Case 2 - Down's Syndrome

Question 1

how are the DNA strands arranged in interphase

Answer 1

loosely coiled and cannot be seen

Question 2

what happens in interphase generally

Answer 2

some cells prepare for division

perform normal functions

Question 3

what happens in g0

Answer 3

not preparing for division
stem cells never enter it
neurones and skeletal muscles always here bc never divide

Question 4

what happens in g1

Answer 4

8 hours
cell doubles mitochondria and organelles
first stage
centriole replication begins

Question 5

what happens in s phase

Answer 5

6-8 hours

dna replication and histone synthesis

Question 6

what happens in g2 phase

Answer 6

protein synthesis

centriole replication is completed

Question 7

stages of mitosis

Answer 7

read !!!!!

Question 8

meiosis stages

Answer 8

read !!!!!

Question 9

differences in mitosis and meiosis

Answer 9

2 vs 4 DC
diploid v haploid DC
1 v 2 step process
somatic v gametic

Question 10

what are mutations and how are they caused

Answer 10

change in number or sequence of nucleotide bases in an aa
exposure to mutagenic agents or can be inherited
spontaneously through errors in DNA replication

Question 11

what is a single base substitution

Answer 11

replacement of a single nucleotide

transition: with same nucleotide
transversion: with different nucleotide

Question 12

what is a missense mutation

Answer 12

when nucleotide changes and forms codon that codes for a diff aa

Question 13

what is a nonsense mutation

Answer 13

forms a stop codon

Question 14

what is a silent mutation

Answer 14

forms codon that codes for same amino acid

Question 15

what are insertion and deletion mutations

Answer 15

loss or addition of a nucleotide

frameshift mutation

Question 16

what is a truncating mutation and how is it caused

Answer 16

no protein or wrong sized protein is formed

by nonsense, insertion or splicing mutation

Question 17

what is a non-truncating mutation and how is it caused

Answer 17

missense and silent mutations

expansion of trinucleotide repeats

Question 18

what is a modest expansion and what does it cause

Answer 18

repeats of one tri-nucleotide e.g. CAG in huntingtons

Question 19

what is a large expansion and what does it cause

Answer 19

repeats of varieties of tri-nucleotides on promotor regions or non coding regions
causes: inhibition of gene expression

Question 20

what is promoter methylation

Answer 20

switching on/off of gene transcription by adding ch2 or removing from cytosine

Question 21

what is hypermethylation

Answer 21

inapt switching off of genes

Question 22

what is hypomethylation

Answer 22

inapp switching on of genes

Question 23

what is a recessive loss of function mutation

Answer 23

when disease arises bc all of normal protein is lost and 2 genes are knocked out
MOST COMMON LOF

Question 24

what is a dominant loss of function mutation

Answer 24

when 1 gene is knocked out and disease arises: 50% of functional protein left

Question 25

what is a dominant negative mutation

Answer 25

???

Question 26

how is a loss of function mutation caused

Answer 26

failure of synthesis or synthesis of non-functional protein

Question 27

is a gain of function usually dominant or recessive

Answer 27

dominant

Question 28

what causes a gain of function mutation

Answer 28

abnormal or novel function of protein or inapp synthesis

Question 29

what is a synonymous effect

Answer 29

polypeptide product not altered

due to silent mutation

Question 30

what is a non-synonymous

Answer 30

pp product altered
missense, frameshift or non-sense
selective advantage or fatal phenotype