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Biology Unit 1 > 1.3 - Gene Expression > Flashcards

1.3 - Gene Expression Flashcards

1
Q

What 6 elements to Proteins contain?

A

Hydrogen, oxygen, nitrogen, carbon and often contain sulphur and phosphorus.

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2
Q

What are proteins made up of?

A

sub-units called amino acids.

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3
Q

How many essential amino acids are there?

A

There are 20 essential amino acids.

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4
Q

How are proteins held in a 3-Dimensional shape?

A

Peptide bonds, hydrogen bonds and other interactions between individual amino acids.

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5
Q

What are chains of amino acids called?

A

Polypeptide chains.

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6
Q

What determines the proteins structure and function?

A

The sequence of amino acids.

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7
Q

What two 3D shapes can proteins be?

A

Globular (round) or Fibrous (flattened)

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8
Q

Give an example of a Globular protein.

A

Antibody

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9
Q

Give an example of a Fibrous protein.

A

Keratin

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10
Q

What is a gene?

A

A section of DNA which carries the code for the production of proteins.

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11
Q

Define Genotype.

A

The types of gene an organism possesses - determined by the sequence of DNA bases.

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12
Q

Define Phenotype.

A

Physical characteristics of an organism - determined by proteins synthesised as a result of gene expression.

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13
Q

What is gene expression influenced by?

A

intra- and extra-cellular environmental factors.

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14
Q

How many genes in a cell are expressed?

A

only a fraction.

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15
Q

What is gene expression controlled by?

A

The regulation of transcription and translation.

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16
Q

What is the second type of nucleic acid in the cell?

A

RNA. (ribose nucleic acid)

17
Q

What does RNA do?

A

plays a vital role in the production of protein from the code in DNA.

18
Q

What does an RNA nucleotide looklike?

A

A phosphate connects onto a ribose sugar and that connects onto a base.

19
Q

Give 3 comparisons between DNA and RNA.

A

DNA is double stranded, has a deoxyribose sugar and its complementary base pairs are (adenine + thymine, Guanine + Cytosine) Whereas RNA is single stranded, has a ribose sugar and its complementary base pairs are (Adenine + Uracil, Guanine and Cytosine.)

20
Q

What is mRNA?

A

Messenger RNA, formed in nucleus from free nucleotides, carries copy of DNA code from nucleus to ribosome. - where protein synthesis occurs.

21
Q

What is mRNA made up of?

A

Sequences of 3 nucleotides (triplet of bases) called codons.

22
Q

What is tRNA?

A

Transfer RNA, collects specific amino acids and brings them to ribosome to build proteins.

23
Q

What is the structure of tRNA?

A

Made of a single chain of nucleoides, folded into a 3D structure held by hydrogen bonds.

24
Q

What is rRNA?

A

Ribosomal RNA, combines with proteins to create the ribosome.

25
Q

What is transcription?

A

Transcription is the synthesis of mRNA from a section of DNA.

26
Q

Explain process of transcription

A
  • transcription of a gene starts from a region of DNA known as the promoter
  • RNA polymerase is responsible for transcription, binds promoter, unwinds DNA, adds nucleotides onto end of growing molecule of mRNA
  • the mRNA will be complementary to the DNA
  • the molecule elongates until it reaches the terminator sequence
  • the molecule produced is called the primary transcript
27
Q

What is translation?

A

The synthesis of protein following the code within the mature mRNA transcript

28
Q

What is the process of translation

A
  1. Ribosome binds to 5’ end of the mRNA so that start codon is in site P
  2. Next a tRNA carrying its amino acid becomes attached to site p as the mRNA start codon bonds with its complementary tRNA anti codon
  3. Another tRNA becomes attached at site A, the mRNA codon bonds to its complementary tRNA anticodon carrying a specific amino acid
  4. A peptide bond then forms between the two amino acids at site P and A
  5. The tRNA from site p is moved to site E and released
  6. The ribosome then moves along the codon
  7. The translation process is repeated until it reaches a stop codon
29
Q

How can the same gene be used to make several different proteins?

A

Alternative RNA splicing

Post translational modification

30
Q

What is alternative RNA splicing

A

Under certain conditions alternative segments of RNA maybe treated as introns and exons, meaning one gene can produce several different mature mRNA transcripts, therefore several different proteins

31
Q

What is post translational modification

A

Once translation is completed proteins can be modified by

Cleavage, a single polypeptide chain can be cleaved by enzymes to make it active

Addition of other molecules, carbs and phosphate groups can be added to proteins

32
Q

Process of RNA splicing

A

After mRNA has been transcribed, introns are removed
Remaining exons are spliced together to form a continuous sequence. This is the mature transcript, it leaves nucleus and goes to cytoplasm

33
Q

What does each codon code for?

A

Each codon codes for 1 amino acid

Biology Unit 1 (8 decks)

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