Gene expression and regulation

Question 1

What is a point mutation?

Answer 1

A point mutation or substitution is a genetic mutation where a single nucleotide base is changed, inserted or deleted from a DNA or RNA sequence of an organism’s genome.

Question 2

What is an operator?

Answer 2

An operator is a genetic sequence which 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 3

What is the nuclear envelope?

Answer 3

The nuclear envelope, also known as the nuclear membrane, is made up of two lipid bilayer membranes which in eukaryotic cells surrounds the nucleus, which encases the genetic material

Question 4

What is a metabolic pathway?

Answer 4

A metabolic pathway is a series of chemical reactions in a cell that build and breakdown molecules for cellular processes.

Question 5

What is a release factor?

Answer 5

A release factor is a protein that allows for the termination of translation by recognizing the termination codon or stop codon in an mRNA sequence. They are named so because they release new peptides from the ribosome.

Question 6

What is a co-repressor?

Answer 6

In the field of molecular biology, a corepressor is a substance that inhibits the expression of genes. In prokaryotes, corepressors are small molecules whereas in eukaryotes, corepressors are proteins.

Question 7

What is protein targeting?

Answer 7

Protein targeting or protein sorting is the biological mechanism by which proteins are transported to their appropriate destinations in the cell or outside it.

Question 8

What is the lac operon?

Answer 8

The lactose operon (lac operon) is an operon required for the transport and metabolism of lactose in E.coli and many other enteric bacteria. Although glucose is the preferred carbon source for most bacteria, the lac operon allows for the effective digestion of lactose when glucose is not available through the activity of beta-galactosidase.

Question 9

What are the lac genes encoding enzymes?

Answer 9

The lac genes encoding enzymes are lacZ, lacY, and lacA.

Question 10

What is an enhancer?

Answer 10

In genetics, an enhancer is a 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.

Question 11

What is a mutagen?

Answer 11

A mutagen is a chemical or physical phenomenon, such as ionizing radiation, that promotes errors in DNA replication. Exposure to a mutagen can produce DNA mutations that cause or contribute to diseases such as cancer.

Question 12

What is a TATA box?

Answer 12

A TATA box is a DNA sequence that indicates where a genetic sequence can be read and decoded. It is a type of promoter sequence, which specifies to other molecules where transcription begins.

Question 13

What is transcription?

Answer 13

Transcription is the process by which the information in a strand of DNA is copied into a new molecule of messenger RNA (mRNA). DNA safely and stably stores genetic material in the nuclei of cells as a reference, or template.

Question 14

What are silencers?

Answer 14

In genetics, a silencer is a DNA sequence capable of binding transcription regulation factors, called repressors. DNA contains genes and provides the template to produce messenger RNA (mRNA). That mRNA is then translated into proteins. … Thus, silencers prevent genes from being expressed as proteins.

Question 15

What is splicing?

Answer 15

During splicing, introns (non-coding regions) are removed and exons (coding regions) are joined together. For nuclear-encoded genes, splicing takes place within the nucleus either during or immediately after transcription.

Question 16

What is missense mutation?

Answer 16

In genetics, a missense mutation is a point mutation in which a single nucleotide change results in a codon that codes for a different amino acid. It is a type of nonsynonymous substitution.

Question 17

What is a frameshift mutation?

Answer 17

A frameshift mutation is a type of mutation involving the insertion or deletion of a nucleotide in which the number of deleted base pairs is not divisible by three. … If a mutation disrupts this reading frame, then the entire DNA sequence following the mutation will be read incorrectly.

Question 18

What is a proteasome?

Answer 18

Proteasomes are protein complexes which degrade unneeded or damaged proteins by proteolysis, a chemical reaction that breaks peptide bonds. Enzymes that help such reactions are called proteases.

Question 19

What is a chaperone protein?

Answer 19

Chaperones are a group of proteins that have functional similarity and assist in protein folding. They are proteins that have the ability to prevent non-specific aggregation by binding to non-native proteins.

Question 20

What is pre-mRNA?

Answer 20

a precursor mRNA (pre-mRNA) is a type of primary transcript that becomes a messenger RNA (mRNA) after processing. Pre-mRNA is synthesized from a DNA template in the cell nucleus by transcription. Pre-mRNA comprises the bulk of heterogeneous nuclear RNA (hnRNA).

Question 21

what is an snRNA?

Answer 21

A small nuclear RNA (snRNA) is one of many small RNA species confined to the nucleus; several of the snRNAs are involved in splicing or other RNA processing reactions.

Question 22

What is alternative splicing?

Answer 22

Alternative splicing is a process that enables a messenger RNA (mRNA) to direct synthesis of different protein variants (isoforms) that may have different cellular functions or properties. It occurs by rearranging the pattern of intron and exon elements that are joined by splicing to alter the mRNA coding sequence.

Question 23

What are RNA nucleotides?

Answer 23

Each nucleotide in RNA contains a ribose sugar, with carbons numbered 1’ through 5’. A base is attached to the 1’ position, in general, adenine (A), cytosine (C), guanine (G), or uracil (U). Adenine and guanine are purines, cytosine and uracil are pyrimidines.

Question 24

What are exons and introns?

Answer 24

Introns and exons are nucleotide sequences within a gene. Introns are removed by RNA splicing as RNA matures, meaning that they are not expressed in the final messenger RNA (mRNA) product, while exons go on to be covalently bonded to one another in order to create mature mRNA.

Question 25

What are anticodons?

Answer 25

Anticodons are sequences of nucleotides that are complementary to codons. They are found in tRNAs, and allow the tRNAs to bring the correct amino acid in line with an mRNA during protein production.

Question 26

What is the 5’UTR and 3’UTR?

Answer 26

Within the 5’ UTR is a sequence that is recognized by the ribosome which allows the ribosome to bind and initiate translation. … The 3’ UTR is found immediately following the translation stop codon. The 3’ UTR plays a critical role in translation termination as well as post-transcriptional modification.

Question 27

What is Positive/Negative Gene regulation?

Answer 27

n negative regulation a repressor protein binds to an operator to prevent a gene from being expressed. In positive regulation a transcription factor is required to bind at the promoter in order to enable RNA polymerase to initiate transcription.

Question 28

What is 3’ Poly-A tail?

Answer 28

The poly-A tail is a long chain of adenine nucleotides that is added to a messenger RNA (mRNA) molecule during RNA processing to increase the stability of the molecule. … The processing of the 3’ end adds a poly-A tail to the RNA molecule. First, the 3’ end of the transcript is cleaved to free a 3’ hydroxyl.

Question 29

What is transcription factor?

Answer 29

Proteins that regulate gene expression by binding to specific sequences that are associated with a transcription initiation site.