Transcript BIO 103 - Genes

Genes and How They Work
Chapter 15
The Nature of Genes
information flows in one direction:
DNA (gene)
Transcription
RNA
Translation
protein
2
3
GENE
The Genetic Code
codon: set of 3 nucleotides(mRNA) that
specifies a particular amino acid (64
possible codons)
stop codons: (UUA, UGA, UAG) used to
terminate translation
start codon: (AUG) used to start translation
5
6
Gene Expression Overview
template strand: used to make RNA
coding strand: complementary to the
template strand
RNA polymerase: puts nucleotides together
to make RNA strand
7
Gene Expression Overview
types of RNA:
messenger RNA (mRNA) carries the info
from DNA that encodes proteins
ribosomal RNA (rRNA) part of ribosome
transfer RNA (tRNA) carries amino acids to
the ribosome
8
Transcription
Transcription proceeds through:
1. initiation
2. elongation – RNA nucleotides are
added to the 3’ end of the new RNA
3. termination
9
10
Eukaryotic pre-mRNA Splicing
• introns – non-coding sequences
• exons – sequences that will be translated
11
tRNA and Ribosomes
tRNA
– amino acids carried by the acceptor arm
– the anticodon loop 3 nucleotides
complementary to mRNA codons
12
13
tRNA and Ribosomes
The ribosome has two primary functions:
– decode the mRNA
– form peptide bonds
14
Translation
1. initiation
2. elongation – tRNAs bring amino acids
to the ribosome
3. Termination – stop codon
15
16
17
Firefly website
18
Mutation: Altered Genes
Point mutations alter a single base.
Chromosomal mutations change part of a
chromosome (deleted/repeated/moved)
19
20
21
22
23
24
Mutation: Altered Genes
Too much genetic change (mutation) can be
harmful to the individual.
However, genetic variation (caused by
mutation) is necessary for evolutionary
change of the species.
25