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Genetics
Chapter 20
Genetics
 Study of HEREDITY
 Traits that are passed from parent  offspring
 Sexual Repro.  2 parents, offspring is a combo.
 This VARIATION leads to EVOLUTION
 Asexual Repro.  1 parent, offspring is identical
Genetics
 Gregor Mendel
“Father of Genetics”
 1800’s
 Worked with pea
plants
 Easy traits to study
Vocab:
Genetics:
 Study of heredity
Heredity:
 Passing of genetic info.
from parent to offspring
Genes:
 Located on homologous
chromosomes
 2 genes for each trait
(1from mom,
1 from dad)
 Units of heredity
 Determines
traits/characteristics
Hereditary Information




DNA- DeoxyriboNucleic Acid…
Organic (C, H, O, N)
Double Stranded
Organized in the form of genes on the
chromosomes found in the nucleus
 Genetic Recombination:
Sperm & egg combine to form a zygote
That organism has a complete set of genetic
info.
DNA
The DNA Molecule and Chromosomes
The Genetic Code
 Structure was discovered by
James Watson & Francis Crick
 Model of DNA  The Double Helix
 A twisted ladder
Structure of DNA
 POLYMER –
long chain of repeating units
called NUCLEOTIDES
 A nucleotide contains:
 Phosphate Group
 Deoxyribose (sugar)
 Nitrogenous Bases
(Adenine, Thymine,
Cytosine &Guanine)
Nucleotide
1. Phosphate group
2. Bond
3. Deoxyribose sugar
4. Bond
5. Weak hydrogen bond
6. Bond
7. A – adenine (base pair)
8. T – thymine (base pair)
9. G – guanine (base pair)
10. C – cytosine (base pair)
• Sides are made of
Phosphate & Sugar that alternate
•
•
•
•
“Steps” are made of NITROGENOUS BASES
SPECIFIC PAIRING:
A–T
C–G
– Hint: At GC or A Tall Cover Girl
• Weak Hydrogen bonds holds the bases together
Answer the Question:
• What would the
sequence of the
complimentary
strand be?
DNA Replication
• When a cell goes through MITOSIS
• DNA of the cell makes a copy of itself
•
•
•
•
1.
2.
3.
4.
DNA UNRAVELS - unwinds
DNA UNZIPS
New nucleotides attach to template strand
Result: 2 identical DNA molecules
DNA Replication
DNA Replication:
DNA Replication
Mutations:
• Causes a change in the DNA code
• Random
• Can be increased b/c of radiation,
chemicals
• If a mutation happens in a body cell 
person is affected
• If a mutation happens in a sex cell 
offspring is affected
Mutation:
Types of Mutations:
1.
2.
3.
4.
Original DNA Template:
CACCGTATTA
Substitution: one base for another
CACCTTATTA
Deletion: missing a base
CACCG ATTA
Addition: adding a base
CACCGTAATTA
Inversion: bases are rearranged
CACCTAGTTA
Types of Genetic Mutations
What types of Mutations are
these?
Answers:
1. Addition
2. Inversion
3. Addition
Proteins & Cell Functioning
• Proteins Long chains of
amino acids
• Order of amino acids influences the
shape of the protein
• Proteins include:
enzymes, insulin, eye color and hair color
DNA-PROTEIN
CONNECTION
• Genes contain genetic code
• This info. is used to make proteins that are
required for its structure & function
• RIBOSOMES: make PROTEINS based on the
GENETIC CODE order of
A, T, C, & G’s
RNA
•
•
•
•
•
•
•
Ribonucleic Acid
Single stranded
Nitrogenous Bases:
A- Adenine
U- Uracil
C- Cytosine
G- Guanine
Types of RNA
1. Messenger RNA:
• mRNA
• Copies genetic code
from DNA
• Brings code to
ribosome
2. Transfer RNA:
• tRNA
• Brings amino
acids to the
ribosome so
proteins can be
assembled
Protein Synthesis
• DNA is the code for proteins
• Proteins are chains of amino acids
Steps of Protein Synthesis:
1.
2.
3.
4.
5.
Begins in the nucleus with DNA
DNA code is copied by mRNA
mRNA brings code to ribosome
tRNA brings AMINO ACIDS to ribosome
amino acids are put together  making a
protein
How did researchers make the connection between
DNA and Protein?
Protein Synthesis and Sickle Cell
Karyotype- Picture of chromosomes

Needed to diagnose genetic disorders
Ex) Down’s Syndrome – Trisomy 21
DNA and Individuality



Every cell in an organism has the SAME
DNA
Each cell is different because it uses
different parts of the DNA
The ENVIRONMENT influences gene
expression
Ex) Himalayan Rabbit
cold temp  black fur
warm temp  white fur
Ex) Freckles:
UV radiation from sun increases melanin in
skin
Genetic Engineering

Genetic EngineeringUsed to alter DNA in
an organism.
1.
Gene Splicing- Process
that uses enzymes to
cut and combine DNA
from 2 organisms
Steps of Gene Splicing:
Bacteria producing human insulin
1.
2.
3.
4.
Use enzyme to cut DNA
from bacterial cell
Human DNA + Bacterial
DNA are combined
Insert combined DNA
into bacterial cell
Bacterial cell now
produces human insulin
Gene Splicing Examples:
• Uses of gene splicing:
1. Bacteria producing human insulin
2. Plants with genes for insecticide (to kill pests,
prevent crop destruction)
Selective Breeding
1.
Selective Breeding
- Breed for the best
traits
Ex) Lean cows
Ex) Large Fruits
Ex) Breeds of dogs