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BIOLOGY 1A03 > T3M3 > Flashcards

T3M3 Flashcards

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1
Q

All embryonic stem cells are…

A

identical

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2
Q

How many distinct cell types in adult human?

A

200

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3
Q

Transcription factors are

A

proteins that bind to specific DNA sequences

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4
Q

Controlling which gene is active along the chromosome leads to

A

vast array of cell types found throughout our bodies

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5
Q

Both prokaryotes and eukaryotes have

A

proteins that are involved with activating and repressing transcription and utilize RNA polymerase to bind to promoters that are upstream of genes to initiate transcription

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6
Q

In the prokaryotic genome

A

groups of related genes with similar functions can often be found clustered together into operons transcribed by a single promoter

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7
Q

eukaryotic genome

A

each gene is controlled by its own promoters
and enhancers

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8
Q

DNA in eukaryotes is organized into

A

highly compacted chromatin

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9
Q

DNA in tightly wound chromatin fibers makes for

A
  • fit all the DNA within the nucleus
  • DNA to be moved around during cell division
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10
Q

Winding of DNA in nucleosomes can affect

A

whether DNA is transcribed or not

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11
Q

Genes within this tightly wound heterochromatin are usually

A

not expressed

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12
Q

To be able to transcribe a specific gene product

A

Must unwind DNA

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13
Q

DNA compaction regulates

A

gene expression

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14
Q

In eukaryotes DNA is

A

around a complex of histone proteins, forming the nucleosome structure

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15
Q

Each nucleosome contains

A

an octamer of 8 histone proteins around which approximately 150 DNA base pairs wrap around

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16
Q

When DNA is tightly wound into chromatin

A

the DNA is not accessible due to the tight winding around the histone proteins

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17
Q

For transcription to occur chromatin must be

A

unravelled

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18
Q

chromatin unravelled through

A

chromatin remodelling

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19
Q

chromatin remodeling begins when

A

an activator protein or transcription factor is
able to bind to an accessible enhancer site. This
leads to the further recruitment of other proteins that can lead to further chromatin remodeling

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20
Q

Transcription requires changes to chromatin structure to enable

A

transcription factors to bind important DNA regions, recruit RNA polymerase, and facilitate the transcriptional process

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21
Q

DNA is tightly wound around histone proteins due to

A

the interactions of the positively charged tails of histone proteins with the negatively charged phosphates in DNA

22
Q

During the chromatin remodeling process, activator proteins can

A

recruit the coactivator enzyme histone
acetyltransferase (or HAT)

23
Q

HAT can

A

attach acetyl groups to lysine amino acids along the positively charged tails of nucleosome histone proteins

24
Q

When tails are acetylated

A

positive charge is reduced, and the interaction between the histones and the wound DNA is weakened

25
Q

other chemical modifications

A

methylation of lysine and arginine and phosphorylation of serine and threonine amino acids along the histone protein tails

26
Q

Acetylation and methylation with a single
methyl group allows for

A

transcriptional activation

27
Q

Methylation with 3 methyl groups leads to

A

repression of transcription

28
Q

Most transcription factors can be classified based on

A

structures of their distinct DNA binding motifs

29
Q

DNA binding motifs include

A

the basic helix-loop-helix, helix-turn- helix, zinc finger and leucine zipper regions

30
Q

To initiate transcription in eukaryotes

A

specific DNA sequences (or cis-sequences) are required

31
Q

The TATA box and transcriptional start sites form

A

part of the core promoter

32
Q

The core promoter is

A

the binding site that is required for binding of RNA polymerase and associated transcription factors

33
Q

The TATA box and BRE regions are generally situated

A

in close proximity to the transcription start site

34
Q

The enhancer regions are able to

A

bind cell or region-specific transcription factors

35
Q

Flexible nature of DNA allows for

A

assembled transcription factors and RNA
polymerase to come to close proximity by looping of the DNA

36
Q

Adaptor or mediator proteins are
able to

A

connect the proteins that are bound to the
enhancer regions with proteins that are bound to the core promoter region

37
Q

When the silencer regions of the DNA
are activated by a repressor protein

A

interference of the general transcription factor
assembly and mediator activity which is needed for the binding of RNA polymerase and subsequent transcription

38
Q

Blood cell progenitors (or stem cells)
differentiate into

A

functional red blood cells that contain haemoglobin

39
Q

Progenitor cell must

A

activate transcription of globin proteins that are
appropriate for the fetus or the adul

40
Q

Fetus globin proteins

A

2 alpha-globin proteins making up half of their tetrameric hemoglobin protein, 2 gamma-globin proteins

41
Q

Adult globin proteins

A

2 alpha-globin proteins making up half of their tetrameric hemoglobin protein, beta-globin proteins making up the other half of the hemoglobin protein

42
Q

Gamma globin can bind

A

oxygen more strongly than beta globin

43
Q

In the fetal blood cell progenitors

A

chromatin is wound up around the beta-globin gene to inhibit transcription, while the chromatin around the gamma-globin gene
is open to allow transcription

44
Q

In adult cells chromatin

A

reorganized to prevent transcription of the gamma-globin gene but allow transcription of the adult beta-globin gene

45
Q

histone modifications permit

A

Unwinding of DNA from the nucleosomes to allow DNA-binding transcription factors to associate with enhancer and promoter sequences on the DNA and start transcription

46
Q

DNA modifications, such as methylation
of certain nucleotides, can still

A

inhibit transcription

47
Q

In eukaryotic systems, transcription is affected by

A

the chemical modification of cytosine bases in the DNA sequence

48
Q

Most common cytosine base modification is

A

addition of a methyl group

49
Q

addition of a methyl group occurs

A

within a string of cytosine and guanine bases called a “CpG” island

50
Q

When a CpG island contains many methylated cytosine bases

A

the shape of the DNA binding site for the proteins has changed and the proteins can no longer bind

51
Q

Heavily methylated promoters

A

are not transcriptionally active because the RNA polymerase cannot bind to the methylated sequences

52
Q

DNA methylation is an example of

A

epigenetic mechanism that controls
gene expression

BIOLOGY 1A03 (24 decks)

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