Mendelian Genetics Flashcards
what did gregor mendel use to observe simple characteristics
pure breeding lines
how many characteristics mendel observe
seven
normal or wild type refers to what
the most common allele in a given population
single gene disorders are also known as
mendelian or monogenic diseases
single gene disorders are caused by mutations in
one gene
what can pedigree analyses of large families with many affected individuals tell us about a monogenic disease?
whether it is located on an autosome, sex chromosome, whether it is dominant or recessive
individuals are called heterozygotes and with one copy of the altered gene they are affected. this is?
dominant
homozygotes must have two copies of the altered gene to be affected, this is?
recessive
males with an altered gene on the x-chromosome are always affected, this is?
x linked recessive
give some examples of autosomal dominant conditions
huntington disease, marfan syndrome, FAP famiilial adenomatous polyposis
with an autosomal dominant inheritance pattern what chance is there that the child will be affected
50/50
list three complications in autosomal dominant inheritacne
new mutations - sporadic de novo cases, variable penetrance and anticipation
what are sporadic de novo cases
a new germline mutation that was not inherited from either parent
what is variable penetrance
proportion of individuals with a mutation that exhibit clinical symptoms, e.g. 95% penetrance, 5% will have mutation but not have symptoms
what is anticipation
genetic disorder passed onto next generation, symptoms become apparent at an earlier age and severity is also increased
anticipation is common in which types of mutation
triplet repeat expansion such as Huntingtons
with familial adenomatous polyposis the patient has to inherit a single mutant APC allele and they will
have the disease
familial adenomatous polyposis is described to be what in terms of penetrance and colorectal cancer risk
100% penetrant, 100% CRC risk
familial adenomatous polyposis shows what type of inheritance
autosomal dominant
polyp numbers can vary depending on the
position of the germline mutation
what is APC
a tumor suppressor in which mutations lead to colon cancer
APC mutations are also very common in
sporadic CRC
how many different mutations can occur in the APC gene
300 different mutations
in the APC gene large deletions account for around
15% of the problem
list some examples of autosomal recessive conditions
sickle cell, cystic fibrosis, congenital deafness,
why are deleterious mutations sometimes prevalent?
heterozygote advantage
with an autosomal recessive trait there is a 1 in
4 chance of the child having the disease
what is consanguinity
(blood relation) being from the same kinship as another person - most common between first cousins
with a recessive disease, the gene mutation comes together and causes an
autosomal recessive disease
list some x linked recessive diseases
haemophilia, duchenne muscular dystrophy,
in x linked recessive diseases, one copy of an altered gene on the x chromosome causes the disease in
males
in a x linked recessive disease, an altered copy on one of the x chromosome pairs causes what in females
carrier status
the risk of being affected with an x linked recessive disease depends on the
gender of the child
carrier females have a ___ chance of having an affected son with an x linked recessive inheritance pattern
50%
affected males with xlinked recessive are usually born to an _____ parent,
unaffected, the mother is usually an asymptomatic carrier
with x linked recessive inheritance there is no male to
male transmission
an x linked dominant condition is the dominant gene being carried on
an x chromosome
in an x linked dominant condition, how many copies of the allele can cause the disorder
one
if the mother is affected with an x linked dominant disorder, what is the inheritance pattern
50% of children will have disorder
if the father is affected with a x linked dominant disorder, what is the pattern of inheritance for the children?
100% of daughters will have disorder, 0% of sons
what does the Hardy Weinberg Distribution state?
that allele and genotype frequencies in a population willl remain constant from generation to generation in the absence of evolutionary influences
single gene disorders are common or rare
quite rare
most traits are
polygenic
what is a polygenic disease
a genetic disorder that is caused by the combined action of more than one gene
examples of polygenic diseases include
cancer, diabetes, alzheimers
polygenic diseases have how many mutations
many (10s-100s)
describe the penetrance in polygenic diseases
low, variable
describe the penetrance in monogenic diseases
high
what interaction is important in polygenic and monogeneic diseases
gene/environment interaction
