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Flashcards in Gene Expression Deck (41)
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1
Q

How is gene expression controlled in bacteria?

A

Genes are turned on and off by starting or stopping transcription.

2
Q

What are operons?

A

a unit of genetic function which consists of a promoter, operator, and genes that are grouped together based on their job

3
Q

What are the two types of negative gene regulation (feedback)?

A

repressible and inducible operons

4
Q

Explain repressible operons.

A
  • transcription is usually on but can be turned off
  • function in anabolic pathways (building large molecules)
  • regulatory gene codes for a repressor upstream from the operon and makes it when there is enough of a protein, a corepressor (the protein) then binds to a repressor which activates it and causes it to bind to the operator which inhibits RNA polymerase from binding to the operon
5
Q

Explain inducible operons.

A
  • transcription is usually off but can be turned on
  • function in catabolic pathways (break down molecules)
  • when a repressor is made, it is immediately activated and attaches to the operator, preventing the binding of RNA polymerase. The presence of a substance (the inducer) then attaches to the repressor and deactivates it. RNA polymerase is then free to bind and transcribe.
6
Q

How is positive gene regulation controlled?

A

an activator (protein) binds to the promoter and stimulates transcription of a gene by attracting RNA polymerase

7
Q

Give an example for a repressible operon, an inducible operon, and positive gene regulation.

A
  1. tryptophan synthesis
  2. Lac operon- makes enzyme (B-galactosidase) that breaks down lactose (inducer)
  3. CAP (catabolite activator protein) which is activated by cAMP
8
Q

What are the 7 places gene expression can be controlled in humans?

A

Chromatin modification, DNA methylation, Regulation of transcription initiation, Alternative RNA splicing, mRNA Degradation, Regulatory proteins, Protein Degradation

9
Q

Chromatin modification

A

Loosens the chromatin (loosens the DNA from the proteins) in a nucleosome, structure of 8 histone proteins with DNA coiled around twice. This is done by histone modification - that addition of acetyl groups
-encourages gene expression

10
Q

DNA methylation

A

Inactivates the DNA

  • addition of methyl groups
  • how x inactivation happens
11
Q

Epigenetic inheritance

A

The inheritance of traits not directly involved DNA

  • the way genes expressed are affected by chemicals so they are different
  • even identical twins look different this way
  • different genes are expressed at different times
12
Q

Regulation of transcription initiation

A

Transcription factors called activators attach to control elements called enhancers upstream from the genes both of which are specific to each gene. Control elements are non-coding segments of DNA. The activators are attracted to other transcription factors on the promoter with mediator proteins with the help of a DNA-bending protein. The combination of these proteins allows RNA polymerase to transcribe.

13
Q

How is the regulation of transcription initiation an example of cell type-specific transcription?

A

Gene expression varies from cell to cell because different activators are available in different cells so liver proteins may be expressed in one cell but eye proteins may be expressed in another.

14
Q

Alternative RNA splicing

A

Different mRNA molecules can be made from the same portion of DNA depending on which introns are spliced out

15
Q

mRNA degradation

A

mRNA can last days or weeks. This controls how many proteins are made from that strand.

16
Q

Regulatory proteins

A

Can block the attachment of mRNA to ribosomes thus preventing translation, enzymes controlling a feedback mechanism

17
Q

Protein degradation

A

By proteasome, broken into pieces

18
Q

What are noncoding RNAs and what are the two types?

A
ncRNA's
Do not help protein synthesis
MicroRNAs - miRNA
 -break down mRNA
 -block translation
Small interfering RNA's - siRNAs
 -block translation
19
Q

Why is regulated gene expression especially important in an embryo?

A

Differentiation

Morphogenesis by homeotic genes and cytoplasmic determinants

20
Q

Differential gene expression

A

Expression of different genes by different types of cells that all have the same genome

21
Q

Differentiation

A

The process by which your cells become specialized in structure and function

22
Q

Morphogenesis

A

Creation of form - to change shape

The physical process that gives and organism it’s shape

23
Q

Cytoplasmic determinants

A

Substances in cytoplasm of mom’s egg cell that influence early gene expression in an embryo

24
Q

Homeotic genes

A

Pattern formation in late embryo and larvae (head, bone, tissue, etc.) and (head, thorax, abdomen)

25
Q

What is cancer?

A

Changes in cell division/cell cycle

26
Q

Oncogenes

A

Abnormal mutated cancer-causing genes

27
Q

Mutagens and carcinogens

A

Anything that leads to a mutation

Cancer-causing substances

28
Q

Proto-oncogenes

A

Code for proteins that stimulate normal cell growth and division (normal)

29
Q

Tumor-suppressor genes

A

Code for proteins that inhibit cell division (normal)

30
Q

How is cell division controlled by these genes?

A

Signal pathways

31
Q

The discovery of viruses

A

TMV- tobacco mosaic virus

32
Q

Why aren’t viruses living things?

A
  1. Cannot reproduce on their own
  2. Cannot perform protein synthesis so can’t grow

Obligate Intracellular Parasites- requires a host for survival

33
Q

Restriction enzymes

A

Enzymes that cut apart viral DNA, restrict virus’ ability to infect bacteria

34
Q

Lytic Cycle

A
  1. Attachment- tail fibers connect with receptors
  2. Entry- nucleic acid through capsid, degrades host’s DNA
  3. Synthesis- uses host’s contents and enzymes to copy genome and make proteins
  4. Assembly- create heads, tails, etc. packs genome into capsid
  5. Release- enzyme damages walls, allows fluid into cell which cause cell to burst
35
Q

Lysogenic cycle

A
  1. Entry- factors decide whether lytic or lysogenic cycle
  2. Combination- viral DNA with host’s DNA, creating a prophage
  3. Cell division- creates large population of cells with prophages
  4. Result- daughter cells with prophages
    Triggers- an environmental/chemical signal that causes a change from the lysogenic cycle to the lytic cycle
36
Q

What phases can be replicated by both the lysogenic and the lytic cycles?

A

Temperate phages (phage lambda)

37
Q

Retroviruses - RNA virus

A

Reverse transcriptase - an enzyme which transcribes mRNA into DNA

38
Q

What is an example of this?

A

HIV- human immuno deficiency that attacks white blood cells, destroying immune system, this can be inactive in your body for long time but then replicates, is activated, and turns into AIDS (acquired immuno deficiency syndrome)

39
Q

How do viruses make you sick?

A

Cell/tissue destruction

Release toxins

40
Q

How are viruses treated?

A

Vaccination programs and antiviral drugs

41
Q

How do viruses spread?

A

Indirect- coughing, sneezing

Direct- touch