Chapter 17: Genetics Flashcards
who is Mendel and and what did he study, theory?
an Australian monk in 1860s
he studied inheritance patterns of simple traits=genes in the garden pea and these traits had distinguishable types or alleles
theory of inheritance
phenotype
visible type of trait, appearance
genotype
combination of alleles
monohybrid cross
Study the inheritance of one trait
use true breeding homozygous parents for cross- Mendel started with this
P1
F1
F2
parental
first filial- first gen children
second filial - second gen children
what kind of experiments did Mendel do?
controlled experiments and observed the results
PP x pp=
all Pp
Pp x Pp=
3 purple, 1 white
1 PP, 2 Pp, 1pp
the dihybrid crosses are based on
monohybrid cross ratios
law of segregation
each organism is diploid: has 2 copies/ alleles of each gene
during meiosis these alleles segregate so that each gamete contains only one allele for each gene
each trait is controlled by
2 alleles
dominant allele
can mask the expression of the recessive allele
needs only 1 dominant allele to see the dominant phenotype
alleles for a gene occur at the same
gene locus= position on homologous chromosomes
homozygous
organism has 2 of the same alleles
heterozygous
organism has 2 different alleles
visual appearance of organism
phenotype
genetic composition of an organism
Genotype
homozygous dominant
heterozygous dominant
homozygous recessive
PP
Pp
pp
since all Pp and PP individuals all have the dominant phenotype there is a difference between
phenotypic and genotypic ratio
which is the phenotypic ratio and which is genotypic?
1 PP: 2 Pp: 1 pp
3 purple: 1 white
genotype
phenotype
if mom is Tt, what gametes can she give?
T and t
how do you know the genotype of an organism if heterozygous and homozygous dominants look the same?
one trait test cross
test cross- cross an organism with the dominant phenotype with an organism with the recessive phenotype.
the ratio of dominant: recessive phenotype will tell you the genotype of the dominant parent
what kind of game yes can dominant parents make?
recessive?
T and?
t
if the dominant parent is a heterozygous the expected phenotype with a recessive is
homozygous
1 tall: 1 short
all tall
If TT x tt expect ___ offspring
of Tt x tt expect ___ offspring
All T
1/2 T 1/2 t
if there are any recessive offspring the genotype of the dominant parent must be
Tt
dihybrids cross study the inheritance of
example
2 traits
seed color and shape
law of independent assortment
the inheritance of one trait is independent in the inheritance of another trait
(assume the genes are not linked)
what kind of gametes can YYRR make?
YyRr
Y,R
Y,y,R,r
a monohybrid cross between 2 heterozygotws produces a ___ ratio
3:1
a dihybrid cross can be split into
what method?
2 monohybrid crosses
branching method
two trait test cross is used to
determine whether an individual is heterozygous or homozygous dominant for either of 2 traits
incomplete dominance
example
in some monohybrid crosses it’s possible to get 3 phenotypes instead of the expected 2
there is 1 gene with 2 alleles
CRCR- red
CRCW- pink (intermediate phenotype)
CWCW- white
in incomplete dominance the phenotype of the heterozygous is a
blending of the dominant and recessive traits
in codominance the heterozygote shows
both the dominant and recessive traits
black, salt and pepper, white
in codominance there is one gene with 2 alleles but
both alleles are expressed
multiple alleles
example
the trait is controlled by 1 gene that has more than 2 forms
ABO blood type
there is 1 gene with _ possible alleles
alleles for type ABO blood
3
A: IA
B: IB
O: i
codominance with multiple alleles can get ______, not______
expression of both alleles
blending
IA allele codes for
IB allele codes for
i allele codes for
a functional enzyme A
a functional enzyme B
a nonfunctional enzyme
functional is dominant over nonfunctional
enzyme X adds the _____ to a ____ on the RBC
core oligosaccharide to a surface protein
enzyme A adds __ to the RBC
enzyme B
A antigen
B antigen
the A and B antigen are
sugars located in the surface of the RBC
Type A: needs
possible genotypes
1 functional enzyme A coded for by the allele A
IAIA, IAi
Type B: needs
possible genotypes
1 functional enzyme codes for by the allele B
IBIB, IBi
Type AB: needs
possible genotypes
1 functional enzyme codes for by allele A
1 functional enzyme codes for by allele B
IAIB
Type O: need
possible genotypes
no functional alleles
ii
antigens
located on the surface of RBC determines blood type (self)
antibody
protein in blood serum
produced against antigen of opposite bloodtype
what antibodies do you produce?
the ones that aren’t against your own antigens
a person with type A has the ___ antigen on RBC
possible genotypes
antibodies on blood serum
A
IAIA, IAi
anti-B antibodies
a person with type B has the ___ antigen on RBC
possible genotypes
antibodies on blood serum
B
IBIB, IBi
anti-A antibodies
a person with type AB has the ___ antigen on RBC
possible genotypes
antibodies on blood serum
A and B
IAIB
no antibodies
a person with type O has the ___ antigen on RBC
possible genotypes
antibodies on blood serum
no
ii
anti- A antibodies
anti-B antibodies
Rh factor is determined by
a different gene than the gene for ABO blood type
Rh+
Rh-
Rh antigen in RBC (present)
no Rh antigen on RBC (absent)
a person with Rh+ blood has the ___ antigen on RBC
possible genotypes
antibodies on blood serum
Rh
Rh+Rh+, Rh+Rh-
no antibodies
a person with Rh- blood has the ___ antigen on RBC
possible genotypes
antibodies on blood serum
no Rh
Rh-Rh-
anti-Rh antibodies
during a blood transfusion a person receives
RBC from donated blood
a person can receive blood if a different blood type as long as
the antibodies in his blood serum do not react with the antigens in the RBC of the donated blood
Agglutination
clumping
if a person has antibodies in his serum that react with the antigens on the RBC of the donated blood
anti-A antibody attaches to
anti-Rh antibody attaches to
during agglutination
A antigens
Rh antigen
each anti-A antibody can bind to
2 antigens in incompatible RBC causing cells to clump - lethal
a person with type AB + has the ___ antigen on RBC
possible genotypes
antibodies on blood serum
what type of blood can it receive
A, B, Rh
IAIB, Rh+Rh+
IAIB Rh-Rh-
no antibodies
all blood types=universal receiver
what type of blood can they receive?
no anti-A
no anti-B
no anti Rh-
A
B
Rh+ and Rh-
a person with type O- has the ___ antigen on RBC
possible genotypes
antibodies on blood serum
what blood can they receive?
none= universal donor
ii Rh-Rh-
only O-
autosomes
same between sexes
sex chromosome
pair that determines sex of an individual
X chromosomes vs Y chromosome
X has many genes where y only has a few
human male:
human female:
XY
XX
y is present it is a male
if you see a trait in only one sex it is probably a
X linked trait
heyerozygotes are carriers so
they do it show trait but can pass it on to their offspring
sex linked traits: __=___=___
carrier=heterozygote=female
no allele on which chromosome
Y
recessive traits show up more in what gender
male because the only have one X
dosage compensation
in humans and mammals, only….
the other…
one cope of X chromosome is active
X chromosome is inactivated= Barr body (folded up very tightly to make it inactive)
how is which X chromosome is inactive decided in dosage compensation?
at a certain point in development each cell in the embryo randomly chooses one X chromosome to inactivate. everytime a cell divides, that’s when you get the patch of color
females are ____ in dosage compensation
mosaics: different cells express different genes
tortoiseshell cats have payches of black and orange fur. what is the genotype?
XBXb
XB= all cells derived from this cell have black fur
Xb= all cells derived from this cell have orange fur
after one X chromosome is inactivated, everytime the cell divides…
the same X chromosome remains insctivated -> patches of cells with the same color
what gender is normally tortoiseshell?
female, very rare for males to be but can happen
polygenic inheritance
one trait is caused by several genes
each gene has 2 alleles
contributing alleles have ___ letter
each has a
they are
capital
quantitative effect on trait
additive
polygenic inheritance: skin color
genes for skin color are
which allele makes color?
darker color=
A or a, B or b, C or c
contributing
more contributing alleles the darker the color
polygenic inheritance
all 6 recessive
all 6 contributing
creates a
pale
very dark
characteristic bell shaped curve
polygenic inheritance increases
the chance that a phenotype suited to the environment will be produced
___ interacts with polygenic inheritance to produce ___
examples
environment
many phenotypes
skin color modified by sun exposure
height modified by nutrition
both the genotype and environment affect the ___ in polygenic inheritance
especially ___ can have an extreme effect
example with flowers
phenotype
temperature
Blue flowers- acidic soil
pink flowers- basic or neutral soil
Himalayan rabbits
what?
why?
white fur in body with black fur on extremities (ears, feet, tail)
due to temperature - polygenic inheritance
Ch form of enzyme only functions at low temperatures, unstable at high so body and head don’t make black fur
epistasis
alleles
a gene at one locus interferes with the phenotypic expression of a gene at a different locus
usually a pair of recessive alleles for one gene prevents the expression of the dominant phenotype
genes work ___ or in ___
together
pathway
in epistasis, both genes must produce ___ to see the dominant phenotype
a functional enzyme
genes code for
Enzymes / proteins
epistasis in peas pathways
2 genes required to make purple
enzyme A: precursor (white) -> intermediate (white)
enzyme B: intermediate (white) -> product (purple)
enzyme A in epistasis in peas
produced
functional enzyme
nonfunctional enzyme
by the A gene
AA or Aa
aa
enzyme B in epistasis peas
produced
functional enzyme
nonfunctional enzyme
by the B gene
BB or Bb
bb
epistasis in peas
how to get white flowers?
if either enzyme A or enzyme B is nonfunctional
what are the genotypes of a white flowered pea plant in epistasis
aaBB, aaBb, aabb, AAbb, Aabb, aabb
What are the genotypes of a purple flowered pea plant in epistasis?
need
AABB, AABb, AaBB, AaBb
need functional A and B enzymes
fur color in labs is due to
what are they?
2 genes
epistasis
B gene codes for color of pigment (B= black, b= brown)
E gene codes for how much pigment is put into fur (E= normal amt pigment, e= very little pigment) golden
epistasis in labs
ee =
E_=
golden color regardless of pigment
black or brown color
what genotype will give black puppies?
need in E and B
BBEE, BBEe, BbEE, BbEe
what genotypes will give chocolate puppies?
need one E and bb
bbEE, bbEe
what genotype will give golden puppies?
need ee
BBee, Bbee, bbee
aren’t white so they have a trace amount of color
types of prenatal testing and their definition
amniocentesis: removes amniotic fluid and culture fetal cells (14th - 16th week)
CVS = chronic villi sampling: remove cells of chorionic villi (8th - 10th week)
what is the least common type of prenatal testing?
CVS but it can be done earlier
karyotype
chromosomes are photographed and arranged so homologous chromosomes are paired up
type of chromosomal abnormalities
non disjunction
nondisjunction
inherit an abnormal number of chromosomes
caused by a mistake during meiosis
homologous chromosomes do not separate in meiosis 1
sister chromatids do not separate during meiosis 2
since they don’t separate one cell will get 2 and the other will get nothing
chromosomal abnormalities can get an extra chromosome in
if this fuses with a normal gamete the offspring will have
gametes (n+)
3 copies of one chromosome instead of 2
chromosomal abnormalities can result in the loss of a chromosome in
if this fuses with a normal gamete the offspring will have
gametes (n-1)
1 copy of one chromosome instead of 2
trisomy
3 copies of one particular chromosome
monosomy
1 copy of one particular chromosome
and 2 copies of all other chromosomes
trisomy happens with the
monosomy happens with the
gain of chromosomes
loss of chromosomes
Down syndrome is also called
symptoms
inherited
Trisomy 21
mental retardation, wide flat face, slanting eyelids
extra chromosome usually inherited from mom but can be from dad
chance of having a child with downs increases in moms over
40 years
young moms may still have kids with Down syndrome
Down syndrome: in some cases (5%) a translocation occurs so that
part of chromosome 21 becomes attached to another chromosome
gart gene
causes increased levels of purines in blood, mental impairment
trisomy of other autosomal chromosomes is rare and usually
lethal
trisomy 16
miscarried fetus
triploid
3 copies of every chromosome
3n
disorders caused by an abnormal number of sex chromosomes are
turner syndrome: XO
Klinefelter syndrome: XXY
triple-X: XXX
Jacob syndrome: XYY
Turner syndrome
XO
Only 1 x chromsome
Only females have this
practically normal besides the ovaries can’t make eggs so they are infertile, poor breast development, and rudimentary ovaries
Klinefelter syndrome
XXY or XXXY
has 2 or more X chromosomes
only males because there is a y
with extra X things become more feminized, under developed testes, reduced body and facial hair
development of sex organs will not be made correctly
Triple-O
XXX
only females
appear normal: fertile
may have tendency towards learning disabilities
may have menstrual irregularities
increased risk of having XXX daughters or XXY sons (don’t know they have it until they have kids)
Jacob syndrome
XYY
Taller than average
Persistent acne
tend to have speech and reading problems
only males
current study (no more criminal than general population)
types of chromosome mutations
aneuploidy: change in number of one chromosome (trisomy -Down syndrome, monosomy)
chromosome rearrangement: deletion, other
chromosome rearrangement 2: chromosome deletion
dosage problems:
Loss of a region of DNA
only have 1 copy of some gametes
humans usually need 2 copies for normal development and health
Cri du chat: 5P-
Caused by a deletion j. Short arm of chromosome 5
occurs in 1/20,000-1/50,000
new mutation: no family history
chromosome with deletion usually from dad (80%)
infants make sound like cat meow
small head, wide eyes
Decreased mental capacity
behavioral problems
motor delay
speech problems
some have heart defects
may have difficulty walking and talking
severity of cri du chat depends on
How much of chromosome 5 is deleted
Cri du chat
CTNND2 -> delta care in protein
active in _
in _
communication at _
TERT:
brain development
dendrites and nerves
synapse
Involved in telomere replication
chromosome deletions in humans: William syndrome
look like pixies
poor academic skills
excellent verbal and musical skills
cardiovascular problems
deletion of chromosome 7
autosomal genetic disorders
on autosomes
medical condition inherited from either parent
may be dominant or recessive
Huntington disease
develop several nuerological problems and eventual death
adult onset
develops when person is 40’s or older
may have reproduced before have symptoms of diesease
Huntington is
HH:
Hh:
hh:
Dominant
Huntingtons
huntingtons
normal
Huntington disease is caused by
causes proteins in brain to
progressive
CAG repeats in Huntington protein
clump and nerve cells die
degeneration of brain
types of recessive diseases and definitions
cystic fibrosis: Thick mucus in lungs and digestive tract
tay Sachs: develop neurological problems, seizures, death by 5
phenylketunuria (PKU): can’t metabolize phenylalanine, leads to mental impairment if not detected early and put on special diet
Tay sachs
missing
bulging
symptoms
parents
type
missing lysosomal enzyme
bulging lysosomes in body cells and brain
neurological problems, blind, seizures, death of baby
mom and dad will be normal
autosomal recessive disease
homozygous recessive individuals may
die
heterozygotes appear ___ but ___
normal
are carries for the disease
(sometimes can be an advantage)
balanced polymorphism
heyerzygotes may be protected from a totally different disease
sickle cell anemia caused by
what does it lead to
point mutation in gene for hemoglobin
sickle shape clogs narrow arteries, especially in joints-> poor circulation, anemia, internal hemorrhaging
genetics of sickle cell anemia
Hb^A=
Hb^S=
Hb^AHb^A =
Hb^AHb^S =
Hb^SHb^S=
normal hemoglobin
sickle cell allele
normal (susceptible to malaria)
sickle cell trait (mild symptoms, resistant to malaria)
sickle cell disease (serious, no malaria)
Balanced polymorphism: sickle cell trait is more common __
when malaria parasite infects RBC of individuals with sickle cell trait the cells_
in regions where malaria was prevalent: Africa, parts of Middle East and India
sickle and the malaria parasite can’t survive: heterozygotes are protected from malaria
cystic fibrosis defects in
transport proteins for chloride ions which affects osmosis so thick mucus
pleiotropy: cystic fibrosis
many different symptoms of disease, all caused by same mutant protein found in many tissues
due to mutated CFTR (chloride channel transports cl out of cell)
The CFTR is missing or nonfunctional
very common in people of European descent
carriers 1/25, incidence of disease 1/2500
before 1959 people with this dies by age of 2
Cystic fibrosis and typhoid
typhoid fever is caused by
spread by
binds to
can’t bind to
salmonella typhi
contaminated food and water-> huge epidemics
normal CFTR in intestine and brought into cells as part of the infection process
mutated or absent CFTR in people with cystic fibrosis so heterozygotes are resistant to typhoid
