genetics Flashcards
what are pathological polymorphism
mutations
what is PCR
ability to amplify a small amount of DNA millions of times
what is a DNA probe
piece of single stranded DNA that can locate and bind to its complementary sequence
what is hybridisation
when thousands of probes are analysed
what is PCR
when a primer acts as a starting point for DNA polymerase to build a new DNA chain that is complimentary to the sequence under investigation
what do single nucleotide polymorphs consist of
two nucleotides at a particular site
what chromosome is the cystic fibrosis gene on
chromosome 7
what is DNA wound around
histone proteins
what is DNA + histone called
nucleosome
how many chromosomes in human cell
46
23 inherited from each parents
what sex chromosome do males have
XY
what sex chromosome do females have
XX
what is the middle of chromosome called
centrosome
what is the short arm
p
what is the long arm
q
when can chromosome be stained
in metaphase
where exactly is the CFTR gene
chromosome 7 on band 21
7q21
what occurs in mitosis
each chromosome divides into 2 daughter cells
what happens to the X chromosomes in a female
X inactivation that is random
it can affect either X chromosomes
what is at the end of a chromosome
telomeres contain many repeats of TTAGGG
what are the ends of the chromosomes susceptible to
single-stranded DNA degradation back to double-stranded DNA
what happens to the ends of telomeres when they differentiated
they get shorter
what happens to germ cells when they replicate
they do not shorten as they have telomerase
what is telomerase
protects against telomere shortening by acting as a template primer
what do cancer cells switch on to become immortal
telomerase
how many pairs of chromosome in a human
23
what is the mitochondrial chromosome
circular DNA
what does mitochondria produce
ATP
what else do mitochondria have a critical role in
apoptotic cell death
where are all mitochondria inherited from
mother
is somatic inherited
no
what do somatic cell mutation give rise to
tumours
what is aneuploidy
whole extra or missing chromosome
what is non-dysfunction
chromatid or chromosome fails to separate
what is an extra chromosome called
trisomy
what is having only one chromosome called
monosomy
what is trisomy 21
Down syndrome
what abnormalities cause klinefter
XXY
what is it called when individual only have one chromosome monosomy X or Y
Turner syndrome
what do micro deletions in chromosome 22 give rise to
DiGeorge syndrome
what do inversions involve
end to end reversal of a segment within a chromosome
example of disease caused by inversion
haemophilia
what is translocation
two chromosome regions join together
what is a reciprocal translocation
two non-homologous chromosome break simultaneously and rejoin
what is robertsonian translocation
two acrocentric chromosome join
short arm is lost
what is risk of passing on robertsonian translocation
children may have unbalanced
what mutation causes down syndrome
trisomy 21
clinical features of Down syndrome
- flat face
- slanting eyes
- small ears
- short and stubby fingers
- learning difficulties
etc
what is trisomy 13 cause
patau syndrome
survive few weeks
what does trisomy 18 cause
edwards syndrome
clinical features of Edwards syndrome
- low set ears
- rocker bottom feet.
- learning difficulties
who does turner syndrome affect
women
what mutation cause turner syndrome
45 X
clinical features of turner syndrome
- infantilism
- short stature
- webbed neck
who gets triple X syndrome
women
who gets klinefter syndrome
men
what mutation cause klinefter syndrome
47 XXY
clinical features of klinefter syndrome
- decreased crown pubis
- testicualr atrophy
- infertility
- gynaecomastia
- learning difficulties
what are most mitochondrial disease
myopathies and neuropathies
what else does mitochondrial disease cause
- retinal degeneration
- diabetes mellitus
- hearing loss
what is most common cause of blindness in young men
leber’s hereditary optic neuropathy
what detects imbalances
array CGH
what environmental causes can lead to mutations
- radiation
- ultraviolet light
- chemicals
what is point mutations
substitution of one nucleotide for another
example of disease caused by point mutation
sickle cell anaemia
what is the change in sickle cell anaemia
GAG to GTG
when is insertion or deletion more malicious
if the insertion or deletion are a multiple of 3 bases as it causes the sequence to be out of frame
what can splicing mutations lead to
alter amino acid composition
what is a nonsense mutation
point mutation in a sequence of DNA that results in a premature stop codon
what is autosomal dominant disorder
occurs when one of the two copies has a mutation
what are the chances of offspring inheriting disease in heterozygotes
50% chance of inheriting the chromosome
what are the parents in an autosomal recessive disorder
both unaffected carriers
autosomal recessive:
if carriers marry with are the chances of kids being a carrier or affected
1 in 4
X-linked:
what are the chances an affected mother will pass it on
half the male or female offspring will be affected
X-linked:
what are the chances an affected father will pass it on
all female will be affected
example of X-linked recessive disorder
haemophilia A
what will the male offspring of a male with haemophilia and a normal female be
male will not have the disease as they do not inherit their X chromosome form their father
what is the inheritance of mitochondrial disease
incomplete penetrance maternal inheritance
what is the altered gene in Angelman syndrome
UBE3A
what are mutations used by multiple genes termed
polygenic
what is risk of being affected by chromosomal abnormalities
low
what is risk of being affected by mendelian disorder
high
when does the risk of down syndrome increase
in mothers over the age of 35
what is done at 7-11 weeks for prenatal screening
ultrasound to confirm viability, fatal number and gestation by crown-rump measurement
what is done at 11-13 weeks for prenatal screening
- ultrasound to detect major chromosomal abnormalities
- testing of maternal serum for pregnancy associated plasma protein
what test are done at 14-20 weeks for prenatal screening
- testing maternal serum
- quadruple test is to measure inhibin A
what does it mean if inhibin A is high
down syndrome
what test are done at 14-22 weeks at prenatal screening
- ultrasound detects structural abnormalities
when is best time to detect congenital heart defects
18-22
what are the mutations in cystic fibrosis
F508del
what does mutation in F508del cause
CFTR protein is misfiled, causing ineffective biosynthesis therefore disrupting the delivery of the protein to the cell surface
what other mutation can cause cystic fibrosis
G551D
what does mutated G551D cause
the channel to not open properly
what is apoptosis
programmed cell death
what are the mutation in cancer
somatic
what is retinoblastoma cancer
eye tumour in younger children
what tumours are likely to develop with eye tumour
osteosarcoma
what are 2 major genes that are mutated in breast cancer
BRCA1
BRCA2
what are oncogenes
those that promote cell growth
point mutation in KRAS can cause
- colorectal cacner
- pancreatic cancer
point mutation in BRAF can cause
- melanoma
- thyroid
point mutation in ALK can cause
lung cancer
DNA amplification of MYC can cause
neuroblastoma
DNA amplification of HER2 can cause
breast cancer
chromosome translocation between BCR and ABL can cause
- chronic myeloid leukaemia
chromosome translocation between PML and RARA can cause
leukaemia
chromosome translocation between Bcl2 and IGH can cause
follicular lymphoma
chromosome translocation between MYC and IgH can cause
Burkitt’s lymphoma
examples of where carcinogens can be found
- cigarette smoke
- ionising radiation
- UV light
what can carcinogens cause
point mutation in genomic DNA
what do tumour suppressor do
restrict undue cell proliferation
what can mutation in tumour suppressors cause
uncontrolled cell growth
example of tumour suppressor
p53
in what tumours have p53 mutations been found
- colorectal
- carcinomas of breast and lung
- brain tumour
- osteosarcoma
- leukaemia
Oncogene examples
Ras
Myc
Tumour suppressors
p53
APC
BRCA 1/2
Rb
