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► Biology > Chapter 18.2 and 18.3 > Flashcards

Chapter 18.2 and 18.3 Flashcards

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AP® Biology flashcards Biology 101 flashcards
1
Q

Prokaryotes and eukaryotes alter gene expression in response to

A

their changing environment

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2
Q

In multicellular eukaryotes,

A

gene expression regulates the development and is responsible for differences in cell types
Ex. Muscle cell v. nerve cell

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3
Q

RNA molecules play many roles in

A

regulating gene expression in eukaryotes

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4
Q

Eukaryotic gene expression is regulated at

A

many stages

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5
Q

All organisms must regulate which genes are

A

expressed at any given time

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6
Q

In multicellular organisms regulation of gene expression is

A

essential for cell specialization

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7
Q

Almost all the cells in an organism are

A

genetically identical

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8
Q

Differences between cell types result from

A

differential gene expression, the expression of different genes by cells with the same genome

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9
Q

Abnormalities in gene expression can lead to

A

diseases including cancer

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10
Q

Gene expression is regulated at

A

many stages

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11
Q

Genes with highly packed heterochromatin are

A

usually not expressed

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12
Q

Chemical modifications to histones and DNA of chromatin

A

influence both chromatin structure and gene expression

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13
Q

In histone acetylation,

A

acetyl groups are attached to positively charged lysines in histone tails.

This loosens chromatin structure, thereby promoting the initiation of transcription

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14
Q

The addition of methyl groups (methylation) can condense chromatin; the addition of phosphate groups (phosphorylation)

A

next to a methylated amino acid can loosen chromatin

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15
Q

The histone code hypothesis proposes that

A

specific combinations of modifications, as well as the order in why they occur, help determine chromatin configuration and influence transcription

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16
Q

DNA methylation, the addition of methyl groups to certain bases in DNA, is

A

associated with reduced transcription in some species

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17
Q

DNA methylation can

A

cause long-term inactivation of genes in cellular differentiation

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18
Q

In genomic imprinting,

A

methylation regulates expression of either the maternal or paternal alleles of certain genes at the start of development

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19
Q

Although the chromatin modifications just discussed do not alter DNA sequence,

A

they may be passed to future generations of cells

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20
Q

The inheritance of traits transmitted by mechanisms not directly involving the nucleotide sequence is called

A

epigenetic inheritance

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21
Q

Chromatin-modifying enzymes provide

A

initial control of gene expression by making a region of DNA either more or less able to bind the transcription machinery

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22
Q

Associated with most eukaryotic genes are multiple control elements,

A

segments of noncoding DNA that serve as binding sites for transcription factors that help regulate transcription

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23
Q

Control elements and the transcription factors they bind are critical to

A

the precise regulation of gene expression in different cell types

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24
Q

To initiate transcription,

A

eukaryotic RNA polymerase requires the assistance of proteins called transcription factors

25
Q

General transcription factors are

A

essential for the transcription of all protein-coding genes

26
Q

In eukaryotes, high levels of transcription of particular genes depend on

A

control elements interacting with specific transcription factors

27
Q

Proximal control elements are located close to

A

the promoter

28
Q

Distal control elements, groupings of which are called enhances, may be

A

far away from a gene or even located in an intron

29
Q

An activator is a

A

protein that binds to an enhancer and stimulates transcription of a gene

30
Q

Activators have two domains,

A

one that binds DNA and a second that activates transcription

31
Q

Bound activators facilitate a

A

sequence of protein-protein interactions that result in transcription of a given gene

32
Q

Some transcription factors function as

A

repressors, inhibiting expression of a particular gene by a variety of methods

33
Q

Some activators and repressors act indirectly by

A

influencing chromatin structure to promote or silence transcription

34
Q

Transcription alone dow not account for

A

gene expression

35
Q

Regulatory mechanisms can

A

operate at various stages after transcription

36
Q

Such mechanisms allow a cell to

A

fine-tune gene expression rapidly in response to environmental changes

37
Q

In alternative RNA splicing,

A

different mRNA molecules are produced from the same primary transcript, depending on which RNA segments are treated as exons and which as introns

38
Q

The life span of mRNA molecules in the cytoplasm is a

A

key to determining protein synthesis

39
Q

Eukaryotic mRNA is more long lived than

A

prokaryotic mRNA

40
Q

Nucleotide sequences that influence the lifespan of mRNA eukaryotes reside in the

A

untranslated region (UTR) at the 3’ end of the molecule

41
Q

The initiation of translation of selected mRNAs can be

A

blocked by regulatory proteins that bind to sequences or structures of the mRNA

42
Q

Alternatively, translation of all mRNAs in a cell may be

A

regulated simultaneously

43
Q

For example, translation initiation factors are

A

simultaneously activated in an egg following fertilization

44
Q

After translation,

A

various types of protein processing, including cleavage and the addition of chemical groups, are subject to control

45
Q

Proteasomes are

A

giant protein complexes that bind protein molecules and degrade them

46
Q

Noncoding RNAs play

A

multiple roles in controlling gene expression

47
Q

Only a small fraction of DNA codes for proteins, and

A

a very small fraction of the non-protein-coding DNA consists of genes for RNA such as rRNA and tRNA

48
Q

A significant amount of the genome may be

A

transcribed into noncoding RNAs (ncRNAs)

49
Q

Noncoding RNAs regulate gene expression at two points:

A

mRNA translation and chromatin configuration

50
Q

MicroRNAs (miRNAs) are

A

small single-stranded RNA molecules that can bind to mRNA.

These can degrade mRNA or block its translation

51
Q

The phenomenon of inhibition of gene expression by RNA molecules is called

A

RNA interference (RNAi)

52
Q

RNAi is caused by

A

small interfering RNAs (siRNAs)

53
Q

siRNAs and miRNAs are similar but

A

form from different RNA precursors

54
Q

In some yeasts siRNAs play a role in

A

heterochromatin formation and can block large regions of the chromosome

55
Q

Small ncRNAs called piwi-associated RNAs (piRNAs) induce

A

heterochromatin, blocking the expression of parasitic DNA elements in the genome, known as transposons

56
Q

RNA-based mechanisms may also block

A

transcription of single genes

57
Q

Small ncRNAs can regulate

A

gene expression at multiple steps

58
Q

An increase in the number of miRNAs in a species may have allowed

A

morphological complexity to increase over evolutionary time

59
Q

siRNAs may have evolved first, followed by

A

miRNAs and later piRNAs

► Biology (29 decks)

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