D1.3 Mutation & Gene Editing

Question 1

Why are knockout organisms useful to scientists studying the function of specific genes?

Answer 1

To study how a specific gene may cuase/contribute to human disease

Question 2

causes of mutation within a species

Answer 2

Meiosis, mutation and random fertilisation

Question 3

What happens during huntingtons disease

Answer 3

• trinucleotide repeat expansion
• many copies of CAG are added to HTT gene
• in chormosome 4

Question 5

Sickle Cell Anemia

Answer 5

• blood cells are in sickle shape instead of biconcave disk
• causes heart stroke/attack, bone malformation, pneumonia
• due to single base substitution of A to T
• 6th triplet changes from GAG (GLU) to GTG (VAL)
• prim & second structure of Beta subunit is altered
• quaternary structure of haemoglobin changes
• fibres are deformed

1. long fibres poke into cell membrane = distorts shape
2. ability to carry oxygen decreases
3. block blood vessels
4. puts strain on liver as it removes cells
5. bone marrow has to continuously produce more

Question 6

mutation

Answer 6

change in the genetic composition of a cell

Question 7

single nucleotide polymorphism

Answer 7

Replacement of a single nucleotide with another, producing variation within a species.
* synonymous
* non synonymous

Question 7

Synonymous mutation

Answer 7

change in the DNA sequence resulting in the production of the same amino acid

silent mutation

Question 7

non synonymous

Answer 7

change in the DNA sequence resulting in the production of a different amino acid

Question 8

Frameshift mutation

Answer 8

Mutations altering the reading frame of a DNA sequeneces triplets

• insertion
• deletion

Question 9

Types of base substituation methods

Answer 9

• nonsense= stop codon
• missense= wrong AA
• same sense= same AA

Question 10

Causes of mutations

Answer 10

• errors in DNA replication
• mutagens

Question 10

Mutagen

Answer 10

Chemical/physical agents which have the ability to alter genetic sequences

Question 11

Mutagen examples

Answer 11

chemical
* mustard gas
* nitrous acid
* ethyl urethane
* formaldehyde

physical
* UV
* X Ray

Question 12

Randomness of Mutation

Answer 12

• cytosine is most likely= spontaneous: deamination)
  0> loses amine group = turns to uracil

Question 13

Somatic cells

Answer 13

all body cells except germ cells

Question 14

Effects of mutations to proteins

Answer 14

• same P produced
• different but functioning P produced
• non functioning P produced
• no protein produced
• improvement

=> genetic variation

Question 15

Pros & Cons of gene mutation

Answer 15

Pros
* better survival rate
* better adaption
ex: sickle cell = malaria resistance

Cons
* out of control cell multiplication
* mutation opf gamete = death of foetus
ex: Cystic Fibrosis, Haemophilia, Red-green color blindness, huntingtons disease

Question 15

Effects of mutations to cells

Answer 15

Somatic = disease (not passed to offspring)

germ= inhertited mutations

Question 16

Gene Mutation Diseases

Answer 16

Cystic Fibrosis, Haemophilia, Red green color blindness, Huntingtons disease

Question 17

gene knockout

Answer 17

technique in which a specific gene is intentionally removed or changed so that the expression of it is permanently prevented

Question 18

Knockout orgnaism example

Answer 18

Obese knockout mice
* leptin= hormone involved in regulating energy intake vs expernditure
* removed coding segment for leptin
=> Mice rapidly gained weight

Question 19

P53 - Knockout gene

Answer 19

• when P53 is inactive = higher prevelance of cancerous growth
• inhibts tumor development

Question 20

CRISPR- Cas9

Answer 20

Clustered Regularly Interspaced Palindromic Repeats
Cas9= endonuclease enzyme which cuts specific target sites

Question 21

CRISPR Mechanism

Answer 21

1. foreign DNA that matched CRISPR spacer = corresponding crRNA molecule identifies & binds to iral sequence
2. guides Cas9 to target DNA
3. Cas9 makes precise cuts
4. double strand break = can be repaired by cells DNA machienery

Question 22

Use of CRISPR in gene editing

Answer 22

• RNA targets & binds to particular DNA sequnece
• adapted in genetic engeneering
• scientists can add, delete or modify DNA at that point

Question 22

Ethical Implication of CRISPR

Answer 22

• gene therapy = treating by correction
• agriculture= enhance traits
• disease modelling= insight & forecast
• genetic engeneering= pharma & enhance production

Question 23

conserved dna

Answer 23

sequneces that remian indentical accross a species or group of species
=> very little genetic mutation

Question 24

conservation hypothesis

Answer 24

1. Functional constraints; selective pressures that prevent the accumulation of mutations that disrupt the function of a gene or its products
   => unhelpful mutations wont persist
2. Slower rates of mutation ; natural selection pushes mutation rates down to a lower limit set by the power of random genetic drift rather than by intrinsic physiological limitations.
   => reduced levels of replication, transcription, translation.