Bio test 3 Lecture 22 – Flashcards

The nucleolus -is surrounded by a thin nucleolar membrane. -is found, one per cell, in eukaryotes. -contains the NOR of rRNA genes. -synthesizes ribosomal proteins. -all of the above

DNA replication is highly accurate. It results in about one mistake per billion nucleotides. For the human genome, how often would errors occur? -on average, once a lifetime in 10 percent of the population -on average, once every six cell divisions -on average, six times each time the entire genome of a cell is replicated -on average, once or twice in the lifetime of an individual

The epsilon (ε) subunit of DNA polymerase III of E. coli has exonuclease activity. How does it function in the proofreading process? The epsilon subunit _____. -excises a segment of DNA around the mismatched base -adds nucleotide triphosphates to the 3' end of the growing DNA strand -can recognize which strand is the template or parent strand and which is the new strand of DNA. -removes a mismatched nucleotide

Which of the following statements about rRNA is/are correct? Choose all that apply. -RNA Polymerase II transcribes the 5S rRNA genes. -The tandem arrays of 5S rRNA genes are located in an NOR. -The 45S pre-rRNA transcript is processed by complexes of RNA and protein known as snoRNPs. -The 45S and 5S rRNA genes are located on chromosomes 13, 14, 15, 21 and 22. -No productive association of the small and large ribosomal subunits occurs until the subunits are exported into the cytoplasm. -The 45S rRNA genes have very strong promoters for optimal transcription.

Which of the following is least likely to be found in the dense fibrillar region of the nucleolus? -18S rRNA -Ribosomal proteins -5.8S rRNA -28S rRNA -Pre-ribosomal particles

Which one of the following is least likely to cause mutations in DNA? -ultraviolet radiation from sunlight -aflatoxins that are found in moldy grains -light from an incandescent bulb -hydroxyl radicals formed as by-products of aerobic respiration

Which of the following statements about mutations is incorrect? -Proofreading by DNA polymerases helps reduce a cell's observed frequency of mutation. -Mistakes in transcription lead to alterations in the nucleotide sequence in the DNA. -If a mutation occurs in a bacterial cell, all subsequent progeny cells will carry that mutation. -If a mutation occurs in a germ line cell, the resulting fertilized embryo will carry the mutation in every cell. -Mistakes in translation are not as critical as mistakes in replication.

Which of the following statements about mutations is/are incorrect? Choose all that apply. -Mutations arise from sources other than just mistakes made during DNA replication. -DNA replication machinery generates errors at a lower rate than RNA transcription machinery. -Mistakes in transcription are not as critical as mistakes in replication. -Germ-line mutations can be passed down to offspring. -Somatic mutations are often passed down to offspring. -Mistakes in DNA replication do not lead to heritable mutations. -Mutations in RNA during transcription are not inherited by daughter cells over multiple generations.

The nucleus is the site for

RNA polymerase III

TFIID

snRNPs

eukaryotic ribosomes consist of

active mammalian cells have 5-10 million ribosomes that must be synthesized each time the cell divides, so

tandem arrays of genes for 5.8S, 18S, and 28S rRNAs are transcribed by

45S gene arrays

5S gene

the nucleolus

NORs

fibrillar region/center

dense fibrillar region

granular zone

mutations

gene-

gene+

DNA polymerase

mismatch repair

damage to DNA can be done by

nucleotide excision repair