Question 1

Which of the following is TRUE regarding plasmids?

Accepted Answer

Plasmids are usually small, circular, extrachromosomal pieces of DNA ranging from a few thousand to ten thousand base pairs.

Question 2

Genome databases have been created for all of the following model organisms except?

Accepted Answer

Genome databases have been created for the fruit fly (Drosophila), mouse (Mus musculus), humans (Homo sapiens), and Escherichia coli, but not for the American alligator (Alligator mississippiensis) at the time of writing this answer.

Question 3

What is required for the transposition of a retroelement? Select all that apply.

Accepted Answer

B,C,D

Question 4

A researcher is interested in comparing the DNA sequence for the gene encoding myosin between a cheetah (mammal)and a red snapper (fish).What database would be most helpful to her?

Accepted Answer

GenBank is a database that stores genetic sequences, including DNA sequences for genes. It includes sequences from a diverse range of organisms, including mammals and fish, which would be relevant for comparing the myosin gene between a cheetah and a red snapper. Swiss Prot and PIR are databases that store information about protein sequences, which would not be useful for comparing DNA sequences. GenPept is a database that includes both DNA and protein sequences, but GenBank is more specifically designed for genetic sequences. PDB is a database of three-dimensional structures of proteins, which is not directly relevant to DNA sequence comparison.

Question 5

What is the most likely explanation of how 14 genes for globins,each specialized in their function (i.e. ,hemoglobin,myoglobin),arose in the genome of animals?

Accepted Answer

The most likely explanation for the origin of 14 specialized globin genes in the animal genome is a combination of misaligned crossover events and gene mutations. Misaligned crossovers can result in duplications or deletions of genes, while mutations can lead to the development of new gene functions. Together, these processes may have allowed for the differentiation and specialization of globin genes for specific functions such as oxygen transport (hemoglobin) or oxygen storage (myoglobin). Gene deletion and misaligned crossover alone are less likely to explain the development of specialized globin genes.

Question 6

Which of the following statements is TRUE of highly repetitive sequences?

Accepted Answer

Highly repetitive sequences are short DNA sequences that are repeated over and over again, and can be found millions of times in a eukaryotic genome. These sequences do not play a direct role in transcription or translation, but they are important for chromosome structure and stability. In some cases, highly repetitive sequences can cause genetic disorders or increase susceptibility to certain diseases, so they may decrease fitness of the organism.

Question 7

A researcher has mapped the entire genome of an insect.She notices that the genome contains around a thousand copies of a particular DNA sequence.What is the most likely function of this DNA sequence?

Accepted Answer

The presence of a thousand copies of a particular DNA sequence in an insect's genome suggests that the sequence is highly repetitive and likely serves a structural or functional role that requires multiple copies. Such sequences are often involved in the production of ribosomal RNA (rRNA), which is essential for protein synthesis in the cell. Ribosomes are made up of rRNA and proteins, and because cells need a large number of ribosomes to meet the protein synthesis demand, genes coding for rRNA are typically found in multiple copies throughout the genome.

Question 8

The nuclear genome of Species A is three times as large as the nuclear genome of Species B.
Review portions of section 17.2 pertaining to genome size.  What are some potential explanations for the larger size of Species A's genome? Select all that apply.

Accepted Answer

The answer of The nuclear genome of Species A is...

Question 9

Which pair of organisms would have the most homologous b-globin genes?

Accepted Answer

Humans and chimpanzees are known to share a common ancestor relatively recently, and their genomes show high levels of similarity. The b-globin gene is highly conserved across different species, and given the close evolutionary relationship between humans and chimpanzees, they are likely to have the most homologous b-globin genes.

Question 10

What functions does transposase perform during transposition of a DNA transposon? Select all that apply.

Accepted Answer

Transposase recognizes inverted repeats, cleaves the transposon ends, moves it to a new site, and cleaves the target DNA in a staggered manner.

Question 11

How many genes are generally found for every million bases of prokaryotic DNA?

Accepted Answer

Prokaryotic DNA is highly efficient and compact, with a typical gene density of about 1,000 genes per million bases. This high density is due to the relatively small size of prokaryotic genomes and their limited non-coding DNA compared to eukaryotic genomes.

Question 12

Which of the following statements about the differences between prokaryotic and eukaryotic genomes is FALSE?

Accepted Answer

Prokaryotic genomes do not have centromeres, whereas eukaryotic genomes have centromeres. The centromere is a part of the chromosome that plays a crucial role in cell division by ensuring proper separation of sister chromatids.

Question 13

If the nitrogenous bases of both a DNA transposon and a retroelement were tagged with fluorescent markers,what statement best describes the result after transposition of both types of TEs has occurred?

Accepted Answer

DNA transposons move directly from one location in the genome to another, carrying their original DNA sequence (including any markers) with them. Retroelements, however, transpose through an RNA intermediate; the original DNA sequence is transcribed into RNA, which is then reverse-transcribed into DNA and inserted at a new location. The fluorescent markers on the original DNA of the retroelement would not be present on the newly synthesized DNA at the new site.

Question 14

Researchers are interested in the genomes of prokaryotic species for all of the following reasons EXCEPT

Accepted Answer

The statement "bacteria are more highly advanced than humans" is incorrect and not a valid reason for studying prokaryotic genomes. All of the other options are valid reasons for studying prokaryotic genomes.

Question 15

Homologous chromosomes pair with each other during meiosis,but are misaligned.What is the likely outcome if crossing over occurs?

Accepted Answer

Misalignment of homologous chromosomes during meiosis can result in crossing over between non-allelic regions, leading to deletion or duplication of genetic material. If crossing over occurs in misaligned homologous chromosomes, one daughter chromosome can have a gene deletion while the other has a gene duplication. Therefore, Option E "One daughter chromosome contains a gene duplication, one contains a gene deletion, and the remaining two are normal" is the correct choice.

Question 16

14 homologous genes encoding globins (hemoglobin,myoglobin)in the human genome were originally derived from a single ancestor that duplicated 500-600 million years ago.What term best describes the relationship between these genes?

Accepted Answer

Homologous genes encoding globins in the human genome are derived from a single ancestor that duplicated 500-600 million years ago, indicating that these genes belong to a gene family. Gene families are groups of genes that share a common ancestor and have diversified in structure and function through gene duplication and evolutionary divergence.

Question 17

DNA can be found in all of the following cellular locations EXCEPT the

Accepted Answer

DNA is not found in the golgi apparatus. It is primarily found in the nucleus, as well as in the mitochondria and chloroplasts in eukaryotic cells. Plasmids are small DNA molecules found in bacteria and some other organisms, but they are not considered a cellular location.

Question 18

Functionally important gene sequences such as those encoding ribosomal RNA are

Accepted Answer

Functionally important gene sequences such as those encoding ribosomal RNA are moderately repetitive sequences. These sequences are significant because they occur in multiple copies within the genome and are essential for vital cellular processes. However, they are not highly repetitive like transposable elements, nor highly mutated like some other non-functional sequences in the genome.

Question 19

Small chromosomal duplications provide raw material for the addition of genes into a species' genome.These duplications create two or more copies of the same gene,where one or both of the genes can subsequently mutate.These genes are referred to as

Accepted Answer

Small chromosomal duplications create homologous genes, where one or both of the genes can subsequently mutate.

Question 20

Which of the following most adequately describes how the Alu element may have proliferated to constitute 10% of the human genome?

Accepted Answer

A single retroelement, like the Alu element, can be transcribed into many RNA copies, which can then be reverse transcribed and inserted back into the genome at multiple locations, leading to its proliferation.

Quiz 17: Genomes, Repetitive Sequences, and Bioinformatics