Lab Exam 2 Flashcards
What pigments are required for wild type eye colour?
All of them:
no mutations
Pteridine AND ommochroome pigments
What pigments and mutations cause the brown eye colour?
Brown gene mutation inhibits Pteridine pathway:
only ommochrome pigment
What pigments and mutations cause the white eye colour?
No pigments are present because,
a mutation in the white gene impairs the transport of both precursor molecules
therefore both the pteridine pathway and the ommochrome pathway are inhibited
What pigments and mutations cause the scarlet eye colour?
Scarlet gene mutation inhibits the ommochrome pathway
so all the pigments of the pteridine pathway create this eye colour
What pigments and mutations cause the sepia eye colour?
Only the drosopterin pigment is absent
the mutation takes place in the specific area of the pigment in the pteridine pathway
How are the Pteridine pigments arranged in order of migration on the chromatogram?
Top:
yellow (Isosepiaterin and Sepiapterin)
Blue (Biopterin and 2-amino-4-hydroxypteridine)
Green-blue (Xanthopterin)
Violet-blue (Isoxanthopterin)
Orange (Drosopterins)
Bottom:
You Better Go Vote Opposition
What is the order of epistatic hierarchy for eye colour?
(1) Wild-type
(2) White
(3) Scarlet
(4) Brown
(5) Sepia
What is an alternative way to have white-eyed offspring, other than a mutation in the white gene?
White eyes can also result by crossing brown and scarlet eyed flies
(when both mutant alleles are present)
What are the two main reasons the observed segregation does not match those predicted based on Mendel’s Laws?
(1) the differences are due to random chance alone
(2) the initial assumption to calculate the expected frequencies is invalid
What is the X^2 formula?
First find the observed and then the expected values (punnet square)
Then do the formula for each and add together
find the Critical value and compare to the calculated X^2
How do you interpret the results of a chi-squared test?
Degrees of freedom (df) = # of phenotypic classes - 1
oc= 0.05
If the calculated X^2 value is larger than the value from the table, then you reject the null hypothesis
Can you see the difference between wild-type and scarlet flies on the chromatography plate?
No, because this test does not show the ommochrome pigment
Both eye colours contain all the pigments of the pteridine pathway and so they appear the same
Can you see the difference between brown and white eyed flies on the chromatography plate?
No, both of the colours lack all the pigments of the pteridine pathway
How do you tell the difference between sepia and scarlet on the chromatography plate?
Sepia lacks the drosopteria pigment while scarlet has all the pteridine pathway pigments
The highest observed phenotype is the _________ recombinant and the lowest is the _______ recombinant. The remaining are ________ recombinant.
The highest observed phenotype is the PARENTAL recombinant and the lowest is the DOUBLE recombinant. The remaining are SINGLE recombinant.
How do you determine gene order of a trihybrid cross?
The two alleles that remain the same as in the parental recombinants in the double recombinant genotype are on the outside. The gene that changes from the parental is in the middle.
How do you calculate genetic distance?
(1) First two genes in the order: add the amounts everytime they differ from parental then divide by total and times by 100
(2) Do the same for the middle and last gene in the order
(3) now do this for the first and last but, add the double recombinant numbers multiplied by two
How do you determine the Coincidence and Interference?
In the white-1
mutation (w), the transcription is disrupted,
and the white protein is not produced. Hence,
because white does not partner with brown and
scarlet, the eye cells are unable to uptake
pigment precursors, causing the white-eye
phenotype (absence of pigmentation).
How does this occur?
Further molecular studies on the white-1 mutation
indicated that an insertion of a Doc-retroposon
(4,700 bp) in the promoter region resulted in its
inactivation, and thus, the disruption of
transcription.
What is the Polymerase Chain Reaction (PCR) test?
a unique molecular biology technique to make
multiple copies of a desired piece of double
stranded DNA in a test tube. This technique is
known as the Polymerase Chain Reaction and is
based on the natural process of DNA
replication.
What are the three main steps of a PCR test?
Denaturation, annealing, and extension
What does the process of PCR look like?
How is the DNA of wild-type and mutant flies determined through PCR?
specific primers bind to the promoter region on both, wild type and mutant flies
For instance, the combination of primer 1 and primer 3 are specific to the wild-type and will produce a 467 bp DNA fragment (active w+ allele). The combination of primer 2 and primer 3 will produce a 704 bp fragment specific to the doc-retroposon (non-active allele).
What is DNA gel electrophorasis?
the separation of molecules based on their size using their attraction to an electrical charge
Note that DNA is negatively charged due to phosphate groups
Review the last lab
