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Biology > 4.1 DNA, RNA and protein synthesis > Flashcards

4.1 DNA, RNA and protein synthesis Flashcards

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1
Q

what is a gene?

A

a section of DNA on a chromosome that codes for one or more polypeptides

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2
Q

what is a locus?

A

the position of a gene on a chromosome

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3
Q

what is an allele?

A

different versions of the same gene

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4
Q

what is a genome?

A

all the genetic material inside a cel

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5
Q

what is an intron?

A

a section of DNA within a gene that doesn’t code for anything

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6
Q

what is an exon?

A

a section of DNA within a gene that codes for amino acids

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7
Q

what are homologous chromosomes?

A

a pair of chromosomes (one maternal, one paternal) that contain the same genes but potentially different alleles.

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8
Q

what is a triplet?

A

a series of three bases that code for an amino acid in a protein

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9
Q

what is a proteome?

A

the full range of proteins that a cell or organism can produce

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10
Q

what does it mean for the genetic code to be non-overlapping?

A

each base is only read once

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11
Q

what does it mean for the genetic code to be degenerate?

A

more than one triplet can code for the same amino acid

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12
Q

what does it mean for the genetic code to be universal?

A

each triplet codes for the same amino acid in all organisms

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13
Q

what organic bases are present in DNA?

A

adenine, thymine, guanine, cytosine

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14
Q

describe the structure of prokaryotic DNA [3]

A

short, circular, not associated with proteins

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15
Q

describe the structure of eukaryotic DNA [3]

A

long, linear, associated with histone proteins to form chromosomes

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16
Q

describe the structure of mitochondrial and chloroplast DNA [3]

A

short, circular, not associated with proteins

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17
Q

how is eukaryotic DNA compact?

A

DNA is wound around histone proteins then coiled up tightly to make a chromosome

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18
Q

how is prokaryotic DNA compact?

A

circular DNA is supercoiled

19
Q

what is a codon?

A

a triplet/three adjacent nucleotides in DNA or mRNA that codes for an amino acid

20
Q

what is functional RNA?

A

RNA molecules other than mRNA that perform special tasks during protein synthesis

21
Q

when are chromosomes visible?

A

when a cell is dividing

22
Q

where does transcription take place in eukaryotic cells?

A

the nucleus

23
Q

where does transcription take place in prokaryotic cells?

A

the cytoplasm

24
Q

what does RNA stand for?

A

Ribonucleic acid

25
Q

describe the structure of RNA [3]

A
  • polymer made up of mononucleotide sub-units
  • nucleotides are made up of a ribose sugar, phosphate group and organic base
  • single strand
26
Q

what organic bases are present in RNA?

A

adenine, uracil, guanine, cytosine

27
Q

what are the two types of RNA used in protein synthesis?

A

mRNA (messenger RNA)
tRNA (transfer RNA)

28
Q

describe the structure of mRNA

A

a single-stranded polynucleotide chain arranged in a single helix that carries information in the form of codons

29
Q

when is mRNA made?

A

during transcription

30
Q

what is the function of mRNA?

A

to carry the genetic code from DNA in the nucleus to ribosomes in the cytoplasm, where it is used as a template for protein synthesis during translation

31
Q

how is the structure of mRNA suited to its function?

A

it carries information in the form of codons, which determine the amino acid sequence of a specific polypeptide

32
Q

describe the structure of tRNA

A
  • single-stranded polynucleotide chain folded into a clover shape
  • one end of chain extends further than the other, making amino acid binding site
  • anticodon loop is on opposite end, which has a sequence of three organic bases (the anticodon) specific to an amino acid
33
Q

what is the function of tRNA?

A

pairing the tRNA anticodon with the three organic bases on a complimentary mRNA codon

34
Q

how is the structure of tRNA suited to its function?

A

it has an amino acid binding site and anticodon made of three organic bases, allowing it to line up amino acids on the mRNA template during protein synthesis

35
Q

what is transcription? [1]

A

the first stage of protein synthesis, in which an mRNA copy of a gene is made from DNA

36
Q

what is the first stage of protein synthesis?

A

transcription

37
Q

describe the process of transcription [5-6]

A
  • RNA polymerase enzyme attaches to DNA double helix at the start of a gene
  • RNA polymerase breaks hydrogen bonds between DNA strands, causing them to separate and expose nucleotide bases
  • one strand is used as a template strand, to which free nucleotides pair with complimentary bases
  • RNA polymerase moves along strand, joining nucleotides together to form pre-mRNA molecule
  • once RNA polymerase has passed, DNA coils back to double helix
  • when RNA polymerase reaches stop codon, it detaches and process is complete
38
Q

what is splicing?

A

the removal of introns and joining of exons in pre-mRNA to produce mRNA

39
Q

where does splicing occur?

A

the nucleus

40
Q

does splicing take place in prokaryotic cells?

A

no, as there are no introns in prokaryotic DNA

41
Q

what is the second stage of protein synthesis?

A

translation

42
Q

where does translation take place?

A

cytoplasm

43
Q

what is translation?

A

the second stage of protein synthesis, in which amino acids join to form a polypeptide chain by following codons carried by mRNA

44
Q

describe the process of translation [5-6]

A
  • ribosome attaches to start codon on mRNA
  • tRNA carries amino acids to it
  • anticodon on tRNA attaches to first codon on mRNA strand by complimentary base pairing
  • second tRNA attaches to next codon in same way
  • peptide bond forms between adjacent amino acids
  • first tRNA moves away, leaving the amino acid behind
  • third tRNA binds to next codon on mRNA strand and its amino acid binds to the others
  • second tRNA moves away
  • process repeats until stop codon is reached, at which point chain of amino acids (polypeptide) moves away from the ribosome, and translation is complete

Biology (11 decks)

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