Download Chapter 4 Section 4 – The DNA Connection

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.