Chapter 17

Question 1

what form is the content of DNA in?

Answer 1

specific sequences of nucleotides that is inherited by an organism and leads to specific traits by dictating the synthesis of proteins

Question 2

Gene Expression

Answer 2

the process by which DNA directs protein synthesis

two stages: 1) transcription 2) translation

Question 3

2 stages of gene expression

Answer 3

1) transcription

2) translation

Question 4

the study of metabolic defects …

Answer 4

provide evidence that genes specify proteins

Question 5

Archibald Garrod

Answer 5

first to suggest that genes dictate phenotypes through enzymes that catalyze specific chemical reactions in the cell

1909

Question 6

Beadle and Tatum

Answer 6

developed the “one gene-one enzyme theory”

cause bread mold (neurospora cassia) to mutate with X-rays creating mutants that could not survive on minimal medium

1930s

Question 7

“one gene-one enzyme theory”

Answer 7

states that the function of a gene is to dictate the production of a specific enzyme

DNA => RNA => protein (enzymes)
* not all proteins are enzymes {i.e. actin and tubuline}

Question 8

Genes code for …

Answer 8

polypeptide chains or for RNA molecules

Question 9

RNA is…

Answer 9

the bridge to proteins (from DNA)

Question 10

Transcription

Answer 10

the synthesis of RNA under the direction of DNA that produces messenger RNA (mRNA)

the DNA-directed synthesis of RNA

the conversion of DNA into RNA

Question 11

Translation

Answer 11

the actual synthesis of a polypeptide which occurs under the direction of mRNA and occurs on ribosomes

the conversion of nucleotide (RNA) into polypeptide

Question 12

Gene expression in Prokaryotes

Answer 12

lack a nuclei, so transcription and translation occur together
DNA => RNA => protein

Ribosomes help: attach to the leading end of mRNA and start translating while transcription is still in progress (to synthesize proteins)

Question 13

Ribosomes

Answer 13

attach to the leading end of mRNA and start translating while transcription is still in progress (to synthesize proteins)

Question 14

Gene expression in Eukaryotes

Answer 14

RNA transcripts (primary transcripts) are made in the nucleus are modified before becoming true mRNA

mRNA will leave the nucleus and be translated by the ribosomes

Question 15

mRNA

Answer 15

can leave the nucleus and be translated by the ribosomes

Question 16

Genetic Code: Cells are governed by a cellular chain of command

Answer 16

DNA => RNA => protein

Question 17

Genetic information is encoded

Answer 17

as a sequence of non overlapping base triplets or codons

Question 18

DNA is a series of …

Answer 18

3-nucleotides with instructions for RNA and a specific polypeptide chain

Question 19

Codons

Answer 19

3 mRNA nucleotides that refer to a specific amino acid

Question 20

During transcription, the gene determines…

Answer 20

the sequence of bases for an entire strand of mRNA

Question 21

Condon in mRNA

Answer 21

either translated into an amino acid or serves as a translational stop signal (codon).

must be read in the correct reading frame for the specified polypeptide to be produced

Question 22

Start Codon

Answer 22

AUG

Question 23

Stop Codon

Answer 23

UGA

UAG
UAA

Question 24

Components of Transcription

Answer 24

RNA synthesis is catalyzed by the enzyme RNA polymerase, which opens the DNA strands and hooks together the RNA nucleotides (5’ - 3’)

RNA follows the same base-pairing rules as DNA, excepted that in RNA, uracil substitutes for thymine

Question 25

3 stages of Transcription

Answer 25

1) Initiation (find DNA) 2) Elongation (synthesis of growing RNA strand) 3) Termination (stop codon recognized)

Question 26

Promoters

Answer 26

sequences of DNA that signal the initiation of RNA synthesis i.e. TATA box: rich in A and T and is located about 25nucleotide upstream of the transcription start site

Question 27

Transcription factors

Answer 27

help eukaryotic RNA polymerase recognize promoter sequences and start transcription

Question 28

Initiation in transcription

Answer 28

Promoters (TATA box) | Transcription factors

Question 29

During Elongation | in transcription

Answer 29

RNA polymerase moves along the DNA unraveling the double helix, for pairing with RNA nucleotides

Question 30

Termination mechanisms | in transcription

Answer 30

require the removal of RNA polymerase from the DNA and is different in prokaryotes and eukaryotes

Question 31

Enzymes in eukaryotic cells...

Answer 31

modify the mRNA in the nucleus after transcription for its dispatch to the cytoplasm (proof-read) ?

Question 32

Translation

Answer 32

3 stages 1) Initiation 2) Elongation 3) Termination into language of amino acids and polypeptides

Question 33

a cell translates or interprets... | in translation

Answer 33

a series of codons of an mRNA message into protein with the help of transfer RNA (tRNA)

Question 34

tRNA transfers | in translation

Answer 34

amino acids from eh cytoplasmic pool to a ribosome and the ribosome adds (catalyzes) each amino acid carried by tRNA to the growing end of the polypeptide chain

Question 35

Molecules of tRNA are not all identical

Answer 35

each carrie a specific amino acid on one end and has an anticodon on the other end to recognize the mRNA

Question 36

tRNA pairs...

Answer 36

with the codons of the mRNA to ensure the correct polypeptide is synthesized

Question 37

structure of tRNA

Answer 37

consists of a single RNA strand that is only about 80nucleotides long and is roughly L-shaped

Question 38

aminoacyl - tRNA synthetase

Answer 38

joins each amino acid to the correct tRNA, in an ATP-dependent manner synthesizes the bond between an amino acid and tRNA

Question 39

Ribosomes facilitate

Answer 39

the specific coupling of tRNA anticodons with mRNA codons during protein synthesis binds tRNA and facilitates protein synthesis

Question 40

ribosomal RNA or rRNA

Answer 40

are RNA molecules, along with proteins, that construct the ribosomal subunits

Question 41

Initiation in translation

Answer 41

brings together mRNA, tRNA bearing the first amino acid of the polypeptide, and two subunits of a ribosome

Question 42

Elongation in translation

Answer 42

amino acids are added one by one to the preceding amino acid

Question 43

Termination in translation

Answer 43

the final stage of translation and occurs when the ribosome reaches a stop codon in the mRNA

Question 44

Polyribosome

Answer 44

formed when a number of ribosomes can translate a single mRNA molecule simultaneously help with speed and quantity

Question 45

A single protein can be translated

Answer 45

in less than 1 minute

Question 46

Completing and targeting the functional protein

Answer 46

polypeptide chains undergo further modifications after the translation process (post-translation modification) that affects their shape, function, or destination in the cell proteins destined for the endomembrane system or secretion must be transported and synthesized directly into the ER these proteins have signal peptides enabling the translating ribosome to bind to the ER and synthesize into the ER center i.e. insulin important words: 1) post-translation modification; 2) endomembrane system; 3) signal peptides SRP: signal recognition protein after signal peptide: brings ribosome to ER

Question 47

Mutations

Answer 47

in nucleic acids can affect protein structure and function changes in the genetic material of the cell can occur during DNA or RNA replication, recombination, or repair

Question 48

Point Mutations

Answer 48

changes in one base pair of a gene that leads to the production of an abnormal protein i.e. sickle cell disease change from CTT (Glu) => CAT (Val)

Question 49

2 types of point mutations

Answer 49

1) Base-pair substitutions | 2) Base-pair insertions or deletions

Question 50

Base-pair substitutions

Answer 50

replacement of one nucleotide and its partner with another pair of nucleotides

Question 51

Base-pair insertions or deletions

Answer 51

additions or losses of nucleotides pairs in a gene and may produce frameshift mutations

Question 52

Mutagens

Answer 52

physical or chemical agents that can cause mutations i.e. UV, oxygen radicals, alkylating agents

Question 53

Genetic Code

Answer 53

and its associated machinery is nearly universal is shared by organisms from the simplest bacteria to the most complex animals

Question 54

in laboratory experiments, genes can be

Answer 54

transplanted between organisms or species then these genes can be transcribed and translated to make the same proteins i.e. tobacco plant expressing firefly genes causes the plant to "glow"