Chapter 17 Flashcards Preview

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Flashcards in Chapter 17 Deck (69):
1

gene expression

the process by which DNA directs protein synthesis, two stages: transcription and translation

2

information content of DNA is in the form of _____ _____ of _____

specific sequences of nucleotides

3

The DNA inherited by an organism leads to specific traits by....

dictating the synthesis of proteins

4

RNA is the bridge between ____ and ____ for which they code

genes and proteins

5

transcription

the synthesis of RNA under the direction of DNA

6

Translation

the synthesis of a polypeptide using information in the mRNA

7

Ribosomes

the sites of translation

8

in a eukaryotic cell, the nuclear envelope separates _____ from _____

transcription and translation

9

in prokaryotes, _____ of mRNA can begin before ____ has finished

translation
transcription

10

primary transcript

the initial RNA transcript from any gene prior to processing

11

central dogma

the concept that cells are governed by a cellular chain of command: DNA -> RNA -> protein

12

how many amino acids are there?

20

13

how many necleotide bases are in DNA

4

14

triplet code

a series of nonoverlapping, three-nucleotide words... the flow of information from gene to protein is based on these triplet codes

15

The words of a gene are transcribed into complementary nonoverlaping three-nucleotide of words of ____
---these words are then translated into a chain of ____ ___, forming a polypeptide

mRNA
amino acids

16

template strand

*happens during transcription
** provides a template for ordering the sequence of complementary nucleotides in an RNA transcript
***the template strand is always the same strand for a given gene

17

codons

during translation, the mRNA base triplets are codons (read in the 5' to 3' direction)

18

each codon specifies the ____ _____ to be placed at the corresponding position along a polypeptide

amino acid

19

how many triplets signal for "stop" to end translation

3 triplets

20

true or false:
genetic code is nearly universal, shared by the simplest bacteria to the most complex animals

true

21

what is the first stage of gene expression

transcription

22

RNA polymerase

RNA synthesis is catalzyed by RNA polymerase which pries the DNA strands apart and hooks together the RNA nucleotides
-RNA is complementary to the DNA template
-RNA synthesis follows same base pairing other than thymine is now uracil

23

promoter

the DNA sequence where RNA polymerase attaches

24

terminator

the sequence signaling the end of transcription

25

transcription unit

the stretch of DNA that is transcribed

26

what are the three stages of transcription

1. initiation
2. elongation
3. termination

27

start point (transcription in eukaryotic cells)

promoters signal this trancriptional start point and usually extend several dozen nucleotide pairs upstream of the start point

28

transcription factors
(transcription in eukaryotic cells)

mediate the binding of RNA polymerase and the initiation of transcription

29

Transcription initiation complex
(transcription in eukaryotic cells)

the completed assembly of transcription factors and RNA polymerase bound to a promoter...this is transcription initiation complex

30

TATA box
(transcription in eukaryotic cells)

a promoter.. crucial in forming the initiation complex in eukaryotes

31

in transcription the RNA polymerase moves along the DNA, it ____ the double helix

untwists

32

nucleotides are added to the _' end of the growing RNA molecule in transcription

3'

33

how does termination work in bacteria versus eukaryotic

bacteria: stops transcription at the end of the terminator and mRNA can be translated without further modification
eukaryotes: RNA polymerase transcribes the polyadenylation signal sequence; The RNA transcript is released 10-35 nucleotides past this polyadenylation sequence

34

what do eukaryotic cells do the RNA after transcription?

1. enzymes in eukaryotic nucleus modify pre-mRNA before the genetic messages are dispatched to the cytoplasm
2. During RNA processing, both ends of the primary transcript are altered
3. some interior parts of the molecule are cut out, and others are spliced together

35

what does the 5' end get in mRNA
what does the 3' end get in mRNA

-5' cap
- 3' poly- A tail

36

what is the functions of these 5' and 3' ends

1. facilitate export of mRNA
2. protect mRNA from hydrolytic enzymes
3. help ribosomes attach to the 5' end

37

introns

regions that are taken out and will not be expressed

38

exons

regions that are eventually expressed and translated into amino acid sequence

39

RNA splicing

removes introns and joins exons, creating mRNA molecule

40

what carries out RNA splicing

splicesomes

41

ribozymes

catalytic RNA molecules that function as enzymes and can splice RNA

42

what are the three properties of RNA enabling it to function as an enzyme

– It can form a three-dimensional structure because
of its ability to base-pair with itself
– Some bases in RNA contain functional groups that may participate in catalysis
– RNA may hydrogen-bond with other nucleic acid molecules

43

domains

-proteins have a modular architecture consisting of descrete regions called domains
-different exons code fro the different domains in a protein

44

genetic information flows from ____ to ___ through the process of translation

-mRNA
-protein
-Translation

45

transfer RNA

a cell translates an mRNA message into protein "language"
--tRNA transfer amino acids to the growing polypeptide in a ribosome

46

anticodon

the anticodon base-pairs with a complementary codon on mRNA

47

accurate translation requires what two steps

First: a correct match between a tRNA and an amino acid, done by the enzyme aminoacyl-tRNA synthetase
– Second: a correct match between the tRNA anticodon and an mRNA codon

48

wobble

flexible pairing at the third base of a codon is wobble. allows some tRNAs to bind to more than one codon

49

ribosomes

-facilitate specific coupling of tRNA anticodons with mRNA codons in protein synthesis

50

what are the two ribosomal subunits made up of?

proteins and ribosomal RNA

51

what are the ribosomes three binding sites?

P site
A site
E site

52

what is P site?

holds the tRNA that carries the growing polypeptide chain

53

what is A site?

holds the tRNA that carries the next amino acid to be added on the chain

54

what is E site?

the exit site, where discharged tRNAs leave the ribosome

55

what does the initiation stage of translation do?

brings together mRNA, a tRNA with the first amino acid, and the two ribosomal subunits
1st: a small ribosomal subunit binds with mRNA and a special initiator tRNA
2nd: the small subunit moves along the mRNA until it reaches the start codon (AUG)
3rd: proteins called initiation factors bring in the large subunit that completes the translation initiation complex

56

what does the elongation stage of translation do?

-amino acids are added one by one to the preceding amino acid at the C-terminus of the growing chain
-each addition involves proteins called elongation factors and occurs in three steps (1) codon recognition (2) peptide bond formation (3) translocation
-translation proceeds along the mRNA in a 5' to 3' direction

57

what happens in the termination stage of translation

-a stop codon in the mRNA reaches the A site of the ribosome
-A site accepts a protein called a release factor
-release factor causes the addition of a water molecule instead of an amino acid
-this reaction releases the polypeptide, and translation assembly falls apart

58

polyribosome

a number of ribosomes that can translate a single mRNA simultaneously

59

during and after synthesis, a polypeptide chain spontaneously ___ and ____ into a _____ ____

-coils
-folds
-3D shape

60

signal peptide

polypeptides destined for the ER or for secretion are marked by a signal peptide

61

SRP (signal recognition particle)

binds to the signal peptide
-the SRP brings the singal peptide and its ribosome to the ER

62

point mutations

chemical changes in just one base pair of a gene

63

what two general categories are there for point mutations

-nucleotide pair substitutions
-one or more nucleotide pair insertions or deletions

64

nucleotide pair substitution

replaces one nucleotide and its partner with another pair of nucleotides

65

silent mutations

have no effect on the amino acid produced by a codon because of redundancy in the genetic code

66

missense mutations

still code for an amino acid, but not the correct one

67

nonsense mutations

change an amino acid codon into a stop codon, nearly always leading to a nonfunctional protein

68

frameshift mutation

caused by insertions or deletions of nucleotide pairs

69

mutagens

physical or chemical agents that can cause mutations