Gene Expression & Regulation Flashcards

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1
Q

Define Epigenetics

A

The study of heritable phenotype changes that do not involve alterations in the DNA sequence.

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2
Q

Define Operon

A

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

An operon consists of a promoter, an operator, and structural genes.

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3
Q

Define Promoter

A

The site where RNA polymerase attaches, signaling the start of the gene.

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4
Q

Define Operator

A

The site where a repressor binds, stopping the transcription of that gene.

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5
Q

Define Structural Genes

A

Genes coding for an enzyme that are transcribed as a unit.

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6
Q

Define Inducible Gene

A

A gene that needs to be “turned on” or activated in order to be expressed.

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7
Q

Define Repressible Gene

A

A gene that needs to be “turned off” or deactivated in order to stop being expressed.

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8
Q

Define Enhancer

A

A DNA sequence that promotes transcription. Each enhancer is made up of short DNA sequences called distal control elements.

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9
Q

Define Single-Nucleotide Polymorphism (SNP)

A

A DNA sequence variation occurring when a single nucleotide in the genome differs between members of a species or paired chromosomes in an individual.

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10
Q

Define Homeotic Genes (HOX)

A

Master regulator genes that direct the development of particular body segments or structures.

When HOX are changed by mutations, body plans may undergo drastic changes.

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11
Q

Describe the evolution of gene regulation in prokaryotes

A

Prokaryotes are single-celled. They evolved to grow and divide rapidly, and must respond quickly to changes in external environment.
Gene regulation:
• turn genes on and off rapidly
• flexibility and reversibility
• adjust levels of enzymes for synthesis and digestion

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12
Q

Describe the evolution of gene regulation in eukaryotes

A

Eukaryotes are multicellular. They evolved to maintain constant internal conditions while facing changing external conditions, and regulate the body as a whole. They have long term processes for growth and development.
Gene regulation:
• turn on and off a large number of genes
• coordinate the body as a whole rather than serve the needs of individual cells

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13
Q

What are the points of control in gene expression?

A
The control of gene expression can occur at any step in the pathway from gene to functional protein.
•  packing/unpacking DNA
•  transcription
•  mRNA processing
•  mRNA transport
•  translation
•  protein processing
•  protein degradation
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14
Q

How does DNA packing regulate gene expression?

A

DNA packing regulates transcription. If DNA is wrapped tightly around histones, the gene isn’t transcribed.

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15
Q

How do histones contribute to gene regulation?

A

Histones are eight protein molecules containing positively charged amino acids. These amino acids bind tightly to the negatively charged DNA, regulating transcription.

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16
Q

How does DNA methylation regulate gene expression?

A

The methylation of DNA blocks transcription factors. The gene doesn’t get transcribed into protein.

DNA methylation attaches methyl groups (—CH3) to cytosine, and is a nearly permanent inactivation of genes.

17
Q

How does histone acetylation regulate gene expression?

A

The acetylation of histones unwinds DNA, turning on the gene and enabling transcription.

Histone acetylation attaches acetyl groups (—COCH3) to histones, enabling transcription factors to have easier access to genes.

18
Q

What are the control regions on DNA?

A

Promotor: nearby control sequence on DNA where RNA polymerase and transcription factors bind. “Base” rate of transcription.
Enhancer: distant control sequences on DNA where activator proteins bind. “Enhanced” rate of transcription.

19
Q

How do proteins interact with DNA control regions to regulate gene expression?

A

Activator proteins bind to enhancer sequences and stimulate transcription, increasing the rate. Silencer proteins bind to enhancer sequences and block gene transcription.

20
Q

How does post-transcriptional control regulate gene expression?

A

Alternative RNA splicing causes variable processing of exons and creates a family of proteins.

22
Q

How does mRNA interference regulate gene expression?

A

Small interfering RNAs (siRNA) are short segments of RNA (21-28 bases) that bind to the mRNA template. They create sections of double-stranded mRNA that acts as a tag for degradation of that mRNA. This causes gene “silencing.”

24
Q

How does translation control regulate gene expression?

A

The initiation of the translation stage is blocked by regulatory proteins attached to the 5’ end of mRNA. This prevents the attachment of ribosomal subunits and initiator tRNA, which blocks the translation of mRNA into protein.

25
Q

How does protein processing regulate gene expression?

A

Proteins are folded, cleaved, and have sugar groups added, targeting them for transport or destruction.

25
Q

How does protein degradation regulate gene expression?

A

Ubiquitin tagging: a 76 amino acid polypeptide called ubiquitin acts as a “death tag” to mark unwanted proteins for destruction.

Proteasome degradation: breaks down any proteins into 7-9 amino acid fragments.

26
Q

Francois Jacob and Jacques Monod

A

Conducted experiments in 1961 with E. Coli bacteria that offered insight into the process of gene regulation.

26
Q

How do distal control elements regulate gene expression?

A

Activators bound to the distal control elements interact with mediator proteins and transcription factors. Two different genes may have the same promoter but different distal control elements, enabling differential gene expression.