Genetics: Study of Heredity
Aim: What is Genetics?
http://www.youtube.com/watch?v=eOvMNOMRRm8
Sexual Reproduction:
• Two parents
• Half of the genetic information is
received from one parent, half from
the other.
• Variation Evolution
Asexual Reproduction:
• One parent
• Offspring is identical to parent.
• Clones- identical genetic copies.
Genetics:
• Gregor Mendel- 1800’s
• “Father of Genetics”
• Pea plants: easy to grow
• Contrasting traits
• Easily self and cross pollinate.
• From his studies, Mendel arrived at
conclusions that are the basis for genetics
today!
Additional Vocabulary
• Genetics: Study of heredity
• Heredity: Passing of genetic information
from an organism to it’s offspring.
• Genes: units of heredity
•
– Determines traits/ characteristics an
offspring will have.
– Located on chromosomes.
– For each trait-> minimum of 2 genes. One
from mom, one from dad.
There are many genes located on a
Chromosome.
Genes
Hereditary Information:
•
•
•
•
DNA- deoxyribonucleic acid
Organic (C, H, O, N, P).
Double stranded
Organized in the form of genes located on the
chromosomes.
Hereditary Information:cont.
• Homologous chromosomes- are same size
and shape (one from each parent)
– This allows for crossing over and variation to
occur.
http://www.youtube.com/watch?v=lJzZ7p-47P8
Genotype vs. Phenotype:
Genotype- genes
Ex: B,b,S,s
Phenotype-Physical
appearance
Ex: Fur Color, Fur
Length
http://www.youtube.com/watch?v=jHWJqzlHl3w
Genetic Recombination:
• Sperm and egg combine to form a
new cell.
• New cell (offspring) has a complete
set of genetic information (DNA).
Each offspring is unique.
The Genetic Code:
– Structure of DNA
was discovered by 2
scientists:
– 1953 James Watson
and Francis Crick
– Created a model
known as the
Double Helix a
twisted ladder.
What is the structure of DNA?
Structure of DNA
• Long chain of repeating units ( polymer) called
•
nucleotides.
A nucleotide unit contains:
1. phosphate group O
2. deoxyribose (sugar)
3. nitrogenous base:
– A- adenine
– T- thymine
– C- cytosine
– G- guanine
Structure of DNA
One Strand of DNA
• The backbone
of the molecule
is alternating
phosphate and
deoxyribose, a
sugar, parts.
• The teeth are
nitrogenous
bases.
phosphate
deoxyribose
bases
Two Stranded DNA
• Remember, DNA
has two strands
that fit together
something like a
zipper.
Types of nitrogen bases
•
•
•
•
A= adenine
G= guanine
C= cytosine
T= thymine
Structure of a Double Helix
• Sides of the “ladder” are
alternating phosphate group
and deoxyribose sugar.
• “rungs” of the ladder are made
of 2 nitrogenous bases.
• Specific pairings:
– There is a weak Hydrogen
bond
Between the base pairs.
– Structure as a double helix
– When a cell goes through
mitosis(cell division) the
DNA must also make a
copy of itself.
DNA by the numbers
• Each cell has about 2
•
•
•
m of DNA.
The average human
has 75 trillion cells.
The average human
has enough DNA to
go from the earth to
the sun more than
400 times.
DNA has a diameter
of only 0.000000002
m.
The earth is 150 billion m
or 93 million miles from
the sun.
Aim: How does DNA replicate?
Do Now: Please answer the questions on
the handout found on the front desk, omit
questions 5-7.
Genetics Can
Tell All
G-Guanine
C-Cytosine
T-Thymine
A-Adenine
Base Pairing
• Which bases always
•
•
•
•
match up?
A-T
G-C
Adenine always binds
with Thymine
Cytosine always binds
with Guanine
Steps of Replication:
1. DNA unwinds
2. DNA unzips
3. Old strands become
templates for new
strands
4. Result- 2 identical DNA
molecules
Characteristics of a Double
Helix
• Proteins and Cell Functioning:
–Proteins- long chains formed from
20 kinds of amino acids.
–Sequence(order) of the amino acids
influences the shape of the
molecule.
–Proteins include: enzymes, insulin,
eye color, and skin color.
DNA- Protein Connection:
– Genes contain coded information.
– This information is used to make
proteins that are required for it’s
function and structure.
– Ribosomes construct proteins based on
the cell’s DNA code (combo of A, C, T,
G’s).
– Parent and offspring produce similar
traits that is why there is resemblance
between them. They produce similar
proteins.
Aim: How does protein synthesis
Work?
Protein Synthesis:
• The building of protein
molecules.
• Synthesizing protein from
DNA.
• Proteins are chains of amino
acids.
Steps:
–Begins in the nucleus with DNA.
–DNA code is read by a “ messenger
molecule” messenger RNA; ;
–mRNA.
–“messenger molecule: travels into
the cytoplasm of the cell to the
ribosome.
Steps cont.:
– With the help of “transfer molecules”
tRNA amino acids move to the
ribosomes to make proteins.
– The ribosomes “reads” the code and a
chain of amino acids is produced
forming a protein.
– ***Protein structure is determined by
DNA***
RNA:
• Ribonucleic Acid
• Single stranded
• Nitrogenous bases
– A- adenine
– U- uracil
– C- cystosine
– G- guanine
Types of RNA
– Messenger RNA (mRNA)
Copies code from DNA
Brings to ribosome
– Transfer RNA (tRNA)
Brings amino acids to ribosome for
protein assembly
– Mutations:
Alteration of DNA sequence.
Causes a change in code carried for by
the gene.
Random, but can be increased because
of chemicals, radiation.
Aim: What are different genetic
mutations?
• Do Now: Please complete the handout on
the front desk.
Different Types of Mutations:
• Original DNA Template C A A T G C T A C
– 1. Substitution: one base pair for another.
CAACGCTAC
– 2. Deletion: missing a base.
CAATOCTAC
– 3. Addition: adding an extra base
CAATAGCTAC
– 4. Inversion: bases are rearranged.
CAGATCTAC
Causes of Mutations
• Environmental Conditions can affect how
genes are expressed.
– Ex. Himalayan rabbit
– Warmer body temperature white fur
– Colder body temperature black fur
• ** Identical twins- separated- different
•
personalities
Chemicals, hormones can activate a gene,
causing certain proteins to be produced.
Genetic Engineering
• Used to alter instructions in organisms.
• Produce more desirable traits.
Selective Breeding:
•Produces animals and plants
with desirable traits.
•Horse & donkey= mule.
(outbreeding)
•Ex. Larger, juicier fruits…
•Pure dog, pure cat.
(inbreeding)
Inbreeding/ Outbreeding
Breeding continued:
• ** In sexually reproducing
organisms only mutations found
on sex cells can be inherited by
the offspring.
• Mutations occurring in body cells
will only affect that organism.
DNA and Individuality:
• The order of the nitrogenous base pairs,
•
•
A,T,C,G’s are what makes each person an
individual and unique. This is because the order
allows for certain proteins to be produced.
In an organism every cell contains the same
genetic code.
However, each cell is different: hair cells, skin
cells, liver cells, stomach cells.
Gene Expression.
• Each cell only uses some of the
genetic information from the
chromosomes.
• Certain parts of the chromosomes
get “turned on” or “turned off.”
Gene Manipulation:
• Altering genes using enzymes
• By manipulating the DNA in plant
cells or animal cells; favorable
offspring can be produced
• Produce bacteria that can be
beneficial.
Steps:
• Cut DNA segment with enzymes
• This segment can be spliced (moved) and
attached to DNA of a new organism.
• New organism will make the protein coded
for by DNA code.
Gene Manipulation
Biotechnology:
• Apply technology to biology.
• Applications of Biotechnology:
–By using gene therapy and applying
it to modern medicine scientists
may:
–Produce hormones, enzymes and
other body chemicals.
–Provide at a low cost.
–Provide a purer form.