General Genetics- Test Questions

If there are two alleles, A and a, in a population and the population is at Hardy-Weinberg equilibrium, which frequency of A would produce the greatest frequency of heterozygotes?

0.5

Which of the following is NOT required during the process of tRNA charging? Correct Answer 1. All are required 2. ATP 3. tRNA 4. Amino acid 5. Aminoacyl-tRNA synthetase

1. All are required

Which of the following was not one of Mendel's conclusions based on his monohybrid crosses 1. Genes are carried on chromosomes. 2. Genes exist in pairs. 3. Members of a gene pair segregate equally into gametes. 4. One member of a gene pair can mask the expression of the other member. 5. All of the above were concluded by Mendel

1. Genes are carried on chromosomes.

Which of the following statements about histone and gene expression is correct? 1. In a general sense, highly condensed DNA bound with histone proteins represses gene expression. 2. Acetylation involves the addition of acetyl groups to histone proteins, and it usually results in repression of transcription. 3. Addition of methyl groups to the tails of histone proteins always results in activation of transcription. 4. All statements above are correct.

1. In a general sense, highly condensed DNA bound with histone proteins represses gene expression.

The following testcross produces the progeny shown: Aa Bb × aa bb yields 40 Aa Bb, 10 Aa bb, 10 aa Bb, 40 aa bb. What is the percent recombination between the A and B loci?

20%

You are studying a small eukaryotic gene of about 2000 bp in length. Estimate how many copies of histone H4 and H1 you would find along this region of the chromosome.

20, 10

In transcription, to which end of the elongating strand are nucleotides always added?

3'

To which part on tRNAs would an amino acid attach to during tRNA charging?

3′ acceptor arm

Which of the following would NOT necessarily be true for a DNA molecule? 1. A = T 2. C = G 3. A + G = C + T 4. A + T = G + C

4. A + T = G + C

Order the common steps in DNA repair 1. Ligation 2. Excision 3. Polymerization 4. Detection

4. Detection 2. Excision 3. Polymerization 1. Ligation

There are ______ different codons, which encode 20 amino acids and 3 stop codons.

64

The human gene encoding for calcitonin contains six exons and five introns and is located on chromosome 11. The pre-mRNA transcript from this gene can generate either calcitonin or calcitonin gene related peptide (CGRP) in a tissue-specific manner. Calcitonin produced from the thyroid gland is 32 amino acids long and functions to regulate the calcium while CGRP, which contains 37 amino acids, is produced by the brain cells and involved in transmission of pain. Which of the following processes makes production of two functionally and structurally different proteins from the same gene possible?

Alternative RNA processing

When a structural gene is under positive inducible control, what would be the result of a mutation that eliminates the activator protein?

As transcription requires an activator protein, the transcription will be turned off.

Fill in the blank with the best answer below. The polymerase that synthesizes _____________ uses DNA as a template and synthesizes new strands from 5′ to 3′.

Both RNA and DNA

If there is random mating in a population and no evolutionary forces are acting on the population, what will be the expected outcome?

Both the genotype distribution and the allele frequencies will remain the same.

Over time, DNA replaced RNA as the primary carrier of genetic information and the chemical stability of DNA is believed to be the key reason for this. Which attribute of DNA is the reason behind its chemical stability?

DNA lacks a free hydroxyl group on the 2′-carbon atom of its sugar.

When one gene masks the expression of another gene

Epistasis

Which of the following is found on the primary product of transcription but not on a mature mRNA molecule?

Introns

How does histone acetylation affect chromatin?

It loosens the chromatin and allows increased transcription.

_______________ is the movement of genes between populations.

Migration

What are the components of the nucleotides that compose DNA?

Nitrogenous bases, phosphate, deoxyribose

Which amino acid is coded by the stop codons in most organisms? 1. met 2. pro 3. trp 4. cys 5. None

None

What would be the result of replication in a mutant organism with non-functional DNA ligase?

Okazaki fragments would not be joined into a single piece of DNA.

Which of the mechanisms involving siRNA- and miRNA-based gene regulation is INCORRECT?

Post-translational modification

Which of the following is NOT required for transcription?

RNA primers

DNA synthesis during replication is initiated from

RNA primers.

The following testcross produces the progeny shown: Aa Bb × aa bb yields 10 Aa Bb, 40 Aa bb, 40 aa Bb, 10 aa bb. What was the arrangement of the genes in the Aa Bb parent?

Repulsion

Although operons are not common in eukaryotes, eukaryotic genes may be activated by the same stimulus. Which of the following DNA regulatory sequence makes this coordinated gene expression possible?

Response element

If an organism does not produce a functional DNA polymerase I,. what will be the most likely consequence?

The DNA strands would contain pieces of RNA.

A linkage map shows which of the following? 1. The distance in numbers of nucleotides between two genes 2. The number of genes on each of the chromosomes of a species 3. The linear order of genes on a chromosome 4. The location of double crossovers that occur between two genes

The linear order of genes on a chromosome

A large population can be used to create a high- resolution linkage map. If the individuals of the population are also carefully measured for a quantitative trait what can be learned?

The number and general location of chromosome regions controlling the phenotype can be determined.

You are studying two linked genes in lizards. You have two females and you know that both are the same genotype, heterozygous for both genes (A/a and B/b). You test-cross each female to a male that is fully homozygous recessive for both genes (a/a and b/b) and get the following progeny with the following phenotypes: Female 1 Female 2 AaBb 37 AaBb 5 aabb 33 aabb 4 Aabb 4 Aabb 35 aaBb 6 aaBb 36 How can you explain the drastic difference between these two crosses?

The two alleles are in the coupling configuration in female 1 but in the repulsion configuration in female 2.

Dr. Disney has been raising exotic fruit flies for decades. Recently, he discovered a strain of fruit flies that in the recessive condition have baby blue eyes that he designates as bb. He also has another strain of fruit flies that in the recessive condition have pink wings that are designated as pw. He is able to establish flies that are homozygous for both mutant traits. He mates these two strains with each other. Dr. Disney then takes phenotypically wild-type females from this cross and mates them with double recessive males. In the resulting testcross progeny he observes 500 flies that are of the following make-up: 41 with baby blue eyes and pink wings 207 with baby blue eyes only 210 with pink wings only 42 with wild-type phenotype What is the relationship with respect to location between the two genes?

They are linked and 16.6 cM apart.

During elongation, an incoming charged tRNA enters at the _______ site of the ribosome.

aminoacyl (A)

The function of aminoacyl-tRNA synthetases is to

attach appropriate amino acids to corresponding tRNAs.

What would be a likely result of expressing telomerase in somatic cells?

cancer

Recombination occurs through

crossing over and independent assortment.

A eukaryotic DNA sequence that affects transcription at distant promoters is called a(n)

enhancer

Insertion or removal of one or more nucleotide base pairs in DNA within a gene often results in a ____________ mutation.

frameshift

Rapid changes in allelic frequencies by __________ take place in populations that are small.

genetic drift

The information needed during RNA editing comes most directly from

guide RNA

Which of the following is a type of RNA that gets translated?

mRNA

What would be the result if a mutation occurred that destroyed the 3' - 5' exonuclease?

more mutations than normal would occur

Heritability indicates the

proportion of the phenotypic variation of a trait observed in a population that is due to genetic differences.

Linked genes always exhibit

recombination frequencies of less than 50%.

The________ is a type of regulator protein that binds to a region of DNA in the promoter of a gene called the operator and prevents transcription from taking place.

repressor

An example of a gene product encoded by a regulatory gene is

repressor protein

Degradation of a eukaryotic mRNA is generally initiated by

shortening of poly(A) tail followed by removal of the 5′ cap.

In prokaryotic RNA polymerases, the holoenzyme consists of the core enzyme and the

sigma factor

The central dogma states

that genetic information can be passed to the next generation because of DNA replication. that phenotypes are created through transcription and translation.

In eukaryotes, tRNAs are transcribed in

the nucleus but function in the cytoplasm.

Prokaryotic chromosomes do not have telomeres because:

they are circular

The 5′ cap on an mRNA is important for all the processes listed below except for the _________ of an mRNA molecule.

transcription

An mRNA has the stop codon 5′-UAA-3′. What tRNA anticodon will bind to it? 1. 5′-ATT-3′ 2. 5′-AUC-3′ 3. 5′-ACU-3′ 4. 5′-UUA-3′ 5. None

5. None

The only way for evolution to take place is if there is _______________ within a population.

genetic variation

In prokaryotes, rho-independent transcription termination depends on a secondary structure formed in

the RNA that is being transcribed.

Suppose that in a population the frequency of a particular recessive condition is 1/400. Assume the presence of only a dominant allele (A) and a recessive allele (a) in the population and that the population is at HardyWeinberg equilibrium. What is the frequency of heterozygotes in the population?

0.095

A Previous study has shown that the freckles gene is located at the locus marked F, and the hair color gene is located at the locus marked H, on a different chromosome. The individual from whom this cell was taken has inherited different alleles for each gene - freckles (F) and black hair (H) from one parent and "no freckles" (f) and blond hair (h) from the other parent. Predict the allele combinations in the gametes from this meiotic event.

1 FH, 1Fh, 1fH, 1fh

Which of the following statement is not true?: 1. All the answers are true 2. The third base pairing between the tRNA and mRNA is relaxed. 3. There are multiple codons that may code for the same amino acids. 4. There is a flexible pairing between tRNA and amino acid as there are more tRNAs than the number of amino acids. 5. There are multiple tRNA that may bind to the same amino acids.

1. All the answers are true

Which of the following in NOT true about centromeres? 1. Centromeres are composed of a specific DNA repeated sequence 2. Unique centromeric nucleosomes are integral to the functioning of the centromere. 3. Centromere DNA is heterochromatic 4. Nucleosomes associated with centromeres have a CENH3 histone replacing the H3 histone.

1. Centromeres are composed of a specific DNA repeated sequence

Which of the following statements are TRUE regarding transcription in most organisms? 1. Different genes may be transcribed from different strands of DNA. 2. The DNA template strand is used to encode double-stranded RNA. 3. All genes are transcribed from the same strand of DNA. 4. Both DNA strands are used to transcribe a single gene.

1. Different genes may be transcribed from different strands of DNA.

Suppose that a diploid cell contains 8 chromosomes (2n = 8). How many different combinations in the gametes are possible due to independent assortment?

16

An organism has G + C = 64%. What are the percentages of A, T, C, and G

18,18,32,32

The list of events below describes intron removal and splicing during pre-mRNA processing. Please select the choice that lists the events in correct sequential order. 1. Attachment of snRNP U1 to the 5′ splice site 2. Transcription of the DNA template into the pre-mRNA molecule 3. Release of lariat structure 4. Splicing together of exons 5. Transesterification reaction at the branch point adenine

2, 1, 5, 3, 4

Which of the following types of eukaryotic gene regulation is at the level of DNA? 1. mRNA stability 2. Alternation of chromatin structure 3. Post-translational modification 4. mRNA processing 5. RNA interference

2. Alternation of chromatin structure

Flower diameter in sunflowers is a quantitative trait. A plant with 6-cm flowers, from a highly inbred strain, is crossed to a plant with 30-cm flowers, also from a highly inbred strain. The F1 have 18-cm flowers. F1 × F1 crosses yield F2 plants with flowers ranging from 6 to 30 cm in diameter, in approximately 4-cm intervals (6, 10, 14, 18, 22, 26, 30). How many genes are involved?

3

All DNA polymerases synthesize new DNA by adding nucleotides to the _____ of the growing DNA chain.

3' OH

Which of the following is not true about DNA packaging? 1. There are multiple levels of DNA packaging. 2. Prokaryotes have some level of DNA packaging 3. DNA packaging does not vary from cell type to cell type of a given organism. 4. DNA packaging varies through the cell cycle.

3. DNA packaging does not vary from cell type to cell type of a given organism.

Which of the following facts about eukaryotic gene regulation is TRUE? 1. Eukaryotic enhancers are a part of basal transcription apparatus. 2. Transcriptional activator proteins bind to the DNA in a non-specific manner. 3. Mediators are protein complexes involved in regulating transcription rates. 4. The transcriptional repressors always bind to the insulator elements.

3. Mediators are protein complexes involved in regulating transcription rates.

Which of the following statements about DNA binding protein is NOT true? 1. Specific amino acids within the motif form hydrogen bonds with DNA. 2. Most DNA binding proteins bind dynamically. 3. Once bound, most of DNA binding proteins remain on DNA permanently. 4. These proteins can affect the expression of a gene.

3. Once bound, most of DNA binding proteins remain on DNA permanently.

Which of the following statement about the formation of the peptide bond between amino acids is incorrect? 1. A polypeptide formed by a series of peptide bonds will result in two distinct free ends, one with a free amino group and the other with a free carboxyl group. 2. The number of peptide bond formed in a polypeptide varies from protein to protein. 3. The amino group of the first amino acid and the carboxyl group of the second amino group are involved in forming a peptide bond. 4. Carboxyl group of the first amino acid reacts with the amino group of the second amino group to form a peptide bond. 5. The formation of peptide bond results in the formation of a water molecule.

3. The amino group of the first amino acid and the carboxyl group of the second amino group are involved in forming a peptide bond.

Which of the following enzymes do NOT aid in unwinding of DNA for replication? 1. helicase 2. single-stranded binding proteins 3. primase 4. gyrase 5. topoisomerase

3. primase

Total phenotypic variance can be broken down into all but one of which of the following components? 1. Genetic-environment interaction variance 2. Genetic variance 3. Environmental variance 4. All of the above can impact phenotypic variance

4. All of the above can impact phenotypic variance

Which of the following events do not increase genetic variation in a population? 1. Independent assortment 2. Recombination 3. Fertilization 4. All of the above increase genetic variation 5. None of the above increase genetic variation

4. All of the above increase genetic variation

Which of the following has repetitive DNA and heterochromatin? 1. Telomere 2. Centromere 3. Mitochondria 4. Both Telomeres and Centromeres 5. All of the above

4. Both telomeres and centromeres

Which of the following statements are untrue about homologous chromosomes? 1. Have the centromere in the same position 2. Are the same size 3. Are divided during Meiosis I 4. Have the exact same genetic makeup 5. All are true

4. Have the exact same genetic makeup

Which of the following statements about regulation of the eukaryotic gene expression is INCORRECT? 1. The presence of a nuclear membrane separating transcription and translation in eukaryotes led to the evolution of additional mechanisms of gene regulation. 2. Eukaryotic mRNAs are generally more stable than prokaryotic mRNAs. 3. The rate of degradation of mRNAs is important in regulation in eukaryotes. 4. In eukaryotes, most structural genes are found within operons. 5. Post-translational regulation of histones is unique to the eukaryotes.

4. In eukaryotes, most structural genes are found within operons.

Which of the following mutagens is most likely to cause a frameshift mutation? 1. Ionizing radiation 2. Base analog 3. UV light 4. Intercalating agent 5. Alkylating agent

4. Intercalating agent

Which of the following statements about CpG islands is correct? 1. The CpG island methylation is universal across both prokaryotes and eukaryotes. 2. CpG islands are commonly found at the 3′ UTR regions. 3. There is an association between increased DNA methylation at the CpG island and increased acetylation of histone via recruitment of acetylases. 4. Methylated CpG islands are associated with long-term gene repression. 5. Transcriptionally active DNA has a higher frequency of methylated CpG.

4. Methylated CpG islands are associated with long-term gene repression.

Which of the following does NOT bring about evolution in a population? 1. Small population size 2. Migration of individuals from a population with a different genetic structure 3. Mutation 4. Random mating

4. Random mating

Which of the following best describes nonsense mutations? 1. They change the nucleotide sequence of a gene but do not change the sequence of the resulting protein. 2. They cause a nonfunctional amino acid to replace a functional amino acid. 3. They result in the insertion or deletion of a small number of nucleotides to the DNA. 4. They convert a codon for a particular amino acid within a gene into a stop codon.

4. They convert a codon for a particular amino acid within a gene into a stop codon.

What would be the advantage of regulating gene expression at many levels rather than simply regulating at one level? 1. regulation at various levels can fine tune control by involving several levels for the regulation of a single product 2. regulation at translation can ensure more rapid response 3. regulation at transcription can save energy 4. all of the above are advantages

4. all of the above are advantages

Map distances based on recombination rates between distant genes often underestimate the true physical distances between genes because: 1. some genes are lethal 2. interference increases as the distance between genes increase 3. rates of crossing over are not uniform 4. some multiple crossover go undetected

4. some multiple crossover go undetected

If one strand is 5'-GGCATTACACT-3', what is the sequence of the complementary strand?

5'-AGTGTAATGCC-3'

If the following DNA strand was used as a template, what would the sequence of an RNA be? 5′ GTACCGTC 3′

5′ GACGGUAC 3′

An mRNA has the codon 5′-UAC-3′. What tRNA anticodon will bind to it?

5′-GUA-3′

If a mutation prevents the formation of the antiterminator 2+3 loop in the trp operon, what would be the effect?

Constitutive attenuation of transcription

Which model best explains inheritance of complex traits such as height, weight, and IQ?

Control of the traits by more than one gene plus environmental effects

Some genetic diseases can strike at an earlier age and bring about a more rapid degeneration and death in successive generations within a family. This phenomenon can be explained by which mechanism?

Expansion of a trinucleotide repeat in the coding sequence of the gene

Which of the following sequences if double stranded would be the hardest to make single stranded?

GCTGCCGAGCT

How do germ-line mutations differ from somatic mutations?

Germ-line mutations result in mutant gametes, while somatic mutations do not.

Which of the following is NOT true of negatively supercoiled DNA?

Has less than 10 bp per turn of its helix

On rare occasions a chromosome may suffer a deletion that removes the centromere. What would happen to that chromosome?

It would not be found in the subsequent daughter cells.

___________________ ultimately produces all new genetic variation in a population.

Mutation

What types of bonds are created between nucleotides during the process of transcription?

Phosphodiester

A key modification in the 3′ end of eukaryotic mRNA is the addition of 50 to 250 adenine nucleotides at the 3′ end, forming a poly(A) tail. Which of the following statements is not a salient feature of this polyadenylation reaction?

Poly(A) tail at the 3′ end translates to a long stretch of repeated amino acids.

What is the consequence of methylation of DNA sequence called CpG islands?

Transcription repression

One way to define ______________ is any change in allele frequencies within a population.

evolution

Which of the following types of mutations does NOT lead to a change in the amino acid sequence of the gene product?

silent

During initiation, the _____ subunit is the first part of the ribosome to associate with the mRNA.

small