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Genetics > The Genetic Code and DNA > Flashcards

The Genetic Code and DNA Flashcards

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1
Q

Nucleoside?

A

Nucleotide without phosphate group

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2
Q

What is the difference between Ribose and Deoxyribose sugar?

A

Deoxyribose lacks hydroxyl group at carbon ‘2

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3
Q

What is significant about the phosphate group?

A

It possesses a negative charge

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4
Q

What type of molecule is cAMP?

A

A chemical signaling molecule

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5
Q

Which nitrogenous bases are the purines?

A

Adenine and Guanine (double ring structure)

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6
Q

Which nitrogenous bases are pyramidines

A

Cytosine and Thymine and Uracil

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7
Q

Which Nitrogenous Base is complementary to Thymine?

A

Adenine (two hydrogen bonds)

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8
Q

Which Nitrogenous Base is compatible to Cytosine?

A

Guanine (three hydrogen bonds)

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9
Q

What kind of interactions take place with adjacent bases stacked on top of one another?

A

Hydrophobic interactions

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10
Q

What is Chargaff’s Rule?

A 
A:T = 1:1
C:G = 1:1
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11
Q

How are individual nucleotides joined together?

A

They are joined together in a linear strain known as the sugar phosphate backbone

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12
Q

What is directionality?

A

Nucleotides are linked together by phosphdiester linkages that link nucleotides together by binding the 3’ carbon sugar on one nucleotide and the 5’ on the other from 5’ to 3’

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13
Q

What must be true when a DNA molecule hybridizes with RNA

A

Complementary strand must be both complementary and antiparallel

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14
Q

Identify the DNA sequence that is complementary to 5’ ACTG 3’

A

5’ CAGT 3’

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15
Q

What can be used to seperate DNA Strands?

A

heat

chemical denaturants

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16
Q

What is the melting temperature (Tm)?

A

50% of DNA strands are denatured

DNA with higher G-C content are associated with a higher melting temperature (Tm)

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17
Q

Is denaturation reversible?

A

Yes - through annealing

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18
Q

What kind of helix is DNA?

A

Right Handed helix

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19
Q

What is the most common form of DNA?

A

B DNA - 10.5 base pairs per turn of the double helix

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20
Q

What is A DNA?

A

Dehydrated form of B-DNA
(tighter/more condensed)
formed by DNA-RNA hybrid helices

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21
Q

What is Z DNA?

A

Left Handed

Looser

22
Q

What is deoxyribonucleic acid responsible for?

A

storage and transmission of genetic information (true for nuclear DNA and mitochondrial DNA)

23
Q

What is messenger RNA (mRNA)?

A

Communicates information about genetic code to translational machinery in the cytoplasm in order to make the right proteins (gene expression)

24
Q

What is heterogenous nuclear RNA (hnRNA)?

A

Precursor to mRNA

spliced/modified to mature RNA

25
Q

What is transfer RNA (tRNA)?

A 
Cloverleaf structure
Transfer amino acids to growing polypeptide chain
Recognize codons (mRNA)
Incorporate AA's they code for into the protein
26
Q

What is ribosomal RNA (rRNA)?

A

Synthesized in the nucleolus

Make up 50% of the ribosome

27
Q

What are ribozymes?

A

Inhibit expression of specific genes (destroy mRNA sequences)
ex. siRNA - small interfering, miRNA - microRNA

28
Q

What is helicase?

A

Separates strand of ds-DNA

29
Q

What is ligase?

A

Joins Okazaki fragments on laggins strand

30
Q

What is reverse transcriptase?

A

Enzyme that synthesizes DNA from an RNA template used by retroviruses (HIV) to integrate DNA into a host

31
Q

What is telomerase?

A

Extends telomeres

32
Q

In which direction is DNA synthesized on the lagging strand?

A

From 5’ to 3’

33
Q

What is DNA polymerase?

A

Adds complementary bases

34
Q

What is primase?

A

Initiates replication

35
Q

Which enzyme is the primary DNA proofreader?

A

DNA polymerase

36
Q

In semiconservative replication

A

one strand of each daughter molecule is from the parent while the other strand in each daughter molecule is newly synthesized.

37
Q

What is the major synthetic enzyme of bacterial DNA replication?

A

DNA polymerase III

38
Q

Okazaki fragments of the lagging strand during DNA synthesis are connected by which enzyme?

A

DNA ligase - DNA poly cannot continually synthesize a new continuous strand due to the lagging strands directionality. Ligase connects and repairs these fragments to make a continuous strand.

39
Q

In prokaryotes DNA polymerase:

A

reads the lagging strand in the 3’ to 5’ direction

40
Q

DNA is a polymer of:

A

Nucleoside monophosphates
-nucleic acids are nucleotide polymers comprised of nucleosides (nitrogenous base, five carbon sugar, and attached phosphate)

41
Q

Which of the following pairs with uracil?

A

Adenine - Uracil replaces Thymine in RNA

42
Q

When does Tm increase?

A

increases as DNA polymer length increases and as the nucleotide sequence GC content increases

43
Q

Which of the following are the functional differences between DNA and RNA

A

Certain RNA molecules possess the ability to catalyze biochemical reactions while DNA molecules cannot - ribozymes can catalyze RNA/DNA ligation and peptide bond formation

44
Q

What are the three stop codons?

A

UAA, UAG, UGA (a truncuated protein product forms when a mutation replaces a normal codon with a stop codon causing premature protein termination.

45
Q

In the human cell nucleic acids can be found in:

A

-the nucleus
-the mitochondria
the cytoplasm

46
Q

Where does DNA replication occur?

A

In eukaryotes, DNA localizes to the nucleus

47
Q

A geneticist radiolabeled a fragment of dsDNA and allowed it to replicate. After four successive replication cycles, what proportion of ds DNA molecules contain at least one strand of the original material?

A

In semiconservative replication, the parent dsDNA denatures. Each denatured strand serves s a template for newly formed DNA - as a result in the first replication cycle the two daughter dsDNA molecules each contain a parent DNA strand and a new DNA strand. After the fourth replication cycle 16 dsDNA molecules exist. Only two molecules contain an original DNA strand.

48
Q

True or False: The unwinding of the parental double helix during DNA replication requires the activity of a DNA polymerase functional domain.

A

False - Helicase unwinds the DNA double helix. This creates tension from supercoiling that is relieved by topoisomerase.

49
Q

What purpose do primers serve in the initiation of DNA replication?

A

They provide sites to which a vital enzyme can bind to proceed with DNA replication - DNA Poly can only bind to a free -OH group that is already present on the developing strand. RNA primers provide these free 3’ hydroxyl groups allowing for DNA synthesis to occur.

50
Q

Fluoroquinolones are antibiotics that interfere with the prokaryotic enzymes directly responsible inducing changes in supercoiling state of bacterial chromosomes. The enzyme targeted by fluoroquinones most likely belongs to which class?

A

DNA topoisomerases

51
Q

Which of the following enzymes possesses a 3’ to 5’ exonuclease activity?

A

DNA polymerase - in addition to synthesizing DNA strands that are complementary. DNA poly is also able to excise mismatched bases and replace them with the correct base at that position.

Genetics (2 decks)

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