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Biology > Nucleic Acids > Flashcards

Nucleic Acids Flashcards

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1
Q

What are nucleotides?

A

Biological molecules that participate in most biochemical processes

Form the monomers of nucleic acids, DNA and RNA

May be components of many coenzymes

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2
Q

What is a phosphorylated nucleotide?

A

A nucleotide that contains more than one phosphate group

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3
Q

What is the nucleotide pentose sugar in
1 DNA and
2 RNA?

A

1 Ribose

2 Deoxyribose

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4
Q

What can nucleotides help regulate?

A

Many metabolic pathways

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5
Q

What is DNA?

A

A nucleic acid - deoxyribose nucleic acid

The material that carries coded instructions used in the development and functioning of all known living organisms

One of the macromolecules that make up the structure of living organisms

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6
Q

Where is DNA found?

A

In the nuclei of all eukaryotic cells

Within the cytoplasm of prokaryotic cells

Inside some types of viruses

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7
Q

What is the structure of DNA?

A

A polymer made up of nucleotides

Two polynucleotide strands running in opposite directions (antiparallel)

Phosphate group

A five-carbon sugar(deoxyribose)

1/4 nitrogenous bases (adenine, guanine, thymine, cytosine)

Long - can carry a lot of genetic info

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8
Q

What are purines and pyrimidines?

A

Nitrogenous bases that differ in each nucleotide

Purine - adenine or guanine

Pyrimidine - thymine or cytosine

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9
Q

What is the different between a purine and pyrimidine?

A

Purine have two carbon-nitrogen rings

Pyrimidine have one carbon-nitrogen ring

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10
Q

What bonds hold together the two antiparallel DNA strands?

A

Hydrogen bonds

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11
Q

Which purines and pyrimidine always pair up?

A

Adenine always pairs with thymine

Guanine always pairs with cytosine

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12
Q

How many hydrogen bonds can nucleotides with adenine as the base make with nucleotides with thymine as the base?

A

Two hydrogen bonds

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13
Q

How many hydrogen bonds can nucleotides with guanine as the base make with nucleotides with cytosine as the base?

A

Three hydrogen bonds

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14
Q

What gives a DNA molecule it’s stability?

A

The double helix formed from the two antiparallel DNA strands twisting around each other

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15
Q

What is the sugar-phosphate backbone?

A

The chain formed from the nucleotides joining up between the phosphate group of one and the sugar of another via a phosphodiester bond

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16
Q

How is DNA organised in eukaryotic cells?

A

Majority of the genome is in the nucleus

Each molecule of DNA is tightly wound around histone proteins into chromosomes

There’s also a loop of DNA without the histone proteins inside mitochondria and chloroplasts

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17
Q

What is meant by genome?

A

All of the DNA content within a cell

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18
Q

How is DNA organised in prokaryotic cells?

A

Within the cytoplasm in a loop, not enclosed in a nucleus

Not wound around histone proteins, described as naked

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19
Q

What does all DNA carry within every cell of an organism?

A

The coded instructions to make and maintain that organism

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20
Q

Why does DNA have to be copied every time a cell divides?

A

So that each new daughter cell receives the full set of instructions

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21
Q

What is semi-conservative replication?

A

How DNA replicates, resulting in two new molecules, each of which contains one old strand and one new strand

22
Q

What does each DNA molecule do to make a new copy of itself?

A

The double helix is untwisted a bit at a time

The hydrogen bonds between the nucleotide bases are broken

Resulting in two single strands of DNA with exposed nucleotide bases

23
Q

What happens to the DNA after it unwinds and unzips?

A

Free phosphorylated nucleotides are bonded to the exposed bases

DNA polymerase catalyses the addition of the new bases to the strands of DNA, using each strand of unzipped DNA as a template

The unzipped strand is synthesised continuously

Hydrolysis of activated nucleotides, to release extra phosphate groups, supplies the energy to make phosphodiester bonds between the deoxyribose of one nucleotide and the phosphate group of the next

24
Q

What is the product of DNA replication?

A

Two DNA molecules, identical to each other and to the parent molecule

25
Q

How are the loops of DNA in prokaryotes and inside mitochondria and chloroplasts replicated?

A

Also semi-conservatively

A bubble sprouts from the loop and this unwinds and unzips, and then complementary nucleotides join to the exposed nucleotides

Eventually the whole loop is copied

26
Q

What are mutations?

A

Errors that may occur during DNA replication

27
Q

How can mutations occur during DNA replication?

A

If the wrong nucleotide is inserted

28
Q

What could happen as a result of a mutation?

A

The genetic code could change

29
Q

How can the rate of mutations be reduced?

A

There can be enzymes during the replication process that can proofread and edit out any incorrect nucleotides

30
Q

What is an allele?

A

Different versions of a particular gene

31
Q

How can some mutations be advantageous?

A

If they provide a survival advantage

32
Q

How is RNA structurally different from DNA?

A

The sugar molecule is ribose

The nitrogenous base uracil replaces thymine as a pyrimidine base

Polynucleotide chain is usually single-stranded and shorter

There are three different forms

33
Q

What are the 3 forms of RNA?

A

Messenger RNA (mRNA)

Transfer RNA (tRNA)

Ribosomal RNA (rRNA)

34
Q

What is a gene?

A

A length of DNA that contains a code determining the sequence of amino acids in a particular polypeptide or protein

35
Q

What makes up a polypeptide’s primary structure/determines the sequence of amino acids in a polypeptide or protein?

A

A sequence of DNA base triplets within each gene

36
Q

Why is there a need for transcription?

A

Because as genes are inside the nucleus and proteins are made in the cytoplasm, the instructions inside the genes have to be transcribed into a length of mRNA as they cannot pass out of the nucleus

37
Q

What are base triplets called when in the form of mRNA?

A

Codons

38
Q

What is the nature of the genetic code?

A

It is universal, degenerate and non-overlapping

39
Q

Why is the genetic code described as universal?

A

Because in most living organisms, the same triplet of DNA bases codes for the same amino acid

40
Q

Why is the genetic code described as degenerate?

A

Because for most amino acids there is more than one base triplet

41
Q

How can the genetic code being degenerate reduce the effect of mutations?

A

A change in one base of the triplet could produce another base triplet that still codes for the same amino acid

42
Q

Why is the genetic code described as non-overlapping?

A

It is read starting from a fixed point in groups of three bases, separate from the triplet before it and after it - base triplets don’t share their bases

43
Q

Summarise the process of transcription of a gene into a length of mRNA

A

A gene unwinds and unzips

Hydrogen bonds between complementary nucleotide bases break

RNA polymerase catalyses the formation of temporary hydrogen bonds between RNA nucleotides and their complementary unpaired DNA bases

A length of RNA complementary to the template strand of the gene is produced

mRNA passes out of the nucleus, through the nuclear envelope, and attaches to a ribosome

44
Q

Where and how are ribosomes formed?

A

Formed in the nucleolus in two smaller subunits

They pass out of the nucleus separately through pores in the nuclear envelope

Come together to form a ribosome

Mg ions help bind the two subunits

45
Q

What is the structure of transfer RNA?

A

Single stranded polynucleotides that can twist into a hairpin shape

At one end they have a trio of nucleotide bases that recognise and attach to specific amino acids

At the loop of the hairpin there is an anticodon (another triplet of bases) that is complementary to a specific codon of bases on the mRNA

46
Q

Where are tRNA molecules made?

A

In the nucleolus

47
Q

What is translation?

A

The formation of a protein, at ribosomes, by assembling amino acids into a particular sequence according to the coded instructions carried from DNA to the ribosome by mRNA

48
Q

Describe the process of translation

A

tRNA molecules bring the amino acids and find their place when the anticodon binds by temporary hydrogen bonds to the complementary codon on the mRNA molecule

Ribosome moves along the length of mRNA, reading the code - peptide bonds form between adjacent amino acids

mRNA breaks down and can be recycled into new lengths of mRNA with different codon sequences

New polypeptide folds into its tertiary structure in order to carry out its function

49
Q

What is needed for polypeptide synthesis?

A

Energy in the form of ATP

50
Q

What is the amino acids sequence for the polypeptide ultimately determined by?

A

The sequence of triplets of nucleotide bases on the length of DNA - the gene

Biology (7 decks)

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