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Bio 1A03 > Theme 3- Module 3 > Flashcards

Theme 3- Module 3 Flashcards

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Biology 101 flashcards
1
Q

Development of a eukaryotic organism from a single fertilized zygote is dependent on the ____________

A

Molecular communication between cells

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2
Q

What determines the fate of an embryonic cell?

A

The signals that are exchanged

Which genes are switched on or off at specific times

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3
Q

On what type of cell did differentiation occur (that eventually led to the variation in specialized cell types)?

A

Stem cells

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4
Q

What does the body use to control which genes get activated along the chromosome during development?

A

Transcription factors (det pathway)

Proteins (that can result in various changes in gene expression)

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5
Q

All embryonic stem cells are

a) Different
b) The same

A

B) The same

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6
Q

Muscle cells and liver cells are different because:

a) They have different DNA blueprints
b) They were transcribed differently
c) They removed unnecessary genes from the genome

A

b) They were transcribed differently

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7
Q

How does winding the DNA into chromatins affect gene expression?

A

Genes within this tightly wound heterochromatin are usually not expressed. To be able to transcribe a specific gene product, it is necessary to unwind the DNA.

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8
Q

Describe the structure of a nucleosome

A

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

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9
Q

Describe the basic steps of chromatin remodeling

A

1) Activator protein recruits histone acetyltransferase (or methyltransferase, etc)
2) Add acetyl group to lysine (or specific amino acid) along histone tails
3) (+) charge of tails reduced
4) Interaction b/w histones and DNA are weakened

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10
Q

What is the histone code?

A

Degree of modifications to histone tails controls activation and repression of transcription

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11
Q

Does acetylation and methylation with a single methyl group allow for transcriptional activation or repression?

A

Activation

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12
Q

Does methylation with three methyl groups allow for transcriptional activation or repression?

A

Repression

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13
Q

Why are transcription factors able to recognize and bind to nucleic acid sequences in DNA?

A

Bc of structural and chemical complementarity between the proteins and DNA

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14
Q

Most transcription factors are classified based on what?

A

The structures of their distinct DNA binding motifs (basically, they’re classified based on their structure and how it helps them bind to DNA)

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15
Q

What are the four different types DNA binding motifs?

A

Basic helix- loop-helix

Helix-turn-helix

Zinc finger

Leucine zipper

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16
Q

Most of these transcription factors have _________ that tend to fit nicely within the major grooves of DNA

A

Alpha-helical domains

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17
Q

What is the core promoter?

A

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

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18
Q

What elements are part of the core promotor?

A

TATA box
BRE region
Transcriptional start site

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19
Q

The TATA box region is usually recognized by the __________ subunit of the transcription factor ___________

A

TATA-binding protein (or TBP)

TFIID

20
Q

What is another region that is recognized by TFIID?

A

BRE (B recognition element)

- closely related to the TATA box

21
Q

How are enhancer regions able to facilitate the formation of the transcriptional complex?

A

Enhancer regions are able to bind cell or region specific transcription factors. These transcription factors interact with the basal machinery at the promoter to enhance the transcription of a gene

22
Q

What binds to enhancer regions?

a) Transcriptional activator proteins
b) General transcription factors

A

a) Transcriptional activator proteins

23
Q

What binds to promotrr regions?

a) Transcriptional activator proteins
b) General transcription factors

A

b) General transcription factors

24
Q

How do transcriptional activator proteins and general transcription factors work together to help regulate transcription?

A

Loop the DNA and bring regulatory sequences (which are situated far from the actual transcription sites) close to transcription sites

25
Q

What do adaptor or mediator proteins do?

A

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

26
Q

What do silencer regions and repressor proteins do?

A

Interfere with the general transcription factor assembly and mediator activity

27
Q

What are blood cell progenitors?

A

Stem cells

28
Q

In order for blood cell progenitors to differentiate into functional red blood cells that contain haemoglobin, progenitor cell must activate transcription of what protein?

A

Globin proteins

29
Q

How many alpha- globin proteins does a fetus have compared to an adult?

A

Both have 2 (making up half of their tetrameric hemoglobin protein)

30
Q

How many gamma- globin proteins does a fetus have compared to an adult?

A

Fetus has 2

Adult has 0

31
Q

How many beta- globin proteins does a fetus have compared to an adult?

A

Fetus has 0

Adult has 2

32
Q

Why do fetuses have gamma proteins while adults have beta proteins?

A

Gamma globin binds oxygen more strongly than beta globin

Allows fetus to be able to sequester enough oxygen while growing in the womb

33
Q

Both a fetus and adult have both the beta-globin and gamma-globin genes. Why the difference between the two then?

A

In the fetal blood cell progenitors, the chromatin is WOUND UP around the beta-globin gene to inhibit transcription

The chromatin around the gamma-globin gene is OPEN to allow transcription

(opp in adults)

34
Q

How does the body switch from gamma to beta-globin proteins after birth? (what is it regulated by)

A

Specific transcription factors silence gamma-globin gene transcription

Others activate the beta-globin gene transcription

35
Q

Besides histone modifications, what else affects transcription in eukaryotes?

A

Chemical modification of cytosine bases in the DNA sequence

36
Q

What is the common chemical modification of cytosine bases?

A

Addition of a methyl group

37
Q

True or false: if methylation occurs, it happens on every cytosine

A

False

It happens within a “CpG” island (a string of cytosine and guanine bases)

38
Q

What does the “p” rep in CpG island?

A

The phosphate in the backbone between the two bases

39
Q

Where are CpG islands frequently located?

A

In or near promoter sequences (or mammalian genes)

40
Q

When a CpG island contains many methylated cytosine bases, why can’t transcription occur?

A

Bc methylations causes the shape of the DNA binding site for the proteins to change

Therefore, the proteins can no longer bind

41
Q

True or false: methylation state can change in response to environmental and developmental cues

A

True

it’s an epigenetic mechanism

42
Q

True or false: methylation state is heritable from mother cell to daughter cell

A

True

It maintains the same state of transcriptional activation with subsequent cell divisions

43
Q

What are histone deacetylases (HDAC) and what do they do?

A

Proteins that can only bind to methylated DNA

They promote the removal of the acetyl groups from the neighbouring histones

44
Q

Why is deacetylation of the histones important?

A

Allows nucleosomes to reassemble and can once again lead to the masking of enhancer and promoter sequences (and repressing transcription)

45
Q

Is the default chromatin transcription conformation of eukaryotes “on” or “off”?

A

Off

Genes are only transcribed when chromatin is remodelled to expose the promoter sequences

46
Q

Is the default genome transcription conformation of prokaryotes “on” or “off”?

A

On

Bio 1A03 (18 decks)

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