Download The Universal Genetic Code - Willimon-PHS

The Universal Genetic Code
Genetic code – the rules by which information in genetic material is
translated into proteins
• Universal – almost all living things use the same translation rules
(the same mRNA strand would be translated into the same protein in
different organisms)
• Rules can be summarized into a codon chart
Components of the genetic code
• DNA – stores the sequence of nucleotides
• RNA – carries the nucleotide sequence to the cytoplasm, aids in
translation
Biology 6B
Transcription & Translation
How is DNA used to create proteins?
1) Transcription – process by which DNA is used to produce mRNA
a) RNA polymerase – protein that initiates and operates transcription
b) mRNA – messenger RNA, carries information into cytoplasm
Use the steps below to determine an mRNA strand sequence.
2) Editing and processing – process of modifying mRNA in eukaryotes
a) introns removed
b) exons spliced together
c) cap and tail added
d) sent out of the nucleus
Biology 6C
Transcription & Translation
How is DNA used to create proteins (cont.)?
3) Translation – process by which information in mRNA strand is used to create
amino acid chain (polypeptide chain)
a) Ribosome – protein complex where translation occurs, made of rRNA
b) tRNA – transfer RNA, bring amino acids to the ribosome
Use the steps below to determine a polypeptide chain sequence.
4) Editing and folding
a) editing – sections of polypeptide chain removed
b) folding – chain folds to make 3D shape, critical for protein function
Biology 6C
Natural Selection,
Adaptation, & Diversity
Adaptation – trait that helps an organism survive and/or reproduce in its
unique environment
• Natural selection favors variations of traits that increase organism’s
ability to survive and reproduce
Natural selection can increase or decrease variation within a species
Directional selection – a single variation of a trait that was not previously
favored is now favored in a species, usually a result of migration or
environmental changes
• May increase or decrease diversity within a species
Diversifying selection – multiple variations of a trait are favored in a single
species
• Increases diversity within a species, might lead to separate species
Stabilizing selection – a single variation of a trait is favored in a species
• Decreases diversity within a species
Natural selection can increase or decrease variation among species
• If different traits are favored in different species, diversity increases
o Different food sources for birds, different beaks across species
• If similar traits are favored in different species, diversity decreases
o Same need to retain water in plants, same leaves across species
Biology 7E
DNA
Components of DNA
Deoxyribonucleic acid (DNA) is a double-stranded macromolecule, made of
building blocks called nucleotides
Each nucleotide contains a
• Phosphate base
• Deoxyribose sugar
• Nitrogenous base
Bonding in DNA
• The sides of one DNA molecule is connected with bonds between the
phosphate group and the deoxyribose sugar
• The two DNA strands connect by bonds between nitrogenous bases
o A always bonds with T
o G always bonds with C
Role of DNA
DNA is the genetic material of organisms.
• Information coded in the order of the bases used to create proteins
• Proteins act as enzymes, cell signals, and structural elements,
contributing to the traits seen in organisms.
• Different DNA can lead to different proteins
Biology 6A
Regulation of Gene Expression
Gene regulation occurs at all four levels of gene expression
Condensed DNA less likely to be
used, transcription factors promote or
suppress transcription
Modification (splicing) of initial
mRNA transcript into mature
transcript changes protein
Proteins limit export of mature
mRNA from nucleus to cytoplasm
mRNA structure and proteins affect
initiation, environmental factors
increase or decrease translation
Biology 6D
DNA Mutations
Mutation – a random change in the sequence of a gene, caused by mistakes
in DNA replication process and environmental agents.
Mutation
Point mutation
(Substitution)
Definition
One base replaced with another base
Example
ABCDEFG
ABZDEFG
Inversion
Order of two or more bases reversed
ABCDEFG
ABEDCFG
Insertion
Addition or one or more new bases
ABCDEFG
ABCHDEFG
Deletion
Removal or one or more bases
ABCDEFG
ABEFG
Translocation
Movement of one or more bases to a
new location in a different DNA
sequence
CD
ABCDEFG
ABEFG
ABCDEFG
ABCDCDEFG
Determine effect of mutation during translation
1. Determine amino acid chain made by original mRNA strand
2. Determine amino acid chain made by mutant mRNA strand
3. Compare the two chains
a. No changes = silent mutation
b. One amino acid changed = missense mutation
c. Amino acid chain ends sooner = nonsense mutation
d. Multiple amino acids changed = frameshift mutation
Mutation in traits can be organized by their effect
• Neutral mutations – no effect on survival (eye color)
• Harmful mutations – decrease survival (cancer)
• Beneficial mutations – increase survival (disease resistance)
Biology 6E
Biology 6F - Genetics and Punnett Squares
Vocabulary
character - a recognizable feature controlled by genetics (ex: fur color)
trait - a version of a character (ex: white fur)
allele - the section of DNA that codes for a specific trait
genotype - an organism’s genetic makeup for a character (ex: Ww)
phenotype - an organism’s appearance for a character (ex: white fur)
homozygous - having two of the same alleles for a character (ex: WW)
heterozygous - having two different alleles for a character (ex: Ww)
Types of dominance
• complete dominance - heterozygous individuals display dominant trait
• incomplete dominance - heterozygous individuals display an intermediate between traits
• codominance - heterzygous individuals display both traits at once
Punnett Squares
G
G GG
g
Gg
g Gg
gg
Organize outcomes from
genetic crosses
Each box represents an
equally likely outcome
gR
gr
GR
Gr
G GGRR GGRr GgRR GgRr
R
G GGRr GGrr
r
GgRr Ggrr
g GgRR GgRr ggRR ggRr
R
g GgRr Ggrr
r
ggRr
ggrr
You can use the five steps below
to solve any genetics problem
Biology 6F
Meiosis & Sexual Reproduction
Meiosis – type of cell division in which daughter cells receive only half the
number of chromosomes present in parent cell
• Produces gametes – specialized sex cells
Homologous chromosomes – chromosomes that control the same
hereditary traits, similar in size and shape
• Synapsis – pairing of homologous chromosomes)
o Crossing over – event during synapsis in which material is
exchanged, mixing genes.
• Independent assortment – homologous chromosomes have equal
chance of going to either gamete
Sexual reproduction – reproduction in which a new individual (zygote) is
produced by the union (fertilization) of the nuclei of two gametes
• Significance of meiosis
o Produces gametes needed
o Increases genetic variation through independent assortment
and crossing-over
Biology 6G
DNA Technology
Chromosomal analysis – procedure used to determine chromosomal
abnormalities
• Karyotype – photograph of arranged chromosomes from a cell
• Patient karyotype compared to normal karyotype to determine
presence of genetic diseases
DNA fingerprinting – technique that creates a pattern of DNA fragments
• Used to identify individual organisms or compare individuals
• Procedure
1. Samples taken from individuals
2. DNA separated from cells, cut by restriction enzymes
3. Cut DNA run through gel electrophoreses, separates by size
4. Samples compared
Genetic engineering – direct manipulation of genes
Cloning – process used to make multiple copies of a desired gene,
• Used for gene therapy, pharmaceutical drug production, increasing
agricultural productivity
• Procedure
1. DNA containing gene is isolated from organism
2. Gene copies are inserted into plasmids
3. Recombinant DNA is inserted into bacteria cells
4. Bacteria cells reproduce, each contain desired gene
Gene mapping – technique used to determine the location of a gene
• Used to identify the location of a gene and for genetic screening
• Procedure
1. Radioactive or fluorescent DNA probe created to match sequence
of desired gene
2. Organism’s DNA is unwound
3. DNA probe base-pairs with complementary sequence
Biology 6H