genetics- not finised Flashcards
chromosome structure
chromatids are made from ___ and are the site of ___
repetitive sequences of DNA- satellite DNA
kinetochore- attatches chromatids to spindle
heterochromatin is made of
silenced genes- condensed structure
euchromatin is made from
active genes- open structure- where transcribed genes are
chromatin structure
DNA packed with histones into nucleosomes
histones have positive charge and DNA have negative
characteristics of autosomal dominant inheritance
each child has a 50% chance of inheriting
no skipped generations
equally transmitted to females and males
male to male transmission
characteristics of sex linked inheritance
only males affected usually
can skip generations
unaffected women and men can transmit
no male to male transmission
is sickle cell recessive or dominant
recessive- both parents must be carriers
is CF recessive or dominant
recessive- needs both parents to be carriers
child’s chances of illness in recessive conditions when both parents are carriers
1 in 4
childs chances of carrying with one parent is a carrier in a recessive condition
2 in 4
huntingtins dominant or recessive
dominant
how is Duchenne’s spread
X linked inheritance
how are sex genes inherited
females get X from dad and X from mum
males get X from mum and Y from dad
X linked inheritance: mother carrier chances
50% chance each son will have
50%chance each daughter
both get an X from mother
X linked inheritance: father carrier chances
none of sons will have
all daughters will carry
3 types of chromosome abnormality
numerical
structural
mutational
numerical abnormality: non disjunction mainly comes from
the mother
except turner syndrome 45,X
numerical abnormality: whats non disjunction
chromosomes don’t line up properly during meiosis 1 or 2
sister chromatids don’t separate or 2 homologues end up in 1 cell
numerical abnormality: autosomal aneuploidy syndromes
trisomy 21
trisomy 13- patau syndrome
trisomy 18- edwards syndrome
all mainly by non disjunction
numerical abnormality: trisomy 13 patau syndrome
dysmorphic features and mental retardation
poor survival
numerical abnormality: trisomy 18 edwards syndrome
severe developmental problems
poor survival
numerical abnormality: sex chromosomes aneuploidy syndrome
45,X- turner syndrome
47, XXY Klinefelter syndrome
numerical abnormality: turner syndrome 45, X
spontaneous loss common
always female- no Y
short stature
infertile
webbed neck and widely spaced nipples
numerical abnormality: klinefelter syndrome 47,XXY
tall stature and long limbs
always male
infertile and small testes
mild learning difficulties
structural abnormality: include
balanced or unbalanced rearrangements
translocations
deletions, insertions and inversions
structural abnormality: reciprocal translocations
breaks in 2 chromosomes making 2 new derivative chromosomes
structural abnormality: robertsonian translocations
fusion of 2 acrocentric chromosomes (far away from eachother)
how are chromosome mutations detected
PCR
gel electrophoresis
RFLP
ARMS
DNA sequencing
genetic processes associated with cancer
oncogenes
tumour suppressor genes
DNA damage response genes
what do tumour supressor genes do
cells brakes for growth
inhibit cell cycle or promote apoptosis
cancer happens when both breaks fail
what are microsatellite sequences
repeated sequences of DNA
