lecture 11- genetics Flashcards
what do the law of segregation and the law of independent assortment have in common
both contribute to genetic diversity
what is incomplete dominance
neither allele is dominant
mix/blend of both homozygous alleles
pink flower = mix of homozygous red and white
what is the notation for incomplete dominance alleles (red pink and white)
R^1R^1
R^1R^2
R^2R^2
in incomplete dominance what terms do you use for the middle allele
heterozygous
in incomplete dominance what is the genotype ratio compared to the phenotype ratio
they are equal
all allele combination will display their phenotype
what is codominance
both alleles’ phenotype being expressed
not a mix, are independent
what is the notation for codominance
same as incomplete dominance (R^1R^2)
is a gene limited to having only two alleles
no (blood type antigens)
how many alleles can an individual have for a specific gene
two because theres only two homologous chromosomes for that gene
what are the blood cell antigens
I^A - type A
I^B - type B
i - type O
what are all the blood types you can have and their notations
type A - I^A I^A or I^A i
type B - I^B I^B or I^B i
type AB (codominant) - I^A I^B
type O - ii
what is epistasis
presence of a certain allele in one locus that can mask the expression of alleles in a different locus
is the epistasis gene dominant or recessive
recessive ee
how does epistasis work
if the epistasic gene is homozygous recessive then it blocks another gene from being expressed
what is pleiotropy
a single gene that can affect multiple phenotype
how does pleiotropy work
when a gene product is used in different cell types or a signaling functions on various targets it affects multiple organs
what are examples of pleiotropy
cystic fibrosis (defective protein found in the plasma membrane): affects lungs, intestines, pancreas, liver, sweat glands
sickle cell anemia (defective protein in red blood cells): symptoms such as heart failure, jaundice and pain
what is polygenic inheritance
many genes interacting to affect the expression of one trait (opposite of pleiotropy)
example of polygenic inheritance
skin color is controlled by at least three genes
what is sex-linked inheritance
characteristics inherited on sex chromosomes other than sex related ones (mostly X)
what types of genes do sex chromosomes contain
sex assigned
control of development of secondary sex characteristics (breasts, voice, etc)
other genes: hemophilia and color blindness
are sex chromosomes homologous
no but they act as homologous (pair up during meiosis)
have a homologous region (bottom, small)
where are sex linked genes
on one of the sex chromosomes but not on the other
what is a hemizygous allele
allele that determines the condition in males because they only have that gene on one sex chromosome
what is dosage compensation
mechanism that makes the 2 doses in females (XX) and the one dose in males (XY) equivalent
how does dosage compensation work in mammals
inactivation of an X chromosome or part of it
creation of a barr body (inactive chromosome)
what is the point of dosage compensation
avoiding over expression of X genes in females
due to X inactivation what changes in the genetic material
nothing, they all keep the same genetic material
what is polyploidy
presence of multiple sets of chromosomes (normal)
what is aneuploidy
abnormalities caused by the presence or absence of a single chromosome (only affects one chromosome type)
what is a nondisjunction
chromosomes failing to separate during meiotic division
what is the result of nondisjunction
aneuploidies
what is disomy
a normal pair of chromosomes
what is trisomy
having an extra chromosome in a pair (3)
what is monosomy
missing a chromosome in a pair (1)
where can aneuploidies happen
autosomes and sex chromosomes
what is the reason for down syndrome
trisomy 21 (extra chromosome #21)
so 47 chromosomes instead of 46
what are the four chromosome structure mutation
deletion
duplication
inversion
reciprocal translocation (different chromosomes exchanging genes)
is a phenotype solely based on genes and why
no its also based on the environment (height = how much you eat, sleep, etc)
what are the different types of abnormal sex chromosome numbers
XXX
XXY
XYY
X0
Y0
how will a XXX person develop
female
mild disorders
only one X active
taller than average
normal sexual development
how will a XXY person develop
male
have some female characteristics
how will a XYY person develop
male
normal sexual development
taller than average
how will a X0 person develop
female
underdeveloped ovaries
male characteristics (lack breasts)
how will a Y0 person develop
death
humans cannot live without at least one X chromosome
