Genetics Exam 1

In species in which females are the homogametic sex, gender of offspring is determined by the male.

True

A female with androgen insensitivity may have XY sex chromosomes rather
than XX.

True

Species in which individuals have only male or only female reproductive
structures are called dioecious.

True

Red-green color blindness is X-linked recessive. A woman with normal color
vision has a father who is color blind. The woman has a child with a man with
normal color vision. Which phenotype is NOT expected?
A. a color blind female
B. a color blind male
C.

A. a color blind female

If a female Drosophila that is heterozygous for a recessive X-linked mutation is crossed to a wild-type male, what proportion of female progeny will have the
mutant phenotype?
A. 100% B. 0% C. 33% D. 25%

B. 0%

In a germ-line cell from a female grasshopper (XX-XO sex determination system), when do the homologous X chromosomes segregate?
A. during mitosis
B. during meiosis I, anaphase
C. during meiosis II, anaphase
D. they do not segregate; gametes contain a copy

B. during meiosis I, anaphase
[NOTE] also, in germ-line cell from a human male that is dividing, X and Y chromosomes segregate during anaphase

A eukaryotic diploid cell from an organism with the ZZ-ZW sex determination system has two pairs of autosomes and a pair of sex chromosomes, Z and W, shown below. A cell from this individual begins to go through meiosis. As it goes through meiosis II, it

D. a pair of sister chromatids with a allele, a pair of sister chromatids with B allele, a pair of sister chromatids W

A eukaryotic diploid cell from an organism with the ZZ-ZW sex determination system has two pairs of autosomes and a pair of sex chromosomes, Z and W, shown below.
Assume A and B are dominant alleles. If this individual were crossed to an individual of gen

D. 9/32

A eukaryotic diploid cell from an organism with the XX-XO sex determination system has two pairs of autosomes and one X chromosome, shown below.
A cell from this individual begins to go through meiosis. When the cell reaches meiosis II, it becomes two cel

C. a pair of sister chromatids with A allele, a pair of sister chromatids with B allele
and
D. a pair of sister chromatids with a allele, a pair of sister chromatids with B allele, a pair of sister chromatids X

A eukaryotic diploid cell from an organism with the XX-XO sex determination
system has two pairs of autosomes and one X chromosome, shown below. What is the probability of a gamete from this individual having the following genotype: alleles A and b, chrom

d. 1/8

Which of the following human genotypes is associated with Klinefelter
syndrome?
A. XXY
B. XXYY
C. XXXY
D. all of the above
E. none of the above

D. all of the above

A Barr body is a(n)

inactivated X chromosome, visible in the nucleus of a cell that is from a female mammal.

If a male bird that is heterozygous for a recessive Z-linked mutation is
crossed to a wild type female, what proportion of the progeny will be mutant
males?
A. 0%
B. 100%
C. 75%
D. 50%
E. 25%

A. 0%

List three dosage compensation strategies for equalizing the amount of sex
chromosome gene products.

1. Inactivation of one sex chromosome in the homogametic sex
2. Halving the activity of genes on both sex chromosomes in the homogametic sex
3. Increasing the activity of genes on the sex chromosome in the heterogametic sex

List six different sex determination systems and a representative organism for
each.
A. XX-XO
B. XX-XY
C. ZZ-ZW
D. Haplodiploidy
E. Geneic balance
F. Environmental

A. XX-XO = grasshopper
B. XX-XY = human
C. ZZ-ZW = birds
D. Haplodiploidy = bees
E. Genic balance = drosophila
F. Environmental = many turtles, mollusks, crocodiles, reptiles

List different mechanisms for generating sexes in dioecious species (organism has either male or female reproductive structures, but not both).

1. Chromosomal sex determination (XX-XO, XX-XY, or ZZ-ZW)
2. Haplodiploidy
3. Genetic sex determination
4. Environmental sex determination

Species in which sex is determined by number of chromosome sets�males are haploid, females are diploid, are __________.

Haplodiploid

Human males, with XY chromosomes are ____________ and produce two different kinds of gametes, while females with XX chromosomes are ______________ and produce only one kind.

heterogametic, homogametic

In humans, the presence of the SRY gene, normally on Y, determines maleness. In Drosophila, an X: A (autosome) ratio of 0.5 determines maleness. Explain the genders of human and Drosophila XXY individuals.

An XXY human is male. The SRY on the Y chromosome determines maleness, in spite of the two X chromosomes. An XXY Drosophila is female. Drosophila is diploid, so there are two of each autosome. If there are two X chromosomes, the X:A ratio is 1.0, which is

In humans, the presence of the SRY gene, normally on Y, determines maleness. In Drosophila, an X: A (autosome) ratio of 0.5 determines maleness. Explain the genders of human and Drosophila XO individuals

An XY human is female. In the absence of SRY from a Y chromosome, the person will develop as a female, in spite of having only one X chromosome. An XO Drosophila is male. Drosophila is diploid, so there are two of each autosome. If there is a single X chr

what will be the phenotypic sex of a human with the following gene or chromosomes or both?
A. XY with SRY gene deleted
B. XY with the SRY gene located on an autosomal chromosome
C. XX with a copy of SRY gene on an autosomal chromosome

A. XY with SRY gene deleted-FEMALE
B. XY with the SRY gene located on an autosomal chromosome-MALE
C. XX with a copy of SRY gene on an autosomal chromosome-MALE

what will be the phenotypic sex of a human with the following gene or chromosomes or both?
D. XO with a copy of SRY gene on an autosome
E. XXY with the SRY gene deleted
F. XXYY with one copy of the SRY gene deleted

D. XO with a copy of SRY gene on an autosome-MALE
E. XXY with the SRY gene deleted-FEMALE
F. XXYY with one copy of the SRY gene deleted-MALE

The cross AABB x aabb is made, and the F1 (AaBb) is back-crossed to the double recessive (aabb) parent. If these two loci are 20 centimorgans apart (i.e., r = 0.20), what is the expected frequency of AaBb in the resulting progeny?
A. 10%
B. 20%
C. 40%
D.

C. 40 %
- 1 map unit (centimorgan) = 1% recombination i.e. 20% for this cross
- since the two genes are linked F1 is AB/ab, ab is one of the parental classes (AB is the other) than progeny AaBb should be (1/2) of the total parentals
i.e. 20% recombiants =

The trait represented by the filled symbols in the pedigree below is a rare inherited trait with complete penetrance. What mode of inheritance does the pedigree suggest?
A. autosomal dominant
B. X-linked
C. Y-linked
D. autosomal recessive
E. mitochondrial

D. Autosomal recessive
- Typically appear with equal frequency in both sexes and tend to skip generations. When both parents are heterozygous for a particular autosomal recessive trait, ~ 1/4 of their offspring will have the trait
-More likely to appear i

What is an allele?
A. the position that a gene occupies on a chromosome
B. one possible form of a gene at a locus
C. the part of the chromosome that holds the chromatids together
D. the smallest unit of inheritance of a single characteristic
E. the geneti

B. one possible form of a gene at a locus
[NOTE] allele frequency = proportion of specific allele in population

Assuming a 50:50 expected sex ratio, what is the probability of having four children of the same sex?
A. 1/2
B. 1/4
C. 1/8
D. 1/16
E. 1/32

C. 1/8

When we test for linkage between two genes the null model we use in our analyses is based on which of the following:
A. principal of Hellgate High School
B. principle of dominance
C. principle of submission
D. principle of independent assortment
E princip

D. principle of independent assortment
(if two genes are linked because of their location on a chromosome, their alleles will not segregate independently during gamete formation, AND, phenotypic ratio will show higher numbers of offspring with the parenta

Meiosis
A. produces four identical haploid gametes
B. prevents pairing of newly replicated homologues
C. requires two rounds of DNA replication and two rounds of cell division
D. involves one round of DNA replication and two rounds of cell division
E. ens

D. involves one round of DNA replication and two rounds of cell division

Which of the following procedures is used to produce a genetic map of a eukaryotic chromosome?
A. hybridizing fluorescently-tagged genes to whole chromosomes, then observing which chromosomes light up under the microscope (FISH)
B. test-crossing genetic m

B. test-crossing genetic markers to determine their relative distances in cM
(recombination rates used to determine relative order of genes and distances between them on a chromosome, maps based on recombination rates = genetic maps constructed from a ser

Quantitative trait mapping is a technique used to identify the multiple loci that act additively to produce a range of phenotypes.
A. Give an example of a "quantitative trait."
B. QTL mapping requires having 2 tools in hand, one phenotypic, another
molecu

A. Height
B. Phenotypic: Need strains that differ genetically with respect to the trait of interest
Molecular genetic: Require an ordered set of genetic markers such as SNPs, RFLPs, simple sequence repeats, and or transposable elements that distinguish th

Explain how one can experimentally define a "gene" using the principle of
complementation.

A gene can be defined experimentally as a set of mutant alleles that make up one complementation group. Any pair of mutant alleles in such a group fail to complement one another when placed into the same background using heterokaryons (Neurospora), diploi

Match phenomena with the type of extension of Mendelian inheritance they exemplify.
Cross of yellow/agouti heterozygotes (Dd x Dd) produces 2:1 yellow:agouti

Lethal alleles
(causes the death of organism, early in development, not present in progeny of genetic cross --> Recessive lethal: kill individuals homozygous for the allele Dominant lethal: kills both hetero and homo)

Match phenomena with the type of extension of Mendelian inheritance they exemplify.
Mutations in phenylalanine hydroxylase (PAH) can impair cognition, and reduce skin and hair pigmentation

I. Pleiotropy (a single genotype influences multiple phenotypes)

Match phenomena with the type of extension of Mendelian inheritance they exemplify.
A cross of true-breeding red x true-breeding white Four o' clocks produces all pink flowers in the F1

D. Incomplete dominance
(phenotype of a heterozygote that is intermediate between the phenotypes of the two homozygotes)

Match phenomena with the type of extension of Mendelian inheritance they exemplify.
The blood phenotype an individual who is genetically I^A I^B is AB the "universal recipient

C. Codominance
(allelic interaction in which the heterozygote simultaneously expresses traits of both homozygotes)

Match phenomena with the type of extension of Mendelian inheritance they exemplify.
In wild sweet pea purple flowers can result from the mating of white flowered parents

F. Epistasis
(gene interaction in which a gene at one locus masks or suppresses the effects of a gene at a different locus)

Base substitutions in coding regions that result in changed amino acids are called
A. Conditional mutations
B. Transversions
C. Missense mutations
D. Nonsense mutations
E. Silent mutations

C. Missense mutations
(alters a codon in mRNA resulting in different amino acid in the protein encoded)

T to C or A to G mutations are:
A. Transition mutations
B. Transversion mutations
C. Translation mutations
D. Transcription mutations
E. Conditional mutations

A. Transition mutations
(base substitutions in which a purine is replaced by a different purine or pyrimidine)

Ultraviolet light primarily damages DNA by:
A. Forming pyrimidine dimers
B. Forming purine dimers
C. Alkylating DNA
D. Depurinating DNA

A. Forming pyrimidine dimers
(structure in which a bond forms between two adjacent pyrimidine molecules on same DNA strand; disrupts H-bonding between complementary bases, distorts normal DNA configuration

A chromosome in which linear order of a group of genes is the reverse of normal order has a(n):
A. Duplication
B. Deletion
C. Inversion
D. Translocation
E. Position effect variegation

C. Inversion
(sequences on same strand, inverted and complementary)

Some XY individuals are phenotypically females. What chromosomal abnormality could account for this?
A. Mosaicism
B. Dosage compensation
C. A deletion of the portion of the Y chromosome containing the testis-determining factor
D. Mitotic segregation
E. Fr

C. A deletion of the portion of the Y chromosome containing the testis-determining factor

The genomic DNA of an organism has a base composition of 20% C-G base pairs and 80% A-T base pairs. Assuming a random sequence of bases, what is the expected frequency of the Tsp E1 restriction sites 5'-CCGG-3'?
A. (0.1)^4
B. (0.1)^2
C. (0.2)^4
D. 4 � (0.

A. (0.1)^4
- 20% C-G base pair
- Tsp E1 5'-CCGG-3', 4 base pairs assuming random 50% expected frequency i.e. 20% x (1/2) = 10% = 0.10
- restriction site has 4 bases (0.10)^4

Each new DNA strand is initiated by a:
A. Short RNA primer
B. Single-stranded DNA-binding protein
C. Precursor fragment
D. Restriction fragment
E. Specific DNA primer

A. Short RNA primer
(chemically synthesized oligonucleotides, with a length of about twenty bases. They are hybridized to a target DNA, which is then copied by the polymerase)

What is the base sequence of a DNA strand that is complementary to 5'-ATCGGATTC-3'
sequence?
A. 5'-ATCGGATTC-3'
B. 5'-CTTAGGCTA-3'
C. 5'-GAATCCGAT-3'
D. 5'-TAGCCTAAG-3'

C. 5'-GAATCCGAT-3'
- reverse sequence 5'-ATCGGATTC-3' and complement C to G and T to A then reverse 5' and 3 ' on the complementary strand:
[Old] 3'-CTTAGGCTA-5'
[New] 5'-GAATCCGAT-3'

If guanine makes up 23% of the nucleotides in a sample of DNA, then thymine would make up
what percentage of the bases?
A. 15%
B. 22%
C. 27%
D. 30%
E. 40%

C. 27%

All of the following may result from promoter mutations, except:
A. Decreased affinity for RNA polymerase
B. Increased affinity for RNA polymerase
C. Mutant RNA polymerase
D. Unregulated transcription
E. A new phenotype

C. Mutant RNA polymerase
(promoter mutations = can either turn the gene on constitutively, resulting in overexpression or inappropriate expression of the gene, or it can silence the gene, resulting in a loss of function)

_______________ transcribes all protein-coding genes as well as the genes for small nuclear RNAs

RNA polymerase II
(mRNA, sRNA, miRNA)

Conditional mutations

Mutations whose effects can be turned on or off at will are called ___________.

The molecular basis of the fragile-X chromosome has been traced to an ____________ of the 5'-GGC-3' present in the DNA at the site where the breakage takes place.

Expansion

In most organisms, a mechanism of ________________ has evolved in which the unequal dosage in the sexes is corrected either by increasing the activity of genes in the X chromosome in males or by reducing the activity of genes in the X chromosome in female

Dosage compensation

Genes that do not undergo independent assortment but are transmitted together are said to be ____________.

Linked

Recombination/crossing over

The physical exchange of segments between homologous chromosomes is called
________________________.

A benefit of alternate splicing of introns out of mRNAs is that
____________________________________________________________________.

it increases the number of proteins that the genome encodes.
(introns are removed, by spliceosome, from the RNA after transcription; the pre-mRNA can be spliced in more than one way yielding multiple mRNA's translated into different AA's and proteins)

Polypeptides are synthesized by adding successive amino acids to the ______________________
end of the growing chain.

carboxyl (3' end)

Retrotransposon, RNA, class 1

A transposable element that inserts into the genome via a "copy and paste" mechanism is classified as a ____________________.
(Retrotransposons: possess some characteristics of retroviruses and transposes through an RNA intermediate)

The __________ of telomerase is needed to provide the template for synthesizing complementary DNA telomere sequences at the end of chromosomes.

RNA
(RNA portion has a template complementary to repeated sequences in the telomere and pairs with them, providing template for synthesis of additional copies of repeats)

Briefly explain how the observed phenotype could arise at the hypoxanthine guanine phosphoribosyl transferase (HPRT) locus.
A. A normal amount of HPRT protein but no enzymatic activity

A. Point mutation leading to an amino acid substitution important for enzyme function
(point mutation = causes the replacement of a single base nucleotide with another nucleotide of the genetic material, DNA or RNA)

Briefly explain how the observed phenotype could arise at the hypoxanthine guanine phosphoribosyl transferase (HPRT) locus.
B. No mRNA detectable

B. Gene deletion or mutation affecting the promoter

Briefly explain how the observed phenotype could arise at the hypoxanthine guanine phosphoribosyl transferase (HPRT) locus.
C. A normal amount of mRNA but no protein that is present

C. Nonsense mutation affecting message translation

Briefly explain how the observed phenotype could arise at the hypoxanthine guanine phosphoribosyl transferase (HPRT) locus.
D. Altered restriction enzyme pattern (through restriction digest reaction and running the reaction out on a gel) at the HPRT locus

D. Mutation in the gene altering the restriction pattern but not affecting the protein, for instance, the mutated nucleotide is in the third codon position of the open reading frame.

For the following restriction endonucleases, calculate the average distance (in base pairs) between restriction sites in an organism in which the DNA has a random sequence and equal proportions of all four nucleotides. The symbol R means any purine (A or

For each site, the probability equals the product of the probability of each of the nucleotide pairs in turn (1/4) for any of the specified pairs (1/2) for R-Y , 1 for N average spacing (distance between sites) of the reciprocal of the probability:
RsaI 5

In this DNA sequence
5'-TCGTATAATGTGAGACATCCCTATT
AGCGCCATCTACATGTTACTTGCC-3'
A. Place parentheses around the TATA box.
B. Put parentheses around initiation codon.
C. What would the 3rd amino acid be if a cytosine were inserted right after the initiation

A.
5'-TCG [TATA] ATGTGAGACATCCCTATT
AGCGCCATCTAC [ATG] TTACTTGCC-3'
B. initiation codon [ATG]
C. Cys

If this DNA molecule were transcribed from left to right, what:
A. Is the mRNA sequence?
B. Is the amino acid sequence?
C. Would be the effect of a C�>A mutation at position 9 in the DNA sequence?
5'-TCGACTTGCAGGACCCTGCGGTAC-3'
3'-AGCTGAACGTCCTGGGACGCCATG

A. transcribe the bottom line L to R, (C to G), (G to C), (T to A), (A to U)
3'-AGCTGAACGTCCTGGGACGCCATG-5'
5'-UCGACUUGCACCACCCUGCGGUAC-3'
B. RNA reads 3' to 5' use genetic code table [UCG]-[ACU]-[UGC]-[ACC]-[ACC]-[CUG]-[CGG]-[UAC] translation =
Ser-Thr-C

A study found an increased rate of non-Hodgkins Lymphoma among golf course
superintendents who had been exposed to pesticides as well as other chemicals, such as diesel fumes and fertilizers. You are a caddy and instructor at a golf course in Arizona spen

A method of studying the effects of pesticides is to examine chromosomal aberrations, and, by inference, future cancer risk, in people exposed to pesticides

Next your family physician offers to look at specific gene polymorphisms in your DNA. First, what is a polymorphism and second, what genes would be initially examined (not the exact names but what function/processes could the gene products likely be accom

Looking at gene polymorphisms in genes that produce products that (genetically determine the ability to) metabolize substances slowly or quickly could also provide information on the susceptibility of an individual to pesticide exposure

In question 9 you described a phenotypic and a molecular genetic tool required to perform QTL (Quantitative trait locus) analysis of a quantitative trait. For 4 EC points, please describe the overall QTL procedure ?

1. Need strains of study species that differ genetically with respect to trait of interest
2. Require ordered set of genetic markers such as SNPs, RFLPs, simple sequence repeats, and or transposable elements that distinguish the two lines.
3. P1xP2�F1 the

After exposing cells of the fungus Neurospora crassa to UV radiation, they won't grow in minimal media. Mycelia from these two cell lines to fuse, forming a heterokaryon. This new cell line
is able to grow in minimal media lacking serine.
(i) Genetically,

(i) In a genic complementation assay we add genetic material to a growth deficient mutant, via fusion of two cell lines in this example. If experiment results in wildtype growth, mutations are in different genes and are said to complement one another beca

After exposing cells of the fungus Neurospora crassa to UV radiation, they won't grow in minimal media. Mycelia from these two cell lines to fuse, forming a heterokaryon. This new cell line
is able to grow in minimal media lacking serine.
(i) To obtain ev

To obtain greater insight into the mutations in the two strains of Neurospora, we could grow both strains individually on minimal media supplemented with intermediates of the serine biosynthesis pathway. Data from this experiment could be used to determin

Multiple alleles occur when more than two alleles are present in a population at a particular locus, though diploid individuals still only have two alleles in their genome. Inheritance of characteristics encoded by multiple alleles are no different than t

An example of multiple alleles is the ABO blood group. Allele I^A produces A antigen, allele I^B produces B antigen, and allele i produces no antigen, resulting in individuals with type O blood. Both antigen producing alleles (I^A and I^B) are dominant to

An allele shows complete dominance if homozygous individuals are phenotypically indistinguishable from heterozygotes, one allele completely masking the effect of the other

An example of complete dominance is pea color in Mendel's experiments. Yellow (Y) is dominant to green (y), individuals with the genotype Yy are phenotypically identical to those with the genotype YY.

Though tortoiseshell cats are by and large female, occasionally males express this phenotype. What is a possible genotype of a male tortoiseshell cat and what is the most probable cause of this
aneuploidy?

A possible genotype of a male tortoiseshell cat is X^B X^b Y; aneuploidy would most likely result from nondisjunction.

Tortoiseshell cats are the result of two different alleles at an X-linked gene that contributes coat color; XB gives rise to an orange coat and Xb gives rise to a coat that is usually black. Describe how tortoiseshells come to have their characteristic pa

XIST and TSIX are at the exact same locus on the X chromosome, both encode RNA products. When transcribed:
- XIST "turns off" the X chromosome that it resides via epigenetic modifications.
- TSIX inhibits the stabilization of XIST and thus XISTs ability t

Briefly explain the difference between dominance and epistasis.

Dominance involves one allele at a particular locus producing a particular phenotype that masks the phenotype of an alternative allele at the same locus on a homologous chromosome (involves single loci)
Epistasis refers to an allele interacting with the e

You perform a cross between the following parental genotypes: aaBBCcDD x AabbccDd. Assuming segregation and independent assortment, what is the probability of obtaining an F1 offspring with the genotype aaBbccDD?

P(aa | aa x Aa) = �
P(Bb | BB x bb)= 1
P(cc | Cc x cc) = �
P(DD| DD x Dd) = �
Since these are independent events, we can use the multiplication rule to arrive at the answer of 1/8

The master sex?determining gene SRY that codes for the testis?determining factor, resides on
A. the X chromosome.
B. one of the autosomes.
C. the pseudoautosomal region of the X chromosome.
D. the pseudoautosomal region of the Y chromosome.
E. in the shor

E. in the short arm of the Y chromosome, but out of pseudoautosomal region

The products of crossing?over within the paracentric inversion include
A. submetacentric chromosome.
B. Robertsonian translocation.
C. a dicentric and an acentric chromatid.
D. two monocentric chromatids with deletions and duplications

C. a dicentric and an acentric chromatid.

How many Barr bodies would be present in white blood cells of an individual with karyotype 48, XXYY?
A. 0
B. 1
C. 2
D. 3
E. 4

B. 1

Individuals that are heterozygous for a translocation produce
A. the normal number of offspring.
B. about one?half as many offspring as normal.
C. about one?fourth as many offspring as normal.
D. about one?tenth as many offspring as normal.
E. no offsprin

B. about one?half as many offspring as normal.

Nuclear DNA is transcripted by three different eukaryotic ________

RNA polymerases

What are all the stop codons?

UAA
UGA
UAG

In Eukaryotes, The sequence -30 bases at which the TBP binds and the Transcription Factor bind to the TBP before transcription

TATA-box

What results will you get if you cross two organisms of the same species that are both heterozygous for a particular trait in a monohybrid cross?

(1/4) homozygous dominant
(1/2) heterozygous
(1/4) homozygous recessive

What are the pyrimidine and purine bases?

pyrimidine: cytosine, uracil, and thymine
purine: adenine and guanine

Why does a wild-type fly have 'brick red' colored eyes (genotype and phenotype at the molecular/biochemical level)?

A wild-type fly has "brick-red"-colored eyes because it is homozygous dominant for both the brown and scarlet genes.
This means that both the brown and neon-orange colors go into the eye color, combining the two into "brick-red".
If either of the channels

This is the equation that determines the number of phenotypes possible by taking the number of alleles into account.

[n(n+1)]/2

This is where the presence of one recessive genotype masks the other gene at one loci

Single recessive epistasis
ratio is 9:3:4

Duplicate Recessive Epistasis

This is where recessive alleles at either loci are capable of suppressing a phenotype.
9:7 ratio

RNA polymerase III

is used in producing all transfer RNA genes as well as the 5S component of ribosomal RNA in eukaryotic cells.

The 3' termini of eukaryotic mRNA molecules are usually modified by the addition of a ___________________________.

poly-A-tail

Exon shuffle model

The model of protein evolution through the combination of different exons

Which of the following best describes a test Cross?
A. F1 to mahogany eyes and stubble bristles
B. Recombinants divided by the total � 100
C. Mahogany eyes and normal bristles
D. Wild-type red eyes and normal bristles.
E. Genes that do not segregate indep

A. F1 to mahogany eyes and stubble bristles

In the offspring resulting from an F1 testcross, what percentage of recombinant phenotypes is expected if the genes under study are independently assorting?
A. 5%
B. 33%
C. 50%
D. 90%
E. The percentage cannot be predicted.

C. 50 %

A two-point test-cross is a cross between

a double heterozygote for two linked genes and a double recessive genotype.

The cross represented by a+b+c+/abc � abc/abc

three point test cross

If you performed a test cross with respect to three linked genes (ABC/abc x abc/abc), found in the order A-B-C or C-B-A, the offspring genotypes expected to be least frequent are
A. ABC, abc.
B. aBC, Abc.
C. AbC, aBc.
D. abC, ABc.

C. AbC, aBc.

In his notes, Thomas Morgan indicated the genotype of a particular fruit fly as w+m+/Y. This indicates that:

the w+ and m+ (eye color and wing form) genes are on the X chromosome.

The recombination frequencies between three genes were determined. Genes k and a had a recombination frequency of 39%, while genes a and e had a recombination frequency of 26%. Genes k and e showed 50% recombination. What is the distance in map units betw

C. 65 mu
- since genes k and e showed 50% recombination (39% +36%) = 65%

x^2 = E (observed-expected)^2/ expected

Chi squared formula

If a geneticist describes a trait as being 70% penetrant, what would they mean?
A. The expression of the trait varies by individual
B. It is lethal in 30% of individuals who have the trait
C. Only 70% of the individuals who carry the trait express the tra

C. Only 70% of the individuals who carry the trait express the trait

What did Beadle and Tatum study and what did they discover?

Used fungus to lay ground for the definition of a "gene", classified mutant genotypes

Particulate nature of inheritance and 3 principles (dominance, segregation, independent assortment)

Mendels major contributions

co-localization of genes on same chromosome in an individual or species

Synteny
(syntenic group: group or block of genes occurring in the same order in different species)

What are the 5 chromosomal abnormalities?

Chromosome inversions
polyploidy
chromosome deletions
reciprocal translocations
gene locations

What are the key considerations in designing PCR (polymerase chain reaction) primers?

Specificity, annealing the temperature, avoiding dimerization and secondary structures
(Necessary PCR components: primers, DNA, nucleotides/polymerase, buffer)

What enzyme functions to deal with supercoils in DNA?

Gyrases/Topisomerases

The zipper-like complex that forms in meiosis occurs during __________ and is called the __________.

prophase I; synaptonemal complex

Given that the synaptonemal complex disappears by the end of prophase, how would the two homolgos be associated if crossing over did not occur? What effect might this ultimately have on gamete formation?

If crossing over did not occur, the two homologs would not be associated in anyway. This might result in incorrect arrangement of homologs during metphase I and ultimately in formation of gametes with an abnormal number of chromosomes.

During prophase I of meiosis, crossing over is indicated by what microscopically visible structure?

Chiasmata (chiasma) or the synaptonemal complex

What is a backcross?

A backcross is the mating of F1 progeny back to one of their parents. Backcrosses can also be testcrosses if the original parent is homozygous for the recessive allele(s). Backcrosses are typically used to introgress allele(s) of interest, which segregate

List three dosage compensation strategies for equalizing the amount of sex chromosome gene products.

(1) Inactivation of one sex chromosome in the homogametic sex
(2) Halving the activity of genes on both sex chromosomes in the homogametic sex
(3) Increasing the activity of genes on the sex chromosome in the heterogametic sex