Study Unit 2 Flashcards
constitutional variation
between individuals
inherited
post-zygotic/somatic variation
within individuals
DNA changes that occur to all cells throughout life
natural selection
process whereby some allele or combination of alleles determines the phenotype that may confer an increased or decreased chance of survival and reproductive success
results in an increased frequency of favorable alleles or a reduced frequency of disadvantageous alleles
occurs when pathogens are under independent genetic control as they originate from another organism
natural selection in humans
maximizes genetic variation in the frontline immune system genes that help recognize antigens of pathogens
natural selection in pathogens
maximizes genetic diversity of external molecules in microbial pathogens in an effort to escape immune system detection
mutation
process that produces altered DNA sequences by changing the base sequence or the number of copies in a specific DNA sequence
originates as a result of DNA that is not corrected by DNA repair systems
induced by radiation, chemicals in the environment but mainly from endogenous sources
crosslinking
formation of a covalent bond between two bases on the same or complementary strand
hydrolysis
cleaves a bases from a sugar creating an abasic site
depurination
loss of a purine base
deamination
loss of amino acids resulting in a carbonyl group being left
ionizing radiation
X-rays and gamma rays interact with cellular molecules to generate ROS that break chemical bonds in the sugar-phosphate backbone, in turn breaking DNA strands
non-ionizing radiation
UV radiation causes covalent bonding between adjacent pyrimidines on a DNA strand
human genetic variation
occurs by changes to base sequence
DNA variants
alternative forms of DNA resulting from mutations
polymorphisms
if more than 1 variant is common in the population
frequency > 0.01
rare variant
frequency < 0.01
restriction fragment length polymorphism (RFLP)
difference in homologous DNA sequences that can be detected by the presence of fragments of different lengths after DNA digestion by restriction endonucleases
array
continuous sequence of multiple tandem repeats
satellite DNA
from 20 to hundreds of of kb
located in centromeres and some heterochromatic regions
minisatellite DNA
100bp to 20kb
located in telomeres and sub-telomeric regions
synonymous/silent substitution
coding sequence substitution that does not change the amino acid
nonsynonymous substitution
missense mutations cause one amino acid to be replaced by another
conservative substitution
one amino acid is replaced by another of the same chemical class
minimal consequences for protein function
non-conservative substitution
replacing one amino acid with another from a different class
significant consequences for protein function - loss of normal function, incorrect function, missense mutations
LOF hypomorph
significantly reduced ability to work normally
LOF neomorph
acquires new altered function
cells die or behave inappropriately
nonsense mutations
directly replaces an amino acid with a stop codon
UAA, UAG, UGA, AGA, AGG
frameshift mutation
indirectly changes amino acids to premature stop codons
coding sequences not divisible by 3 are deleted or inserted
net result of nonsense and frameshift mutations
non-sense mediated decay (NMD)
non-sense mediated decay (NMD)
mRNA is degraded and translated to form a truncated protein
can have a dominant negative effect
dominant negative effect
mutated gene interferes with the wild-type proteins and affects their function
latent/cryptic splice site
sequences that are almost identical to a genuine splice donor or acceptor site
activated by mutations elsewhere in the body and can become novel splice sites with a single nucleotide change and produce truncated or extended proteins
