Genetics final questions

In the CRISPR/Cas9 system, the purpose of the guide RNA is

to bind to a single stranded target sequence and trigger Cas9 to cleave the DNA

Which of the following is NOT a characteristic of a pedigree for an autosomal dominant trait?

unaffected persons may be carriers

Consider the experiment by Meselson and Stahl that proved the mode of DNA replication. If these researcher had started their bacterial cultures in 14N (instead of 15N), and then flooded the media with 15N (instead of 14N), what would you expect the ratios of DNA molecules to be following TWO generations in medium containing 15N.

50% 15N15N: 50% 15N14N

If a boy's maternal grandfather (the boy's mother's father) is bald (an X-linked, sex-influenced, trait), he has

50% chance of going bald

In garden peas, the allele for tall plants is completely dominant to the allele for dwarf plants and the allele for violet flower color is completely dominant to the allele for white flower color. The genes controlling each trait are on different chromosomes and are independently assorting. You cross a dwarf, white plant with tall, violet plant that is homozygous at the tall locus and heterozygous at the flower color locus. What phenotypic ratios would you predict to observe in their progeny?

50% tall violet and 50% tall white

You perform DNA analysis to determine the actual genotype at the locus controlling hair length in a population of domestic house cats. You find: 20 aa 320 AA 160 Aa What is the allele frequency of the A allele?

80%

Individuals that produce the rhesus antigen D will have a blood type that is Rh positive, while those that don't will have an Rh negative blood type. Rh negative children may be born to either Rh positive or Rh negative parents, but Rh positive children always have at least one Rh positive parent. Which phenotype is due to a dominant gene?

Rh positive

A segment of mRNA that forms under certain temperatures and regulated translation is called a thermosensor. Thermosensors are considered to be

Riboswitch

A main difference between DNA replication in prokaryotes vs. eukaryotes is

termination in eukaryotes requires telomerase to replicate linear ends of chromosomes.

When testing for linkage, it is most appropriate to perform a Chi-squared _______, in order to ________

test of independence, determine if the co-inheritance of two traits are statistically likely to be due to random chance

In prokaryotes, what site on the RNA does the ribosome bind to initiate translation?

the Shine-Dalgarno sequence

Which of the following is not likely to occur due to a mutation that eliminates a stop codon?

there will be an increase in size of the encoded mRNA

If the genetic distance between 2 genes is 50 cM,

they could be on the same chromosome or on different chromosomes.

Which of the following in true for X-linked recessive traits? (select all that apply)

trait occurs in males more frequently than females because males have 1 X chromosome 1/4 of the children from a carrier female will be affected 1/2 of the sons from an affected females will be affected males cannot be carriers

Which of the following does NOT require a particular RNA sequence?

transcriptional initiation

The recombination rate between genes s and k is 9%. A third gene, w, has a recombination rate of 12% with s and a recombination rate of 4% with k. What is the order of these three genes on the chromosome?

s - k - w

A mutation that changes a nucleotide in the DNA but not the amino acid that it encodes is called a:

silent mutation

When testing for linkage using a Chi squared test of independence, the degrees of freedom are determined as

(rows -1) * (columns - 1) from a contingency table

Type in the 3-letter amino acid abbreviation for the 3rd amino acid coded for by the following mRNA sequence that comes from the beginning of the mRNA (remember which direction the ribosome reads mRNA!). 3'AAAAAAAAAAAACGCGCGUUAUAUGGCAUUGCCGCCAGUUUGAGCGUACCAG5' The 3rd amino acid is

Val

Which of the following statements is true about expressivity?

Variable expressivity means that the variation in phenotypes among individuals with the same genotype is high

Which of the following are not observed when performing a karyotype?

position of a gene

Which of the following is a correct order in which the events of eukaryotic transcription can occur?

promoter recognition, transcriptional elongation, 5' capping, splicing, termination, 3' polyadenylation

Which of the following is/are not true regarding most linkage/QTL mapping experiments using RILs?

Mapping resolution is generally quite high (actual causative genes are often identified).

Which locus is in the middle, given the haplotypes below?(All three loci are on the same arm of the same chromosome.) Genotypes of parental gametes: q, r, s and Q, R, S Genotypes of DCO gametes: Q, r, s and q, R, S

q

Voles (Microtus achrogaster) were trapped in fields near Binghamton, NY and genotyped for a locus that encodes transferrin (a blood protein). The following genotypes were recorded, where TE and TF represent different alleles: 407 TE TE 170 TE TF 23 TF TF What is the allele frequency of the TF allele?

0.18

Cells from an XXY male would stain positive for ______ Barr bodies

1

A duplication of a segment of a chromosome can occur as a result of which DNA repair pathway?

Homologous direct repair

Albinism(wite color) in corn plants is caused by a recessive lethal gene that results in death before maturity. If two heterozygous (white) corn plants are crossed, what will the phenotypic ratio of their F1 offspring adult plants be?

1 colored: 2 white

In watermelons, the genes for green color and for short length are dominant over their alleles for striped color and for long length. Suppose a plant with long striped fruit is crossed with a plant heterozygous for both of these characters. What phenotypes would this cross produce and in what ratios?

1 short striped : 1 short green : 1 long striped : 1 long green

Peas are diploid with 14 total chromosomes in somatic cells. Assuming no crossing over events occur, how many unique gametes could one pea plant produce?

128

There is a 30% recombination frequency between 2 genes. Consider an individual (Ahmir) with the genotype AaBb, where the paternally inherited chromosome contains the AB alleles and the maternally inherited chromosome contains the ab alleles. What proportion of Ahmir's gametes will contain Ab alleles?

15%

Order the processes involved with the CRISPR/Cas9 genome editing tool.

1: targeting 2: binding 3: cleaving 4: DNA repair

Suppose that gene b is X-linked, recessive, and embryonic lethal. A man marries a woman who is heterozygous for this gene. If this couple had many normal children, what would be the predicted sex ratio of these children?

2 female : 1 male

Bearcats are typically found in Southeast Asia. However, there is a elusive population of bearcats in Binghamton NY. Bearcats have black fur controlled by the B allele, but the Binghamton population has an autosomal recessive allele (b) that results in green fur (bb). 100 bearcats make up a population that lives in the nature preserve of the BU campus. Of these 25 are green (bb) and 75 are black (BB and Bb). Genetic testing has revealed that of the 75 black bearcats, 50 are Bb and 25 are BB. What is the phenotype frequency for green furred bearcats?

25%

Fur striping in cats is due to a single gene, where the striped allele (A) is dominant to the non-striped allele (a). If two cats that are both heterozygous at the striping locus have four kittens, what is the probability that they are: Non-agouti, agouti, non-agouti, non-agouti, in that exact order?

3/256 = 0.011

There is a 30% recombination frequency between 2 genes. The genetic distance between them is:

30 map units

There is a 30% recombination frequency between 2 linked genes. Consider an individual with the genotype AaBb, where the paternally inherited chromosome contains the AB alleles and the maternally inherited chromosome contains the ab alleles. What proportion of this individual's gametes will contain ab alleles?

35%

How many phenotypic classes are produced by a dihybrid test-cross where one parent is heterozygous for both pairs of genes?

4

Human skin color is a polygenic trait, involving a minimum of 378 different loci. Consider the unlikely situation where a population was homozygous at all of these loci, except for 2. The alleles of these genes have additive and equivalent effects on skin color. In matings between individuals that were heterozygous at these 2 loci (A1A2 B1B2 x A1A2 B1B2), how many different phenotypic categories would be expected in the offspring?

5

Which of the following is the least likely to require a consensus sequence?

5' capping region of a new eukaryotic mRNA

Which of the following codons is the mRNA start codon that binds the initiator tRNA to begin translation?

5'-AUG-3'

Consider the following mRNA that you hope to reverse transcribe in the lab later this week: 5'- AGGTCACTGTCAGTAACGCAATGAAAAAAAAAAAAAAA-3' The bold, underlined sequence denotes your desired primer binding site. The sequence of the reverse primer is

5'-TTTTTTTTTTTTTTTCAT-3

The -10 elements of four bacterial gene promoters are 5-TAAAGAC-3, 5-TCTACAG-3, 5-AATAGAG-3 5-TACAGAG-3. Which of the following is the consensus sequence for these four elements?

5-TATAGAG-3

Manx cats lack tails, due to a recessive lethal allele. If a manx cat is crossed with a cat with a normal tail, what proportion of the kittens are expected to be tail-less?

50%

During the initiation of translation,

rRNAs within the small subunit of the ribosome bind to the RNA transcript and scan it for a start codon, followed by recruitment of the initiator tRNA and the large subunit of the ribosome. Initiation requires energy in the form of GTP.

Which site in the ribosome allows for tRNAs to enter the translation complex?

A-site

Which of the following is NOT a characteristic of a pedigree for an X-linked dominant trait?

Affected females can produce carrier daughters

Which of the following is NOT a characteristic of a pedigree for an X-linked recessive trait?

Affected females will have affected daughters

Heather is heterozygous for two genes and her genotype is represented as Bb Dd. The "Bb" indicates:

Alleles on homologous chromosomes

Orange and black coat color in cats are due to different alleles of an X-linked gene. Twenty years ago at Texas A&M, Copycat was cloned from a cell taken from Rainbow, an orange and black calico female. Surprisingly, Copycat's coloration didn't match Rainbow's: Copycat had no orange coloring. The cell used for cloning was from a black portion of Rainbow's body, so the researchers hypothesized that all Copycat's cells had inactivated the X-chromosome with the orange allele. Another hypothesis was that Copycat wasn't a clone after all, and instead had two copies of the black allele. Copycat was mated with a male carrying a black allele. What offspring would be evidence that she really is a clone that is genetically identical to Rainbow?

An orange male

Which of the following best describes the differences between race and ancestry?

Ancestry can be defined as genetic characteristics, whereas race incorporates physical and social characteristics.

The map distance between genes A and B is 3 map units, and between B &C is 10 map units and between C&A 7 map units. What is the order of these three genes on the chromosome?

B-A-C

Glycosylases that recognize specific base-pairing mistakes and remove a base (without affecting the phosphate backbone) are used in which type of DNA repair mechanism?

Base excision repair

The following are recombination frequencies between genes B-D: 4% A-B: 7% A-D: 13% C-D: 29% Based on this information, what is the likely gene order?

C - A - B - D

Which of the following is NOT a characteristic of a pedigree for a Y-linked trait?

Can skip generations if there are no sons in that generation

Which of the following is most likely to occur in a cell if there is a mutation in the enzyme that phosphorylates the TF ChREBP?

ChREBP will be unable to respond to changes in cellular energy status.

Which of the following is NOT a characteristic of a pedigree for an autosomal recessive trait?

Children of affected females are always affected

An allele of the gene that encodes tyrosinase exists in cats known as Siamese. The enzyme encoded by this allele is defective at warm temperatures and produces low amounts of the pigment melanin. At cold temperatures, the encoded protein is stable and functions to produce more melanin. Therefore, these cats have a characteristic dark color only in their extremities, where the temperature is lower. This type of allele is called:

Conditional

Would you expect that a single mutation introduced into the coding sequence of a gene by a single DNA polymerase, RNA polymerase or ribosome would have a larger effect on the phenotype?

DNA polymerase

When testing for linkage between two genes, which is the appropriate null hypothesis for the Chi-squared test?

Deviations between the expected and observed numbers of progeny traits (phenotypes) for the testcross are due to random chance/sampling error.

Which of the following DNA repair activities function without breaking the phosphate backbone?

Direct the glycosylase component of base excision repair

FBN1 codes for fibrillin-1, a protein that helps to create connective tissue. A nonsense mutation in FBN1 results in a truncated copy of fibrillin, and interrupts the connective tissue, characterized as Marfan syndrome in humans. Would you predict this mutation to be dominant or recessive?

Dominant

X-inactivation occurs in typical (46-chromosome) males and females

False

Which of the following is NOT a characteristic of a pedigree for a trait affected by mitochondrial DNA?

Females are more likely to be affected than males

Consider two different mismatches: G:A and G:T. Which is more likely to be recognized by DNA repair pathways?

G:A because this is a purine-purine pair and have four total aromatic rings causing a bulge in the DNA structure, while G:T is a purine-pyrimidine pair that would be less obvious to DNA repair pathways.

What type of variation is directly observed in the chromosomes from this karyotype

Heterochromatin and euchromatin differences

Which DNA repair pathway involves strand invasion and the copying of a DNA sequences from the homologous chromosome?

Homologous Recombination

Linkage prevents:

random segregation of alleles

Which of the following is a difference between genomics and transcriptomics? Select all that apply.

If you do genomics and transcriptomics on the same tissue sample (split in half), you'll get different results from genomics and transcriptomics Genomics gives you information on changes, but transcriptomics can be more informative because it shows the direction of a change (increase or decrease) Genomics gives you information on DNA, whereas transcriptomics gives you information on RNA Transcriptomics requires reverse transcriptase whereas genomics does not require this enzyme

What is a major difference between transcription and translation in prokaryotes and eukaryotes?

In prokaryotes, translation can begin before transcription terminates, while in eukaryotes, transcription must finish before translation can begin.

Which of the following is true regarding X-inactivation?

In some cells, a paternally inherited X chromosome will be inactivated, while in other cells, a maternally X-chromosome will be inactivated

________is required to make phosphodiester bonds between 2 adjacent Okazaki fragments

Ligase

If DNA polymerase fails to correct a mismatched base incorporation, which of the following repair pathways is most likely to correct the mistake immediately after DNA replication?

Mismatch repair

You designed a CRISPR guide RNA but forgot to search the genome for alternate binding sites before you generated your colony of mutant mice. This mistake produced mice with UV sensitivity, where they appear phenotypically normal under dark conditions but exhibit abnormal skin morphology when exposed to light. What type of repair pathway do you think was affected by your sloppy CRISPR approach?

NER

In the absence of arabinose, an alternate sugar source for E. coli, the "C" protein binds to a promoter sequence and prevents the transcription of an operon encoding proteins that function in arabinose metabolism. This is an example of

Negative regulation

In humans, the blood types A and B are codominant to each other and both are dominant to blood type O. Mrs. Smith and Mrs. Doe were roommates at Wilson Hospital and both had daughters at about the same time. After Mrs. Smith took Susie home, she became convinced that these two babies had been switched by a hasty nurse in the hospital nursery just after birth. Blood tests were performed with the following results: Mr. and Mrs. Smith were both type AB; Mr. Doe and Mrs. Doe were type A; The babies: Susie Smith was type A and Debbie Doe was type O. Could these two babies have been switched?

No

Small insertions and deletions are often the result of which DNA repair pathway?

Non-homologous end joining

What is a difference between an insertion of one nucleotide and an insertion of two nucleotides at the same location in an exon of a pre-mRNA?

One will produce a smaller mRNA than the other

Which of the following is not involved in DNA replication?

Promoter

What would be the most likely effect of a DNA mutation in the gene encoding the sigma factor subunit of RNA polymerase that removed the helix-turn-helix domain?

Sigma factor would be unable to bind to promoter regions, blocking transcription. Because sigma factor is required for initiation of the majority of prokaryotic genes, this mutation would likely be a lethal mutation.

You are studying feather colors in a rare bird species in South America. A striping pattern is controlled by a single gene where the S allele is incompletely dominant to the s allele. The feather color is controlled by a different gene, where the B allele is dominant to the b allele. If you only have access to phenotyping data, which of the traits would you use to test if it was held in Hardy-Weinberg equilibrium?

Striping patterns, because it is possible to determine the genotypes of homozygous dominant, homozygous recessive, and heterozygous individuals.

Which of the following statements is true about bacterial promoters?

The -10 element is approximately 10 base pairs upstream of the transcription start site

Female mammals can be chromosomal (and phenotypic) mosaics regarding the X chromosome due to X-inactivation

True

Mendelian Inheritance refers to patterns of inheritance of alleles with dominant/recessive relationships, where the phenotypic ratio of the offspring from a monohybrid cross is 3:1. Non-Mendelian inheritance refers to patterns of inheritance that deviate from this expectation.

True

Once the Cas9/guide RNA complex has cleaved dsDNA at a precise location, it is up to the cell to repair the double stranded break.

True

Ultraviolet light damages DNA. Which of the following best describes the type of mutation and repair pathways associated with UV-damage?

Ultraviolet light causes covalent bonds between adjacent thymine residues. These are most often repaired by the nucleotide excision repair pathway.

Epistasis describes when 2 different genes interact, so that the effect of one gene masks the effects of another

True

Consider the results from physical, genetic, and hormonal sex determination tests for a female athlete: Physical: characteristics: genitals neither typically male nor typically female Genetic test findings: Barr body present, SRY gene absent Hormone test findings: Testosterone (T) = 6.3 nmol/L What is the most likely karyotype and diagnosis of this individual?

XX with congenital adrenal hyperplasia

Consider the results from physical, genetic, and hormonal sex determination tests for a female athlete: Physical characteristics: female genitals fully formed Genetic test findings: Barr body present in some cells and absent in others, SRY gene present in all cells tested Hormone test findings: Testosterone (T) = 3 nmol/L What is the most likely karyotype of this individual?

XXY/XY mosaic

For CRISPR/Cas9 genome editing, scientists introduce what into the cell?

a Cas9 and guide RNA complex

Genetic admixture refers to

a genome that is comprised of chromosomal regions that are ancestrally related to different populations

What would be the most immediate consequence of a mutation in DNA helicase (DnaB) that prevented helicase activity?

a very small single stranded replication bubble would occur at the ori sequence

Consider an E.coli cell that has a mutation in the operator sequence of the lac operon that prevents the lac repressor from binding. Would you expect this mutant lac operon to be inducible, repressed, or constitutively expressed?

constitutively expressed

Why do calculated recombination frequencies between pairs of loci that are located far apart underestimate the true genetic distance between loci?

double-crossover events will result in progeny that will not be counted as recombinant.

A polyA tail is found on

eukaryotic mRNAs

Sister chromatids refer to

identical strands of DNA that are part of the same chromosome following DNA replication

What would be most likely to occur following a mutation in a DNA polymerase that inhibited proofreading?

increased error rate during DNA replication

A high degree of heterozygosity is beneficial to organisms because: (select all that apply)

it increases diversity in the alleles produced Reduces the frequency of deleterious(bad trait) alleles it reduces the risk of developing a genetically inherited disease

Which of the following DNA repair pathways require that a segment of the damaged DNA chain is resected (removed), and then resynthesized? (Select all that apply).

mismatch nucelotide homologous

S-adenosylmethionine (SAM) binds to regions of in the 5'UTRs of certain mRNAs, causing a stem-loop structure that prevents the translation of enzymes required for the production of SAM. This is an example of:

negative feedback loop