JMU BIO 240 Final practice

Which of the following is not a component of DNA?

Deoxyribose

Nucleotide bases

Phosphate

Ribose

ribose

The four nitrogenous bases found in DNA are cytosine, thymine, adenine, and guanine. Which of the following statements regarding the bases is correct?

Thymine is a purine and pairs with adenine in the DNA double helix.

Cytosine has a single ring structure and pairs with guanine in the DNA double helix.

Adenine is a pyrimidine and pairs with cytosine in the DNA double helix.

Guanine has a double ring structure and pairs with thymine in the DNA double helix.

Cytosine has a single ring structure and pairs with guanine in the DNA double helix.

Which of the following statements about dNTPs are true? Please select all that apply.

A hydroxyl group is attached at the 3' Carbon

A nitrogenous base is attached at the 5' Carbon

A hydroxyl group is attached at the 2' Carbon

A triphosphate group is attached at the 5' Carbon

A hydroxyl group is attached at the 3' Carbon

A triphosphate group is attached at the 5' Carbon

Which of the DNA sequences is complementary to 5' CGTAAGTA 3'

5' TACTTACG 3'

5' CGTAAGTA 3'

5' ATGAATGC 3'

5' GCATTCAT 3'

5' TACTTACG 3'

Which of the following statements about RNA are true? Please select all that apply.

RNA has the complementary sequence to the sense DNA strand

RNA has the complementary sequence to the antisense DNA strand

RNA has the same sequence as the template DNA strand (except the RNA has Uracils instead of Thymines)

RNA has the same sequence as the coding DNA strand (except the RNA has Uracils instead of Thymines)

RNA has the complementary sequence to the antisense DNA strand

RNA has the same sequence as the coding DNA strand (except the RNA has Uracils instead of Thymines)

Cells use the template/non-coding/antisense strand as a template to create RNA. The resulting RNA is therefore complementary to the template/non-coding/antisense strand, and the RNA has the same sequence as the coding/sense strand.

How many reading frames does the following mRNA contain?5' AGTCGTGATCAGTCA 3'

4

2

6

3

3

Which of the following transcription elements is a protein?

Core promoter

Transcriptional start site

Transcription factor

Coding region

Transcription factor

Which of the following statements is true?

Introns are removed from mRNA during splicing

The coding region is removed from mRNA before translation

Open reading frames carry the same information as introns

An open reading frame is a length of DNA sequence containing multiple start and stop codons

Introns are removed from mRNA during splicing

DNA contains thymine where RNA contains uracil. What are some of the evolutionary advantages for DNA having thymine rather than uracil? Please select all that apply.

Uracil is recognized by DNA repair systems

Cytosine can be readily converted to thymine

Thymine base-pairs using three hydrogen bonds

Thymine is more limited in its base-pairing than uracil

Uracil is recognized by DNA repair systems

Thymine is more limited in its base-pairing than uracil

Which of the following statements about bacteria are true? Please select all that apply.

Bacteria usually have nuclei

Bacterial chromosomes are usually larger than plasmids

Bacterial chromosomes are usually circular

Bacteria usually have multiple chromosomes

Bacterial chromosomes are usually larger than plasmids Bacterial chromosomes are usually circular

Most bacteria have a single, circular chromosome, but this is not held in a membrane-bound nucleus. Plasmids are small extrachromosomal DNA molecules that are much smaller than chromosomes.

Which genome features are generally found in eukaryotes but not in bacteria? Please select all that apply.

Telomeres

Plasmids

Chromosomes

Centromeres

Telomeres

Centromeres

Bacteria and eukaryotes can both have plasmids, and both have chromosomes. Telomeres are features at the ends of linear chromosomes in eukaryotes. Centromeres are features in linear chromosomes that help chromosomes separate accurately during cell division. Circular chromosomes do not have telomeres or centromeres.

Where can extrachromosomal DNA be found in eukaryotes? Please select all that apply.

Chloroplasts

Plasmids

Mitochondria

Ribosomes

Chloroplasts

Plasmids

Mitochondria

Chloroplasts and mitochondria both contain their own small genomes. They likely derived from prokaryotes that were engulfed by eukaryotic cells early in evolutionary development. Some unicellular eukaryotes contain plasmids. Ribosomes are partly comprised of ribosomal RNA, but do not contain DNA.

The two chromosomes in one pair are referred to as which of the following?

Homologous

Alleles

Centromeres

Sister chromatids

Homologous

Sequence differences between homologues are greater than between sister chromatids.

true

false

true

What is a genetic locus?

A place in a genome where a gene resides

A map of all gene positions in a genome

A distance between positions on a genome

A specific gene

A place in a genome where a gene resides

A random base change is less likely to affect phenotype in humans than in bacteria. Why? Please select all that apply.

Humans have two copies of a gene whereas bacteria have one copy.

A higher percentage of the human genome consists of genes than the bacterial genome.

Less of the human genome is functional than the bacterial genome.

A third base change is more likely to occur in bacteria than in humans.

Humans have two copies of a gene whereas bacteria have one copy

Less of the human genome is functional than the bacterial genome

Orthologs are different members of the same gene family within an organism, whereas paralogs are genes in different species that have shared ancestry, encode similar proteins, and often have similar functions (e.g. all members of the Hox gene family function as specific transcription factors).

true

false

false

After a gene is duplicated, there are several possible outcomes. One of these outcomes is that the new copy takes on a novel role that was not played by the ancestral gene. What is the term for this outcome?

Retrofunctionalization

Degeneration

Neofunctionalization

Hyperfunctionalization

Neofunctionalization

The answer is neofunctionalization. You can remember this because the prefix neo- means new, and the gene has taken on a new function. The other possible outcomes are subfunctionalization and degeneration. In subfunctionalization the ancestral gene functions are divided between the two copies, and in degeneration one copy accumulates mutations and becomes a non-functional pseudogene. Hyperfunctionalization and Retrofunctionalization... don't mean anything at all!

Which of the following characteristics is not true of gene families?

The number of paralogs usually varies widely between individuals in a species

Gene families arise through gene duplications

Functional divergence can arise in gene families because there is no loss of fitness when the function of one copy changes.

The original functions of a gene can be split between two paralogs in a gene family.

The number of paralogs usually varies widely between individuals in a species

What is a pseudogene?

A non-functional gene

A paralogous gene

A member of a gene family

A protein domain

A non-functional gene

During which of the following processes can genes be duplicated?

Replication

Transcription

Translation

Splicing

Replication

A laboratory produced two mutant strains of the plant Arabidopsis from a wild type stock. They sequenced the protein coding region of their gene of interest in the wild type and the two mutants, and obtained the following results for the first exon of the gene. The start codon is highlighted in blue and sets the reading frame, and the mutations are highlighted in orange. A codon table is provided below.

Wild type coding strand sequence: 5'-ATGACTGACCTGGGT-3'

Mutant 1 coding strand sequence: 5'-ATGACTGAACTGGGT-3'

Mutant 2 coding strand sequence: 5'-ATGACT-ACCTGGGT-3'

Which of these mutant strains is more likely to display an altered phenotype?

Strain 1, because this mutation is a deletion that causes a frame shift

Strain 1, because this mutation is a missense mutation that causes an amino acid substitution

Strain 2, because this mutation is a deletion that causes a frame shift

Strain 2, because this mutation is a missense mutation that causes an amino acid substitution

These strains are equally likely to produce a phenotypic result because they are both missense mutations

Strain 2, because this mutation is a deletion that causes a frame shift

The correct answer is mutant 2, because this mutation is a deletion that causes a frame shift. Mutation 1 is a missense mutation that changes only a single amino acid. Frame shift mutations are more likely to alter organismal phenotype because they change the reading frame and alter every amino acid downstream of the mutation location. Missense mutations can definitely have a phenotypic effect, but sometimes changing only a single amino acid does not impact protein function and does not alter the resulting phenotype.

What holds the two strands of the DNA double helix together?

Hydrogen bonds

Ionic bonds

Covalent bonds

Van der Waals forces

Hydrogen bonds

Using the following DNA as template, the sequence of the newly-synthesized strand is 5'______________3'. Template DNA: 5'-ACGTAGCACATGACT-3'

Correct answers must be written from 5' to 3'. DO NOT include the 5' and 3' labels in your answer.

AGTCATGTGCTACGT

Which enzyme separates the strands of the DNA double helix during replication?

DNA helicase

DNA polymerase

DNA ligase

RNA polymerase

DNA helicase

Which of the statements about replication and replication origins in eukaryotes and bacteria are true? Please select all that apply.

Replication origins in both bacteria and eukaryotes are A-T rich

Eukaryotic chromosomes have multiple replication origins

Bacterial chromosomes have a single origin of replication

Eukaryotic replication is faster than bacterial replication

Replication origins in both bacteria and eukaryotes are A-T rich

Eukaryotic chromosomes have multiple replication origins

Bacterial chromosomes have a single origin of replication

Replication origins tend to be A-T rich in both bacteria and eukaryotes. A-T base pairs have two hydrogen bonds, as opposed to C-G pairs, which have three bonds. This means it is easier to separate the strands of the double helix in A-T rich regions than in regions with higher G-C content. Bacterial chromosomes are small, and only a single origin of replication is needed. Eukaryotic chromosomes are much larger, and there would not be enough time to complete replication if there were only one origin. Bacterial replication tends to be faster than eukaryotic replication (~45,000 bp/min vs. 2000-3000 bp/min).

Which of these are found at a replication fork? Please select all that apply.

DNA polymerase

DNA helicase

Double-stranded DNA

Single-stranded DNA

all of the above

What is the function of primase?

To synthesize RNA

To replicate DNA

To separate the DNA double helix

To copy the ends of chromosomes

To synthesize RNA

During DNA replication, the leading strand of the separated double helix is synthesized using continuous replication. The lagging strand is synthesized using discontinuous replication.

true

false

true

Where is the next nucleotide added to the growing chain during DNA replication?

3' hydroxyl

3' phosphate

5' hydroxyl

5' phosphate

3' hydroxyl

What are Okasaki fragments?

DNA pieces made on the lagging strand

Small proteins that protect single-stranded DNA from re-annealing.

Small RNA fragments that prime DNA synthesis

Proteins that join DNA together

DNA pieces made on the lagging strand

The leading strand is more severely affected by the end-replication problem than the lagging strand.

true

false

false

Which of the mutation types is least likely to have a phenotypic effect?

Missense

Frameshift

Nonsense

All the mutation types are equally likely to have a phenotypic effect.

Missense

Which of the following statements about evolution is true?

Neutral mutations are maintained in the population

An adaptive change is a beneficial mutation that arises in response to the needs of a particular environment

Adaptive mutations are subject to purifying selection

Deleterious mutations increase in the population

Neutral mutations are maintained in the population

Ploidy refers to the number of sets of chromosomes found in an organism. Most multicellular organisms are _____

diploid

What term is used for a variety that passes a trait onto all its offspring when crossed to a similar variety?

Self-fertile

Cross-fertile

True-breeding

Dominant

True-breeding

This question relates to Mendel's breeding experiments with peas. A true breeding plant producing smooth peas was crossed with a true-breeding plant producing wrinkled peas (cross 1). The offspring of cross 1 all produced smooth peas. The offspring of cross 1 were then crossed with the wrinkled-pea parent (cross 2). Which of the statements about the cross outcomes are true? Please select all that apply.

Half the offspring of cross 2 had smooth peas

All the offspring of cross 2 had smooth peas

All the offspring of cross 1 had the same genotype

The offspring of cross 2 had a 3:1 smooth:wrinkled ratio

The wrinkled allele is recessive

The wrinkled allele is recessive

Half the offspring of cross 2 had smooth peas

All the offspring of cross 1 had the same genotype

This question relates to Mendel's breeding experiments with peas. Mendel crossed a true-breeding smooth pea plant with a true-breeding wrinkled pea plant. Mendel then crossed the offspring to each other. Which statements are true about the offspring of the second cross? Please select all that apply.

All the offspring had smooth peas

Half the offspring had a genotype with 1 recessive and 1 dominant allele

Half the offspring had smooth peas

The offspring of cross 2 had a 3:1 smooth:wrinkled ratio

Half the offspring had a genotype with 1 recessive and 1 dominant allele

The offspring of cross 2 had a 3:1 smooth:wrinkled ratio

What term describes a situation where two functional alleles are required for proper biological function

Dominant

Heterozygous

Loss-of-function

Haplo-insufficient

Haplo-insufficient

In an experiment, you have a tall plant that produces round peas. Tall and round are dominant and the plant is heterozygous for both traits. The plant is then self-fertilized. What is the probability that a single offspring plant is tall and has wrinkled peas? Express your answer as a decimal.

.1875

Mendel's Law of Segregation refers to the fact that the two alleles for a gene in a diploid organism separate during gamete formation and each gamete receives only one of these alleles.

true

false

true

A cross between tall plants (Tt genotype) and short plants (tt genotype) produced 6 offspring. What is the probability that all 6 offspring are tall?

1/2

1/16

1/64

1/128

1/64

The possible genotypes of the offspring are Tt and tt. Only Tt plants are tall. The probability of an offspring plant being Tt is ½. The probability of every single one of the six offspring plants being Tt can be calculated using the product rule. Probability of ½ and ½ and ½ and ½ and ½ and ½ and ½ = ½ x ½ x ½ x ½ x ½ x ½ = 1/26 = 1/64

A tall plant with purple flowers with genotype TtPp was self-fertilized. There were 8 offspring. What is the chance that at least one of the plants was short?

10%

25%

90%

75%

90%

We are only considering plant height, so we do not need to consider the flower color genotypes. Probability that at least one plant is short + probability that all plants are tall = 1 Probability that all plants are tall = 0.758 = 0.10. Probability that at least one plant is short = 1 - 0.10 = 0.90 = 90%

What is the term used for the first individual identified in a family to be affected by a phenotype?

Pedigree

Heterozygote

Product

Proband

Proband

Which of the statements about inheritance of rare traits in pedigrees are true? Please select all that apply.

An affected child must have at least one unaffected parent

An unaffected child cannot have an affected parent

It is assumed that unrelated individuals who join an affected family do not carry the trait

Males and females are always equally affected by a rare trait

It is assumed that unrelated individuals who join an affected family do not carry the trait

Which of the following characteristics do genes need to possess? Please select all that apply.

They must be expressed

They must be heritable

They must be translated

They must be recessive

They must be expressed

They must be heritable

In a cross between two heterozygotes, the ratio of genotypes is the same as the ratio of phenotypes.

true

false

false

Which phase of the cell cycle has two copies of the genome in the cell for the entire phase?

G1

S

G2

M

G2

Which of the following phases are in mitosis? Please select all that apply.

Metaphase

Interphase

Anaphase

Telophase

Prophase

Metaphase

Anaphase

Telophase

Prophase

The role of checkpoints in the cell cycle is to accelerate the transitions between different phases of the cycle.

true

false

false

Which of the following statements about meiosis and mitosis are true? Please select all that apply.

Meiosis involves two rounds of DNA replication

Meiosis involves four rounds of chromosome/chromatid separation

Mitosis involves one round of DNA replication

Mitosis involves one round of chromosome/chromatid separation

Mitosis involves one round of DNA replication

Mitosis involves one round of chromosome/chromatid separation

What is chromosome pairing?

Recognition and coming together of homologous chromosomes

Replication and joining of the chromatids in each chromosome

Localization of chromosomes at the nuclear envelope

Crossing over between chromosomes

Recognition and coming together of homologous chromosomes

Double-strand breaks (DSB) are needed for crossing-over to occur in meiosis. In a pair of homologous chromosomes, how many chromatids require a DSB in order for crossing over to occur?

1

2

3

4

1

There are four chromatids in a pair of homologous chromosomes (each chromosome has two sister chromatids). One DSB is needed in one sister chromatid of one homologue. This then instigates a crossover with one of the chromatids of the other homologue.

Non-disjunction is when chromosomes fail to separate properly. What factor usually leads to non-disjunction?

Failure of chromosomes to cross-over

Uncontrolled DNA replication

Apoptosis

SPO11 activity

Failure of chromosomes to cross-over

Which part of meiosis explains Mendel's Law of Segregation at the chromosome level?

Separation of homologues at meiosis II

Separation of homologues at meiosis I

Separation of sister chromatids at meiosis II

Separation of sister chromatids at meiosis I

Separation of homologues at meiosis I

Mitosis is more evolutionarily ancestral than meiosis.

true

false

true

Crossing over occurs in which phase of cell division?

Prophase (mitosis)

Prophase I (meiosis)

Prophase II (meiosis)

Crossing over occurs during all of these phases

Both Prophase (mitosis) and Prophase I (meiosis)

Prophase I (meiosis)

Which of the statements about non-disjunction are true? Please select all that apply.

Non-disjunction at meiosis II leads to two normal gametes and two abnormal gametes.

Non-disjunction at meiosis II has a more severe impact than at meiosis I

Non-disjunction at meiosis II leads to three abnormal gametes and one normal gamete.

Non-disjunction at meiosis I leads to four abnormal gametes.

Non-disjunction at meiosis I leads to three normal gametes and one abnormal gamete.

Non-disjunction at meiosis II leads to two normal gametes and two abnormal gametes.

Non-disjunction at meiosis I leads to four abnormal gametes.

Most cases of trisomy 21 in humans occur as a result of:

No crossovers occurring

Translocation of sections of chromosome 21 to another chromosome

Excess crossovers

Crossovers occurring at the end of the chromosome

No crossovers occurring

Which of the following statements applies to human females? Please select all that apply.

Human females usually have XX chromosomes

Human females usually have XY chromosomes

Human females are usually homogametic

Human females are usually heterogametic

Human females usually have XX chromosomes

Human females are usually homogametic

Which of the following factors can impact sex development? Please select all that apply.

Mitosis

Meiosis

Environment

Sex chromosomes

Meiosis

Environment

Sex chromosomes

In meiosis, homologous chromosomes pair and synapse before segregation in meiosis I. How is it possible for the X and Y chromosomes in humans, which are very different, to pair with one another?

The chromosomes are the same size

Some DNA sequences are found on both the X and Y chromosomes

The X and Y chromosomes do not pair during meiosis

X pairs with X and Y pairs with Y during meiosis

Some DNA sequences are found on both the X and Y chromosomes

Genetic experiments by Thomas Hunt Morgan and colleagues examined eye color in Drosophila fruit flies. Males are XY and females are XX, and the gene responsible for eye color is on the X chromosome. Red eye color (wild-type) is dominant to white eye color (mutant). The wild type allele is denoted Xw+ and the mutant allele is Xw. Which of the statements about eye color in these fruit flies is true?

Half of male flies with Xw have white eyes

All female flies with Xw have white eyes

Red-eye females can only produce red-eye offspring

A cross between red-eye males and red-eye females can produce white-eye males

A cross between red-eye males and red-eye females can produce white-eye males

Which of the following leads to gametes receiving incorrect numbers of sex chromosomes?

Apoptosis

Synapsis

Aneuploidy

Non-disjunction

Non-disjunction

Genetic experiments by Thomas Hunt Morgan and colleagues examined eye color in Drosophila fruit flies. Males are XY and females are XX, and the gene responsible for eye color is on the X chromosome. Red eye color (wild-type) is dominant to white eye color (mutant). The wild type allele is denoted Xw+ and the mutant allele is Xw. Rarely, ova receive two X chromosomes or no X chromosomes. Offspring resulting from these ova helped to determine the factors underlying sex determination in Drosophila. In a cross between Xw/Xw and Xw+/Y, which offspring of faulty ova could be distinguished from normal offspring by phenotype alone? Please select all that apply.

XwXwXw+ red-eyed female

XwXwY white-eyed female

Xw+O red-eyed male

OY

XwXwY white-eyed female

Xw+O red-eyed male

Experiments in Drosophila found that XXY flies were female and XO flies were male. This demonstrated that the number of Y chromosomes was critical in determining sex.

true

false

false

Gametes can receive incorrect numbers of sex chromosomes during meiosis. Which of the following statements about chromosome segregation are true? Please select all that apply.

Failure of chromosome separation is more likely at meiosis I than at meiosis II

If chromosome separation fails at meiosis II, all the resultant gametes have an abnormal number of chromosomes.

A gamete can receive both X and Y chromosomes only if chromosome separation fails at meiosis I

Homogametic gametes are produced when chromosome segregation fails at meiosis II.

Failure of chromosome separation is more likely at meiosis I than at meiosis II

A gamete can receive both X and Y chromosomes only if chromosome separation fails at meiosis I

Homogametic gametes are produced when chromosome segregation fails at meiosis II.

Experiments in mice found that XY individuals missing a small region of the Y chromosome developed as females. This suggested that the presence of a Y chromosome was critical in determining sex.

true

false

true

TDF is the major sex-determining component in mammals. What does TDF do?

TDF inactivates one of the X chromosomes

TDF encodes SRY on the Y chromosome

TDF prevents gene expression from the X chromosome

TDF stimulates development of testes

TDF stimulates development of testes

Some organisms, e.g., birds, have a ZW/ZZ system of sex determination rather than the XY/XX system that is familiar from mammals. Which of the following characteristics are true of the ZW/ZZ system? Please select all that apply.

The sex-determining locus is on the W chromosome

Phenotypes resulting from Z-linked genes show up more frequently in males than in females

The Z chromosome in birds and the X chromosome in humans are genetically similar

The ZW/ZZ and XY/XX systems provide evidence of independent evolution of sex determination.

The sex-determining locus is on the W chromosome

The ZW/ZZ and XY/XX systems provide evidence of independent evolution of sex determination.

Which of the following are dosage suppression mechanisms? Please select all that apply.

X-inactivation

Y overexpression

X overexpression

RNA inactivation

X underexpression

X-inactivation

X overexpression

X underexpression

Which of the following are true of epigenetic effects? Please select all that apply.

The effect is retained in daughter cells

The effect is a heritable change in gene activity

The effect is a result of changes in the DNA

The effect is involved in Y chromosome inactivation

The effect is retained in daughter cells

The effect is a heritable change in gene activity

Mendel's law of independent assortment suggests that the inheritance of one gene or trait does not influence the inheritance of a separate unlinked trait.

true

false

true

This question is about Mendel's pea experiments. What genotype and phenotype proportions are expected from a cross between two plants that are heterozygous for pea color and shape? The parent plants have round, yellow peas. Please select all that apply.

1/16 YY RR

4/16 yy rr

3/4 yellow peas

1/4 wrinkled peas

1/2 Yy Rr

1/16 YY RR

3/4 yellow peas

1/4 wrinkled peas

Phenotypes are not always inherited in a predictable Mendelian manner. Which of the following are possible reasons for this? Please select all that apply.

A trait may be affected by the environment

Traits may be influenced by multiple genes

Meiosis is required for Mendelian inheritance

Alleles may not be completely dominant

A trait may be affected by the environment

Traits may be influenced by multiple genes

Alleles may not be completely dominant

What is the difference between co-dominance and incomplete dominance?

In co-dominance, neither allele produces sufficient protein. In incomplete dominance, both alleles make sufficient protein.

In co-dominance, both alleles produce sufficient protein. In incomplete dominance, neither allele makes sufficient protein.

In co-dominance, the phenotype lies between the phenotypes of the parent alleles. For incomplete dominance, the phenotype of both alleles is seen.

In co-dominance, the phenotype reflects both alleles. For incomplete dominance, the phenotype lies between the phenotypes of the parent alleles.

In co-dominance, the phenotype reflects both alleles. For incomplete dominance, the phenotype lies between the phenotypes of the parent alleles.

What term is used for a gene that contributes to more than one phenotype?

Pleiotropic

Epistatic

Dominant

Complex

Pleiotropic

In the ABO blood system, what genotypes do two parents need to have in order to be able to produce children with all the possible ABO blood types. Select two answers from the list below (one genotype for each parent).

IAIB

ii

IAi

IBi

IAIA

IBIB

IAi

IBi

Coat color in Labrador retrievers is usually yellow, black, or chocolate brown. This is determined by alleles of the E gene and the B gene. Dogs with recessive e alleles (ee) are yellow, even when the B locus is functional. This means that the B gene is epistatic to the E gene.

true

false

false

What is a polymorphic gene?

A gene that has accumulated more than the usual number of mutations.

A gene that has more than one common variant

A gene that is always heterozygous

A gene that has multiple functions

A gene that has more than one common variant

Which of the following statements about the offspring of a cross between two carriers of a lethal recessive gene are true? Please select all that apply.

50% of live offspring display the heterozygous phenotype

The genotypes of the offspring follow the same Mendelian patterns as for crosses not involving lethal genes

Where the wild-type gene is dominant, all surviving offspring have the same phenotype

Offspring genotypes follow a 2:1 ratio

The genotypes of the offspring follow the same Mendelian patterns as for crosses not involving lethal genes

Where the wild-type gene is dominant, all surviving offspring have the same phenotype

Redundancy is where more than one gene can perform a particular function. If genes A and B are redundant for a particular phenotype, ___/16 offspring from a cross between AABb and aabb would be expected to exhibit the phenotype.

16

What is the purpose of a complementation test?

To determine whether an organism is homozygous or recessive at a particular locus.

To determine whether an allele is dominant or recessive

To determine whether lethal alleles are present

To determine whether two mutants with the same phenotype have defects in the same gene

To determine whether two mutants with the same phenotype have defects in the same gene

Inferring a genotype from a phenotype can be challenging due to a range of complicating factors that may also affect the phenotype. Which of the following factors can influence phenotype? Please select all that apply.

Exposure to toxins

Temperature

Nutritional conditions

Gene regulation

Exposure to toxins

Temperature

Nutritional conditions

Gene regulation

If fewer than 100% of individuals that are homozygous for a mutant allele exhibit the mutant phenotype, the mutant allele is described as having reduced ______

penetrance

What is meant by variable expressivity?

When an allele is sometimes dominant and sometimes recessive

When penetrance is 100%

When members of a group of true-breeding wild-type individuals sometimes exhibit the phenotype of a recessive gene

When a group of affected individuals do not all have exactly the same mutant phenotype

When a group of affected individuals do not all have exactly the same mutant phenotype

Mutations with more extensive deleterious pleiotropic effects are more likely to be subject to positive selection than mutations with less extensive effects.

true

false

false

Phenotypic ratios in offspring are sometimes unexpected, indicating that not all genetic inheritance follows Mendel's principles.

true

false

false

Which structure that forms during meiosis leads directly to the formation of recombinant chromosomes?

microtubule

centromere

sister chromatid

crossover

crossover

In a cross between parents with the genotypes A/a;B/b and a/a;b/b, where the A and B loci are unlinked, __% of the offspring will have a phenotype that differs from the phenotype of both parents.

50

A cross between two true-breeding strains (P0 generation) with genotypes A/A;b/band a/a;B/B results in an F1 genotype of A/a;B/b. If this is test-crossed to a/a;b/b, which of the following offspring have parental phenotypes? Please select all that apply.

A/a;B/b

A/a;b/b

a/a;B/b

a/a;b/b

A/a;b/b

a/a;B/b

Genes that are located close together on a homologous chromosome are more likely to be inherited together than genes that are further apart.

true

false

true

What is a tetrad?

The cellular structure that contains the four products of meiosis

The structure that joins chromosomes to microtubules

Four paired homologous chromosomes

Two pairs of sister chromatids

Two pairs of sister chromatids

Which of the following statements about genetic and physical maps are true? Please select all that apply.

The order of genes is the same in physical and genetic maps

A physical map shows the location of genes on the DNA molecule

A genetic map unit always corresponds to the same amount of DNA for a particular species

Physical maps give the probability that alleles of two genes will be inherited together

The order of genes is the same in physical and genetic maps

A physical map shows the location of genes on the DNA molecule

If recombination rate is high, then a particular combination of alleles is likely to be transferred to the next generation intact.

true

false

false

Genetic analysis in model organisms such as Drosophila cannot easily be replicated in humans. Which of the following factors are true of Drosophila but not humans? Please select all that apply.

Short generation times

Crossovers between homologous chromosomes

Large numbers of offspring

Haploid gametes

Short generation times

Large numbers of offspring

Which of the following can a genome-wide association study not do?

Identify different haplotypes in different populations

Identify haplotypes associated with a trait

Identify multiple regions of the genome that influence a trait

Identify causative genes underlying a trait

Identify causative genes underlying a trait

Which of the following are components of the preinitiation complex? Please select all that apply.

General transcription factors

RNA polymerase

Initiator elements

Exons

TFIID

General transcription factors

RNA polymerase

TFIID

What is the function of the TATA box?

The TATA box is a signal for transcription termination

The TATA box binds TFIID

The TATA box binds to Mediator

TATA directs the spliceosome to the correct splice sites

The TATA box binds TFIID

Different sigma subunits bind to different promoters in bacteria and play a role in regulation, but TFIID in eukaryotes binds to the promoters of all protein coding-genes.

true

false

true