative size of the chromosomes and their characteristic banding patterns.
Karyotype
Is an individual’s collection of chromosomes.
It describes the number, appearance, and physical characteristics of chromosomes in the nucleus of a cell in an individual organism.
A verbal description with symbols and abbreviations.
Karoygram
A micro-photograph of all chromosomes of a single cell represented in a standard format.
Chromosomes are sorted and re-arranged in pairs by their size and position of their centromeres.
I.e. it is a photograph of the whole set of all 22 identical chromosome pairs plus the 2 gender specific chromosomes (XX/XY)
Chimera
An organism derived from more than one zygote.
Trisomy rescue
In a nonviable trisomic embryo, chance of loss of one of the trisomic chromsomes by anaphase lag, producing a disomic cell that can eventually form a viable embryo.
A cause of uniparental disomy (UPD). UPD may case:
- Rare Mandelian diseases
- Angelman syndrome
- Prader-Willi syndrome
Allelic heterogeneity
Existence of many different mutations but all within the same gene in unrelated people with the same phenotype
Anticipation
Tendency for the severity of a condition to increase in successive generations
Commonly due to bias of ascertainment but seen for real with dynamic mutations
Coding RNA
Messenger RNA that codes for a protein
Common variant
Conventionally, a variant whose frequency is >0.05.
Conserved sequence
A sequence (of DNA or sometimes protein) that is identical or recognizably similar across a range of organisms
Dominant negative effect
Situation where a mutant protein interferes with the function of its normal counterpart in a heterozygous person
Dynamic mutation
An unstable expanded repeat that changes size between parent and child
Exome
Totality of exons in a genome
Exon junction complex
A set of proteins that are bound to mRNAs during splicing, at the positions where introns have been removed
Founder effect
High frequency of a particular allele in a population because the population is derived from a small number of founders, one or more of whom carried that allele
Frame-shift mutation
A mutation that alters the triplet reading frame of a mRNA (by inserting or deleting a number of nucleotides that is not a multiple of 3)
Gain-of-function mutations
Mutations that cause the gene product to do something abnormal, rather than simply to lose function.
Usually the gain is a change in the timing or level of expression
Genotype-phenotype correlation
Extent to which a phenotype can be predicted from a genotype.
Typically poor in humans, better in experimental animals which are inbred and live under standard lab conditions
Haploinsufficiency
A locus shows haploinsufficiency if producing a normal phenotype requires more gene product than the amount produced by a single functional allele
Heteroplasmy
Mosaicism, usually within a single cell, for mitochondrial DNA variants
Homoplasmy
Of a cell or organism, having all copies of the mitochondria DNA identical
Loss-of-function mutations
Mutations that cause the gene product to lose its function, partially or totally
MicroRNAs (miRNAs)
Short (21-22 nt) RNA molecules encoded within normal genomes that have a role in regulation of gene expression and maybe also of chromatin structure
Missense changes
Changes in a coding sequence that cause one amino acid in the gene product to be replaced by a different one.
mtDNA
Mitochondrial DNA — DNA of the 16,569 nt mitochondrial genome
Mutation
- Process of DNA sequence change
- Resultant changed sequence
Noncoding RNA (ncRNA)
RNA that does not contain genetic code for a protein.
ncRNA have many different functions in cells.
Nonsense mutation
A mutation that replaces the codon for an amino acid with a termination codon
Nonsense-mediated mRNA decay
A cellular mechanism that degrades mRNA molecules that contain a premature termination codon (>50 nt upstream of the last splice junction)
Pathogenic
Causing disease
Penetrance
Frequency with which a genotype manifests itself in a given phenotype
Rare variant
A variant whose frequency is <0.01
Homologous recombination
- Normal recombination that is part of meiosis
- A mechanism for repairing DNA damage
Lord score (z)
In linkage analysis, the log of the odds that the loci are linked rather than unlinked.
For Mandelian characters a lod score greater than +3 is evidence of linkage; one that is less than -2 is evidence against linkage
CentiMorgan (cM)
Unit of genetic distance. Loci 1cM apart have a 1% probability of recombination during meiosis
Haplotype
A series of alleles found at linked loci on a single chromosome
Haplotype blocks
Blocks of variants that are in linkage disequilibrium with each other, but not with variants in-adjacent blocks.
Cataloged by the International HapMap project. The consequence of shared remote ancestry.
Relative risk in epidemiology
Relative risk of developing a condition in people with and without a susceptibility factor
Sib
A brother or sister
First-degree relatives
Parents, children, or sibs
Driver mutation
In cancer, mutations that are subject to positive selection during tumorigenesis because they assist development of the tumor
Loss of heterozygosity (LOH)
Homozygosity or hemizygosity in a tumor or other somatic cell when the constitutional genotype is heterozygous.
Evidence of a somatic genetic change.
Gene therapy
Treating a disease by genetic modification.
May involve adding a functional copy of a gene that has lost its function, inhibiting a gene showing a pathological gain of function, or more generally, replacing a defective gene.
