Problem of the Day!!! 3/4 A DNA molecule is made up of 4 nitrogen bases, what are they?

Chapter 4 Section 4 – The DNA Connection

The order of the nitrogen bases along a gene forms a genetic code that specifies what type of protein will be produced. The production of proteins is called

protein synthesis

.

During

protein synthesis

, the cell uses information from a gene on a chromosome to produce a specific protein. Protein synthesis takes place on the ribosome in the cytoplasm of the cell. That lead us to the question – how does the information to produce protein get from the nucleus to the cytoplasm?

The role of RNA RNA – Ribonucleic Acid is the genetic messenger of the cell.

Characteristics of RNA

• RNA is single stranded. DNA is double stranded. • The sugar molecule found in RNA is different from DNA. Ribose verse Deoxyribose. • The nitrogen bases of RNA contain Adenine, Guanine, Cytosine, and Uracil. • RNA comes in several forms. Messenger RNA (mRNA), transfer RNA (tRNA), Ribosomal RNA (rRNA).

Types of RNA produced during transcription ribosomal RNA (rRNA)

•

The rRNA is a component of ribosomes. It catalyzes protein synthesis.

messenger RNA (mRNA)

•Function: Read by ribosomes during translation; the mRNA provides the instructions for building a protein.

•

transfer RNA (tRNA)

• Function: Deciphers the mRNA sequence (in triplets = codon) and brings the correct amino acid (protein building block) to the ribosome for addition to the new protein chain.

How do cells make RNA? Transcription

•DNA is used as a template for the creation of RNA using the enzyme RNA polymerase. •RNA polymerase reads the nucleotides on the DNA template strand and synthesizes a complementary RNA sequence. •The sequence of the resulting RNA will be similar to the DNA coding strand. Uracil will take the place of thymine.

Protein Synthesis

Mutations

• A mutation is a change in the nucleotide sequence of a gene. This mutant allele/phenotype is a change or variation from the most common or wildtype allele/phenotype.

• Mutations may not be good nor bad, just different from the majority in the population.

• Mutations in different parts of a gene may cause the same disorder OR may cause distinct phenotypes/disorders.

• Most are minor.

• Many are harmful.

• Some are lethal.

• Very few are helpful. • •

Types of mutations: Germ mutation

- occur in gametes.

Somatic mutation

- occur in body cells.