EXAM 1 - Genetics Lab

A female fly who carries recessive mini wing size allele (XMXm) is crossed to a mini wing size male (XmY). What portion of the male progeny have mini wings?

Progeny: XmXM XmXm XMY XmY 50% of males have mini wings

If you need a peer reviewed source that analyzes/summarizes the current understanding/state of a research topic, you would look for a ____ article.

Review article (a secondary source)

Chromatids are separated from each other

Sister chromatids separate in Mitosis and Meiosis II

Alfred Sturtevant provided genetic evidence for the existence of 4 chromosome pairs in flies in which ways?

- Constructed a gene map using crossing over frequencies - Drosophila genes cluster into 4 distinct groups of linked genes

Which of the following is not a possible phenotypic class of F1 progeny from marker discriminant cross 1?

- DC1 = determine dom/rec and auto/sex-linked - DC2 = which chromosome gene is on WONT HAPPEN: - all female show mutant - no males show mutant if mutant is dominant: - all progeny show mutant phenotype if mutant is autosomal (chrom. 2,3,4) recessive: - none show mutant phenotype if sex-linked (chrom. 1) recessive: - no females show mutant phenotype - all males show mutant phenotype

Which of the following can increase the rate of mitotic recombination in flies?

- DNA damage - x-ray treatment

What development stage of flies does the initiation of tissue fate segregation take place in the eye-antenna imaginal disc?

- Pupal/ - after 3rd larval stage, pupa undergo metamorph and group of cells called imaginal discs differentiate into adult fly structures

What is transdetermination?

- a process where determines disc cells change fate to that of another disc identity -when a tissue changes from one state into another (ex: fly stem cells called imaginal discs)

What should you do to avoid plagiarism?

- cite sources - summarize (do not copy or quote)

Herman J. Muller, student of Morgan, classified fly mutants based on their phenotypes. Which of the following describes a mutant with a novel/new function?

- gain-of-function? - zebrafish/scarb2a? - distinct genetic alteration - meaning complete new mutation, not just differ variation of one that exists

Independent assortment of chromosomes is a result of

- homologous chromosomes lining up at metaphase plate during Meiosis metaphase I (Law of segregation = anaphase I) (Crossing over = prophase I) - independent assortment = alleles of one gene separate independently of another gene's alleles

If a single nondisjunction event occurs in meiosis II during gamete formation, what will be the result in the completion of meiosis?

- nondisjunction = chromosomes fail to separate properly during cell division If occurs in Meiosis II: - sister chromatids don't separate - 2 = n - 1 = n+1 chromosomes - 1 = n-1 If occurs in Meiosis I: - homologous chromosomes don't separate - all n+1 or n-1

Why are armadillos excellent orgs to study environmental factors on the phenotypic range of gene expression?

- single fertilized egg splits in half, and in half - all 4 are genetically identical - nine banded armadillos almost always give birth to 4 offspring that are genetically identical quadruplets

Flies are incubated at 18C to...

- slow down development - remain virgins for longer

Syntenic genes can assort independently when

- they are far apart on a chromosome and crossing over occurs frequently between the genes - if genes are too close, they will likely display genetic linkage and not assort independently

Using pea plants (Pisum sativum), Mendel performed experiments that led to the discovery of the nature of inheritance. What biological characteristic of flies allowed Thomas Hunt Morgan to discover the chromosomal basis of inheritance that likely couldn't have been found in peas?

- white eyes in fruit flies were x-linked and did not follow mendelian form F2 = all white male, no white female - first person to link the inheritance of a specific trait with a particular chromosome

What does a discriminant cross determine?

-whether a mutant is dominant or recessive to the wild-type - genes that are on the same chromosome are usually inherited together, while genes located on different chromosomes are usually not inherited together

How many pupal stages do flies go through?

15

How many unique gametes could be produced through independent assortment by an individual with the genotype aaBBccDdeeFF?

2 (2^n, with n=1 here)

Individual fly progeny that bear clones of genetically altered somatic cells are called ___.

?

The vestigial (vg) gene plays a critical role in flies' wing development. Flies that are vg/vg (homozygous for the mutant) show a different number of egg strings in ovaries, variation in bristle position on the scutellum, and shorter life. This is an example of

? - lethal homozygous allele - maintained using balancers to keep recessive alleles to maintain heterozygosity

Which of the following is not an acceptable reference source?

? - non-peer-reviewed material, blogs, unsourced

In "Drosophila increase exploration after visually detecting predators", the author uses mutants to determine how flies detect predators. Which mutant is correctly matched to its phenotype?

? - orco^2 = loss of function of odor receptor (can't smell) - norpA^7 = loss of light photo receptor (completely blind) - w^1118 = loss of function shielding for eye pigment (loss of visual acuity)

In "There are many ways to train a fly", the author focusses on olfactory learning. As described in the paper, what type of learning is olfactory learning?

? Associative conditioning

In "The Genetics of Drosophila transgenics", the author describes the GAL4/UAS system. What is the GAL4/UAS system used for?

? Used to induce or knock out expression of fly genes

Flies have homologs for the following mammalian proteins or peptides, except ___.

? flies have similarity to mice and humans

Which is true about chi-square tests?

AKA goodness of fit test - determines whether observed frequency differs from expected statistically significantly - meaning, is the difference merely by chance? - becomes more accurate as degree of freedom (count) gets larger - p = 0.05 --> p>0.05 is by chance - does not "prove" hypothesis: "Fail to reject or reject" hypothesis - null hyp = is caused by chance - high probability assumes that chance alone produced the difference between observed and expected

What is the central dogma of biology?

DNA --> transcription --> RNA --> translation -->protein

What is the mode of chromosomal inheritance in the marker dominant cross 1?

Determines if allele is dominant or recessive to the wild type

After scoring the phenotypes of marker discriminant cross 1 progeny, a mutant allele is determined to be dominant. What is the correct set up for marker discriminant cross 2?

Discriminant (Double Balancer) Cross 1 = female (f/f) x male (Cy/Pm; D/Sb) DC2: if dominant mutant: female (+/+) x male (F1 (from cross 1)) if recessive mutant: female (f/f) x male (f1 (from cross 1))

T/F: male and female flies use chromosomal recombination during gamete formation (meiosis)

F - only females exhibit recombination

Syntenic genes

Genes on the same chromosome

A gene has 2 alleles that are incompletely dominant (C1 and C2). What will be the resulting phenotypic ratio of a heterozygotic (C1C2 v. C1C2) self-cross?

Incomplete dominance results in 1:2:1 phenotypic ratio

For which of the following reasons did Thomas Hunt Morgan question the validity of Mendel's work with pea plant inheritance?

P = red female x white male F1 = all red F2 = (Mendel said 3:1 in pea plants) Strangely, all of Morgan's white-eyed F2s were male (like their grandfather), but there were no white females! - This was the first non-sexual trait that was sex-linked - chromosomes as the basis of inheritance - Mendel choose some genes that were on difference chromosomes, and they were too far away to detect linkage

A female fly who carries recessive stubby wing shape allele (XSXs) is crossed with a male fly who is wild type (XSY). What portion of male progeny will have stubby wings?

Progeny: XSXS XSXs XSY XsY 50% males have stubby wings

"Which of the following is not true about balancer chromosomes?" What are balancer chromosomes?

What we know about about balancers: - contain at least one dom allele and several rec mutant alleles - exist for all drosophila chromosomes except Y -used to maintain fly stocks - carry many inversions (gene positions significantly rearranged) - separate normally in meiosis - suppress recombination (any recombination that does occur is lethal, aneuploidy) to maintain heterozygosity - are lethal in homozygosis - eliminate all genotypes different than parental combination - carry recessive mutations that cause female sterility in homo - present dominant and recessive marker mutations for tracking mutated chromosomes in forward genetics - make sure recessive mutant allele of interest is always kept over dominant marked balancers - maintain recessive lethal mutation of interest - present recombination between difference alleles of genes - no balancers on 4th chromosome since it doesn't have recombination F = first chromosome S = second chromosome T = third chromosome M = multiple inversions # = number for diff. balancers on same chromosome 2nd;3rd = Cy/Pm; D/Sb Cy = curly Pm = plum colored eyes D = dicheate, wings out 45 degrees from body Sb = short, stubble bristles

What is penetrance?

Whether or not a genotype consistently produces the same phenotype (percent of population with expected phenotype from the genotype) - complete penetrance = genotype consistently produces same phenotype - incomplete penetrance = (less than 100% penetrance) same genotype doesn't always produce same phenotype

What is epistasis?

multiple genes determine the phenotype ex: multi-step pathway

How many days are required for a fly embryo to become an adult?

~10 embryo = 1 1st instar/larva = 1 2nd instar;larva = 1 3rd instar/larva = 3 pupa = 4