genetics Flashcards
how many chromosomes does a human have
23 pairs = 46. 1 pair sex linked
what happens in mitosis (brief)
creates identical daughter cell
what happens in meiosis
formation of gametes - crossing over and independent assortment
describe RNA structure
single stranded, ribose backbone, uracil instead of thymine
describe DNA structure
double stranded antiparallel, deoxyribose backbone, ATCG
what determines protein production (4)
rate of transcription, rate of splicing, half-life of mRNA, rate of processing polypeptide
what are polymorphisms
any variation in human genome with a frequency of less than 1%. doesn’t cause a disease but can predispose
what are mutations
changes that cause a disorder
briefly outline the cell cycle
G1–> S–>G2–> M
where does DNA replication happen and therefore where mutations can occur
S phase
what is a telomere in a chromosme
at either end that protects against damage
describe the 3 components of a chromosome
centromere, short arm (p) and long arm (q)
what is an acrocentric chromosome
very short short arm
what is a metacentric chromosome
same length of arms
what is a telocentric chromosome
centromere almost at terminal end. ie no X shape
what is an aneuploidy and what are some types
abnormal number of chromosomes. monosomy = missing from a chromosome. trisomy = extra in a pair
what is robertsonian translocation
two acrocentric chromosomes stuck end to end - short arms normlly lost
what are reciprocal translocations
when chromosomes ‘swap’ genes
what are types of sequence mutations
SNP’s (single nucleotide polymorphisms) or deletions/ insertions which can be more serious
what does monosomy of sex chromosomes cause
turner’s syndrome
what does trisomy of 18 cause
edward’s syndrome
what does trisomy of 21 cause
down’s syndrome
what does trisomy of 13 cause
patau syndrome
why are X trisomy better dealt with
x inactivation
what does the aCGH chromosome test detect
deletions and duplications - not balance rearrangements
what dies FISH show
fluorescence that stains chromosomes, can be used to detects aneuploidy
what doe PCR and NGS look at
very small sequence changes
what is a balanced chromosomal arrangement
all genetic material there
what is an unbalanced chromosomal arrangement
some missing or extra
what is a mosaic individual
has some mutations but seems fine
how can mutations occur
parent –> child, gametogenesis, during development, mitosis
what is a missense mutation
base change causing amino acid change (
what is a nonsense mutation
base change results in stop
what does mendelian inheritance encompass
autosomal dominant, autosomal recessive, x linked, mitochondrial. inherited disorders
what is the penetrance of a mutation
the likelihood of it causing a disease
describe the difference between autsomonal dominant and recessive
dominant: only 1 faulty gene is required from 1 parent to cause disease (50%) chance.
Recessive: 2 faulty genes requires (25%)
when does x-linked occur
carried on X chromosome, Y is irrelevant. If mother has it and passes to boy he will be affected. If mother passes to girl 50% chance. This is due to X inactivation
where does mitochondrial disease come from
mother –> child
what does c. 9T>G. p.His3Gln mean
the 9th RNA base has changed from a T to a G. this has caused the 3rd amino acid to change from his to Gln
what are non-mendelian disorders
mocaicism, imprinting and mitochondrial
what is epigenetic variation and give an example
functional changes that occur not from DNA sequence eg methylation which inhibits DNA transcription
what is imprinting
difference in gene expression depending what gene is inherited
what do oncogenes do
promote cell division
what do tumour suppressors do
inhibit cell division
is cancer normally high penetrance or multifactorial
multifactorial
what is the 2 hit hypothesis
one inherited copy of a gene and another zygotic acquired one
when do mocaism mutations happen
post zygotic
