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Biology 1000 > Unit 10-Molecular Genetics > Flashcards

Unit 10-Molecular Genetics Flashcards

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1
Q

DNA structure

A

nitrogenous bases
- T,G,C,A
backbone
- sugar phosphate

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2
Q

What type of polymer and monomer is DNA and RNA

A 
Polymer = nucleic acids
Monomer = nucleotides
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3
Q

The nucleotides are joined together by what

A

Covalent bonds between the sugar of one and the phosphate of the other
This creates the sugar phosphate backbone

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4
Q

Along a strand of a double helix is the nucleotide sequence GGCATAGGT. what is the complementary sequence for the other DNA strand

A

CCGTATCCA

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5
Q

Define semi conservative model

A

A model of DNA replication that half of the parental molecule is maintained (conserved) in each daughter molecule

The DNA double helix separates and each half acts as a template while free nucleuotides come in and attach in the appropriate sequence to the new daughter strand (synthesis of the complementary stand!)

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6
Q

How does complementary base pairing make possible the replication of DNA

A

When the two strands of the double helix separate, free nucleotides can base pair along each strand leading to the synthesis of new complementary strands

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7
Q

Replication of a DNA molecule begins at _______

A

Special sites called origins of replication

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8
Q

What enzyme is used to create replication bubbles (separate the parental strands)

A

DNA helicase separates the the parental strands to create two forks

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9
Q

DNA replication proceeds in two directions at many sites simultaneously how does this work

A

The leading strand opens in the 3’ to 5’ direction (top strand)

Lagging strand opens in the 5’ to 3’ direction (bottom strand)

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10
Q

On the leading strand in what direction do you read to form the daughter strand

What direction is it synthesized

A

3 to 5 direction

5 to 3 direction

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11
Q

What is the overall direction of replication

A

To the left

From the tip of the fork to the point where it closes

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12
Q

What is DNA polymerase

A

The enzymes that link DNA nucleotides to a growing daughter strand

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13
Q

Where does DNA polymerase add nucleotides

A

ONLY at the 3’ end of the strand!!
Never the 5’
Therefore!
A daughter DNA strand can grow only in the 5’ to 3’ direction

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14
Q

Which daughter strand can be synthesized continuously

Which daughter strand cannot and why

A

The daughter strand that starts at the 5’ and goes to the 3’ TOWRDS the point in which the fork meets
(Continuous)

The daughter strand that starts at the 5’ and goes to the 3’ away from the point the fork meets needs to be synthesized in short pieces

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15
Q

What is DNA Ligase

A

An enzyme that works to link the pieces together of the second daughter strand that was NOT done continuously
These fragments are called Okazaki fragments

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16
Q

DNA strands are ___

A

Antiparallel

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17
Q

On the lagging strand in what direction do you read the DNA

In what direction is it synthesized

A

3’ to 5’

5’ to 3’

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18
Q

What is the function of DNA polymerase in DNA replication

A

As free nucleotides base pair to a parallel DNA strand the enzyme covalently bonds them to the 3’ end of a growing daughter strand

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19
Q

What is the 3’ prime and 5’ prime

A

The primed numbers refer to the carbon atoms of the nucleotide sugars
At one end of each DNA strand the sugars 3’ carbon atoms is attached to an -OH group and at the other end the sugars 5’ carbon is attached to a phosphate group

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20
Q

What are the two main stages of DNA replication and synthesis

A

Transcription
- the synthesis of RNA under the direction of DNA

Translation
- the synthesis of protein under the direction of RNA

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21
Q

What are the functions of transcription and translation

A

Transcription is the transfer of information from DNA to RNA.
Translation is the use of the information in RNA to make a polypeptide

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22
Q

Are both stands of the DNA transcribed

A

No! Only one is transcribed

The template strand

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23
Q

The DNA template strand AAACCGGCAAAA is transcribed into what code for RNA

A

UUUGGCCGUUUU

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24
Q

What is a triplet code

A

The genetic instructions for the amino acid sequence of a polypeptide chain are written in DNA and RNA as a series of non overlapping three base “words” called codons!

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25
Q

What is the genetic code

A

The set of rules that relate codons in RNA to amino acids in proteins

26
Q

What are the three transcripts of RNA synthesis

A

rRNA
mRNA
tRNA

27
Q

What codon codes for Met which starts the sequence

A

AUG

28
Q

What three codons code for stop

A

UAA
UAG
UGA

29
Q

What is a promoter?

What molecule binds to it

A

A promoter is a specific nucleotide sequence at the start of a gene where sigma factor and RNA polymerase attach and begin transcription

30
Q

Define promoter

A

A specific binding site for a protein called sigma factor

31
Q

What is RNA polymerase

A

The RNA nucleotides are linked by this enzyme

32
Q

What are the three phases of transcription

A

Initiation
Elongation
Termination

33
Q

Explain initiation

A

The attachment of RNA polymerase to the promoter and the start of RNA synthesis
Sigma factor binds to specific DNA and RNA polymerase binds to the sigma factor

34
Q

Explain elongation

A

The RNA grows longer

The RNA strand peels away from its DNA template allowing the two separated DNA strands come back together

35
Q

Explain the terminator phase

A

The RNA polymerase reaches a sequence of bases in the DNA template called the terminator
Signals the end of the gene and the polymerase molecule detaches

36
Q

The kind of RNA that encodes amino acid sequence is called __

A

Messenger RNA (mRNA)

It conveys genetic messages from DNA to the translation machinery of the cell
mRNA is transcribed from DNA and then mRNA translates to polypeptides

37
Q

What does the 5’ cap and poly a tail do for the mRNA

A

5’ cap

  • protects the mRNA before exiting the nucleus
  • facilitates ribosome binding

Poly A tail

  • protects the mRNA before exiting the nucleus
  • signals transport to cytoplasm

Are not translated into proteins !

38
Q

What else needs to be done to the RNA before leaving the nucleus

A

Cut the introns out and bind together the exons

Called RNA splicing

39
Q

Why are most eukaryotic genes longer then the mRNA that leaves the nucleus

A

These genes have introns

Which are no coding sequence of nucleotides that are spliced out of the initial RNA transcript to produce mRNA

40
Q

Define transfer RNA (tRNA)

A

To convert words of nucleic acids (codons) to the amino acid words of proteins a cell employs a molecular interpreter a special type of RNA called tRNA
A quasi double helix

41
Q

What do tRNA’s do

A

1) picks up the appropriate amino acids

2) recognize the appropriate codons in the mRNA

42
Q

What is the anticodon

A

tRNA codes for an anticodon triplet that is complementary to a codon triplet on mRNA

43
Q

How many tRNA molecules are there

A

61

44
Q

What is an anticodon and what is its function

A

It is the base triplet of a tRNA molecule that couples the tRNA to a complementary codon in the mRNA
This is a key step in translating mRNA to a polypeptide

45
Q

What is rRNA

A

Ribosomal rna

Used to position mRNA and tRNA close together to catalyst the synthesis of polypeptides

46
Q

What are the two subunits of the ribosome

A

Small on the bottom
Large on the top
Between subunits mRNA binds

P site to the left
A site to the right
P and A site are tRNA binding sites

47
Q

How does a ribosome facilitate protein synthesis

A

A ribosome holds mRNA and tRNA together and connects amino acids from the tRNA to the growing polypeptide chain

48
Q

What are the three stages of translation

A

The same as transcription

Initiation
Elongation
Termination

49
Q

What are the two steps of translation initiation

A

An mRNA molecule binds to a small subunit. A special initiator tRNA binds to the specific codon called the start codon
The initiator tRNA carries the amino acid Met and the anticodon UAC binds to the codon AUG
Then the large ribosomal unit binds to the Amal one and the initiator tRNA fits into the P site

50
Q

What does the P site hold

What does the A site hold

A

The growing polypeptide

Vacant and ready for the next amino acid bearing tRNA

51
Q

What are the three steps of translation elongation

A

Codon recognition
Peptide bond formation
Translocation

52
Q

Explain codon recognition

A

The anticodon of an incoming tRNA molecule carrying its amino acid pairs with the mRNA codon in the A site of the ribosome

53
Q

Explain peptide bond formation

A

The polypeptide speedster from the tRNA in the p site and attaches by a new peptide bond to the amino acid carried by the rRNA in the a site
The ribosome catalyzes formation of the peptide bond adding one more amino acid to the growing polypeptide chain

54
Q

Explain translocation

A

The p site tRNA now leaves the ribosome and the ribosome translocates (moves) the remaining tRNA in the a site with the growing polypeptide to the p site
mRNA and tRNA stays bonded and moves as a unit
Then a new tRNA comes into the a site to translate the mRNA

55
Q

Where does transcription occur

Where does translation occur

A

Nucleus

Cytoplasm

56
Q

Define a mutation

A

Any change in the nucleotide sequence of DNA

57
Q

Define a silent mutation

A

A substitution mutation that has no affect at all

The protein is the same

58
Q

Define a missense mutation

A

A substitution mutation that does change the amino acid coding
Can have little or no affect if the new protein has similar properties as the original protein

59
Q

Define nonsense mutations

A

A nucleotide substitution that leads to a harmful mutation

Change an amino acid codon into a stop codon

60
Q

How could a single nucleotide substitution result in a different protein

A

It changes the reading frame

Biology 1000 (11 decks)

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