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Z. 0Higher Human Biology > 1.3 - Gene Expression > Flashcards

1.3 - Gene Expression Flashcards

1
Q

Are all genes in a cell expressed?

A

No

Only a fractions of the genes in a cell are expressed.

(Expressed - used to make proteins)

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2
Q

What does gene expression involve?

A

Gene expression involves the transcription and translation of DNA sequences.

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3
Q

What do the processes of transcription and translation involve?

A

Transcription and translation involves ribonucleic acid (RNA).

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4
Q

What is vital to protein synthesis

A

RNA is vital to protein synthesis

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5
Q

Describe RNA and what it is composed of

A

RNA is single stranded.

RNA is composed of nucleotides containing:

  • a ribose sugar
  • phosphate group
  • one of the 4 bases (C,G,A or uracil)
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6
Q

RNA complementary base pairing

A

Cytosine - guanine

Adenine - URACIL

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7
Q

3 types of RNA

A

The 3 types of RNA involved in transcription and translation are: mRNA, tRNA and rRNA.

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8
Q

Messenger RNA (mRNA) function

A

Messenger RNA (mRNA) carries a copy of the DNA code from the nucleus to the ribosome.

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9
Q

mRNA transcription

A

mRNA is transcribed from DNA in the nucleus and translated into proteins by ribosomes in the cytoplasm.

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10
Q

mRNA - triplet of bases

A

Each triplet of bases on the mRNA molecule is called a codon and codes for a specific amino acid.

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11
Q

Ribosomal RNA (rRNA)

A

Ribosomal RNA (rRNA) and proteins form the ribosome.

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12
Q

What is the site of protein synthesis

A

Ribosome

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13
Q

Why does tRNA have a folded shape?

A

tRNA folds due to complementary base pairing.

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14
Q

What are the bases of tRNA held together by?

A

The bases of tRNA are held together by WEAK HYDROGEN BONDS.

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15
Q

What is an anticodon?

A

An anticondon is an exposed triplet of bases.

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16
Q

What do tRNA molecules have?

A

tRNA has an anticodon at one end of the tRNA molecule and an attachment site for a specific amino acid at the other end of the tRNA molecule.

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17
Q

tRNA function

A

tRNA carries a specific amino acid to the ribosome.

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18
Q

Protein synthesis process

A

Protein synthesis is the process by which instructions from DNA sequences are carried to ribosomes and proteins are made.

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19
Q

What stage is transcription and where does it take place

A

Transcription is the first stage of protein synthesis and takes place in the nucleus.

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20
Q

What is the process of transcription?

A

Transcription is the process by which mRNA is transcribed from DNA.

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21
Q

What is the complementary base pair to adenine in RNA?

A

Uracil is the complementary base pair to adenine.

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22
Q

Steps of transcription - 1

A

The enzyme RNA polymerase moves along DNA, unwinding the double helix and breaking the hydrogen bonds between the bases thereby unzipping the double helix.

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23
Q

Steps of transcription- 2

A

As RNA polymerase breaks the bonds, it synthesises a primary transcript of mRNA on the DNA template strand using free RNA nucleotides. These RNA nucleotides form hydrogen bonds with the exposed DNA bases by complementary base pairing.

Uracil is the complementary base pair to adenine.

24
Q

Steps of transcription- 3

A

A primary mRNA transcript is formed.

25
Q

What is a triplet of bases on the mRNA molecule called and what do they code for?

A

Each triplet of bases on the mRNA molecule is called a codon which codes for an amino acid.

26
Q

What codes for an amino acid?

A

A codon codes for a specific amino acid.

27
Q

What is the primary transcript made of?

A

The primary transcript (of DNA) is made of introns and exons.

28
Q

What are introns?

A

Introns are non coding regions of the primary transcript of mRNA

29
Q

What are exons?

A

Exons are coding regions (of the primary transcript)

30
Q

What are removed during splicing?

A

During splicing, the introns are removed from the primary transcript.

31
Q

What are joined together during splicing?

A

The exons are joined together to form the mature transcript.

32
Q

What is the process called when introns are removed from the primary transcript and exons are joined together to form the mature transcript?

A

RNA splicing

33
Q

What happens to the order of exons during RNA splicing?

A

The order of the exons is unchanged during splicing.

34
Q

How does the mature transcript leave the nucleus?

A

The mature transcript leaves the nucleus through a nuclear pore in the nucleus membrane.

35
Q

What happens to the mature transcript after it leaves the nucleus?

A

The mature transcript travels through the cytoplasm to a ribosome for the next stage of protein synthesis.

36
Q

What process forms a mature mRNA transcript?

A

RNA splicing forms a mature mRNA transcript.

37
Q

What is the function of RNA polymerase in the transcription of DNA into primary mRNA transcripts?

(STEPS OF TRANSCRIPTION)

A

RNA polymerase moves along DNA unwinding the double helix and breaking the hydrogen bonds between bases. RNA polymerase synthesises a primary transcript of mRNA from RNA nucleotides by complementary base pairing.

The mRNA produced is known as the primary transcript.

38
Q

What end can RNA polymerase add nucleotides onto?

A

RNA polymerase can only add nucleotides onto the 3’ end.

39
Q

What is the mRNA produced from transcription known as?

A

The mRNA produced is known as the primary transcript.

40
Q

What RNA is involved is the translation of mRNA into a polypeptide at a ribosome?

A

tRNA is involved in the translation of mRNA into a polypeptide at a ribosome.

41
Q

What is the process of translation?

A

Translation is the second stage of protein synthesis.

Translation is the synthesis of a polypeptide chain under the direction of mRNA at the ribosome.

42
Q

What do anticodons bond to on the mRNA molecule? What does this do?

A

tRNA anticodons bond to codons on the mRNA molecule by complementary base pairing. This translates the genetic code into a sequence of amino acids.

43
Q

Where does translation begin and end?

A

Translation begins at a start codon and ends at a stop codon.

44
Q

What joins amino acids together?

A

Peptide bonds join amino acids together.

45
Q

What happens to the tRNA at the end of translation?

A

Each tRNA leaves the ribosome (after being joined together by peptide bonds) as the polypeptide is formed.

46
Q

Can different proteins be expressed from one gene? Why?

A

Different proteins can be expressed form one gene as a result of alternative RNA splicing.

47
Q

Depending on which exons are retained, what happens with the production of mature mRNA transcripts?

A

Different mature mRNA transcripts are produced from the same primary transcript depending on which exons are retained.

48
Q

Differences in proteins translated from alternatively spliced mRNA’s

A

Proteins translated from alternatively spliced mRNA’s will contain differences in their amino acid sequence and, often, in their biological functions.

49
Q

What are amino acids joined by and what does this form?

A

Amono acids are joined by peptide bonds to form polypeptides.

50
Q

Polypeptide folding

A

Polypeptide chains fold (due to complementary base pairing) to form the 3D shapes of proteins.

Its (shape) is held together by hydrogen bonds and other interactions between individual amino acids.

51
Q

What does a proteins shape determine?

A

Proteins have a large variety of shapes which determines their function.

52
Q

What is the phenotype determined by?

A

The phenotype is determined by the proteins produced as a result of gene expression.

53
Q

Protein functions

A

Proteins have a large variety of shapes which determines their function.

H - hormones 
A - antibodies (protection)
R - receptors 
E - enzymes 
S - structural
54
Q

What is a phenotype?

A

An organisms phenotype is the outward appearance of their genetic information.

55
Q

What can also influence phenotype?

A

Environmental factors can also influence phenotype.

Z. 0Higher Human Biology (19 decks)

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