test 2: non-mendelian genetics Flashcards
pedigree
inheritance within a family group
- analyzed to determine carriers for a disease
- tracks disease or morphological traits in families
males are represented by what shape in a pedigree?
square
females are represented by which shape in a pedigree?
circle
autosomal recessive
can be hidden and skip generations
autosomal dominant inheritance
each affected child has an affected parent
simple autosomal recessive inheritance
- trait determined by one gene on an autosome
- only expressed by homozygous recessive individuals
- certain diseases found in specific populations
- skips generations // equal chance male or female
- both parents have to be carriers to pass on disease
- homozygous recessive NOT carriers
carrier
keeps allele in population but doesn’t exhibit the disease
exs of autosomal recessive
cystic fibrosis, tay sach’s
cystic fibrosis
- 1 in 20 white north americans are carriers
- deadly: cannot reproduce
- respiratory disease
- determined through genetic analysis and medical symptoms
- all children born in north american are screened
tay sach’s
carriers: eastern european jews and french canadians
- brain swelling (enzyme doesn’t work), death by age 5
sickle cell anemia
- 1 in 4 black people in central Africa are carriers
- carriers more likely to survive malaria
- susceptible to infections, fever, severe pain in chest and extremities
- can’t deal with overexertion, high altitude, or respiratory illnesses
albinism
- 1 in 70 from most populations are carriers
- social/sun are the only risk factors
- genetic condition which strikes all animal species (not just humans): may inhibit camouflage
simple autosomal dominant inheritance
- 1 gene site
- autosomal not gender related
- trait produced with at least one dominant allele
- most inherited traits are not fatal
simple autosomal dominant inheritances - diseases
dwarfism
huntington’s disease
huntington’s disease
- affects individuals 40-50 years old
- fatal disease (only takes one dominant allele)
- two dominant alleles is very rare but they do survive
- disease manifests itself after 40 (too late to not pass it on)
- neuromuscular degeneration
what do both dwarfism and huntington’s display?
double dominance
double dominance in dwarfism
deadly, baby survives a few days
double dominance in huntington’s
very rare, usually a miscarriage
how does one inherit a recessive trait?
- both parents must have allele
- kept in population because being heterozygous is not disagvantageous (carriers)
how does one inherit a dominant trait?
- one parent must have allele
- if allele gives something bad, population will be purged of allele (dies out) - EXCEPTION HUNTINGTONS
sex linked recessive inheritance
- on the x or y
- only looking at x
- trait is recessive and on x, increase rate of males express
- y: few alleles
sex linked recessive inheritance examples
colour blindness, hemophilia
x-inactivation
- female mammals don’t use both x’s
- as embryo: 1 X in each cell becomes inactive and is re-activated later only in ovaries
- inactive x coils up into barr body
- choice of x used is not random
- females are mosaics
incomplete dominance
- offspring have an appearance somewhere between phenotypes of the two parents; “blending of the phenotypes”
- ex: red allele + white allele = red and white OR pink
new heterozygous phenotypic ratio
incomplete = 1 : 2 : 1
codominance (blood type)
- many genes in populations can exist in more than one more
blood types
- 2 carbohydrates (A&B) found on surface of blood cell
- person can have one or the other (A or B), both (AB), or neither (O)
blood antigens
- outside of blood cell has marker protein (antigen)
- antibodies are produced in the blood serum against foreign antigens
- antibodies bind to the “bad” blood and cause it to clump (deadly)
- careful with transfusions
why must blood tranfusions be a certain weight?
- body will react to blood cells with tags they don’t recognize
- won’t react to O (no tags) = universal donor
+/- blood types are extra tags
RH tag (directly inherited, if one parent has it, you must have it)
Rh-
lacks antigen
Rh+
has the antigen
medical problems with Rh+/-
if mother is Rh- and fetus is Rh+ (from dad)
- small amounts of blood are transferred during childbirth
- mother can produce antibodies against the Rh+ factor
- next pregnancy: can kill the child or damage the blood supply system (hemolytic disease)
- prevention: RhoGam (destroys Rh+ antigens: prevents mother from producing any Rh antibodies) - works for short term (hurts immune system in the long run)
epistasis
- a gene at one location affects the phenotypic expression of a gene at another locus
- there are many genes whose sole function is to turn on and off other genes
pleiotrophy
genes have multi phenotypic effects (1 gene = multiple traits)
polygenic inheritance
- some traits are not “either-or”
- 2 or more genes affect a single phenotype
ex: human height, eye color, skin color - these traits are called qualitative traits
- opposite of pleiotrophy (1 gene affects many phenotypes)
- multiple genes working together = one trait
multifactorial inheritance
more than one genetic factor that controls it and it is influenced by environment (ex: the womb)
- root basis is genetic so it tends to run in families
- involves polygenic
ex: human height interacts with nutrition; heart disease interacts with lifestyle
extranuclear inheritance
- mitochondria and chloroplasts that carry their own DNA and replicate themselves (maternal)
- used for studies that involve tracing species and individuals in family trees or orgins of groups; also criminal cases
