Unit 1 - Gene Expression Key Area 3 Flashcards Preview

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Flashcards in Unit 1 - Gene Expression Key Area 3 Deck (31)
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1
Q

What is meant by the term gene expression

A

Gene expression is the process where information in a gene is used to produce a functional gene product, usually a protein.
Gene expression involves the transcription and translation of DNA sequences.

2
Q

How is gene expression controlled

A

Gene expression is controlled by the regulation of Transcription and Translation

3
Q

Are all genes expressed within a cell

A

Only a fraction of genes in a cell are expressed

4
Q

What determines the sequence of amino acids

A

The order of bases on DNA determines the sequence of amino acids that are made

5
Q

What do amino acids join together to make

A

The sequence of amino acids joined together in polypeptide chain determines the structure, shape and function of the protein produced.

6
Q

What is RNA and what is it made up of

A

RNA is another type of nucleic acid
RNA nucleotides contain a ribose sugar, a phosphate and a base
RNA is single stranded

7
Q

State the complementary bases found in RNA

A

Adenine - Uracil

Cytosine - Guanine

8
Q

What is the role of mRNA

A

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

9
Q

What is the role of rRNA

A

ribosomal RNA - along with proteins forms a ribosome

10
Q

What is the role of tRNA

A

transfer RNA - carries a specific amino acid to the ribosome.

11
Q

What are the two processes involved in expressing a gene

A

There are two processes to express a gene:
- Transcription
coping the code from the original DNA
- Translation
converting the code into an amino acid sequence and therefore a protein

12
Q

Where does Transcription occur

A

Transcription occurs in the nucleus

13
Q

Describe the steps of transcription

A
  • copying the code
    Stages in Transcription
    1) RNA polymerase enzyme moves to the specific section of DNA and unwinds and unzips the DNA double helix by breaking hydrogen bonds between the bases
    2) RNA polymerase adds nucleotides by complementary base pairing forming a primary transcript of mRNA
14
Q

What is RNA splicing and why is it important

A

RNA splicing is a process that removes non coding regions from the primary transcript
It is important because NOT ALL nucleotides in a gene play a role in the coding for the amino acids sequence

15
Q

What is the difference between introns and exons

A

The primary transcript produced is made up of exons (coding) and introns (non-coding) regions

16
Q

What is removed from the primary transcript and what is formed as a result

A

The INTRONS must be REMOVED from the primary mRNA transcript.
This process forms the mature mRNA transcript.

17
Q

Where does the mature transcript travel to

A

The mature transcript travels to the cytoplasm. The order of exons remains unchanged.

18
Q

What is translation

A

Translation is the synthesis of a protein from the mature mRNA transcript produced in transcription

19
Q

What is a mRNA codon

A

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

20
Q

Describe the structure of tRNA

A
  • These amino acids are carried by tRNA
  • tRNA folds due to complementary base pairing
  • Each triplet of bases on a tRNA is called an anticodon
  • The codon and the anticodon pair together by complementary base pairing
  • A tRNA molecule has an anticodon (an exposed triplet of bases) at one end and an attachment site for a specific amino acid at the other end.
21
Q

Where does mRNA travel to in the cytoplasm

A

mRNA travels to a ribosome in the cytoplasm

22
Q

Describe the structure and function of a ribosome

A
  • Ribosomes are small spherical structures made up of ribosomal RNA and protein
  • A ribosome’s function is to bring tRNA into contact with mRNA
  • They have binding sites for both tRNA and mRNA
23
Q

Steps of Translation (1-4)

A

1) Translation begins with a start codon on the mRNA
2) The ribosome binds with the mRNA to ensure the start codon is in place
3) Each tRNA picks up specific amino acids in the cytoplasm and carries it to the ribosome
4) The anticodon of a tRNA carrying the correct amino acid binds to a complementary codon on the mRNA lining up the amino acids in a specific order.

24
Q

Steps of Translation (5-8)

A

5) Peptide bonds form between the amino acids to form a growing polypeptide chain
6) A stop codon is present at the end of the mRNA
7) When the chain is complete it detaches from the ribosome
8) When the tRNA detaches from its amino acid, it then collects another

25
Q

Explain how different proteins can be expressed from one gene

A
  • During RNA splicing, depending on circumstances, alternative segments of RNA may be treated as exons and introns
  • The same primary transcript can produce several different mature transcripts depending on where it is spliced
  • This is called alternative RNA splicing
  • This means that different proteins can be expressed from one gene
26
Q

Explain how the three dimensional shapes of proteins form

A
  • Amino acids are linked by peptide bonds to form polypeptides.
  • Polypeptide chains fold to form the three-dimensional shape of a protein,
  • held together by hydrogen bonds and other interactions between individual amino acids.
  • Proteins have a large variety of shapes which determines their functions.
27
Q

What is meant by phenotype and what can influence them

A

Phenotype is the visible characteristics of an organism which occur as a result of its genes and the proteins expressed.
Environmental factors can influence phenotype e.g. availability of nutrients

28
Q

What RNA’s are involved in Transcription and Translation

A

Transcription and translation involves three

types of RNA (mRNA, tRNA and rRNA).

29
Q

a) What is mRNA transcribed from

b) What is mRNA translated to

A

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

30
Q

What does RNA Splicing form?

A

RNA splicing forms a mature mRNA

transcript.

31
Q

What is formed when exons are joined together?

A

The exons are coding regions and are joined

together to form the mature transcript.