Genetics

Question 1

APOE = late onset Alzheimer’s

Answer 1

Chromosome 19

APOE 2 = protective
3 = neutral
4 = increased risk

Question 2

Early Onset AD

Answer 2

APP = chromosome 21. 10-15%
PSEN-1 = chromosome 14 30-70%
PSEN-2 = chromosme 1, 5%

Question 3

CYP450 enzyme encoded by CYP2D6

Answer 3

Encodes debrisquine hydroxylase

Polymorphic, inactive 6% white people.

These people are then more prone to side effects from medication requiring CYP2D6 metabolism and are poor metabolism.

Many antidepressants are metabolised by CYP2D6

Question 4

Missense mutation

Answer 4

A new nucleotide alters the codon producing an altered amino acid in the protein

Question 5

Nonsense mutation

Answer 5

New nucleotide creates a STOP codon (TAA, TAG or TGA).

Question 6

Point mutation

Answer 6

Simple change in one base of the gene sequence

Question 7

Frame-shift mutation

Answer 7

An insertion or deletion of several nucleotides that shifts the sequence resulting in a different translation than the original

Question 8

Silent mutation

Answer 8

Codes for the same amino acid

Question 9

Copy Number Variants

Answer 9

Portions of DNA that vary in number

Associated with autism, schizophrenia and LD

Question 10

Schizophrenia candidate genes

Answer 10

DTNBP1 = Dysbindin = chromosome 6 (p 22.3)
COMT = chromosome 22
DISC-1 chromosome 1
NRG1= Neuregulin-1 = chromosome 8 (p21-22)

Question 11

COMT

Catechol-O-Methyltransferase

Answer 11

Role in dopamine metabolism in the prefrontal cortex. Degradation of catecholamines, especially clearing dopamine for synapse.

Low COMT = schizophrenia and OCD

Strongest candidate gene

Question 12

Neuregulin (chr 8)

Answer 12

Growth factor stimulating neuronal development and differentiation.

Increased signalling in schizophrenia, suppress NMDA receptor and lower glutamate .

Question 13

Dysbindin

DTNBP1 6

Answer 13

Distributed in muscle and brain tissue; production of lysosome organelles.

Decreased in schizophrenia

Question 14

DISC1

Answer 14

Disrupted in schizophrenia; encodes multifunctional protein influencing neuronal development and adult brain function

Question 15

MAPT

Answer 15

Tau, chromosome 17

Tau is involved in making and stabilising microtubules which help to maintain cell shape, are needed in cell division and to transport materials

Question 16

APP

Answer 16

Amyloid precursor protein

Chromosome 21; y-secretase breaks down APP to soluble amyloid precursor protein and amyloid beta protein

Question 17

Recombination fraction

Answer 17

Measure of distance between loci on a chromosome.

0% = very close
50% = different chromosomes

Closer two loci are on a chromosome, less likely they will be separated by crossing over

Question 18

Transmission

Answer 18

Vertical = autosomal dominant
Horizontal = autosomal recessive
Kinght’s move = X-linked

Question 19

Autosomal Dominant

Answer 19

Huntington’s Disease, neurofibromatosis type 1 and 2, tuberous sclerosis, achondroplasia, Noonan’s

Question 20

Autosomal Recessive

Answer 20

Cystic fibrosis, homocytinuria, Wilson’s, PKU, Hurler’s, Tay-sachs

Question 21

Mitochondiral

Answer 21

Levers hereditary optic neuropathy, kearns-sayre syndrome

Question 22

X-linked dominant

Answer 22

Rett syndrome, vitamin d resistant ricketts

Question 23

X-linked recessive

Answer 23

Lesch-nyhan, hunter’s , cerebellar ataxia

Question 24

RNA

Answer 24

Single stranded
Ribose, phosphate and nitrogenous base
Shorter than DNA
Uracil

Question 25

Transcription

Answer 25

Gene from DNA

RNA polymerase binds to the promoter region and prises dsDNA apart.

Template = antisense strand

Elongation = mrna synthesise from 3’-5’

RNA polymerase zips DNA as it works

At end of process, RNA detaches. Now have mRNA.

mRNA leaves nucleus and finds a ribosome in the cytoplasm.

Question 26

Translation

Answer 26

Occurs in the Ribosome

mRNA = code for a specific protein

64 codons from reading frame
AAG, UUC

Each codon has an anti-codon, tRNA and each tRNA is attached to a specific amino acid.

AUG START Codon (Methionine)
UAA, UAG, UGA Stop Codon

Initiator tRNA + mRNA and small ribosome subunit. Large subunit then joins.

When next tRNA joins, 2 amino acid joins and then 1st tRNA leaves

Question 27

Halpotype

Answer 27

Blocks of alleles transmitted as a block through pedigree