Genetics basics, Congenital abn, genetic abn Flashcards
mutaton=
change int he nucleotide sequence of an organisms DNA ultimatey creating genetic diversity
allelle=
any of the alternative verions of a gene that produce distinguishable phenotypic events
An allele is an alternative form of a gene (one member of a pair) that is located at a specific position on a specific chromosome. These DNA codings determine distinct traits that can be passed on from parents to offspring through sexual reproduction.
genotype vs phenotype
genotype is the genetic makeup or set of allelles of an organism
phenotype is the phys and physio. traits of an organism
homozygous vs heterozygous
homozygous=having 2 identical allelles for a given gene
heteroygous is different
a congenital abnormality is____
d/t
any defects present at birth
d/t dev errors durin gestation (wouldnt happen unless theres a disruption)
when is vulnerability to congenital abnormality?
what is it
during organogenesis 15-60 days approx
-a time when vital organs are vulnerable to maternal or external interruption
what is a critical period
each organ of the embryo is forming at a specific time
which organs experience maximal sensitivity to teratogens when?
wk2-5=CNS wk3-6ish=heart wk4-7=extremities wk 4-7.5ish =eyes wk7-9=external genitalia
teratogen=
a factor external tot he fetus, including the mother, that causes birth defects
egs of teratogens
what are positive factors vs negative factors
positive (you must take something)-thalidomide caused limb defects if taken 15-20 days post conception (used for monring sikness)
positive-alcohol–fetal alcohol syndrome
negative (youre missing something)-malnutrition, cigarette smoke, infections
how many chromosomes do people have
23 pairs, the last of which is the sex chromosome. the rest are autosomes
a chromosome is
A chromosome (chromo- + -some) is a packaged and organized structure containing most of the DNA of a living organism.
autosomal conditions affect-
x linked conditions affect-
affct males and females
as the male only gets one x males are more severely affected as these conditions are generally recessive
dominant=
a single copy of the disease assoc mutation is enough to cause the mutation
autosomal recessive=
child has 50% chance of being a carrier, 25% chance of being affected and 25% chance of being unaffected
4 types of genetic abnormalities
1-monogenic
2-mitochondrial gene
3-complex trait or multifactorial (most)
4-chromosomal number and structure
with autosomal dominant how many defective genes do you need for the trait to be possibly present in offspring?
% chance of inheriting
1
50% chance of inheriting
3 types of monogenic problems:
autosomal reessive
autosomal dominant
x-linked recessive
x-linked recessive is an example of hwat kind of genetic abn?
what is it
monogenic
-only appears if you and your prtner have it..or? if a male inherits a recessive x chromosome there cant be another x dominant chromosome as his other chromosome is Y therefore the recessive gene will be expressed
its on sex chromosome
how many mitochondrial genes are there
37
2 are rRNA, 22 transfer or tRNA, 13 structural genes that are encoding subunits of mito. resp. chain enzymes
mitochondrial gene function
code resp chain Es. (nec for ATP)
u
how are mitochondrial genes inherited
maternally because most of the mitochondria are in the flagella which drops off when it enters the ovum. the ovum has more mitochondria than the sperm
what do mitochondrial gene disorders affect most and why
cause neuromuscular defects because nerves and muscles require a lot of ATP
complex trait=
may be a genetic predisposition
- polygenic
- genes and environmental cmponenets
2 types f chromosomal problems
numerical abnormality or stuctural defects
chromosomal numerical abnormaltiy
aneuploidy=
monosmy
trisomy=
aneuploidy=extra or missing chr
monosomy=missing chr in pair
trisom=extra chr in a pair
how are chromosomal numerical abnormailites named
by the chromosome number eg trisomy 21=down syndrome
types of chromosomal structural defects
inversion
translocation
deletion
chromosomal str defect: deletion
loss of geneti material and shortening of the chromosome
chr str defct: inversion
can be pericentric (around centromere
requires two breaks in a single chromosome
paracentric is not around centromere
chr str defect: translocation
can be balanced (look in book
Robertsonian in which one is lost
isochromosomal (from fault centromer division) leads to duplication of long arm and dletion of short arm or vice vers
Klinefelters syndrome vs Turners syndrome which affects males?
klinefelters
klinefelters and turners sydromes are exampes of what
genetic abnormalities
Klinefelters syndrome=
mnfts=
male xxy (1 in 500)
gynecomastia
deficient secondary male sex char
tall stature w longer ower than upper body and long extremities
lang impairment
narrow shoulders wide hips
lack of testosterone and inc hypothalamic gonadotropic hormones
Turners syndrome=
organs affected
female X0 (1 in 3000) one x and no other chromosome -doesnt menstruate o signs of secondary sex char -webbing of neck -nonpitting lymphedema of hands and feet -congeneital heart defects (esp coarctation of the aorta and bicuspid aortic valve) -abn kidney dev -small stature
