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BMSC 220 > Chapter 12 > Flashcards

Chapter 12 Flashcards

1
Q

Define: Nucleosomes

A

lowest level of chromosome organization

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2
Q

A chromosome consists of:

A
  • chromatin fibers
  • histones
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3
Q

A chromosome contains one:

A

Single, continuous DNA molecule

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4
Q

What are nucleosomes?

A

DNA and histones are organized into nucleosomes

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5
Q

Structure of histones contain: (2)

A
  • histone H1
  • core complex forming octamer
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6
Q

What is the purpose of histone Hi?

A

Serves as a linker

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7
Q

What does the core complex in nucleosomes consist of?

A

H2A, H2B, H3, H4 forms an octamer

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8
Q

What is the purpose of a core complex?

A

DNA wraps itself around the core complex

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9
Q

What is histone modifaction?

A

One mechanism to alter character of nucleosomes

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10
Q

What can mediate DNA transcription, compaction, replication, recombination, and repair?

A

Histones, regulatory proteins, and enzymes

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11
Q

What groove faces the histone core?

A

Minor groove

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12
Q

What does each core histone have extending from it?

A

Flexible N-terimus tail

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13
Q

What part of the histone is subject to modification?

A

The histone tale (N-terminus tail)

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14
Q

Define: Cohesion

A

Holding replicated DNA molecules together during mitosis which mutations DNA loops

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15
Q

Describe the Chromatin structure

A

Gathered into series of large, supercoiled loops, compacted into thicker fibers

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16
Q

What is the packing rate of chromatin?

A

10,000:1, 1microm mitotic chromosome contains 1 cm of DNA

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17
Q

What is heterochromatin?

A

Compacted mitotic chromosomes, often with less function

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18
Q

When does heterochromatin form?

A

After mitosis, condensed during interphase

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19
Q

What is constitutive heterochromatin?

A

Remains condensed at all times, consists of highly repeated sequences and few genes

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20
Q

Where is constitutive heterochromatin found?

A

Mostly around centromeres and telomeres

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21
Q

What is facultative heterochromatin?

A

Inactivated in certain phases of life, found in one of the X chromosomes as Barr Body or heterochromatic clump

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22
Q

What is a Barr Body?

A

An inactive X chromosome in individuals that have two X chromosomes

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23
Q

What is the reason for X chromosome inactivation?

A

To silence one of the X chromosomes in genetic females

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24
Q

What is X chromosome inactivation also known as?

A

Heterochromatization

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25
Q

Which X chromosome is silenced? The paternal or maternal?

A

Either, it is randomized

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26
Q

When is an X chromosome silenced?

A

Occurs during early embryonic development and leads to inactivation of genes on that chromosome

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27
Q

What is the histone code hypothesis?

A

States the activity of a chromatin region depends on degree of chemical modification of histone tails

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28
Q

What is the function of histone tails?

A
  • serve as docking sites to nonhistone proteins
  • alter way histones and neighbour nucleosomes interact
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29
Q

Where are the majority of modified amino acids on histones?

A

On the N-termini of H3 and H4

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30
Q

Inactive, heterochromatic X chromosome results in

A

Deacetylated histones

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31
Q

Active, euchromatic X chromosomes results in

A

Normal level of acetylation

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32
Q

Describe the structure of mitotic chromosomes

A

Highly condensed chromatin in mitotic cells

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33
Q

Define: Karotype

A

Preparation of homologous pairs ordered according to size, used to see chromosomal abnormalities

34
Q

What is a telomere?

A

A region of sequences that has a group of specialized proteins at the end of a DNA molecule

35
Q

What is an end-replication problem?

A

If cells are not able to replicate ends of DNA, chromosomes would become shorter with each round of cell division

36
Q

How are new repeats added to DNA?

A

Telomerase

37
Q

What is telomerase?

A

A reverse transcriptase that synthesized DNA from DNA template

38
Q

What are 3 significant aspects of telomeres?

A
  • required for complete chromosome replication
  • form caps that protect chromosomes from nucleases and other destabilizing influences
  • prevent ends of chromosomes from fusing with each other
39
Q

Where are centromeres found?

A

Markedly indented chromosomal site

40
Q

What is a centromere?

A

A constricted region of a chromosome and helps the cell divide up its DNA, also the region where the cell’s spindle fibers attach

41
Q

Genes are moved to sites within the nucleus, site is where transcription machinery is concentrated and genes involved in same response often become co-localized describes what?

A

Transcription factories

42
Q

What are topologically associated domains?

A

Series of regions where DNA within such a region tends to interact strongly with other DNA in the same region than it does with parts of genome

43
Q

What are speckles?

A

Function as dynamic storage depots that supply factors for use at nearby sites of transcription

44
Q

What is transcription?

A

Process by which RNA is formed from a DNA template

45
Q

What is translation?

A

Process by which proteins are synthesized in the cytoplasm from an mRNA template

46
Q

What is an operon?

A

Functional complex of genes containing the information for enzymes of a metabolic pathway

47
Q

What does an operon include?

A
  • structural genes
  • promoter
  • operator
48
Q

What do structural genes in an operon do?

A

Code for enzymes

49
Q

What do promoters do in an operon?

A

Where RNA pol blends

50
Q

What does the operator do in an operon?

A

Site next to promoter where regulatory protein can bind

51
Q

What is a repressor?

A

Binds to a specific DNA sequence to determine whether or not a gene is transcribed, RNA pol is unable to bind to promoter is repressor is bound

52
Q

What is a regulatory gene?

A

Encodes repressor protein

53
Q

When are genes turned off?

A

After interactions with regulatory proteins

54
Q

Regulation of gene expression occurs on 4 levels:

A

1) Transcriptional control
2) Processing control
3) Translational control
4) Posttranslational control

55
Q

What is differential translation?

A

Mechanism by which eukaryotic cells determine which proteins are synthesized

56
Q

What are DNA microarrays?

A

Can monitor the expression of thousands of genes simultaneously

57
Q

Transcription factors contains what two things?

A
  • DNA binding domain
  • activation domain
58
Q

What are response elements?

A

PEPCK is a key element controlled by variety of transcription factors

59
Q

What regulates the initiation of transcription?

A

TATA box

60
Q

What are enhancers?

A

DNA elements that stimulate transcription

61
Q

What are insulators?

A

Promoter and its enhancers can be codoned off from other elements by sequences that are insulated

62
Q

What are coactivators?

A

Transcriptional activator bound to an enhancer can stimulate transcription through coactivators

63
Q

What can alter chromatin structure?

A

Coactivators

64
Q

What are histone deacetylases (HDACs)?

A

Remove acetyl groups and repress transcription, act as corepressors

65
Q

What is alternative splicing?

A

Pattern of intron removal can allow for multiple protein products from same gene, allows different combinations of exons in final mRNA product

66
Q

How can nucleotides be converted to other nucleotides?

A

mRNA editing

67
Q

What can mRNA editing create?

A

new splice sites, stop codons, amino acid substitution

68
Q

Where are mRNAs, tRNAs, and ribosomal subunits manufactured?

A

Nuclear envelope

69
Q

What is the nuclear lamina?

A

A thin meshwork composed of intermediate filaments that lines the inner surface of the nuclear envelope

70
Q

What is the nuclear localization signal?

A

Sequence of aas in a protein that is recognized by a transport receptor leading to translocation of the protein from the cytoplasm to the nucleus

71
Q

What do transport receptors include?

A

Importins and exportins

72
Q

What are importins?

A

They move molecules from cytoplasm into nucleus

73
Q

What are exportins?

A

They move molecules from nucleus to cytoplasm

74
Q

Synthesis of specialized RNAs broad overview:

A

Synthesized in nucleus, modified in cytoplasm, function in nucleus

75
Q

What do RNAs move through the cell as?

A

Ribonucleproteins

76
Q

What can influence the lifetime of mRNA?

A

poly (A) tail length

77
Q

What are P-bodies?

A

Cytoplasmic granules in which RNA is stored or processed for degradation

78
Q

What are miRNAs roles in development?

A
  • patterning of nervous system
  • control of cell proliferation and death
  • leaf and flower development in plants
79
Q

What is the function of piRNAs?

A

Suppress transposon movement

80
Q

How do miRNAs suppress gene expression? (4 things)

A
  • promoting deadenylation and degradation
  • inhibit initiation of translation
  • inhibit elongation
  • activate degradation of nascent peptides
81
Q

What are proteosomes’ function?

A

Degradation of proteins is carried out

BMSC 220 (13 decks)

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