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Mastering Genetics study guide

If the frequency of the M allele in the human MN blood group system is 0.65 in a population at equilibrium, then the frequency of the N allele must be 0.04.

FALSE

If a recessive disease is found in 50 out of 100,000 individuals, what is the frequency of the heterozygote carriers for this disease?

0.043

In a population of birds in Africa, it was observed that birds with small or large beaks could efficiently crack and eat small or large seeds, respectively. Birds with intermediate beaks had trouble with both types of seeds. What type of selection would be expected to occur in this population if small and large seeds were the only types of food available to these birds?

Disruptive

Which of the following statements describes the members of a population?

They must be able to interbreed with one another

What term is given to the total genetic information carried by all members of a population?

gene pool

A number of mechanisms operate to maintain genetic diversity in a population. Why is such diversity favored?

Genetic diversity may better adapt a population to inevitable changes in the environment.

Allele frequencies within a population can be altered by all EXCEPT which of these processes?

Non-random mating

In the case of complete dominance in a population in equilibrium, we cannot tell which individuals are homozygous dominants and which are heterozygous, but by knowing the frequency of the homozygous recessives, we can estimate the frequency of homozygous dominant and heterozygous genotypes.

TRUE

For a given locus, in a population with two alternative alleles, the allele frequencies p + q = 1.0.

True

A certain form of albinism in humans is recessive and autosomal. Assume that 1% of the individuals in a given population are albino. Assuming that the population is in Hardy-Weinberg equilibrium, what percentage of the individuals in this population is expected to be heterozygous?

...

If a gene has three alleles in a population, their frequencies must add up to 1.5.

FALSE

Fitness is a measure of ________.

The reproductive output of organisms relative to the alternative genotypes

Which term is given to the measure of the proportion of offspring that a particular phenotype will contribute to the next generation?

FITNESS

Natural selection occurs when there is nonrandom elimination of genotypes from a population due to differences in viability or reproductive success.

TRUE

Mutations are regarded as a strong evolutionary mechanism for changing allelic frequencies.

FALSE

In small isolated populations, gene frequencies can fluctuate considerably. The term that applies to this circumstance is ________.

genetic drift

Genetic drift is primarily associated with relatively small breeding populations.

TRUE

In large random mating populations, random genetic drift is usually a significant factor in changing gene frequencies.

FALSE

Inbreeding by itself can change gene frequencies.

FALSE

All EXCEPT which of the following mechanisms can work as prezygotic reproductive isolating mechanisms?

Hybrid sterility

Which general term is used to group various biological and behavioral properties of organisms that act to prevent or reduce interbreeding?

reproductive isolating mechanisms

Evolution is dependent on genetic diversity in the evolving population.

TRUE

Tautomers of nucleotide bases are isomers that differ from each other in the location of one hydrogen atom in the molecule.

TRUE

Which nucleotide will base‑pair with the enol form of 5‑bromouracil?

GUANINE

Which of the following events could result in a frameshift mutation?

BASE DELETION

Bacteria can distinguish between a newly replicated DNA strand and the original template strand because the newly replicated strand is methylated, whereas the original template strand is not.

FALSE

Which repair system uses the RecA and LexA proteins?

SOS REPAIR

Why are X rays more potent mutagens than UV radiation?

X rays are of higher energy and shorter wavelength than UV light. They have greater penetrating ability and can create more disruption of DNA.

Nutritional mutations can be defined as ________.

Those mutations that do not allow an organism to grow on minimal medium but do allow growth on complete medium

Two formal terms used to describe categories of mutational nucleotide substitutions in DNA are ________.

Transversions and transitions

A class of mutations that results in multiple contiguous amino acid changes in proteins is likely to be which of the following?

FRAMESHIFT

Although mutation is the original source of genetic variation, its influence on changing allelic frequencies is relatively minor.

TRUE

Mutations that arise in nature, from no particular artificial agent, are called ________.

Spontaneous mutations

Considering the electromagnetic spectrum, identify likely mutagens from the following list:

radio waves, microwaves, infrared, ultraviolet, X-rays, gamma rays, cosmic rays.

The shorter the wavelength of a radiation source, the greater its likelihood of causing damage.

TRUE

A missense mutation causes premature chain (protein) termination.

FALSE

Which enzyme is responsible for proofreading during replication?

DNA Polymerase

Strand discrimination during the process of DNA repair is based on DNA methylation in E. coli.

TRUE

Postreplication repair is a system that responds after damaged DNA has escaped repair and failed to be completely replicated.

TRUE

The Ames test is used to determine whether or not a compound causes _______.

Gene Mutations

All EXCEPT which of the following are good model organisms for genetic studies?

HUMANS

Transposons, or jumping genes, are DNA elements that move within the genome. In which organismic groups are transposons found?

ALL ORGANISM GROUPS

Of the two cell lines that can contain a mutation in an organism, somatic and germ line, the latter is more consequential to subsequent generations.

TRUE

Deaminating agents

change cytosine to uracil and adenine to hypoxanthine by converting an amino group to a keto group.

Alkylating agents

add a methyl or ethyl group to the amino or keto groups of necleotides, changing base-pairs affinities.

Base analogs, such as 5-bromouracil and 2 amino purine, are

incorporated as thymine and adenine, but base pair with guanine and cytosine respectively.

that grow on minimal medium supplemented with biotin have mutations in the same gene

Neurospora

Once elongation is underway, tRNAs involved in the process occupy a series of sites on the complexed ribosome. The occupation of sites occurs in the following order.

A Site, P Site, E Site

When a peptide bond is formed between two amino acids, one is attached to the tRNA occupying the P site and the other _______.

is attached to the tRNA occupying the A site

Which of the following statements concerning peptide bond formation is correct?

It is catalyzed by peptidyl transferase.

In prokaryotes, the methionine that initiates the formation of a polypeptide chain differs from subsequently added methionines in that _______.

a formyl group is attached to the initiating methionine

Translation is directly dependent on all of the following associations except _______.

complementary base pairing between mRNA and DNA

Which of the following best describes the first step in the formation of the translation initiation complex?

The small ribosomal subunit binds to an mRNA sequence near the 5' end of the transcript

The Beadle and Tatum experiments were based on all of the following assumptions except that _______.

two strains of auxotrophic

In their first round of screening, Beadle and Tatum plated spores on minimal medium. The purpose of this screen was to _______.

determine whether any auxotrophic mutants had been generated

Which of the following can be inferred from the Beadle and Tatum experiments?

For a mutation resulting in the production of a defective enzyme involved in a biosynthetic pathway, the compound preceding the corresponding step will accumulate.

During translation, which molecule bears the codon?

messenger RNA

During translation, which molecule bears the anticodon?

transfer RNA

All EXCEPT which of the following are involved in the process of tRNA "charging?"

rRNA

The ribonucleic acid components known to exist in eukaryotic ribosomes are the following: 5.8S, 18S, 28S, and 5S.

True

Which region of a tRNA molecule binds to amino acids?

3′ end

Which of the following statements best describes the function of aminoacyl tRNA synthetase?

It attaches a specific amino acid to a tRNA molecule.

Each aminoacyl tRNA synthetase is specific for one amino acid and a small number of tRNAs.

TRUE

A protein is 300 amino acids long. Which of the following could be the number of nucleotides in the section of DNA that codes for this protein? (Remember: DNA is double-stranded.)

1800

Prokaryotic and eukaryotic ribosomes are structurally and chemically identical.

False

Which compound accumulates in the metabolic disorder alkaptonuria?

Homogentisic acid

Which of the following statements is true of a Neurospora valine auxotroph?

The cells can grow on minimal medium + valine.

Different sets of human hemoglobins are found at different times in development.

True

The β chain of adult hemoglobin is composed of 146 amino acids of a known sequence. In comparing the normal β chain with the β chain in sickle cell hemoglobin, what alteration is one likely to find?

Valine instead of glutamic acid in the sixth position

Which level of protein structure do beta-pleated sheets and alpha helices represent?

Secondary

The primary structure of a protein is determined by ________.

the sequence of amino acids

The secondary structure of a protein includes ________.

α-helix and β-pleated sheet

Side groups of amino acids are typically classified under which of the following?

polar, nonpolar

Proteins are composed of strings of nucleotides connected together by 5'-3' phosphodiester bonds.

False

The primary structure of a protein is composed of the sequence of amino acids in that protein.

True

All except which of the following may occur during post-translational modification of a protein?

Removal of introns

One form of posttranslational modification of a protein includes ________.

removal or modification of terminal amino acids

Which protein class directly controls many of the metabolic reactions within a cell?

Enzymes

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