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Genetics > Chapter 13 > Flashcards

Chapter 13 Flashcards

1
Q

What are protein encoding or structural genes

A

Genes that encode polypeptides
These are transcribed into mRNA

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2
Q

What is the main function of genetic material

A

Encode the production of cellular proteins

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3
Q

What is the one gene one enzyme hypothesis

A

A single gene is controlled by the synthesis of a single enzyme

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4
Q

How can one gene encode multiple polypeptides

A

Alternative splicing

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5
Q

What does translation rely on?

A

The genetic code which is a translator of info on mRNA to determine which amino acid is next

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6
Q

How is genetic information coded

A

Within mRNA in groups of three nucleotides (codons)

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7
Q

What is the start codon

A

AUG or methionine

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8
Q

What are the stop codons

A

UAA, UAG, and UGA

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9
Q

What does it mean that the genetic code is degenerative

A

Some amino acids are coded by more than one codon
Always occurs at the codons third position

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10
Q

What does it mean that the genetic code is universal

A

All organisms for the most part have the same amino acids and share the same code

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11
Q

Which direction does polypeptide synthesis work

A

5 to 3 prime

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12
Q

What happens during each cycle of elongation

A

A peptide bond is formed between the carboxyl group of the last amino acid in the polypeptide chain and the amino group in the amino acid group

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13
Q

What are the two ends of a polypeptide chain

A

N terminus and C terminus
Amino group and carboxyl group

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14
Q

What holds polypeptides together

A

Peptide bonds

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15
Q

What is the primary structure of a protein

A

Amino acid sequence
Can be folded further with the assistance of chaperones

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16
Q

What are protein secondary structures

A

The primary structures form regular repeating shapes
Helix and sheets
Stabilized by hydrogen bonds located in the backbone

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17
Q

What is the tertiary structure of a protein

A

Final confirmation of proteins that are composed of a single polypeptide
Structure is determined by hydrophobic and ionic interactions but also hydrogen bonds

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18
Q

What is the quaternary structure of a protein

A

Various polypeptides associated with one another to make a functional protein

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19
Q

What happens during mRNA - tRNA recognition

A

The anticodon in tRNA binds to a complementary codon in mRNA

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20
Q

How are tRNAs named

A

According to the amino acid they have

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21
Q

What orientation is the anticodon

A

Anti parallel to the codon

22
Q

What is the secondary structure of tRNA

A

A cloverleaf pattern
Three stem loop structures
A few variable sites and an acceptor stem with a three prime single strand region (CCA)

23
Q

In regard to nucleotides which ones do tRNA have

A

U,G,A,C and modified ones too (a lot of modified)

24
Q

What are aminoacyl -tRNA synthetases

A

Enzymes that attach amino acids to tRNAs
Catalyze two step reactions that involve an amino acid, tRNA, and ATP

25
Q

What are the sequences throughout the tRNA used as

A

Recognition sites

26
Q

What are the aminoacyl tRNa synthetases responsible for

A

The second genetic code which means the selection of amino acids must be highly accurate or the polypeptide will be nonfunctional

27
Q

What can modified bases affect

A

Translation rates
Recognition by aminoacyl tRNA synthetases
Codon anticodon recognition

28
Q

What is the wobble hypothesis

A

In the Codon anticodon recognition process the first two positions pair strictly using the AU/GC rule

29
Q

What are isoacceptor tRNAs

A

tRNAs that are able to recognize the same codon

30
Q

Where does translation occur

A

On the surface of a ribosome

31
Q

How many types of ribosomes do bacterial and eukaryotic cells have

A

Bacteria has one in the cytoplasm
Eukaryotic cells have two, one in the mitochondria and one in the chloroplast

32
Q

What are ribosomes composed of

A

Large and small subunits
Each subunit is formed from the assembly of proteins and rRNA

33
Q

Which subunit attaches the mRNA

A

Small

34
Q

What are the small units sedimentation coefficient

A

30s, 50s, 70s

35
Q

What are the eukaryotic sedimentation coefficients

A

40s, 60s, 80s

36
Q

During bacterial translation where does the mRNA lie

A

On the surface of the 30s subunit

37
Q

Where does a a polypeptide exit

A

Through a channel within the 50s subunit

38
Q

What are the three sites within the ribosome

A

Peptidyl site where the growing polypeptide chain is
Aminoacyl site where the codon is opened and a new tRNA is added
Exit site where the tRNA leaves

39
Q

What is the binding of the mRNA to the 30s subunit facilitated by

A

The ribosomal binding site

40
Q

What makes the initiation complex

A

The mRNA, initiator tRNA and ribosomal subunits
This process takes three initiation factors

41
Q

The initiator tRNA recognizes the start codon in mRNA why is this significant

A

It carries a methionine that has been covalently modified to N-formylmethionine

42
Q

How is eukaryotic initiation different than bacterial

A

The initiator tRNA carries a methionine instead

43
Q

How does initiation start

A

The ribosome scans until it reads the first AUG after the 5’ cap
The entire assembly moves along the mRNA

44
Q

What is elongation

A

Amino acids are added to the polypeptide chain
Faster in bacteria than eukaryotes

45
Q

What happens after peptide bond formation

A

tRNAs at the P and A sites move down one into the E and P site

46
Q

How does termination occur

A

The stop codon is reached in the mRNA
Stop codons are also considered to be nonsense codons

47
Q

How are nonsense codons recognized

A

By release factors which hydrolyze the last covalent bond of the last amino acid to tRNA

48
Q

How many release factors do bacteria and eukaryotes have

A

Bacteria have 3
Eukaryotes have 2

49
Q

Why is bacteria lacking a nucleus important

A

Both transcription and translation occur in the cytoplasm

50
Q

True or false: transcription ends then translation begins

A

False, translation starts before the end of transcription (known as coupling)

51
Q

As soon as an mRNA strand is long enough what can happen

A

A ribosomes will attach to the five prime end and translation can start

Genetics (13 decks)

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