Week 5

Question 1

mRNA

Answer 1

single-stranded molecule of RNA that corresponds to the genetic sequence of a gene and is read by a ribosome in the process of synthesizing a protein

Question 2

tRNA

Answer 2

transfer RNA is an adaptor molecule composed of RNA, typically 76 to 90 nucleotides in length, that serves as the physical link between the mRNA and the amino acid sequence of proteins

Question 3

rRNA

Answer 3

Ribosomal ribonucleic acid is a type of non-coding RNA which is the primary component of ribosomes, essential to all cells. rRNA is a ribozyme which carries out protein synthesis in ribosomes

Question 4

ribozymes

Answer 4

RNA molecules that have the ability to catalyze specific biochemical reactions, including RNA splicing in gene expression, similar to the action of protein enzymes

Question 5

transcription

Answer 5

first of several steps of DNA based gene expression in which a particular segment of DNA is copied into RNA by the enzyme RNA polymerase

Question 6

RNA polymerase

Answer 6

enzyme that synthesizes RNA from a DNA template. Using the enzyme helicase, RNAP locally opens the double-stranded DNA so that one strand of the exposed nucleotides can be used as a template for the synthesis of RNA

Question 7

transcription bubble

Answer 7

molecular structure formed during DNA transcription when a limited portion of the DNA double strand is unwound. The size of a transcription bubble ranges from 12-14 base pairs

Question 8

coding strand

Answer 8

coding strand is the DNA strand whose base sequence corresponds to the base sequence of the RNA transcript produced. It is this strand which contains codons, while the non-coding strand contains anticodons

Question 9

template strand

Answer 9

mRNA is built from is called the template strand because it serves as a template for transcription. It is also called the antisense strand. The template strand runs in a 3’ to 5’ direction

Question 10

-10 sequence

Answer 10

promoter

Question 11

TATA box

Answer 11

sequence of DNA found in the core promoter region of genes in archaea and eukaryotes

Question 12

-35 sequence

Answer 12

promoter

Question 13

sigma subunit

Answer 13

protein needed for initiation of transcription in bacteria

Question 14

rho independent

Answer 14

mechanism in prokaryotes that causes RNA transcription to stop and release the newly made RNA. In this mechanism, the mRNA contains a sequence that can base pair with itself to form a stem-loop structure 7–20 base pairs in length that is also rich in cytosine-guanine base pairs

Question 15

housekeeping genes

Answer 15

constitutive genes that are required for the maintenance of basic cellular function, and are expressed in all cells of an organism under normal and patho-physiological conditions

Question 16

positive regulation

Answer 16

regulatory elements that permit RNA polymerase binding to the promoter region, thus allowing transcription to occur

Question 17

activator protein

Answer 17

increases gene transcription of a gene or set of genes

Question 18

negative regulation

Answer 18

repressor protein binds to an operator to prevent a gene from being expressed

Question 19

repressor protein

Answer 19

a DNA- or RNA-binding protein that inhibits the expression of one or more genes by binding to the operator or associated silencers. A DNA-binding repressor blocks the attachment of RNA polymerase to the promoter, thus preventing transcription of the genes into messenger RNA

Question 20

operator sequence

Answer 20

allows proteins responsible for transcription to attach to the DNA sequence. The gene, or genes, which get transcribed when the operator is bound are known as the operon

Question 21

transcription factor

Answer 21

protein that controls the rate of transcription of genetic information from DNA to messenger RNA, by binding to a specific DNA sequence

Question 22

initiator box

Answer 22

core promoter that is similar in function to the Pribnow box (in prokaryotes) or the TATA box (in eukaryotes

Question 23

upstream element

Answer 23

upstream is toward the 5’ end of the coding strand for the gene in question

Question 24

enhancer

Answer 24

short (50–1500 bp) region of DNA that can be bound by proteins (activators) to increase the likelihood that transcription of a particular gene will occur. These proteins are usually referred to as transcription factors. Enhancers are cis-acting.

Question 25

operon

Answer 25

a functioning unit of DNA containing a cluster of genes under the control of a single promoter.

Question 26

polycistronic mRNA

Answer 26

encodes several proteins and is characteristic of many bacterial and chloroplast mRNAs. Polycistronic mRNAs consist of a leader sequence which precedes the first gene

Question 27

monocistronic mRNA

Answer 27

encodes only one protein and all eukaryotic mRNAs are monocistronic

Question 28

cistron

Answer 28

alternative term for "gene". The word cistron is used to emphasize that genes exhibit a specific behavior in a cis-trans test

Question 29

5' cap

Answer 29

a specially altered nucleotide on the 5′ end of some primary transcripts such as precursor messenger RNA

Question 30

Poly A tail

Answer 30

Polyadenylation is the addition of a poly tail to a messenger RNA. The poly tail consists of multiple adenosine monophosphates; in other words, it is a stretch of RNA that has only adenine bases. In eukaryotes, polyadenylation is part of the process that produces mature messenger RNA for translation

Question 31

splicing

Answer 31

a form of RNA processing in which a newly made precursor messenger RNA transcript is transformed into a mature messenger RNA. During splicing, introns are removed and exons are joined together

Question 32

introns

Answer 32

any nucleotide sequence within a gene that is removed by RNA splicing during maturation of the final RNA product. In other words, introns are non-coding regions of an RNA transcript, or the DNA encoding it, that are eliminated by splicing before translation

Question 33

exons

Answer 33

a segment of a DNA or RNA molecule containing information coding for a protein or peptide sequence

Question 34

nucleolus

Answer 34

largest structure in the nucleus of eukaryotic cells. It is best known as the site of ribosome biogenesis

Question 35

RNAi

Answer 35

biological process in which RNA molecules inhibit gene expression or translation, by neutralizing targeted mRNA molecules

Question 36

siRNA

Answer 36

Small interfering RNA, sometimes known as short interfering RNA or silencing RNA, is a class of double-stranded RNA non-coding RNA molecules, typically 20-27 base pairs in length, similar to miRNA, and operating within the RNA interference pathway

Question 37

RISC

Answer 37

RNA-induced silencing complex: multiprotein complex, specifically a ribonucleoprotein, which incorporates one strand of a single-stranded RNA (ssRNA) fragment, such as microRNA (miRNA), or double-stranded small interfering RNA (siRNA).

Question 38

dicer

Answer 38

cleaves double-stranded RNA (dsRNA) and pre-microRNA (pre-miRNA) into short double-stranded RNA fragments called small interfering RNA and microRNA