test 1 genetic disease Flashcards
genes for specific proteins found..
in exactly one chromosome
each person should have how many copies of one gene
two
what is autosomal dominant
when a genetic disease is caused by having just one faulty copy of an autosomal disease
ex of autosomal recessive
Marfan Syndrome
Autosomal recessive
when a gnetic disease is caused by having two faulty copies of an autosomal disease
ex of autosomal recessive
cystic fibrosis
sex-linked genetic condition
when a disease is caused by mutations on a sex chromosome
sex-linked genetic diseases almost always
affecting the X chromosom
sex-linked genetic diseases can be
dominant or recessive
one specific version (DNA sequence of a gene)
Allele
The genes a person has
Genotype
How a person looks
Phenotype
Hetrozygote
has two different alleles
hemizygous
one copy of a gene is missing
how would hemizygous happen
one copy is deleted entirely or not produced, monosomy exists or person is XY
punnet square for recessive disorder
25% chance the offspring will have it
punnet square for dominant disorde
75% chance the offspring will have it
how can mutations be defined
by how they affect DNA sequence
what is a point mutation
one base pair is changed to something else
what is a silent mutation
mutation causes the same amino acid to be produced
missence mutation
mutation causes a new amino acid to be produced
nonsense mutation
mutation creates a premature stop codon (UGA)
what is frameshift mutation
one base paur is added or removed, causing all codons to be misread
insertion frameshift mutation
base pair is added
deletion frameshift mutation
base pair is removed
how can mutations also be defined
by how they affect gene products
ways mutations affect gene products
- loss-of-function
- gain-of-function
- change-of-fucntion
types of loss-of-function mutations
amorphic
hypomorphic
amorphic mutation
mutation that completely eliminates gene productivity
hypomorhic
mutation that slows gene product activity
types of gain-of-function mutations
hypermorphic
what is hypermorphic mutation
mutation speeds up gene product activity
types of change-of-function mutations
neomorphic
neomorphic mutation
causes gene product to do something else
what is PKU
Phenlketonuria
what is Phenlketonuria
disease characterized by a complete lack of functional copies of the enzyme phenylanine hydroxylase
what is phenylanine hydroxylase responsible for
responsible for converting the amino acid phenylalanine into the amino acid tyrosine
so what would a lack of functional phenylanine hydroxylase mean
BOTH copies of the gene suffered loss-of-function mutations
what is the gene for phenylalanine hydroxylase is called what
the PAH gene, found on 12th chromosome
how many loss of function mutations have been found in humans
15
first reason that Phenlketonuria is BAD
With no way for the body to remove excess phenylalanine, the phenylalanine will bind to and block receptors on the brain that allow other neutral amino acids, like valine and tyrosine, to enter the brain.
second reason why phenlketonuria is bad
With no way to produce tyrosine, the body is limited to its dietary supply from digested proteins
what is tyrosine important for
for the synthesis of imporant molecules like the neurotransmitter dopamine, and the pigment melanin
recessive disorders like PKU are always cause by
the complete lack of a protein in the body
depending on ___, recessive disorders__
on where the missing protein should be found and what it does, recessive disorders can be treated by artificially producing and injecting that protein
haploinsufficiency
a loss-of-function mutation impedes one copy of a chromosome
result of haploinsufficiency
one copy of a gene cannot produce enough protein to satisfy the needs of the cell/body , leading to a sick phenotype
what is Marfan Syndrome caused by
a loss-of-function mutation in the FBN1 gene, which codes for a protein called fibrillin-1
what is the job of fibrillin-1
to block a the protein TCF-B from binding to cells
what happens when there are not 2 copies of FBN1
there aren’t enough copies of fibrilli-1 in the body to stop TGF-B from binding to cells
what is TGF-B
a complicated protein that does many things
some of the things TGF-B does
regulation of growth in the body, controlling how elastin fibers develop
how does TCF-B’s regulation of growth in the body manifest
Marfan Syndrome makes people tal
how does TCF-B controlling how elastin fibers develop manifest
it especially effects the eye aorta and heart
what is dominant negative gene action
many enzymes in the body are actually multimers
what does it mean to be a multimers
made of two or more proteins combining to form a bigger protein
some loss-of function mutations cause
cause “bad” protein subunits that can still combine with other functional subunits that do not work, causing problems for the body
p53 is referenced as the
guardian of the genome
what is the main function of p53
directly binds to DNA and turns on some other genes`
the proteins produced by the genes turned on by p53 will either ….
stop the cell cycle if DNA damage is detected
-cause the cell to enter apoptosis is DNA damage is not fixed quickly
what is apoptosis
programmed cell death
what is found in virtually all cancer cells
mutant or inactivated p53
cells must do what to become cancerous
inactivate or circumvent p53 `
how many subunits come together to build p53
4
what happens if any of the gene for any one of the subunits of p53 suffers a loss-of-function mutation
the broken piece will latch on to 3 working subunits and create a “broken” p53 protein
while ____ of p53s will be broken,, ______
half of p53s will be broken, half of the p53 tetramers in a cell will still work
with half of p53s broken
only one p53 will bind to DNA when there is a mutation
what happens if the wrong p53 binds to DNA
p53 won’t properly turn on those genes and the cell will keep dividing and passing down mutant genes.
two ways to “get” a genetic disease
inherited mutations
de novo mutations
inherited mutations
come when your parents or parent have a faulty copy of a chromosome that they pass to you
de novo mutations
happen independently
de novo mutations happen independently where
- a sperm or egg that fertilizes you
- one cell very early in development mutates
if there is a De novo mutation in a sperm or egg
all of your cells will carry this mutation
if there is a De novo mutation in a cell of early development
mosaicism
mosaicism
only some of your cells carry the mutations
every offspring acquires how many de novo mutations
100
as a father ages…
he’ll pass more de novo mutations to his offspring
Mendelian traits also called
monogenic traits
what are mendelian traits
traits affected by exactly one gene
patterns where the mutation can spread depend on
where the gene is located and how the protein functions
5 patterns in which mendelian traits can spread
autosomal dominant autosomal recessive x-linked dominant x-linked recessive y-linked
opposite of mendelian trait
polygenic trait, like height
what are pedigree charts
“family trees” that track a certain phenotype
Males n females on pedigree
males are squares, females circles
ppl with phenotype in question on pedigree
shaded
autosomal dominant
when a genetic disease is caused by having just one faulty copy of an autosomal gene
pedigree for autosomal dominant will reveal
- men n women affected equally
- affected person has affected parent, like mother or father
- if there is no affected person in a generation, transmission stops
- new (de novo) mutations sometimes possible
autosomal recessive
when a genetic disease is caused by having two faulty copies of an autosomal gene
autosomal recessive pedigree will reveal
- affected individuals often have unaffected marriage
- traits typically show up more in consanguineous marriages
- tends to skip generation
- if an affected child is born but neither parent has the disease, future children have a 25 chance of being affected
consanguineous
marriages between ppl w same ancestors
x-linked recessive
occur when all copies of the x chromosome carry the mutation
pedigree for x-linked recessive reveals
- disease more common in men
- sons of affected man will never inherit the trait from him
- daughters of an affected man are carriers
why are x-linked recessive disorders more common in men
men are hemizygous (only one copy of a gene)
x-linked dominant disorderss
occur when any copy of an X chromosome carries the mutation
