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BMSC 220 > Lecture #16 > Flashcards

Lecture #16 Flashcards

1
Q

_________: The Lowest Level of Chromosome Organization

A

Nucleosomes

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2
Q

Each chromosome contains a single, _____ DNA molecule

A

continuous

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3
Q

Chromosomes consist of:
- ________ fibers, composed of DNA and associated proteins (mostly histones).
- ______, a group of highly conserved proteins.
- DNA and histones are organized into repeating subunits called _________.

A

chromatin, histones, nucleosomes

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4
Q

Histone H1 serves as a ?

A

linker connecting adjacent nucleosomes

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5
Q

DNA is wrapped around the ____ ______

A

core complex

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6
Q

Core Complex consists of ____ (H2A, H2B, H3, H4) forming an _______.

A

two, octamer

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7
Q

Histone modification is one mechanism to alter the character of _________

A

nucleosomes

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8
Q

Histones, regulatory proteins, and enzymes _______ mediate DNA transcription, compaction, replication, recombination, and repair

A

dynamically

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9
Q

______ groove faces histone core

A

Minor

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10
Q

Each core histone has a flexible ___-_____ tail that projects beyond the DNA helix

A

N-term

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11
Q

Histone tails are subject to _______

A

modification

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12
Q

30-nm chromatin fibers are gathered into a series of large, supercoiled loops, or _______, compacted into thicker (80–100 nm) fibers

A

domains

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13
Q

DNA loops are tethered at their _____ to proteins that may be part of a poorly defined nuclear scaffold

A

bases

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14
Q

_______, best known for holding replicated DNA molecules together during mitosis maintains these DNA loops

A

Cohesin

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15
Q

1 µm mitotic chromosome length contains 1 cm ____ _____. It has a 10,000:1 packing ratio and is considered an incompletely understood process.

A

DNA length

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16
Q

In chromatin packing, each DNA molecule has been packaged into a mitotic chromosome that is 10,000-fold shorter than its ?

A

fully extended length

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17
Q

After mitosis has been completed, most of the chromatin in highly compacted mitotic chromosomes returns to its diffuse _______ condition

A

interphase

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18
Q

_______ returns to a dispersed state after mitosis, ____________ is condensed during interphase

A

Euchromatin, heterochromatin

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19
Q

_________ __________ remains condensed all the time. It is found mostly around centromeres and telomeres and consists of highly repeated sequences and few genes

A

Constitutive heterochromatin

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20
Q

__________ _________ is inactivated during certain phases of the organism’s life. It is found in one of the X chromosomes as a Barr body through X inactivation, a random process that makes adult females genetic mosaics

A

Facultative heterochromatin

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21
Q

Although cells of females contain two X chromosomes, only one of them is transcriptionally active. The other X chromosome remains condensed as a heterochromatic clump called a _____ ______

A

Barr body

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22
Q

X chromosome affected in female mammals occurs during early ______ development and leads to the __________ of the genes on that chromosome

A

embryonic, inactivation

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23
Q

Random process – paternally or maternally derived X chromosome stand an ______ chance of becoming inactivated in any given cell

A

equal

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24
Q

Reactivation of the heterochromatinized X chromosome occurs in female ______ cells prior to the onset of meiosis

A

germ

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25
Q

Calico cats are an example of a phenomenon called ________

A

epigenetic

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26
Q

_________ is the study of how your behaviors and environment can cause changes that affect the way your genes work

A

Epigenetics

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27
Q

Unlike genetic changes, epigenetic changes are _______ and do not change the DNA sequence, but they can change how your cell reads a DNA sequence

A

reversible

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28
Q

The ? states that the activity of a chromatin region depends on the degree of chemical modification of histone tails

A

histone code hypothesis

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29
Q

Histone tail modifications can:
1. Serve as docking sites to recruit __________ proteins.
2. Alter the way histones of neighboring _________ interact.

A

nonhistone, nucleosomes

30
Q

The majority of modified amino acids reside on the N-termini of ___ and ___

A

H3, H4

31
Q

Each of the bound proteins possesses an activity that alters the structure and/or function of the _________

A

chromatin

32
Q

___________ has many methylated H3 histones, which stabilize the compact nature of the chromatin

A

Heterochromatin

33
Q

Removal of the acetyl groups from H3 and H4 histones is among the initial steps in conversion of euchromatin into _________

A

heterochromatin

34
Q

Inactive, heterochromatic X chromosome → _________ histones.

A

deacetylated

35
Q

Active, euchromatic X chromosome → normal level of _________

A

acetylation

36
Q

Highly condensed chromatin in _______ cells

A

mitotic

37
Q

During mitotic _________, chromosomes adopt a distinct shape determined by the length of the DNA molecule and the position of the centromere

A

prophase

38
Q

A ________ is a preparation of homologous pairs ordered according to size

A

karyotype

39
Q

Chromosome can be labeled with multicolored, fluorescent DNA probes that bind specifically to particular _________

A

chromosomes

40
Q

The pattern on a karyotype may be used to screen chromosomal _________

A

abnormalities

41
Q

Each ________ chromosome contains a single, continuous DNA molecule

A

eukaryotic

42
Q

DNA tips have repeated sequences that, together with a group of specialized proteins, form a cap called a _________

A

telomere

43
Q

The same telomere sequence is found throughout __________, and similar sequences are found in most other organisms

A

vertebrates

44
Q

The ___ end ends of the newly synthesized strands contain a short segment of RNA

A

5’

45
Q

RNA ______ removal causes 5’ DNA end to be shorter relative to the previous generation

A

primer

46
Q

If cells were not able to replicate the ends of their DNA, the chromosomes would become shorter and shorter with each round of cell division, called the “?.”

A

end-replication problem

47
Q

New repeats are added by a _________, a reverse transcriptase that synthesizes DNA from a RNA template

A

telomerase

48
Q

Unlike most reverse transcriptases, the enzyme itself contains the RNA that serves as its _______

A

template

49
Q

Once the ___ end of the strand has been lengthened, a conventional DNA polymerase can return the ___ end of the complementary strand to its previous length

A

3’, 5’

50
Q

Telomere significance:
- They are required for the complete ________ of the chromosome
- They form caps that protect the _________ from nucleases and other destabilizing influences
- They prevent the ends of chromosomes from _______ with one another.

A

replication, chromosomes, fusing

51
Q

In somatic cells, telomere lengths are reduced each cell division to limit cell ________

A

doublings

52
Q

A critical point occurs from telomere shortening when cells stop their growth and ______. In contrast, cells that are able to resume telomerase expression continue to ________. These cells continue to divide and do not show normal signs of aging

A

division, proliferate

53
Q

Approximately 90% of human tumors have cells with active ________.

A

telomerase

54
Q

The _________ is located at markedly indented chromosomal site. Tandemly repeated ________ heterochromatin

A

centromere, constitutive

55
Q

Centromeric DNA is the site of _________ attachment during mitosis via CENP-A H3 variant

A

microtubule

56
Q

________ inheritance depends on factors other than DNA sequences

A

Epigenetic

57
Q

Differences in disease susceptibility and longevity between genetically identical twins may be due, in part, to _________ differences that appear between the twins as they age

A

epigenetic

58
Q

Chromatin fibers of an interphase chromosome are concentrated into distinct ________

A

territories

59
Q

A difference in ______ location may be related to the levels of activity of chromosomes

A

nuclear

60
Q

Chromosome number 18 is relatively devoid of genes, whereas chromosome number 19 is rich in protein-coding sequences, many of which are presumably _________

A

transcribed

61
Q

____________ interactions can be shown through hormone treatment

A

Interchromosomal

62
Q

In response to estrogen, two target genes in humans are repositioned into close physical proximity to one another, and the two gene loci become __________ on the periphery of their territories

A

co-localized

63
Q

Genes are physically moved to sites within the nucleus called _________ _______, where the transcription machinery is concentrated, and genes involved in the same response tend to become co-localized in the same factory

A

transcription factories

64
Q

The genome is packed into a series of _______ where DNA within such a region tends to interact much more strongly with other DNA in the same region than it does with other parts of the genome. These regions are known as ?

A

regions, topologically associated domains (TADs)

65
Q

Understanding 3D genome structure and function by ? methods

A

chromosome conformation capture

66
Q

The processing machinery is concentrated within irregular domains, referred to as “______.”

A

speckles

67
Q

Speckles function as dynamic ______ _____ that supply splicing factors for use at nearby sites of transcription

A

storage depots

68
Q

__________ RNA (mRNA) is an intermediate between a gene and a polypeptide

A

Messenger

69
Q

__________ is the process by which RNA is formed from a DNA template

A

Transcription

70
Q

_______ is the process by which proteins are synthesized in the cytoplasm from an mRNA template

A

Translation

BMSC 220 (22 decks)

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