Sex Linked Drosophilia Flashcards
In the early 20th century, the geneticist ___ used Drosophilia to provide first evidence supporting the chromosome theory of inheritance
Thomas Hunt Morgan
claims that the chromosomes carry genes and that all genes on a chromosome tend to be inherited together
chromosome theory of inheritance
since Morgan’s time, ___ has been used as a model organism in number of experiments
Drosophilia melanogaster
was the first X-linked traits to be identified in Drosophilia
eye color
what chromosome does eye color in Drosophilia attributed in
X chromosome
wild type eye color red
X^W
white eye color drosophilia melanogaster
X^w
males are said to be ___ in sex linked eye trait
hemizygous
term that describes a person who has only one copy of a gene rather than the usual two copies.
hemizygous
are said to be hemizygous, because they have only one allele for any X-linked chracteristic
males
male drosophila genotype can only be
X^WY or X^wY
female drosophila genotype can be
X^WX^W / X^WX^w/ X^wX^w
materials used in sex linked drosophilia experiment
culture and trap bottle
cotton plug
ether
banana and yeast
filter paper
sorting brush
dissecting microscope
test tube
sterilize empty trap bottle using the ___ at 121oC with 15psi for 30 minutes
autoclave
make ___ for these bottles by cutting gauze into squares and fill with cotton balls, make them larger than the bottle opening so the plug will tight fit
cotton plug
peel the ripe ___. mash them until the mixture is ___
bananas
viscous
pour the mashed bananas into the sterilzied trap bottle, about ___ to ___ centimeters thick at the bottom of the bottles
2-3 centimeters
add a drop of yeast suspension to allow ___
fermentation
cut the filter into strips. Hang the strip in the bottle using the cotton plug, this will serve the site for ___of the flies’ progeny
pupation
s the process by which an insect larva transforms into a pupa, and eventually into an adult
pupation
to immobilize the fruit lies, plug the bottle with cotton moistened with ___
ether
Ether immobilizes flies by disrupting their ___ ___ at the cellular level, essentially causing a temporary state of unconsciousness by interfering with the signals that neurons send to muscles, effectively paralyzing them and preventing movement
nervous system
place the immobilize flies in the petri dish and observe the eye color using the ___ ___
dissecting microscope
The female fly may deposit as many as __ to __ eggs per day
50 to 70
will develop after 2 to 3 days after the deposition of 50-70 eggs per day
segmented wormlike larva
optimum temperature for obtaining of F1 progenies
25oC
why is the temperature set at 25oC to obtain the f1 progenies?
stabilize the length of the flies’ life cycle
adult flies will emerge for about ___ to ___ days if kept at optimum temp
10-15
if no larvae appear within __, discard the culture and set up parentals in a fresh culture bottle
5 days
once successful, observe the progenies by transferring the flies into a ___
sterilized empty bottle
plug the empty bottle with cotton moistened ___ to immobilize the flies
ether
give the possible genotypes of the parents and progenies based on the given data:
Red-eyed Female Drosophilia x White-eyed Male Drosophilia
genotype of parental -
Parental Genotypes:
Red-eyed Female (Heterozygous): X^WX^w or X^WX^W
White-eyed Male: X^wY
give the possible genotypes of the parents and progenies based on the given data:
Red-eyed Female Drosophilia (heterozygous) x White-eyed Male Drosophilia
genotype and probability of:
red-eyed male
white eyed female
red eyed male
white eyed female
Possible Progenies and Their Probabilities:
Red-eyed Male: X^WY
Probability: 50%
White-eyed Female: XwXw
Probability: 0% (This genotype is not possible with the given parents)
Red-eyed Female: XWXw
Probability: 50%
White-eyed Female: XwXw
Probability: 50%
give the possible genotypes of the parents and progenies based on the given data:
Red-eyed Female Drosophilia (homozygous) x White-eyed Male Drosophilia
genotype and probability of:
red-eyed male
white eyed female
red eyed male
white eyed female
Based on the Punnett Square:
Red-eyed Male (X^WY): 50% chance.
White-eyed Male (X^wY): 0% chance.
Red-eyed Female (XWXw): 50% chance.
White-eyed Female (XwXw): 0% chance.
give the possible genotypes of the parents and progenies based on the given data:
Red-eyed male Drosophilia x White-eyed female Drosophilia
genotype of parental
male - X^WY
female - X^wX^w
give the possible genotypes of the parents and progenies based on the given data:
Red-eyed male Drosophilia x White-eyed female Drosophilia
genotype and probability of:
red-eyed male
white eyed female
red eyed female
white eyed male
Possible Progenies and Their Probabilities:
Red-eyed Male: X^WY
Probability: 50%
White-eyed Female: XwXw
Probability: 0% (This genotype is not possible with the given parents)
Red-eyed Female: XWXw
Probability: 50%
White-eyed Male: X^wY
Probability: 50%
give the possible genotypes of the parents and progenies based on the given data:
white-eyed male Drosophilia x White-eyed female Drosophilia
genotype and probability of:
red-eyed male
white eyed female
red eyed female
white eyed male
Parental Genotypes:
White-eyed Male: X^wY
White-eyed Female: XwXw
Possible Progenies and Their Probabilities:
Red-eyed Male: X^WY
Probability: 0% (This genotype is not possible with the given parents)
White-eyed Female: XwXw
Probability: 50%
Red-eyed Female: XWXw
Probability: 0% (This genotype is not possible with the given parents)
White-eyed Male: X^wY
Probability: 50%
what is the mode of inheritance manifested in crosses for Drosophilia eye color?
The mode of inheritance for eye color in Drosophila (fruit flies) is sex-linked inheritance, specifically X-linked inheritance.
In cats, the gene for coat color is sex-linked. YY gives yellow color and yy gives black, but the heterozygote has a peculiar combination of yellow and black, a condition known as tortoise shell. SHow the types of offspring expected from a cross between tortoise-shell female and yellow male.
Parental Genotypes:
Tortoise-shell Female (heterozygous): XYXy
Yellow Male: X^YY
Possible Progenies and Their Probabilities:
Yellow Male: X^YY
Probability: 25%
Black Male: X^yY
Probability: 25%
Yellow Female: XYXY
Probability: 25%
Tortoise-shell Female: XYXy
Probability: 25%
Earl has normal color vision while his wife emma is colorblind. Colorblindness is an X-linked trait, and the normal allele is dominant to the colorblindness allele. If they have a large family in what ways should the colorblindness affect their children?
Parental Genotypes:
Earl (normal vision): X^NY
Emma (colorblind): XnXn
Possible Progenies and Their Probabilities:
Since Earl’s Y chromosome determines the sex of the children, we need to consider both sons and daughters separately.
Sons:
Each son inherits the Y chromosome from Earl and one X chromosome from Emma (X^n).
Genotype of Sons: X^nY (colorblind)
Probability: 100%
Daughters:
Each daughter inherits one X chromosome from Earl (X^N) and one X chromosome from Emma (X^n).
Genotype of Daughters: XNXn (normal vision carrier)
Probability: 100%
Summary of Offspring:
All Sons: X^nY (colorblind) - 100%
All Daughters: XNXn (normal vision carriers) - 100%
Implications:
Sons: All sons will be colorblind because they inherit the X^n chromosome from their mother and a Y chromosome from their father.
Daughters: All daughters will have normal vision but will be carriers of the colorblindness gene (XNXn). This means they can pass the colorblindness allele to their offspring.
refers to the association of certain traits with sex chromosomes (X and Y)
sex linkage
In
humans, for example, females typically have what chromosomes
X X
male chromosome
XY
traits linked to XX and XY chromosomes are called
sex-linked traits
X-linked traits example
red-green color blindness and hemophilia
meaning the genes
responsible for these conditions are located on the X chromosome
x linked traits
. Since males have only one X
chromosome, they are more likely to express these traits if the gene is present
x linked traits
s a rare disorder in which the blood doesn’t clot in the typical way because it doesn’t have enough blood-clotting proteins (clotting factors).
hemophilia
Females, on the
other hand, would need __ copies of the gene (one on each X chromosome) to express the
trait
two
Genes located on the X chromosome are called
x-linked genes
Because males have only one X chromosome, they are considered ___
for these genes
hemizygous
3 This means they only have one copy of each X-linked gene
hemizygous
The inheritance of X-linked traits differs from ___traits.7
autosomal
9where the phenotypes of the parents are switched) will
produce different results.
reciprocal crosses
___have been a very important model organism in genetics, and the
work done with sex linked traits in them, helped to create a large portion of
our understanding of genetics.8
drosophilia
o A single copy of the mutated gene is sufficient to cause the disorder.
autosomal dominant
Affected individuals usually have at least one affected parent, The trait appears in every generation.
autosomal dominant
example of autosomal dominant
huntington’s disease
marfan syndrome
Two copies of the mutated gene are required to cause the disorder.
autosomal recessive
o Affected individuals often have unaffected parents who are carriers.
o The trait may skip generations.
autosomal recessive
exampel of autosomal recessive
cystic fibrosis
sicke cell anemia
The mutated gene is located on the X chromosome
x-linked dominant
A single copy of the mutated gene is sufficient to cause the disorder in both
males and females.
x-linked dominant
o Affected males pass the trait to all their ___, but not to their ___.
x-linked dominant
daughter
sons
x-linked dominant
o Affected ___can pass the trait to both sons and daughters.
females
o The mutated gene is located on the X chromosome.
x-linked recessive
o Males are more frequently affected because they have only one X
chromosome.
x-linked recessive
o Females can be carriers without showing symptoms.1
x-linked recessive
Affected males pass the mutated gene to all their ___, who will be
___
daughters
carriers
example of x-linked recessive diseases
Hemophilia, Duchenne muscular dystrophy.
o Mitochondrial DNA is inherited from the mother.
mitochondrial inheritance
o Mitochondrial DNA is inherited from the ___.
mother
o All offspring of an affected female will inherit the trait.
mitochondrial inheritance
o Affected males do not pass the trait to their offspring.
mitochondrial inheritance
Many traits are influenced by multiple genes and environmental factors.
complex inheritance
o These traits do not follow simple Mendelian inheritance patterns.
complex inheritance
example of complex inheritance disease
heart disease
diabetes
analyzing data can be done using (3)
- Pedigree Analysis:
- Genetic Testing:
- Statistical Analysis:
o Creating a family tree to visualize the inheritance of a trait
o Symbols are used to represent individuals and their phenotypes.
pedigree analysis
o Analyzing DNA to identify specific gene mutations.
o Can confirm diagnoses and identify carriers.
what analysis of data
genetic testing
o Using statistical methods to analyze large datasets of genetic information.
o Can identify associations between genes and traits.
what analysis of data
statistical analysis
: The proportion of individuals with a mutated gene who exhibit the
associated trait.
penantrance
The degree to which a trait is expressed in an individual
expressivity
Environmental factors can interact with genes to influence
phenotype
environmental influence
This condition affects the ability to distinguish between red and green hues and is more
common in males due to its X-linked recessive inheritance pattern.
red green color blindness
A blood-clotting disorder where individuals have trouble forming clots, leading to excessive
bleeding. Hemophilia A and B are both associated with mutations on the X chromosome.
hemophilia
A severe muscular disorder characterized by progressive muscle weakness, caused by
mutations in the dystrophin gene located on the X chromosome.
duchenne muscular dystrophy (DMD)
This enzyme deficiency can lead to episodes of anemia, especially when triggered by certain
foods, medications, or infections. The responsible gene is found on the X chromosome
G6PD Deficiency
: Since males have only one X chromosome, if that chromosome carries a
recessive gene for a particular trait (e.g., red-green color blindness), the male will express the
trait. There is no corresponding gene on the Y chromosome to mask the effect.
x-linked recessive trat
Females need two copies of the recessive gene (one on each X
chromosome) to express the trait. If they have only one copy, they become carriers—meaning
they don’t show the trait but can pass it on to their offspring.
x-linked recessive trait
Males only need one copy of the dominant gene on their single X chromosome to
express the trait.
x-linked dominant trait
Females also require just one copy of the dominant gene to show the trait, but
because they have two X chromosomes, they are more likely to inherit the condition than
males.
x-linked dominant trait
example of x-linked recessive condition
hemophilia
is an X-linked dominant condition that primarily affects females.
Males with this mutation rarely survive infancy.
rett syndrome
While rare, _-linked traits are passed from father to son since only males inherit the Y
chromosome.
Y-linked triats
- The mother is a carrier for red-green color blindness (X\X).
- One of her X chromosomes has the gene for color blindness (X), and the other is normal (X).
- The father does not have color blindness (XY).
give the results
- XX (Normal Female): 25% chance.
- X\X (Carrier Female): 25% chance. These females don’t exhibit color blindness but can pass on
the gene. - XY (Normal Male): 25% chance.
- X\Y (Color Blind Male): 25% chance. These males will have red-green color blindness.
Interpretation - Sons have a 50% chance of being normal and a 50% chance of being color blind.
- Daughters have a 50% chance of being carriers and a 50% chance of being unaffected.
The sex of an individual is determined by
the sex chromosomes contributed to the
zygote by the sperm and the egg
sex determination
An egg can donate an __
X
A sperm can donate an
X or Y
Therefore the ___determines the sex
of a child
sperm
Some traits are
located on the
___
chromosomes,
so the
inheritance of
these traits
depends on the
sex of the parent
carrying the trait.
sex
Most known sexlinked traits are
__-linked (carried
on the X
chromosome)
X
This is probably
because the X
chromosome is
much ___than
the Y chromosome
larger
Some sex-linked traits are associated
with disorders.
* Most are found on the __chromosome,
__-linked disorders are rare.
X
Y
___are at a much greater risk for
inheriting sex-disorders because they
only inherit one X, so if the X has the
allele for the disorder, they will suffer
from the disorder.
Male
_____ X-linked traits result
in death.
recessive lethal
pointed end
male or female?
female
blunt end, darker at the back
male or female?
male
larger fruit fly
male or female?
female
smaller fruit fly
male or female?
male
has more stripes
male or female
female
less stripes
male or female
male
___ on
the tarsus of a
fore leg of a male drosophilia
sex comb
sex comb on
the ___of a
fore leg
tarsus
sex comb on
the tarsus of a
___leg
fore
s a male-specific group of bristles located on the foreleg of many species in the family Drosophilidae
sex comb
discovered sex-linked
genes while studying eye
color in fruit flies
thomas morgan
__eyes are rare in
fruit flies
white
P Phenotypes
Wild type (red-eyed) female x White-eyed male
F1 phenotypes are __
all red eyed.
a cross between f1 flies (all red) should give us
A cross between the F1 flies should give us: 3 red
eye : 1 white eye
