Exam 6: Genes and Genomes

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.

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?

In the chromatin around centromeres, nucleosomes are present that have a unique structure in which the core protein _______ is replaced by _______, and this variant of the nucleosome is required for protein assembly at the kinetochore.

Which statement about introns is true?

Introns are nonfunctional sequences between exons.

The specialized regions of eukaryotic chromosomes that serve as sites for association with sister chromatids are called _______.

A single miRNA can target up to 100 different mRNAs.

What is the rationale for developing anti-cancer agents that inhibit telomerase?

Synthesis of different proteins from the same gene is due to

Introns can encode

A gene can be defined as a segment of DNA that codes for

The human genome is distributed among _______ chromosomes.

Simple-sequence repeats

Electron microscopy of chromatin revealed that chromatin has a beaded appearance. The beads were later identified to be _______.

Many of the genetic alterations responsible for inherited diseases may be due to mutations in functional noncoding regions rather than in protein-coding sequences.

Regulation of gene expression by short double-stranded RNAs is not only an important experimental method but is also normally used by cells to control mRNA _______ and _______.

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

Suppose you are working on a set of experiments using Western blotting. Using an antibody that recognizes amino sequences encoded by exon 3 of a five-exon gene, you have demonstrated that a protein is highly expressed in a particular cell line. To assess the mRNA, you design reverse transcriptase polymerase chain reaction (rtPCR) primers to exons 2 and 4, which flank exon 3. Despite all your efforts, you cannot amplify an mRNA. You know that it is indeed expressed, since the protein is detectable. You also know that your controls are working and your experimental procedure is sound, because you are able to detect an mRNA for the other cell lines. Given what you know about the "central dogma" and gene structure, how might you explain this inability to identify the mRNA encoding this exon 3 protein?

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?

Heterochromatin consists of