Study Unit 2

Question 1

constitutional variation

Answer 1

between individuals

inherited

Question 2

post-zygotic/somatic variation

Answer 2

within individuals

DNA changes that occur to all cells throughout life

Question 3

natural selection

Answer 3

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

Question 4

natural selection in humans

Answer 4

maximizes genetic variation in the frontline immune system genes that help recognize antigens of pathogens

Question 5

natural selection in pathogens

Answer 5

maximizes genetic diversity of external molecules in microbial pathogens in an effort to escape immune system detection

Question 6

mutation

Answer 6

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

Question 7

crosslinking

Answer 7

formation of a covalent bond between two bases on the same or complementary strand

Question 8

hydrolysis

Answer 8

cleaves a bases from a sugar creating an abasic site

Question 9

depurination

Answer 9

loss of a purine base

Question 10

deamination

Answer 10

loss of amino acids resulting in a carbonyl group being left

Question 11

ionizing radiation

Answer 11

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

Question 12

non-ionizing radiation

Answer 12

UV radiation causes covalent bonding between adjacent pyrimidines on a DNA strand

Question 13

human genetic variation

Answer 13

occurs by changes to base sequence

Question 14

DNA variants

Answer 14

alternative forms of DNA resulting from mutations

Question 15

polymorphisms

Answer 15

if more than 1 variant is common in the population

frequency > 0.01

Question 16

rare variant

Answer 16

frequency < 0.01

Question 17

restriction fragment length polymorphism (RFLP)

Answer 17

difference in homologous DNA sequences that can be detected by the presence of fragments of different lengths after DNA digestion by restriction endonucleases

Question 18

array

Answer 18

continuous sequence of multiple tandem repeats

Question 19

satellite DNA

Answer 19

from 20 to hundreds of of kb

located in centromeres and some heterochromatic regions

Question 20

minisatellite DNA

Answer 20

100bp to 20kb

located in telomeres and sub-telomeric regions

Question 21

synonymous/silent substitution

Answer 21

coding sequence substitution that does not change the amino acid

Question 22

nonsynonymous substitution

Answer 22

missense mutations cause one amino acid to be replaced by another

Question 23

conservative substitution

Answer 23

one amino acid is replaced by another of the same chemical class

minimal consequences for protein function

Question 24

non-conservative substitution

Answer 24

replacing one amino acid with another from a different class

significant consequences for protein function - loss of normal function, incorrect function, missense mutations

Question 25

LOF hypomorph

Answer 25

significantly reduced ability to work normally

Question 26

LOF neomorph

Answer 26

acquires new altered function

cells die or behave inappropriately

Question 27

nonsense mutations

Answer 27

directly replaces an amino acid with a stop codon

UAA, UAG, UGA, AGA, AGG

Question 28

frameshift mutation

Answer 28

indirectly changes amino acids to premature stop codons

coding sequences not divisible by 3 are deleted or inserted

Question 29

net result of nonsense and frameshift mutations

Answer 29

non-sense mediated decay (NMD)

Question 30

non-sense mediated decay (NMD)

Answer 30

mRNA is degraded and translated to form a truncated protein

can have a dominant negative effect

Question 31

dominant negative effect

Answer 31

mutated gene interferes with the wild-type proteins and affects their function

Question 32

latent/cryptic splice site

Answer 32

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