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Biology OCR A > Nucleic acids > Flashcards

Nucleic acids Flashcards

1
Q

What is DNA?

A

Deoxyribonucleic acid, the hereditary material in living organisms.

DNA carries coded instructions for development and functioning.

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2
Q

What is the structure of a nucleotide?

A

A molecule consisting of a five-carbon sugar, a phosphate group, and a nitrogenous base.

Nucleotides are the monomers of nucleic acids.

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3
Q

What are the two phosphorylated nucleotides mentioned?

A

ADP (adenosine diphosphate) and ATP (adenosine triphosphate).

ATP is used to drive most energy-requiring metabolic processes.

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4
Q

What is a polynucleotide?

A

A large molecule containing many nucleotides.

Polynucleotides are formed by the linking of nucleotides through phosphodiester bonds.

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5
Q

What is the shape of the DNA molecule?

A

Double helix, due to coiling of the two sugar-phosphate backbone strands.

The double helix configuration is right-handed.

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6
Q

What is the difference between a nucleotide and a nucleoside?

A

A nucleotide consists of a pentose sugar, a nitrogenous base, and a phosphate group; a nucleoside consists of only a pentose sugar and a nitrogenous base.

Example: Adenosine is a nucleoside, AMP is a nucleotide.

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7
Q

How do hydrogen bonds contribute to the structure of DNA?

A

Hydrogen bonds join the two antiparallel DNA strands through complementary base pairing.

Adenine pairs with thymine, and guanine pairs with cytosine.

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8
Q

What are the four nitrogenous bases in DNA?

A

Adenine, guanine, thymine, and cytosine.

These bases determine the genetic information carried by DNA.

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9
Q

What is the significance of antiparallel strands in DNA?

A

The two strands run in opposite directions, which is crucial for DNA replication and transcription.

This refers to the orientation of the sugar-phosphate backbones.

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10
Q

Fill in the blank: Adenine always pairs with _______ by means of two hydrogen bonds.

A

Thymine

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11
Q

Fill in the blank: Guanine always pairs with _______ by means of three hydrogen bonds.

A

Cytosine

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12
Q

What type of bond is formed between the phosphate group and the sugar in a nucleotide?

A

Phosphodiester bond.

These bonds are broken during the breakdown of polynucleotides.

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13
Q

True or False: A purine always pairs with a purine in DNA.

A

False

A purine always pairs with a pyrimidine.

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14
Q

What are the components of coenzyme NADP?

A

Adenine nucleotides.

NADP is used in photosynthesis.

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15
Q

What is the role of ATP in biochemical pathways?

A

ATP is an energy-rich end-product used to drive most energy-requiring metabolic processes.

It is formed from ADP and inorganic phosphate.

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16
Q

What is the significance of the sugar-phosphate backbone in DNA?

A

It forms the upright part of the DNA molecule, resembling a ladder.

The backbone is formed by the covalent bonds between the sugar and phosphate groups.

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17
Q

Fill in the blank: Each DNA nucleotide consists of a phosphate group, a five-carbon sugar called ________, and one of four nitrogenous bases.

A

Deoxyribose

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18
Q

What are the roles of nucleotides in metabolism?

A

Regulate metabolic pathways and serve as components of coenzymes.

Examples include ATP, ADP, AMP, NAD, and FAD.

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19
Q

What is the sugar-phosphate backbone in DNA?

A

A structural framework of DNA consisting of alternating sugar (deoxyribose) and phosphate groups

The sugar-phosphate backbone supports the nucleotide bases that are attached.

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20
Q

In eukaryotic cells, where is the majority of DNA found?

A

In the nucleus

The DNA is organized into chromosomes.

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21
Q

How is DNA organized in prokaryotic cells?

A

DNA is in a loop within the cytoplasm and is not enclosed in a nucleus

This DNA is described as naked and does not wind around histone proteins.

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22
Q

What is the role of helicase in DNA replication?

A

Catalyses the breaking of hydrogen bonds between nitrogenous base pairs

This allows the DNA strands to separate.

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23
Q

Define semi-conservative replication.

A

A process where each new DNA molecule consists of one old strand and one new strand

This method conserves one original strand in each new molecule.

24
Q

What is the function of DNA polymerase?

A

Catalyses the addition of new nucleotide bases to the growing DNA strand

It uses a single strand of DNA as a template.

25
Q

What is the difference between purines and pyrimidines?

A

Purines are double-ring structures, while pyrimidines are single-ring structures

Purines include adenine and guanine, whereas pyrimidines include cytosine and thymine.

26
Q

True or False: DNA in mitochondria and chloroplasts replicates independently of the cell cycle.

A

True

These organelles replicate their DNA before the cell divides.

27
Q

What evidence supported the semi-conservative model of DNA replication?

A

The experiment by Meselson and Stahl showed hybrid DNA after one replication cycle in bacteria

This indicated that each new DNA molecule contained one old strand.

28
Q

Explain what is meant by ‘complementary base pairing’.

A

The specific pairing of nitrogenous bases (adenine with thymine, guanine with cytosine) in DNA

This ensures accurate replication and transcription of genetic information.

29
Q

Fill in the blank: The loops of DNA in prokaryotes replicate _______.

A

semi-conservatively

30
Q

List the components of a nucleotide.

A
  • A phosphate group
  • A deoxyribose sugar
  • A nitrogenous base

The nitrogenous bases can be adenine, thymine, guanine, or cytosine.

31
Q

What happens during the unwinding phase of DNA replication?

A

The double helix is untwisted, catalysed by gyrase enzyme

This prepares the DNA for separation into two strands.

32
Q

How do mutations occur during DNA replication?

A

Errors may occur when the wrong nucleotide is inserted

This is estimated to happen in 1 in 108 base pairs, potentially altering the genetic code.

33
Q

What is the direction in which nucleotides are added during DNA replication?

A

5’ to 3’ direction

34
Q

What enzyme catalyzes the addition of new DNA nucleotides during replication?

A

DNA polymerase

35
Q

What is the term used for different versions of a particular gene?

A

alleles

36
Q

True or False: All mutations are harmful.

A

False

37
Q

What is a useful mutation that arose in the FOXP2 gene associated with?

A

human speech

38
Q

What is the term for the process during which a DNA molecule unwinds and unzips?

A

DNA replication

39
Q

Fill in the blank: A _______ is a length of DNA that codes for a polypeptide or RNA.

A

gene

40
Q

What is the primary structure of a polypeptide determined by?

A

the sequence of amino acids

41
Q

What are the three forms of RNA?

A
  • messenger RNA (mRNA)
  • transfer RNA (tRNA)
  • ribosomal RNA (rRNA)
42
Q

What process involves making messenger RNA from a DNA template?

A

transcription

43
Q

What is the role of ribosomes in protein synthesis?

A

formation of proteins by assembling amino acids

44
Q

How is the genetic code described in terms of universality?

A

near universal

45
Q

What does it mean that the genetic code is degenerate?

A

more than one base triplet codes for most amino acids

46
Q

What causes a frame shift in the genetic code?

A

addition or deletion of a base

47
Q

What percentage of an organism’s dry mass is accounted for by protein?

A

75%

48
Q

Where are genes located in a cell?

A

cell nucleus

49
Q

What is the term for the assembly of amino acids into a particular sequence at the ribosome?

A

translation

50
Q

What is the nitrogenous base that replaces thymine in RNA?

A

uracil

51
Q

What is the primary function of DNA helicase during replication?

A

unwinding the DNA double helix

52
Q

During DNA replication, what is the name of the structure where the DNA strands separate?

A

replication fork

53
Q

What is the difference between a polypeptide and a protein?

A

A polypeptide is made of many amino acids; a protein is a large polypeptide of 100 or more amino acids.

54
Q

In which part of the cell are proteins made?

A

cytoplasm, at ribosomes

55
Q

True or False: The genetic code is overlapping.

A

False

Biology OCR A (1 decks)

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