Study Guide for Gene Expression and Protein Synthesis

Nucleotide makeup -

• sugar

• phosphate group

• nitrogen base

Complementary bases -

A-T

C-G

or

A-U in RNA

C-G

Structure of DNA -

Double stranded

Structure of RNA -

Single stranded, contains ribose sugar, and has uracil instead of thymine

Transcription -

• synthesis of RNA using a DNA template

Where does transcription take place?

• nucleus of eukaryotic cells

• cytoplasm of prokaryotic cells

Types of RNA involved in transcription -

mRNA, tRNA, rRNA

How is mRNA involved in transcription?

• mRNA synthesizes in transcription by base pairing with the DNA template

• carries genetic information to the ribosomes for protein synthesis

How is tRNA involved in transcription?

• tRNA delivers amino acids to the ribosome during translation, making protein synthesis easier

How is rRNA involved in transcription?

• rRNA helps form the core of the ribosome's structue

• catalyzes peptide bond formation during translation

mRNA

• carries the genetic
  code from the
  DNA to the
  ribosomes

rRNA

• makes the components of the ribosome which is necessary for protein synthesis

tRNA

• “Taxi” attaches to the
  proper amino acid
  and carries it to
  the ribosome

Translation -

• synthesis of polypeptides using genetic information from mRNA

Where does translation take place?

In the Ribosome- cytoplasm

Types of RNA involved in translation

mRNA, tRNA, and rRNA

How is mRNA involved in translation?

• mRNA carries the genetic code from DNA to the ribosome where the code is read to make proteins

How is tRNA involved in translation?

• tRNA moves amino acids to the ribosome matching them to the corresponding codons on the mRNA

How is rRNA involved in translation?

• rRNA forms the core of the ribosome's structure

Eukaryotes -

• has introns & exons

• Can’t have transcription and translation occur simultaneously

Prokaryotes -

• No introns & exons

• Can have transcription and translation occur simultaneously

introns -

• non-coding segments of a gene

Exons -

• coding segments of a gene that are shown in the final mRNA

Every three nitrogen bases codes for an amino acid or punctuation

is known as a codon

A codon is part of what molecule?

mRNA molecule

What is an anticodon?

A sequence of three nucleotides in tRNA that pairs with a complementary codon in mRNA

What is mutation in general?

• change that occurs in the nucleotide sequence of DNA

 List some factors that can cause mutations

• high temperatures

• chemicals

• radiation

• ultraviolet light

What is a point mutation?

A change in a single nucleotide in the DNA sequence, which may change the resulting protein

Silent mutation -

• does not change the protein,
  because they are mutations where the
  same amino acid is coded for

Missense mutation -

• one wrong base
  substitute results in the coding of a wrong
  amino acid in a polypeptide chain

Nonsense mutation -

• point mutation that results in the coding of a stop codon

Frameshift mutation -

• happens when nucleotides are inserted or deleted, altering the reading of the genetic code

Example of silent mutation ?

• when a DNA codon changes from TTC to TTT

Example of missense mutation ?

• sickle-cell anemia

Example of nonsense mutation ?

• Duchenne muscular dystrophy

Example of frameshift mutation? 

• benzopyrene

• Alfa toxin