D1.3 Mutations and Gene Editing

Question 1

mutations

Answer 1

random, rare change in DNA, some have no effects

Question 2

types of mutations

Answer 2

substitutions, deletions, insertions, point mutation (1 nucleotide modified)

Question 3

locus

Answer 3

fixed position of a gene on a chromosome

Question 4

achromatopsia

Answer 4

mutation of GNAT2 gene on chromosome 1, which controls production of protein transducin, which enables colour vision

Question 5

genome

Answer 5

all DNA in the nucleus and mitochondria of an animal cell

Question 6

phenotype

Answer 6

observable qualities based on genotype and environment

Question 7

polymorphism

Answer 7

occurrence of two different phenotypes

Question 8

genotype

Answer 8

combination of alleles inherited, codes for phenotype

Question 9

single-nucleotide polymorphism

Answer 9

substitution point mutation, results in alleles and explains some diseases

Question 10

missense mutation

Answer 10

substitution mutation that results in 1 different amino acid coded for

Question 11

nonsense mutation

Answer 11

substitution mutation that results in stop codons

Question 12

what causes sickle cell disease and what are its effects?

Answer 12

substitution mutation of gene for haemoglobin results in valine amino acid to be produced instead of glutamic acid, causes red blood cells be shaped like sickles and weakness, fatigue, shortness of breath, and malaria resistance

Question 13

what causes huntington’s and what are its effects?

Answer 13

insertion mutation when trinucleotide repeat expansion of CAG results in HTT gene on chromosome 4 becoming mHTT gene, causing more glutamine production and trouble walking, speaking, and holding

Question 14

only under what conditions does huntington’s show?

Answer 14

after 40 years old and when there are over 40 repeats of CAG

Question 15

trinucleotide repeat expansion

Answer 15

when a set of 3 nucleotides repeats, expanding the polysaccharide region

Question 16

frameshift mutation

Answer 16

when insertions/deletions occur in non-multiples of 3, altering entire sequence

Question 17

chemokine

Answer 17

chemicals that tell leucocytes where an infection is, picked up by leucocyte receptors

Question 18

what forms leucocyte receptors?

Answer 18

co-receptor molecule C-C chemokine receptor type 5

Question 19

how does HIV-1 infect an individual?

Answer 19

enters CD4 leucocytes through receptors, so those with working CCR5 genes on chromosome 3 are at risk; if it destroys the leucocytes, it becomes AIDS

Question 20

what mutation makes an individual resistant to HIV-1?

Answer 20

delta 32 mutation (CCR5-∆32) deletes 32 nucleotides, creating a stop codon for the gene CCR5, preventing formation of receptor

Question 21

what are mutagens and some examples?

Answer 21

chemicals that cause mutations (eg enzymes that transform bases, benzene that causes leukaemia)

Question 22

what can cause mutations?

Answer 22

mutagens and radiation

Question 23

what percentage of DNA is actually coding?

Answer 23

1-2%

Question 24

example of non-coding DNA

Answer 24

satellite DNA found in centromere, structural purposes; much more likely to be mutated than coding DNA (1 every 1000 base pairs vs 1 every 500 mil)

Question 25

example of mutation hotspot

Answer 25

CpG sites, where cytosine followed by guanine; if C replaced by T during methylation, cancer occurs

Question 26

germ cell

Answer 26

uses meiosis to produce gametes; mutations passed down

Question 27

somatic cell

Answer 27

uses mitosis to grow tissues and organs; mutations not passed down

Question 28

germ line

Answer 28

group of all cells involved in reproduction

Question 29

gene knockout

Answer 29

functional gene rendered unusable to observe effects on knockout organism

Question 30

how does CRISPR-Cas9 work?

Answer 30

1. guide RNA that matches DNA is synthesized, Cas9 enzyme injected into cells
2. gRNA binds to DNA, protospacer adjacent motif binds Cas9 to DNA
3. Cas9 cuts of mutation and it’s replaced, discarded, corrected, or rendered inactive by errors

Question 31

what is CRISPR-Cas9 good for?

Answer 31

genetic engineering, curing diseases, increasing crop yield, fuel production, gene therapy/drive

Question 32

gene drive

Answer 32

modifying genes to increase chance of gene being passed on so lab genes spread quickly; capable of stopping malaria, dengue fever, west nile virus in mosquitoes

Question 33

(highly) conserved sequences

Answer 33

show minimal/no changes, required for replication, transcription, translation, respiration

Question 34

purifying/negative selection

Answer 34

eliminating harmful gene variations by natural selection

Question 35

what factors influence mutation rates?

Answer 35

requirement for gene (functional constraint hypothesis), slower rates of mutation hypothesis (eg non-coding zones have higher rate due to lack of proofreading)