Title: Gene Expression How do genotypes become phenotypes?
1Gene ExpressionHow do genotypes become
phenotypes?
23 from dad
23 from mom
2- Chromosome
- Structure found in the nucleus of all cells
- Made of DNA coiled around histone proteins,
compacted - DNA
- Double helix shape
- Stores genetic gene information
- Self-replicates to produce 2 exact copies of
itself - Gene
- A segment of DNA that serves as a code for a
specific phenotype
Gene for Type A Blood
3Genotype
Phenotype
inherit
Propose how this occurs. What other factors might
be included within the blue arrow? How do you
go from alleles (A, a) to an actual phenotype
that is noticeable?
4DeoxyriboNucleic Acid
- Antiparallel strands (gene is 5? 3)
- Monomers nucleotides
- Adenine, Thymine, Cytosine, Guanine
- 1 nucleotide 3 parts
- Deoxyribose sugar
- Phosphate
- Base
- Uses complimentary base pairing rules A ?? T
and C ?? G
5 CGTGGTTAAATCT 3
5The Central Dogma of Biology
6The Central Dogma
Replication
Translation
Transcription
7DNA Replication
- DNA is copied accurately to preserve an
organisms genotype - Occurs before cell division so each chromosome
has 2 copies to give - meiosis (cell division for gametes)
- mitosis (cell division for growth)
- Takes place in the nucleus
- Enzymes used in process
- Helicase - Unwinds double helix
- DNA Polymerase - Creates new strand
8DNA Replication
New DNA strands are formed based off original DNA
sequence
9DNA Replication
Gene 5 ? 3
GAGTCCTGTCATAAAATG 3
- 5 CGTGGTTAAATCT
- 3 GCACCAATTTAGA
Template Strand 3 ? 5
CTCAGGACAGTATTTTAC 5
Lets model DNA Replication!
10Whats next?
- After DNA Replication, there is enough DNA make 2
new cells and then again, and again until the
organism stops performing cell division (i.e.,
never, really). Once a new cell is made, it can
begin to use the DNA to create phenotypes.We
call this next part Gene Expression, or the
production of a phenotype given information from
the genotype (gene segments of DNA) and it
can be divided into 2 steps Transcription and
Translation.
11Transcription
- Produces a RiboNucleic Acid (single) strand using
a DNA template - DNA is read from 3 ? 5 (template strand)
- Transcription enzyme RNA Polymerase
- Takes place in the nucleus
- In gene expression, mRNA is made
- Base pair rules
C ? G G ? C T ? A A ? U
12Lets Transcribe!
- Gene 5 TCATGCAGAGGAGATTAA 3
- Template 3 AGTACGTCTCCTCTAATT 5
- mRNA 5 3
- Gene 5 GATCAGGGAGACTTAGCA 3
- Template 3 CTAGTCCCTCTGAATCGT 5
- mRNA 5 3
13Translation
- Produces an amino acid sequence using mRNA as a
template - mRNA is read from 5 ? 3 in triplets
(codons) - Codons code for amino acids
- Start codon is AUG but stop codon varies
- Enzyme that does this is called tRNA
- Takes place in cytoplasm at a ribosome
- After folding of polypeptide, a protein is formed!
14The Genetic Code
Examples AUG is Met (start) ACC is Thr AGA is
Arg! UAA is Stop UAG is Stop UGA is Stop
15- Use the Genetic Code to figure out what amino
acids are assembled based on mRNA strand
Alanine
Threonine
Glutamate
Leucine
Arginine
Serine
Stop!
16Translation
- Gene 5 GATCATGCGTCTCCTCTAATT 3
- Template
- mRNA
- Amino Acids
17Translation
- Gene 5 3Template 3 CTCATACGGACAGTATTTTA
C 5 - mRNA
- Amino Acids
18Once the amino acid sequence is complete, it
folds into a 3D glob a protein! Proteins do
all of our cellular work, so they create
phenotypes.
Discuss with a neighbor How do you get from
genotype to phenotype?
19Your Task
- Gene Expression Practice Worksheet
- Compare to key when finished to see if you have
the skills! - Homework due Friday
- Snorks
20Discuss with your neighbors
- Where does DNA Replication take place?
- Where does Transcription take place?
- What does Transcription produce?
- Where does Translation take place?
- What does Translation produce?
- The Genetic Code is used to figure out what amino
acids are assembled based on the strand
created from the strand
21What is the deal with 5 and 3?