Question 1

Telomeres are required for the complete replication of linear chromosomes.

Accepted Answer

Telomeres are necessary for the complete replication of linear chromosomes as they provide a protective end-capping structure that prevents the loss of genetic information at the ends of chromosomes during cell division. Without telomeres, chromosomes would shorten and lose important genetic information with each cell division, ultimately leading to cell death or senescence.

Question 2

Epigenetic inheritance is the transfer from parent to progeny of information that is not encoded in DNA sequences.

Accepted Answer

Epigenetic inheritance involves the transfer of information through modifications to DNA or histones, rather than changes to the DNA sequence itself. This is why it is considered "epi" (meaning "above" or "beyond") genetic inheritance.

Question 3

A gene containing three exons would have how many introns?

Accepted Answer

The answer of A gene containing three exons would have...

Question 4

How many possible mRNAs could be derived from a gene with three exons (exon 1, exon 2, and exon 3)?

Accepted Answer

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Question 5

What explains how humans are able to express over 85,000 proteins when we are reported to only have about 21,000 genes?

Accepted Answer

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Question 6

Why would a deleterious genetic mutation in a gene on the X chromosome more likely affect males than females?

Accepted Answer

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Question 7

What was the very important outcome of the ENCODE Project?

Accepted Answer

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Question 8

Describe the mechanisms by which retrotransposons such as SINEs and LINEs get moved around within the genome.

Accepted Answer

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Question 9

When chromatin DNA is partially digested with micrococcal nuclease (an enzyme that degrades DNA) and subsequently run on an agarose gel, it is found to yield DNA fragments approximately 200 base pairs long. What is the explanation for this?

Accepted Answer

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Question 10

Give two reasons why a specific telomere structure is required at the end of a eukaryotic chromosome.

Accepted Answer

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Question 11

What is the difference between telomerase in cancer cells and telomerase in normal somatic cells of an adult, and what is the significance of that difference?

Accepted Answer

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Question 12

Even though its complete genome is significantly smaller than that of humans, the flowering plant Arabidopsis thaliana has about _______ genes, which is about the same number as humans have.

Accepted Answer

Arabidopsis thaliana has approximately 26,000 genes, which is similar to the number of genes in humans despite having a smaller genome size.

Question 13

Which statement about introns is true?

Accepted Answer

Introns are non-coding sequences within a gene that are transcribed into pre-mRNA but are removed during RNA splicing, so they are absent from the mature mRNA.

Question 14

Which statement about exons is false?

Accepted Answer

Exons are sequences in the DNA that are transcribed into mRNA and are involved in coding for proteins or serving as untranslated regions (UTRs) in the mRNA. They do not contain sequences for small nucleolar RNAs (snoRNAs), as snoRNAs are typically found within introns or in their own independent genes, not within exons.

Question 15

Which statement about introns in the yeast Saccharomyces cerevisiae is true?

Accepted Answer

A small percentage of S. cerevisiae genes contain introns, and these introns are often located near the beginning of the gene. This reflects the organism's streamlined genome, where introns are less common compared to many other eukaryotes.

Question 16

The percentage of the average human gene that encodes proteins is approximately

Accepted Answer

Only about 3% of the average human gene encodes for proteins, while the rest consists of non-coding DNA sequences that may still play important roles in gene expression, regulation, and other cellular processes.

Question 17

The human genome is distributed among _______ chromosomes.

Accepted Answer

The correct answer is B) 23. Humans have 23 pairs of chromosomes, for a total of 46 chromosomes. This includes 22 pairs of autosomes and 1 pair of sex chromosomes.

Question 18

If a human gene is found to contain five introns, the mature mRNA encoded by that gene would have how many exons?

Accepted Answer

The answer of If a human gene is found to...

Question 19

The human genome contains only 20,000 to 25,000 actual gene sequences, yet the human genome can produce up to 100,000 gene products. Which of the following processes accounts for this difference?

Accepted Answer

Alternative splicing is the process by which different exons are spliced together in different combinations to produce different mRNA molecules from the same gene. This leads to the production of multiple protein isoforms from a single gene, accounting for the large number of gene products despite a relatively small number of gene sequences. The other options (B, C, and D) are not involved in this process.

Question 20

The ENCODE project revealed that as much as 75% of the genome in humans is actually transcribed into RNA. Most of this is non‒protein-coding RNA. Which of the following include two new classes of noncoding RNA discovered by the ENCODE project?

Accepted Answer

The two new classes of noncoding RNA discovered by the ENCODE project are MicroRNA (miRNA) and Long Noncoding RNA (lncRNA). Therefore, option D is the correct choice. Option A includes mRNA and tRNA, which are not new classes of noncoding RNA. Option B includes rRNA and snRNA, which were already known before the ENCODE project. Option C includes Pre-mRNA and hnRNA, which are intermediate products in the process of mRNA synthesis and not considered as noncoding RNA.

Quiz 6: Genes and Genomes