Chapter 10: From DNA to Protein: Gene Expression Flashcards Preview

AP Biology > Chapter 10: From DNA to Protein: Gene Expression > Flashcards

Flashcards in Chapter 10: From DNA to Protein: Gene Expression Deck (97):
1

Is the one gene-one protein hypothesis completely accurate?

no it is an oversimplification

2

Is the one gene-one polypeptide hypothesis complete accurate?

Whiel this is very useful, it is still a little simpler than real life (some genes do not code for polypeptides)

3

Molecular Biology

study of nucleic acids and proteins, often focuses on gene expression

4

True or false: genes are expressed as RNA

true

5

True or false: all RNA is translated into proteins

false

6

Transcription

the information in a DNA sequence (a gene) is copied into a complementary RNA sequence

7

Translation

the RNA sequence is used to create the amino acid of a polypeptide

8

Messenger RNA

the modified RNA that came from the complimentary DNA strand

9

Where does mRNA travel in eukaryotic cells?

from the nucleus to the cytoplasm
gets translated into a polypeptide
nucleotide sequence of it determines the sequence of the amino acids

10

Ribosomal RNA

rRNA
catalyzes peptide bond formation between amino acids to form a polypeptide

11

ribosome

protein synthesis factory
multiple proteins and rRNAs

12

Transfer RNA

tRNA
mediates between mRNA and protein
can bind a specific amino acid and recognize a specific sequence in mRNA
figures out which amino acid should be added to the growing polypeptide

13

What does DNA expression start with?

transcription to RNA

14

Transcription

tue formation of a specific RNA sequence from a specific DNA sequence

15

What factors are required for transcription?

A DNA template for complementary base pairing
the appropriate nucleoside triphosphates (ex ATP) to act as substrates
an RNA polymerase `

16

RNA polymerases

catalyze the synthesis of RNA from the DNA template
all have common structure
do not require primer

17

Are RNA polymerases processive?

Yes
a single enzyme-template binding event results in the polymerization of hundreds of RNA nucleotides

18

what are the three steps in transcription?

initiation
elongation
termination

19

Initiation (transcription)

needs a promoter
RNA polymerase binds to the promoter

20

Promoter

a special DNA sequence to which the RNA polymerase can bind to very tightly
tell RNA polymerase where to start transcription and which of the two strands to transcribe
orients the RNA polymerase
Tom Haverford

21

transcription initiation site

part of the promoter
where transcription begins

22

upstream

5' on the non-template strand and 3' on the template strand

23

Are all promoters identical?

no

24

Elongation (transcription)

the RNA polymerase unwinds the DNA and reads in the 3' to 5' direction (copying in the 5' to 3')
RNA polymerase uses the ribonucleoside triphosphates as substrates and catalyzes the formation of phosphodiester bonds

25

True or false: RNA polymerases and crew have more efficient proofreading mechanisms than DNA

false they are less efficient

26

True or False; RNA errors are more harmful than DNA ones

false
lots of RNA copies are made/they aren't around for very long, less potential for harm in copying errors

27

Termination (transcription)

occurs at specific sequences

28

Coding reigons

sequences within a DNA molecule that are expressed as proteins

29

introns

intervening regions
interrupt the coding region

30

exons

expressed regions
transcribed regions

31

pre-mRNA

exons and introns (basically the whole section complementary to the DNA)

32

mature mRNA

just exons, no introns

33

Nucleic Acid Hybridization

DNA that you want analyzed denatured and hydrogen bonds broken to separate the pairs
probe incubated within the DNA if it has a base sequence complementary to the target DNA, double helix forms

34

prode

a single-stranded nucleic acid from another source

35

Do introns scramble the DNA sequence of a gene?

no they interrupt it

36

RNA splicing

removes the introns and splices the exons together

37

Consensus sequences

short stretches of DNA that appear with little variation in different genes that acts as borders between introns and exons

38

snRNOs

small nuclear ribonucleoprotein particles
surround the consensus sequences
has RNA with complementary sequences to the consensus sequences

39

spliceosome

RNA protein complex
large
cuts pre-mRNA releases introns and joins the ends of the exons

40

Are all exons included in every mRNA?

no they aren't

41

5' cap

added to the 5' end of the pre-mRNA as it is transcribed
chemically modified GTP
facilitates binding of mRNA to ribosome and protects the mRNA from degradation

42

poly A tail

added to the 3' end of the pre-mRNA at the end of transcription assists in export of mRNA from the nucleus and is important for stability

43

True or false: transcription and translation are coupled in prokaryotes

true
no nucleus and ribosomes bind to mRNA as it is being transcribed

44

Codons

three letter "words"
sequential
nonoverlapping
specify amino acids

45

How many variations could triplet codons code for?

64

46

Start codon

AUG
codes for methionine

47

Stop codons

UAA
UAG
UGA
termination signals for translation
once the machinery arrives here, translation stops and the polypeptide is released from the copmlex

48

True or false: The genetic code is redundant

true

49

True or false: The genetic code is ambiguous

false
each only codes for one

50

Is the genetic code universal?

nearly
very few exceptions

51

Silent mutations

occur because of the redundant of the genetic code

52

Missense mutatiosn

change in the amino acid sequence

53

Nonsense mutatiosn

result in a premature stop codon

54

Frame-shift mutations

result from the insertion or deletion of one or more base pairs within the coding sequence
new triplets are read

55

What key events must take place to ensure that the protein made is the one specified by mRNA?

a tRNA must chemically read each mRNA codon correctly
the tRNA must deliver the amino acid that corresponds to the mRNA codon

56

What molecule links the information contained in each mRNA codon with a specific amino acid?

tRNAs

57

True or false: tRNAs bind to specific amino acids

true

58

When is the tRNA charged?

when it is carrying an amino acid

59

Anticodon

a triplet of bases on the tRNA (t for antiocodon and tRNA)
which is complimentary to the mRNA codon for the particular amino acid that the tRNA has

60

What bonds hold the codon and anticodon together?

hydrogen of course

61

Does tRNA interact with ribosomes?

yes
noncovalently

62

Wobble

the specificity for the base at the 3' end of the codon is not always observed
doesn't always occur
ex. GCA GCC and GCU all are recognized bt the same tRNA

63

True or false; each mRNA codon binds to just one tRNA species, carrying a specific amino acid

true

64

What family of enzymes is responsible for the charging of tRNA?

aminoacyl-tRNA synthetases

65

Are aminoacyl-tRNA synthetases specific for amino acids?

yup and the tRNA

66

How does the reaction that aminoacyl-tRNA synthetases catalyze work?

use ATP to form a high energy cone between the amino acid and tRNA

67

What is recognized the amino acid or the anticodon on the tRNA?

the anticodon on the tRNA

68

How many subunits does the ribosome consist of?

two

69

In eukaryotes, what do the large subunits and small of the ribosome consist of>

rRNA and proteins
they also interact noncovalently

70

When the ribosome isn't translating DNA, are the subunits together?

nope

71

What order does a charged tRNA traverse the ribosome sites in?

A P E

72

A site

amino acid site
charged tRNA anticodon binds to the mRNA codon, living up the correct amino acid

73

P site

polypeptide site
tRNA adds amino acid to the polypeptide chain

74

E site

exit site where the tRNA resides before being released from the ribosome and heading up to the cytosol to pick up another amino acid

75

fidelity function

ribsosome has this
ensures that a charged tRNA with the correct anticodon bings to the right codon
hydrogen bonds form when proper binding occurs, the rRNA makes sires that these hydrogen bonds have formed

76

What three steps occur in translation?

initiation, elongation, and termination
look familiar?

77

Initiation (translation)

initiation complex binds to mRNA
small subunit moves until it reaches start codon (AUG)
methionine is first in amino acid sequence
at the end of initiation the methionine charged tRNA is in the P site

78

Initiation complex

charged tRNA and small ribosomal subunit (both bound to mRNA)

79

Initiation factors

translation
mRNA
ribosomal subunits and methionine charged tRNA

80

Elongation (translation)

chraged tRNA with anticodon complementary to the second mRNA codon enters the A site
large subunit catalyzes two reactions (breaks bond between methionine and tRNA in P site and catalyzes the formation of a peptide bond between methionine and the amino acid on the tRNA in the A site)
first tRNA moves to E site and leaves second tRNA moves to P site
rinse and repeat (in the 5' to 3' direction)

81

Peptidyl transferase activity

large ribosomal subunit has this because it can break bond between tRNA and amino acid and form peptide bonds between different amino acid)

82

True or false: polypeptides grow in the amino to carboxyl direction

true
alphabetical order

83

termination (translation)

elongation ends when a stop codon enters the A site
bond between polypeptide chain and tRNA in P site broken
amino acid separate from the ribosome

84

release factor

part of termination (in translation)
allows hydrolysis of the bond between the pole peptide chain and the tRNA in P site

85

Polyribosome

polysome
the strand of mRNA with multiples ribosomes and their polypeptide chains

86

Can several ribosomes simultaneously translate a signal mRNA molecule?

yup

87

true or false: the site of a polypeptide's function in the cell may be far away from its point of synthesis at the ribosome

true

88

True or false: polypeptides are rarely modified by the addition of new chemical groups that contribute to the function of the mature protein

false
they often are

89

Where is the default location for a protein?

the cytosol

90

Signal sequence

short stretch of amino acids that indicates where in the cell the polypeptide should go

91

Where does a signal sequence bind?

to a receptor protein on the surface of an organelle

92

What happens if a polypeptide has a signal sequence of 5-10 hydrophobic acids at its N terminus ?

it will be directed to the rough endoplasmic reticulum

93

Proteolysis

the cutting of a polypeptide chain

94

PROTEASES

CUT POLYPEPTIDE CHAINS

95

Polyproteins

long polypeptides containing the primary sequences of multiple distinct proteins
these are cut into final products by proteases

96

Glycosylation

addition of carbohydrates to proteins to form glycoproteins

97

Phosphorylation

addition of phosphate groups to proteins
catalyzed by protein kinases
cell signaling