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Higher Human Biology Unit 1 > Unit 1.3 Gene expression > Flashcards

Unit 1.3 Gene expression Flashcards

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1
Q

What is RNA

A

A single stranded molecule, compromised of nucleotides

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2
Q

What do the nucleotides in RNA contain

A

ribose sugar, phosphate & base (cytosine, guanine, adenine & uracil)

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3
Q

What does gene expression involve

A

The transcription & translation of DNA sequences

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4
Q

How much of the genes in a cell are expressed

A

Only a fraction

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5
Q

The differences between DNA & RNA

A

DNA- 2 strands
RNA- 1 strand

DNA- adenine pairs with thymine
RNA- adenine pairs with uracil

DNA- nucleotide contains deoxyribose sugar
RNA- nucleotide contains ribose sugar

DNA- found in the nucleus
RNA- found in the nucleus & cytoplasm

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6
Q

3 types of RNA

A

messenger RNA
transfer RNA
ribosomal RNA

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7
Q

Function of mRNA

A

copies a section of the DNA code & carries it to the ribosome in the cytoplasm

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8
Q

Function of tRNA

A

carries specific amino acids into position at the ribosome

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9
Q

Function of rRNA

A

along with proteins make up the ribosome which is involved in protein synthesis

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10
Q

What is a triplet of bases on a mRNA molecule called

A

a codon

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11
Q

What does one codon code for

A

a specific amino acid

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12
Q

What causes tRNA to fold

A

Complementary base pairing

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13
Q

What type of codon do tRNA molecules contain

A

Anti-codon (an exposed triplet of bases)

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14
Q

What site is at the other end of a tRNA molecule, to help carry the specific amino acids to the ribosome

A

The attachment site

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15
Q

What does DNA carry the code for

A

Making proteins

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16
Q

What are the 3 stages of protein synthesis called

A

Transcription (of gene), RNA splicing, Translation

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17
Q

What happens in the transcription stage

A

The section of the DNA code required (gene) is copied into mRNA. This is known as the primary transcript.

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18
Q

What happens in the RNA splicing stage

A

The non-coding information (introns) in the primary transcript must be removed by splicing. The coding regions (exons) are joined together after the introns are removed, creating a mature mRNA strand.

19
Q

What happens in the translation stage

A

The spliced mature mRNA strand is used to assemble amino acids in the correct order to make the protein

20
Q

Where does transcription occur

A

The nucleus

21
Q

Where does RNA splicing occur

A

The nucleus

22
Q

Where does translation occur

A

The ribosome (in the cytoplasm)

23
Q

Explain the steps in the process of transcription

A

1- RNA polymerase moves along the DNA, unwinding the double helix.
2- weak hydrogen bonds between bases break, so DNA strands separate
3- RNA polymerase adds free moving RNA nucleotides to the growing mRNA strand, by complementary base pairing
4- weak hydrogen bonds form between the new base pairs (of the DNA template & mRNA strand)
5- strong chemical bonds form between the new RNA nucleotides (opposite the DNA), allowing a new strand to be formed
6- weak hydrogen bonds break between DNA & RNA, allowing mRNA to break from the DNA template
7- a primary mRNA transcript is formed & ready to undergo splicing
8- weak hydrogen bonds reunite the 2 original DNA strands into a double helix again

24
Q

What are long sections of DNA that do not code for a polypeptide called

A

Introns

25
Q

Where are introns found

A

In between sections of DNA that do code for the proteins (polypeptides)

26
Q

What are the coding regions on DNA called

A

Exons

27
Q

What makes up the mature mRNA

A

Only exons (order is unchanged)

28
Q

What happens once the mature mRNA is created

A

It leaves the nucleus & enters the cytoplasm for the next stage

29
Q

What enzyme directs transcription

A

RNA polymerase

30
Q

What is translation

A

The process which translates the code found on mRNA into a polypeptide

31
Q

What molecule is involved in the translation of mRNA

A

tRNA

32
Q

Describe the steps in process of translation

A

1- translation is initiated by the start codon (AUG) on the mRNA strand
2- tRNA molecules become attached to their specific amino acid molecules
3- these tRNA molecules then accumulate at the ribosome
4- the first tRNA molecule moves in & its anticodon forms a complementary base pair with the codon on the mRNA
5- another tRNA molecule carries an amino acid to the ribosome. more complementary base pairings occur, bringing the amino acids inline with each other. A peptide bond forms between the amino acids
6- the first tRNA molecule detaches from the mRNA & is free to collect another amino acid from the cytoplasm
7- this process is repeated all along the mRNA transcript until a stop codon is reached at the 3’ end & the newly formed polypeptide chain is complete

33
Q

What is always the start codon

A

AUG

34
Q

Function of a ribosome

A

Site of protein synthesis

35
Q

What type of bond forms between amino acids & what does this create

A

Peptide bonds & a polypeptide

36
Q

How can different proteins be expressed from one gene

A

As a result from alternative RNA splicing

37
Q

How does alternative RNA splicing work

A

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

38
Q

What do polypeptide chains fold to form & what holds this together

A

A 3D shape of a protein, held together by hydrogen bonds & other interactions between amino acids

39
Q

What is a phenotype

A

The physical appearance of an organism

40
Q

What can determine the phenotype

A

The proteins produced from gene expression or environmental factors

41
Q

What is a cells function determined by

A

The sequence of the DNA bases in its genes

42
Q

What is a cells structure determined by

A

The proteins that are synthesised when the genes are expressed

43
Q

What is gene expression influenced by

A

Environmental factors, inside & outside of the cell

Higher Human Biology Unit 1 (8 decks)

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