Chapter 18 Flashcards Preview

AP Biology Semester 1 > Chapter 18 > Flashcards

Flashcards in Chapter 18 Deck (68):
1

how can a cell regulate the production of enzymes?

by feedback inhibition or by gene regulation

2

operons

the entire stretch of DNA that includes the operator, the promoter, and the genes they control

3

operator

the regulatory "switch" is a segment of DNA called an operator
-positioned within the promoter

4

repressor

a protein that switches off the operon
-the repressor prevents gene transcription by binding to the operator and blocking RNA polymerase

5

regulatory gene

the repressor is the product of a separate regulatory gene

6

corepressor

a molecule that cooperates with a repressor protein to switch an operon off

7

how can a repressor be in an active or inactive form?

depends on the presence of other molecules

8

by default the trp operon is __ and the genes for tryptophan synthesis are (not transcribed/transcribed)

-on
-transcribed

9

what happens when tryptophan is present?

binds to the trp repressor protein and turns the operon off

10

when tryptophan levels are high what does this mean?

operon is turned off if tryptophan levels are high

11

what is a repressable operon?

one that is usually on, binding of a repressor to the operator shuts off transcription

12

trp operon is a ____ _____

repressible operon

13

inducible operon

one that is usually off; a molecule called an inducer actives the repressor and turns on transcription

14

lac operon is an ____ operon and contains genes that code for enzymes used in the hydrolysis and metabolism of lactose

inducible

15

when the lac repressor is active what does this do to the lac operon

when the lac repressor is active, it switches the lac operon off

16

inducer

inactivates the repressor to turn the lac operon on

17

CAP (catabolite activator protein)

postive control through a stimulatory protein
-when CAP is activated it attaches itself to the promoter of the lac operon and increases the affinity of RNA polymerase, thus accelerating transcription
-when glucose levels increase CAP detaches its self from the lac operon and transcription returns to normal rate

18

in multicellular organisms, regulation of gene expression is ______

-essential for cell specialization

19

differential gene expression

the expression of different genes by cells with the same genome
-abnormalities can lead to diseases like cancer

20

what can be done to influence both chromatin structure and gene expression

chemical modifications to histones and DNA of chromatin

21

histone acetylation

acetyl groups are attached to positively charged lysines in histone tails
-this loosens chromatin structure and thus promoting the initiation of transcription

22

methylation

-addition of methyl groups
-this condenses chromatin

23

phosphorylation

-addition of phosphate groups next to methylated amino acid to loosen chromatin as well

24

histone code hypothesis

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

25

DNA methylation

the addition of methyl groups to certain bases in DNA
-associated with reduced transcription in some species
-can cause long term inactivation of genes in cellular differentiation

26

genomic imprinting

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

27

epigenetic inheritance

The inheritance of traits transmitted by mechanisms not directly involving the nucleotide sequence
-so smoking before the age of 12 can cause your children to be obese (example)

28

how do chromatin-modfying enzymes provide initial control of gene expression?

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

29

control elements

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

30

transcription factors

-essential for the transcription of all protein-coding genes
-to initiate transcription; gives assistance
-high levels of transcription of particular genes depend on control elements interacting with specific transcription factors

31

enhancers

distal (situated away from the body) control elements

32

proximal control elements

-located close to the promoter

33

activator

a protein that binds to an enhancer and stimulates transcription of a gene
-have two domains
(1) binds to DNA
(2) activates transcription

34

what do bound activators facilitate?

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

35

true or false:
some transcription factors can function as repressors, inhibiting expression a gene

true

36

does each eukaryotic gene have its own promoter and control elements?

yes, a prokaryotic operon doesn't

37

alternative RNA splicing

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

38

which is more long lived in the cytoplasm? eukaryotic mRNA or porkaryotic mRNA

eukaryotic mRNA

39

the nucleotide sequences that influence the lifespan of mRNA in eukaryotes reside in....

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

40

what do the regulatory proteins that bind to sequences or structures of the mRNA do?

block the initiation of translation of selected mRNAs

41

proteasomes

giant protein complexes that bind to protein molecules and degrade them

42

where does noncoding RNAs regulate gene expression (2)

1. mRNA translation
2. chromatin confiugaration

43

true or false:
A significant amount of the genome may be transcribed into noncoding RNAs (ncRNAs

true

44

MicroRNAs

small single stranded RNA molecules that can bind to mRNA
-these can degrade mRNA or block its translation

45

RNA interference

inhibition of gene expression by RNA molecules

46

what causes RNA interference?

small interfering RNAs
-similar to microRNAs
-induce heterochromatin (making DNA tighter) thus can block large regions of the chromosome (in some yeasts)

47

cell differentiation

the process by which cells become specialized in structure and function

48

morphogenesis

the physical processes that give an organism its shape

49

cytoplasmic determinants

maternal substances in the egg that influence early development

50

induction

signal molecules from embryonic cells cause transcriptional changes in nearby target cells
-thus, interactions between cells induce differentiation of specialized cell types

51

determination

commits a cell to its final fate
-determination precedes differentiation
-cell differentiation is marked by the production of tissue-specific proteins

52

myoblasts

produce muscle specific proteins and form skeletal muscle cells

53

MyoD

one of several "master regulatory genes" that produce proteins that commit the cell to becoming a skeletal muscle
-a transcription factor that binds to enhancers of various target genes

54

pattern formation

the development of a spatial organization of tissues and organs
-pattern formation begins with the establishment of the major axes

55

positional information

the molecular cues that control pattern formation, tells a cell its location relative to the body axes and to neighboring cells

56

homeotic genes

control pattern formation in late embryo, larva, and adult stages

57

maternal effect genes

cytoplasmic determinants that initially establish the axes of the body of Drosophila

58

egg polarity genes

maternal effect genes can also be called this...control orientation of the egg and the consequently of the fly

59

bicoid

maternal effect gene
--affects the front half of the body

60

morphogens

establish an embryo's axes and other features

61

what are the three reasons bicoid research is important?

1. identified a specific protein required for some early steps in pattern formation
2. increased understanding of the mother's role in embryo development
3. demonstrated a key developmental principle that a gradient of a molecule can determine polarity and position in the embryo

62

oncogenes

cancer causing genes

63

proto-oncogenes

corresponding normal cellular genes that are responsible for normal cell growth and division

64

how can oncogenes be converted to oncogenes

1. movement of DNA within the genome; if it ends up near an active promoter, transcription may increase
2. amplification of a proto-oncogene; increases the number of copies of the genes
3. point mutations in the proto-oncogene or its control elements; cause an increase in gene expression

65

tumor suppressor genes

help prevent uncontrolled cell growth
-mutations that decrease protein products of tumor suppressor genes may contribute to cancer onset

66

what are three things tumor suppressor genes can do?

1. repair damaged DNA
2. control cell adhesion
3. inhibit cell cylce in the cell cignaling pathway

67

what is common in human cancers?

*mutations in the ras proto-oncogene and p53 tumor suppressor gene

68

what happens if there is a mutation in the ras gene

can lead to production of a hyperactive Ras protein and increased cell division