Case 2 - Down's Syndrome Flashcards
how are the DNA strands arranged in interphase
loosely coiled and cannot be seen
what happens in interphase generally
some cells prepare for division
perform normal functions
what happens in g0
not preparing for division
stem cells never enter it
neurones and skeletal muscles always here bc never divide
what happens in g1
8 hours
cell doubles mitochondria and organelles
first stage
centriole replication begins
what happens in s phase
6-8 hours
dna replication and histone synthesis
what happens in g2 phase
protein synthesis
centriole replication is completed
stages of mitosis
read !!!!!
meiosis stages
read !!!!!
differences in mitosis and meiosis
2 vs 4 DC
diploid v haploid DC
1 v 2 step process
somatic v gametic
what are mutations and how are they caused
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
what is a single base substitution
replacement of a single nucleotide
transition: with same nucleotide
transversion: with different nucleotide
what is a missense mutation
when nucleotide changes and forms codon that codes for a diff aa
what is a nonsense mutation
forms a stop codon
what is a silent mutation
forms codon that codes for same amino acid
what are insertion and deletion mutations
loss or addition of a nucleotide
frameshift mutation
what is a truncating mutation and how is it caused
no protein or wrong sized protein is formed
by nonsense, insertion or splicing mutation
what is a non-truncating mutation and how is it caused
missense and silent mutations
expansion of trinucleotide repeats
what is a modest expansion and what does it cause
repeats of one tri-nucleotide e.g. CAG in huntingtons
what is a large expansion and what does it cause
repeats of varieties of tri-nucleotides on promotor regions or non coding regions
causes: inhibition of gene expression
what is promoter methylation
switching on/off of gene transcription by adding ch2 or removing from cytosine
what is hypermethylation
inapt switching off of genes
what is hypomethylation
inapp switching on of genes
what is a recessive loss of function mutation
when disease arises bc all of normal protein is lost and 2 genes are knocked out
MOST COMMON LOF
what is a dominant loss of function mutation
when 1 gene is knocked out and disease arises: 50% of functional protein left
what is a dominant negative mutation
???
how is a loss of function mutation caused
failure of synthesis or synthesis of non-functional protein
is a gain of function usually dominant or recessive
dominant
what causes a gain of function mutation
abnormal or novel function of protein or inapp synthesis
what is a synonymous effect
polypeptide product not altered
due to silent mutation
what is a non-synonymous
pp product altered
missense, frameshift or non-sense
selective advantage or fatal phenotype
