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Biology > Molecular Genetics (transcription And Translation) > Flashcards

Molecular Genetics (transcription And Translation) Flashcards

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1
Q

What is the features of genetic code?

A
  • genetic code is triplet cord. It is made up of 3 consecutive bases on DNA strand.
  • genetic code is degenerate ( ie.some code codes for same a.a. )
  • genetic code has no gaps and is read in non-overlapping manner.
  • genetic code is universal (ie. The same code codes for same aa in all organisms)
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2
Q

Notes!!

A
  • no gap between the triplet codes on a DNA strand and the triplet codes are trans in non-overlapping manner.
  • the same triplet code codes for the same amino acid in all organism, so the genetic code is universal
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3
Q

Why triplet code is universal

A

•the same triplet code codes for the same amino acid in all organism

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4
Q

What are the two stages of protein synthesis ?

A

•transcription:
~the genetic information carried in DNA is copied to mRNA inside the nucleus
•translation:
~a polynucleotide is made in the cytoplasm according to the genetic information carried in mRNA

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5
Q

What processes involved in the transcription?

A
  • Transcription take place in the nucleus
  • The 2 polynucleotide chains of the DNA helix unwind in the region with genetic code for amylase reproduction.
  • One of the chains of the unwound portion act as the template, which attract free ribonucleotides to it through complementary base-paring
  • The organic base thymine (T) is no present in ribonucleotides and is replaced by another organic base, uracil (U).
  • Adjacent ribonucleotides join up to form mRNA with the help of mRNA polymerase and use of energy.
  • The genetic code transcribed from DNA into mRNA is a triplet code which is formed by 3 bases and called codon.
  • Each codon specifies a particular amino acid.
  • The mRNA leaves the nucleus through the nuclear pore and attaches to ribosome at rough endoplasmic reticulum in the cytoplasm
  • Three consecutive bases (triplet code) in mRNA form a codon that specifies one amino acid.
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6
Q

What process involved in translation?

A
  • Translation takes place at rough endoplasmic reticulum in cytoplasm.
  • Free amino acids in t cytoplasm are activated by a specific amino acid activating enzyme with the use of ATP (amino acid activation) and joined to a specific tRNA.
  • Each tRNA has a specific anticodon consists of three nucleotide bases
  • The RNA, bringing the amino acid with it, binds temporarily with mRNA by its anticodon pairing with the codon bases of mRNA in a complementary manner.
  • When the amino acid of the newly arrived tRNA forms a peptide bond with the polypeptide chain and becomes attached with it.
  • The polypeptide chain frees itself from the preceding tRNA which also detaches from the mRNA-ribosome surface as a free structure.
  • The ribosome moves along the mRNA by one codon at a time so that the following amino acids can be added one by one through the same repeating process.
  • Thus the amino acids are added in sequence according to the sequence of codons of the mRNA
  • Therefore the type of polypeptide synthesized is controlled by mRNA with referring to the genetic information DNA
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7
Q

What happened to the polypeptide after translation?

A

After synthesis, coiling and folding of the polypeptide due to H-bond (as well as other intermolecular bonding) formed bond between different parts of the molecule change it into a protein with tertiary (3-dimensional) structure.

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8
Q

How does transcription compare with translation in the aspects listed below?

A

•occurs in:
~Nucleus vs rough endoplasmic reticulum
•mediated by:
~RNA polymerase vs ribosome
•template used:
~One of the DNA strands (the template strand) of a gene Bases vs mRNA
•type of complementary base pairing involved:
~based on DNA with bases on free ribonucleotides vs a codon on mRNA with an anticodon in tRNA
•raw materials :
~Ribonucleotides vs amino acid
•product:
~mRNA vs polypeptide
•fate of product:
~Transported to cytoplasm for translation vs used in cell

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9
Q

What is mutation ?

A

Mutation is a sudden and permanent change in the DNA of an organism

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10
Q

What is a gene mutation ?

A

Gene mutation is the change in base sequence of the DNA in a gene

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11
Q

Gene mutation can present in what way ?

A
  • deletion
  • insertion
  • inversion
  • substitution
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12
Q

What is the difference between deletion, insertion and substitution,inversion ?

A
  • Deleting or inserting a number of bases that is not a multiple of three will shift the reading frame (grouping of bases). Thus, the whole amino acid sequence after the point of mutation is altered. The resulting protein is usually non-functional.
  • A substitution or an inversion of base(s) usually leads to the change of one triplet code only. This may result in one different amino acid in the polypeptide. If that amino acid alters the conformation of the protein an obvious effect on the phenotype. surficienty, the mutation would have an obvious effet on the phenoype.
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13
Q

Name the disease caused by gene mutation

A

Sickle-cell anaemia

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14
Q

What is sickle-cell anaemia ?

A

It is caused by the substitution of a base in gene that codes for a polypeptide chain in haemoglobin

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15
Q

What is chromosome mutation?

A

It is changes in the structure or number of chromosome

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16
Q

Name the ways that cause chromosome mutation in terms of change in the structure of chromosome

A
  • deletion
  • duplication
  • inversion
  • translocation
17
Q

Name the example of chromosome mutation caused by the change in chromosome number

A

Down syndrome

18
Q

What is Down syndrome?

A
  • People with Down syndrome have an extra chromosome 21 in their body cells. In other words, there are 47 chromosomes instead of the normal 46 chromosomes in each of the body cells. Down syndrome is a disorder resulted from a chromosome mutation in which the total number of chromosomes is changed.
  • During gamete formation (i.e. meiotic cell division), homologous chromosomes or sister chromatids of chromosome 21 fail to separate. They go to the same daughter cell. Therefore, some of the gametes produced have an extra chromosome 21 while some have no chromosome 21
19
Q

What are spontaneous mutations and induced mutations?

A
  • Spontaneous mutations are mutations that occur naturally and randomly.
  • Induced mutations are mutations that are induced by mutagens.
20
Q

Give some examples of mutagens.

A
  • Chemicals: nitrous acid, tar, asbestos, mustard gas

* Radiations: ultraviolet light, X-rays, gamma rays

Biology (15 decks)

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