neurogentics

Question 1

mitosis

Answer 1

somatic cells

• every time the cell divides the daughter cells are identical to the parental cells

Question 2

meiosis

Answer 2

• gamete cells
• crossing over/recombination
• diploid
• haploid

Question 3

mendels law

Answer 3

a dominant gene is expressed over a receesive gene

need tow copies of a recessive gene for it o be expressed

Question 4

Huntingdon’s chorea

Answer 4

example of dominant inheritance

degeneration of the brain leading to deterioration of movement, tempermant and cognition

if you have the mutated gene you are CERTAIN to get the disease

late-onset

excessive repeat of CAG - too many copies causes mutation of the gene to be dominant

Question 5

autosomal dominant inheritance

Answer 5

single copy will be dominant and lead to the development of the disease

Question 6

phenylketonuria

Answer 6

recessive inheritance

both parents have mutation of the gene:
25% of offspring will have the disease

50% will be carriers

build up of enzyme in the brain that is toxic during development

learning disabilities
behavioural difficulties
epilepsy

can ONLY happen if they have the protein that the enzyme breaks down in their diet

SO if remove it from diet they will have the disease but no symptoms

screened at birth bc damage is so easily prevented

Question 7

chromosomal abnormalities example

Answer 7

downs syndrome

trisomy in chromosome 21
error in first meiotic division -

most common bc the error is mild enough for them to survive and grow up

smaller brain size in frontal lobes and cerebellum

mild-moderate intellectual ability

high risk of early onset Alzheimer’s

Question 8

monosomy

Answer 8

single copy of a chromosome

embryonic lethal

Question 9

trisomy

Answer 9

three copies of a chromosome

high rate of embryonic lethality

Question 10

x-linked conditions: the x chromosome

Answer 10

males = XY
female = XX

Y chromosome - very few genes - mostly relating to male sexual function

X chromosome - many genes with vital roles for both sexes

X inactivation in females switches off one copy of X chromosome during embryogenesis - because we only want one

for this reason X-linked disorders look different in males and females

Question 11

X-inactivation in females

Answer 11

each cell switches off one of their X chromosomes

due to random variation - 50% of them switch of their paternal X and 50% switch off their maternal X

they have a mosaic of ‘clones’

within a clone = the same X is inactivated

between clones = different X’s

men only have the MATERNAL X

Question 12

Rett Syndrome - X linked

Answer 12

• almost exclusively affects females
• profound disabilities
• begin developing normally THEN symptoms:
• similar to autism
• more profound with age
• 1 in 10,000

transcriptional repressor turns off the expression of unwanted genes during synapse formation –> this is mutated

• only half of the chromosomes in the brain will be effected bc of x-inactivation
• this is why some cases are mild and some are severe - comes down to which parts of the brain are switched on to the mutated x-chromsomes

Question 13

Fragile X - X-linked

Answer 13

• more prevalent in men
• 1 in 4000 males
• 1 in 6000 females

amplification of a base triplet

• learning disabilities
• males bc EVERY chromosome will be affected –> all maternal X

milder in females due to x-activation so not always recognised

Question 14

epigenetics

Answer 14

the study of how your behaviours and environment can cause changes that affect the way your genes work

change in phenotype that is not due to the gentoype

Question 15

gene methylation

Answer 15

methyl group - found in some dietary sources can tag DNA

activates or represses genes

Question 16

Histone modification

Answer 16

histones = proteins that DNA can wrap around for compaction and gene regulation

epigenetic factors e.g. chemicals can bind to the histone tails -
this alter the extent to which DNA is wrapped around the histones

AND

the availability of genes in the DNA to be activated

Question 17

epigenetics and environment

Answer 17

some gene expression is effected by the environment

e.g. depending on how a mother treats their offspring can affect which genes are turned on or off

which determines what the cells are and what they do

Question 18

rats and maternal care - epigenetics

Answer 18

• pup licking/maternal care = switches on serotonin
• serotonin activates a receptor and in an internal cascade: activates transcription factor - which switches on gene
• the gene expresses a certain protein which is important for regulating stress

absence of licking:
- promoter = methylated
- low levels of GR

• methylation is retained throughout life time —> cannot regulate = increased stress, anxiety and depression

Question 19

GR

Answer 19

glucocorticoid receptor

Question 20

transgenerational epigenetics

Answer 20

• environmental influences on parents can affect offspring
• e.g. smoking causes histone modification in sperm cells
• this modification was prevalent in the grand-offspring of originally exposed