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Biology 102 - Molecular & Classical Genetics > Gene Expression > Flashcards

Gene Expression Flashcards

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1
Q

What helps regulate gene expression?

A

Structural organization of chromatin

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2
Q

What are usually not expressed?

A

Genes with highly packed heterochromatin

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3
Q

What is heterochromatin?

A
  • Chromosome material of different density from normal
  • Heavier
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4
Q

What influences chromatin structure and gene expression?

A

Chemical modifications to histones and DNA of chromatin

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5
Q

What are histone tails?

A
  • Protruding ends of histone proteins that extend from the nucleosome
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6
Q

What is acetylation?

A

The addition of acetyl groups to histone tails

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7
Q

Acetylation benefits

A

Promotes loose chromatin structure that permits transcription

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8
Q

What is DNA methylation?

A

The addition of methyl groups to DNA

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9
Q

DNA methylation effects

A
  • Can reduce transcription in some species
  • Can cause long-term inactivation of genes
  • Regulates expression of either maternal or paternal alleles of certain genes at the start of development
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10
Q

Methylation in histone effects

A

Can either tighten chromatin structure

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11
Q

How does phosphorylation affect chromatin?

A

Addition of phosphate groups next to a methylated amino acid can loosen chromatin

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12
Q

What is epigenetic inheritance

A

Chromatin modifications do not alter the DNA sequence, they may be passed to future generations of cells

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13
Q

What is regulation of transcription initiation?

A
  • Chromatin modifying enzymes provide initial control of gene expression
  • Make region of DNA more or less able to bind to transcription machinery
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14
Q

What are control elements?

A

DNA sequences that regulate gene expression by binding transcription factors

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15
Q

Where are control elements located?

A

Near (proximal) or far (distal) from the promoter

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16
Q

What is an activator?

A

A protein that binds to an enhancer and stimulates transcription

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17
Q

Distal elements

A
  • located far from the gene they regulate
  • can be grouped as “enhancers”
  • Can be located in the intron
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18
Q

What are the two domains of activators?

A
  1. DNA-Binding Domain
  2. Activation Domain
19
Q

DNA-Binding Domain

A

Binds to specific DNA sequences like enhancers

20
Q

Activation Domain

A

Activates transcription

21
Q

What is the poly-A signal?

A

A sequence in the last exon transcribed into RNA that signals where the transcript is cleaved

22
Q

What happens after the poly-A signal is transcribed?

A

Transcription continues for hundreds of nucleotides beyond the poly-A signal before terminating

23
Q

Transcription Factors - Functions

A
  • Initiates transcription
  • Some factors function as repressors, inhibiting expression of gene
  • Act indirectly by influencing chromatin structure
24
Q

What is combinatorial control of gene activation?

A

Transcription is activated only when a specific combination of control elements and appropriate activator proteins are present

25
Q

How are co-expressed eukaryotic genes organized?

A

Not in operons; each has its own promoter and control elements

26
Q

Where are co-expressed eukaryotic genes located?

A

They are scattered across different chromosomes but share the same combination of control elements

27
Q

How are co-expressed genes transcribed simultaneously?

A

Activators recognize shared control elements and promote simultaneous transcription of these genes

28
Q

How can the initiation of translation be blocked?

A

Regulatory proteins can bind to mRNA sequences or structures, preventing translation

29
Q

Why is mRNA lifespan important?

A
  • It determines how much protein is synthesized
  • The longer it lasts, the more protein is made
30
Q

How does eukaryotic mRNA lifespan compare to prokaryotic mRNA?

A

Eukaryotic mRNA is longer-lived than prokaryotic mRNA

31
Q

Where is the lifespan of eukaryotic mRNA determined?

A

It resides in the 3’ UTR of the mRNA

32
Q

What happens to proteins after translation?

A

Proteins undergo processing such as cleavage or the addition of chemical groups

33
Q

How is the length of time a protein functions regulated?

A

By selective degradation

34
Q

What does ubiquitin do in protein degradation?

A

Ubiquitin is a small protein that tags proteins for degradation by proteasomes

35
Q

What do proteasomes do?

A

They are large protein complexes that recognize ubiquitin-tagged proteins and degrade them

36
Q

Noncoding RNAs (ncRNAs)

A
  • They do not code for proteins but regulate gene expression at mRNA translation and chromatin configuration
  • Significant amounts of the genome can be transcribed into ncRNAs
37
Q

What are microRNAs (miRNAs)?

A
  • Small single-stranded RNA molecules that bind to mRNA to degrade it or block its translation
  • Expression of at least half of all human genes can be regulated by miRNAs
38
Q

How do miRNAs interact with mRNA?

A
  1. miRNA binds to mRNA with at least 7 complementary bases
  2. If bases are complementary along the whole thing, mRNA is degraded
  3. If the match is less complete, translation is blocked
39
Q

What is RNA interference (RNAi)?

A
  • The inhibition of gene expression by RNA molecules
  • Also used in labs to disable genes and study their functions
40
Q

What controls RNAi?

A

Small interfering RNAs (siRNAs)

41
Q

What is cell differentiation?

A

When cells become specialized

42
Q

What is morphogenesis?

A

Physical process giving an organism its shape

43
Q

Process to transform from zygote to adult

A
  1. Cell division
  2. Cell differentiation
  3. Morphogenesis

Biology 102 - Molecular & Classical Genetics (8 decks)

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