hey guys i wasn't in class on Friday, but i hear you took a few quizzes and got the take home quiz packet for chapters 18, 19, and 20.

heres the vocab for chapter 18:

operator- In bacterial DNA, a sequence of nucleotides near the start of an operon to which an active repressor can attach. The binding of the repressor prevents RNA polymerase from attaching to the promoter and transcribing the genes of the operon.

operon- A unit of genetic function found in bacteria and phages, consisting of a promoter, an operator, and a coordinately regulated cluster of genes whose products function in a common pathway.

repressor- A protein that inhibits gene transcription. In prokaryotes, repressors bind to the DNA in or near the promoter. In eukaryotes, repressors may bind to control elements within enhancers, to activators, or to other proteins in a way that blocks activators from binding to DNA.

regulatory gene- A gene that codes for a protein, such as a repressor, that controls the transcription of another gene or group of genes.

corepressor- A small molecule that binds to a bacterial repressor protein and changes its shape, allowing it to switch an operon off.

inducer- A specific small molecule that binds to a bacterial repressor protein and changes the repressor's shape so that it cannot bind to an operator, thus switching an operon on.

histone acetylation- The attachment of acetyl groups to certain amino acids of histone proteins.

genomic imprinting- A phenomenon in which expression of an allele in offspring depends on whether the allele is inherited from the male or female parent.

epigenetic inheritance- Inheritance of traits transmitted by mechanisms not directly involving the nucleotide sequence of a genome.

control elements- A segment of noncoding DNA that helps regulate transcription of a gene by binding a transcription factor. Multiple control elements are present in a eukaryotic gene’s enhancer.

enhancers- A segment of eukaryotic DNA containing multiple control elements, usually located far from the gene whose transcription it regulates.

alternative RNA splicing- A type of eukaryotic gene regulation at the RNA-processing level in which different mRNA molecules are produced from the same primary transcript, depending on which RNA segments are treated as exons and which as introns.

proteasomes- A giant protein complex that recognizes and destroys proteins tagged for elimination by the small protein ubiquitin.

microRNAs- A small, single-stranded RNA molecule, generated from a hairpin structure on a precursor RNA transcribed from a particular gene. The miRNA associates with one or more proteins in a complex that can degrade or prevent translation of an mRNA with a complementary sequence.

oncogenes- A gene found in viral or cellular genomes that is involved in triggering molecular events that can lead to cancer.

tumor-suppressor genes- A gene whose protein product inhibits cell division, thereby preventing the uncontrolled cell growth that contributes to cancer.


Roots:

morph: form gen: produce
proto: first onco: tumor

Multiple Choice Questions:

1. The initiator tRNA attaches at the ribosome's _____ site.

A) A
B) translocation
C) E
D) P
E) Q

2. What enzyme catalyzes the attachment of an amino acid to tRNA?

A) aminoacyl-tRNA synthetase
B) rubisco
C) dextrinase
D) argininosuccinate lyase
E) nuclease

3. The RNA segments joined to one another by spliceosomes are _____.

A) caps
B) exons
C) snRNPs
D) tails
E) introns

4. Which of the following in NOT true of RNA processing?

A) Exons are cut out before mRNA leaves the nucleus
B) Nucleotides may be added at both ends of the RNA
C) Ribozymes may function in RNA splicing
D) RNA splicing can be catalyzed by spliceosomes
E) A primary transcript is often much longer than the final RNA molecule that leaves the nucleus

5. Which component is NOT directly involved in translation?

A) mRNA
B) DNA
C) tRNA
D) ribosomes
E) GTP
Answers:

1. D
2. A
3. B
4. A
5. B