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CHAPTER 14 AND 15 - Coggle Diagram
CHAPTER 14 AND 15
*CHAPTER 15: GENE EXPRESSION
GENE EXPRESSION
GENE: Genetic information that codes for a protein
CENTRAL DOGMA OF BIOLOGY
DNA → mRNA → Protein
Proteins do all the work in the cell
Example
Insulin gene → insulin protein → controls blood sugar
TRANSCRIPTION
DNA-mRNA
Happens in nucleus (eukaryotes)
STEPS
Initiation
RNA polymerase attaches to promoter (before gene)
DNA strands unwind
Elongation
RNA polymerase copies template strand
Builds mRNA 5’ → 3’
Termination
RNA polymerase stops at stop sequence
pre-mRNA is released (in eukaryotes)
RNA Processing (Eukaryotes only)
Pre-mRNA → Mature mRNA
Three modifications
5’ Cap
Methyl-guanine added
Protects mRNA / helps ribosome attach
Poly-A Tail (3’ end)
100–300 A’s added
Protects against degradation
RNA Splicing
Exons = coding parts (kept)
Introns = filler / non-coding parts (removed)
Spliceosome cuts introns out → Exons join together
ALTERNATIVE SPLICING
Exons can be rearranged or skipped
One gene can make many proteins
One gene can make many proteins
TRANSLATION (mRNA - PROTEIN)
Happens in cytoplasm on ribosomes
Ribosome = “3D printer of proteins”
mRNA has
Codons (3 bases = 1 amino acid)
64 codons total
Genetic code is
Redundant (multiple codons → same amino acid)
Not ambiguous (each codon = only one amino acid)
Start codon: AUG (methionine)
Stop codons: UAA, UGA, UAG
tRNA (Printer Cartridge Example)
tRNA (Printer Cartridge Example)
Amino acid on top (acceptor end)
Anticodon at bottom (matches codon)
Loaded by enzyme aminoacyl-tRNA synthetase
Loaded by enzyme aminoacyl-tRNA synthetase
Ribosome Structure
A Site = Accepts next tRNA
P Site = Peptide bond forms (peptidyl transferase)
E Site = Exit (uncharged tRNA leaves)
Translation Stages
Initiation
Initiation
Elongation
New tRNAs enter A site
New tRNAs enter A site
Ribosome shifts (translocation)
Chain grows one amino acid at a time
Termination
Stop codon enters A site
Release factor binds
Protein released + ribosome falls apart
Ribosome small subunit attaches to mRNA 5’ end
Finds AUG start codon
tRNA (UAC anticodon) brings methionine
Large subunit attaches
CHAPTER 14: MENDEL AND HEREDITY
GREGOR MENDEL
studied pea plants in monastery garden
discovered how traits pass from parents to offspring
used math to predict inheritance patterns
pea plants had many traits to test (color, shape, height)
father of genetics
PEA PLANT MODEL
easy to grow and reproduce quickly
many observable traits
can self-fertilize or be cross-fertilized
allowed Mendel to control mating and track traits
KEY TERMS
character: heritable feature (flower color)
trait: form of character (purple or white)
true-breeding: always produces same trait (purple - purple)
hybrid: offspring from two different true-breeders
P generation: parents
F1: first offspring
F2: offspring of F1 self-fertilization
MONOHYBRID CROSS (ONE TRAIT)
crossed purple x white - all purple (F1)
F1 self-cross - 3 purple: 1 white (F2)
phenotype ratio: 3:1
genotype ratio: 1 PP: 2 Pp: 1 pp
white trait was hidden, not lost
MENDEL'S LAWS
LAW OF SEGREGATION
each organism has 2 alleles per trait
alleles separate during gamete formation
each gamete gets 1 allele
LAW OF DOMINANCE
one allele masks another
dominant = shown (P=purple)
recessive = hidden (p=white)
HOMOZYGOUS
same alleles (PP, pp)
HETEROZYGOUS
different alleles (Pp)
DIHYBRID CROSS (TWO TRAITS)
studied seed color and shape
RRYY x rryy - all RrYy (round yellow)
F2 showed 9:3:3:1 pattern
new combos appeared - traits assort independently
LAW OF INDEPENDENT ASSORTMENT
genes for different traits separate independently
traits mix freely during meiosis
happens when chromosomes line up randomly in meisosis
CONNECTION TO MEIOSIS
SEGREGATION
when alleles separate in meiosis
INDEPENDENT ASSORTMENT
random arrangement of chromosomes pairs
Mendel's results explained how meiosis creates variation