genetics Flashcards
what is a de novo mutation
mutation that arises for the first time in an individual
what is fitness
the ability to pass on genetic information
how do mutations effect an individual
mostly - neutral
some - deleterious
few - advantageous
if you have 1000 people how many ales will you have
2000`
what is the Hardy–Weinberg equilibrium
the relative frequencies of alleles between generations remains constant
unless changes
assumptions with the hardy-Weinberg equilibrium
- mating is random
- migration is negligible
- no selection pressure
what is natural selection
reduces reproductive fitness of an organism
positive selection
increases reproductive fitness
what is the founder effect
when a small sub set of a population (bottle necks) and forms a new colony with less allele variation
what is genetic drift
widespread
natural
random by chance
what types of non random mutations are there
assertive mating (smart with smart/ deaf with deaf)
consanguinity
marriage between close blood relatives
how are genetic mutations classed
from 5 (being parthenogenic) to 1 being Benin)
what are variants of uncertain significance
a mutation that cannot be determined to be either neutral or deleterious
what is cultural isolation and example of
founder effect
what is the the of DNA
the double helix and complimentary base pairing.
what dose each nucleotide contain
sugar base and a phosphate
where do transcription factors bind
on the major group
why is the minor group not used
the proteins are too big to interact
what dose the nucleolus do
make ribosomal RNA -
what dose DNA wrap around
a histone
what is a nucleosome
8 histones
what is chromatin
what is the banding pattern
looks like a big bowl of spaghetti
all the DNA, proteins, RNA that make up a chromosome
due to the chromatin
how is chromatin made more accessible
histones are modified by enzyme
what way is replication
5’ to 3’ end
what bits are coding regions what are non coding
introns don’t code
exons do code
what happens from dna to protein
DNA transcription mRNA,tRNA,rRNA translation protein
what is heterochromatin
Condensed structure
Silenced genes
what is Euchromatin
Open structure
Active genes
what are okazaki fragments
the fragments made as part of the lagging strand
what makes new DNA
DNApolymease
what binds the okazaki fragments
DNAlgase
what is the structure of a nucleosome
a solenoid structure
what one phat to analysed by photograph chromosomes
a karyotype
what is FISH
it is fluorescent in situ hybridisation
a piece of fluorescent probe DNA binds to its complementary section
what is Oogenesis
in the end what dose it make
process of egg formation
4 polar bodies and one egg
what is Spermatogenesis
what dose it make
process of sperm formation
4 sperm cells
what are examples of FISH probes
centromeric - chromosome No.
telomeric
whole chromosome probes - spectral karyotype
when dose recombination occur
prophase 1
what do two haploid cells form
a diploid - zygote which then becomes a embryo
what is maternal inheritance
the inheritance of mitochondrial DNA via the egg
what is x inactivation
when a sex linked allele i.e. is not on the y it is the only one expressed
however a female has to inactivate one x chromosome
what is autosomal inheritance
what are the two type
a pattern of inheritance that is not on a sex chromosome
dominant
recessive
what is sex linked inheritance
related to the sex chromosomes (it is a mutated x chromosome)
characteristics of sex linked
examples
no mail to male transmission
skip generations
only men affected
Duchenne muscular dystrophy
an arrow on a pedigree model shows
who you are doing this for
a line through someone means
deceased
a boy is
and a girl is
square boy
circle girl
what are the characteristic of autosomal dominant
examples
no skipped generations
male to male transmission
50% of inheriting the condition
Huntington’s
dwarfism
what are the characteristic of autosomal recessive
examples
need both parents to be carriers
carriers can have symptom like presentation
cystic fibrosis
what are the 3 types of chromosomal abnormalities
numerical, structural and mutational
what are the majority of chromosomal mutations in the trimester and after birth
trisomy
what is trisomy
example
an extra chromosome - maternal origin
down syndrome
what is monosomy
example
only having one chromosome
turner 45,X
45 chromosomes not 46
lost a bit of x chromosome
what is trisomy 21
Down syndrome
1 in 650
Characteristic facial features
IQ less than 50
Average life expectancy (50-60 years)
what is trisomy 13
Patau syndrome
Multiple dysmorphic features and mental retardation
About 5% die within first month, very few survive beyond first year
what is turners syndrome
short stature infertile
neck webbing - wide nipples
what is Klinefelter syndrome
47,XXY 1 in 1000 tall stature, long limbs mild learning difficulties small testes
when do partial trisomy and partial monosomy occur
when there is unbalanced translocation
what is Robertsonian translocation
Robert
loss of the short arms of a chromosome
what is the outcome of deletions
it depends on what was deleted
variable outcome
what is the outcome of inversions
it depends on where and what genes are expressed on either side of the break
what is a unbalanced chromosomal change
when there is a duplicate of come DNA however there is not the full complement
what are the genetic mutation tyoes
germline or somatic
gene disruption / disease-associated
polymorphism
what are the types of coding mutations
silent - doesn’t effect protein
missense - changes protein
nonsense - changes to a stop codon
frame shift - completely changes the outcome
what are the two type of point mutation
transitions - purine to purine
A to G
transversions - purine to pyrimidine
A to C
Cto G
what are detecting mutations
Polymerase chain reaction (PCR) Gel electrophoresis RFLP ARMS DNA sequencing
what are the 3 steps of PCR
Denature - 95oC
Anneal - 50-70oC
Extend - 70oC
what happens in gel electrophoresis
Separate DNA fragments by size
Apply an electric field
DNA is negatively charged
what are the advantages/disadvantages of arms
Cheap
Electrophoresis required
Limited amplification size
Limited amounts of product
what is the best way for detecting mutations
DNA sequencing
Automation and high throughput
Expensive equipment
what are microarrays
collection of microscopic DNA spots - seeing expression of gene
what is penetrance
the frequency with which a trait is manifested by individuals carrying the gene.
what is non-medilian inheritance
Several variants in several genes acting together
what are examples of non medeilian inheritance
Incomplete Penetrance Genomic Imprinting Extranuclear Inheritance Complex Anticipation
what is complex inheritance
when there are multiple low variants present
what is extran nuclear in heritance
what dose it effect
example
basically a mutation in the mitochondria
tissue with high metabolic demand
DAD
what is homoplasmy
uniform mtDNA
what is heterolasmy
two ore more types of mtDNA
what is anticipation
when a section of DNA that normally repeats is mutated
and repeats 50 times more
what is incomplete penetrance
when a phenotype does not manifest as the gene suggests
leading to a inaccurate pedigree without genetic testing
what is uniparental disomy
Inheritance of a chromosome pair from one parental origin
what is genomic imprinting
when there are genes expressed from only one parent and this goes wrong
what is PEG and MEG
paternally expressed gene, maternally expressed gene
Genetic drift
Random fluctuation of one allele transmitted to high proportion of offspring by chance
Founder effect
reduction in genetic variation that results when a small subset of a large population is used to establish a new colony
what are somatic mutations
non germline tissue
are nonheritable
what are germline mutations
Present in egg or sperm
Are heritable
Cause cancer family syndromes
what are the 3 genetic processes associated with cancer
Oncogenes
Tumour suppressor genes
DNA damage-response genes
what do tumour suppressor genes have
a two hit hypothesis
what is a DNA response gene
it fixes a mismatch ie when two purines are together
MMR gene
what are MSIs
MSI is the phenotypic evidence that MMR is not functioning normally
examples of tumour suppressor genes
Rb
p53
BRAC1
examples of oncogenes
RET
VEGF
what can a failure of mismatch repair gene do
lead do hereditary colorectal cancer
CRC
what are the 5 classes of variant
5 = parthenogenic 1= benign
