Download Genetics

Today’s Goal
 I can complete a Punnett Square
 I can name two people and their
contributions to genetics
Homework Study for vocab quiz Friday
Warm-up: Define adaptation.
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WHAT IS GENETICS?
 Genetics
– The study of how heredity
information is passed from parents
to offspring
WHAT IS GENETICS?
The Modern Theory of Evolution =
Genetics + Darwin’s Theory of Natural Selection
GREGOR MENDEL
Law of Dominance
(see above)
• Studied inheritance of traits in
pea plants
• Published research shortly after
Darwin’s book (but it was in an
obscure journal)
• He received credit for his work in
1900 (15 years after his death)
• The pea traits he studied later
became known as GENES
• He became the Father of
Genetics
•DNA = Deoxyribonucleic acid
WHAT IS DNA?
•DNA stores information
•Subunit = nucleotides
•Nucleotides contain a nitrogen base
DNA IS DOUBLE
STRANDED
DOUBLE HELIX
•4 different nitrogen bases
•adenine (A)
•guanine (G)
•thymine (T)
•cytosine (C)
•Complimentary Strands (A-T) (G-C)
*3,000,000,000 nitrogen base pairs
make you who you are*
WHAT IS A GENE?
A segment of DNA
is called a gene
A gene codes for a
specific trait
Chromosomes
contain your DNA
sequence
Each nucleus
contains pairs of
chromosomes
Each cell in your
body contains a
nucleus
Your body is made
up of cells
Most cells in your
body have 46
chromosomes.
Sperm and Egg
cells have 23
chromosomes.
JAMES WATSON & FRANCIS CRICK
ROSALIND FRANKLIN(1953)
Franklin’s x-ray of
the DNA molecule
– view is above
helix, looking down
(x pattern is from
nucleotide bases)
Discovered the structure of a
DNA molecule (double helix)
which provided details on
genes & how they work
AND
WHAT IS AN ALLELE?
 Most
organisms have TWO copies of every gene
and chromosome (one from each parent)
 Alleles are the different forms of a gene for a
specific trait

Ex: Flowers can be violet or white
WHAT IS AN ALLELE?


REMEMBER genes exist as pairs, so often one allele is
considered the dominant allele and the other the
recessive allele
Dominant: trait observed in the first generation
when parents that have different traits are bred


Given a capital letter symbol (ex: Purple flower= P)
Recessive: a trait that reappears in the second
generation after disappearing in the first
generation when parents with different traits bred
 Given

a lower case letter symbol (ex: White flower= p)
Which is the purple allele?
Purple is dominant
because it “covers up”
the white allele in the
offspring
DOMINANT & RECESSIVE ALLELES



Since genes are found in pairs, a pea plant could have
the following combinations of alleles for flower color
 PP = purple
Pp = purple pp = white
The genetic make-up is called the genotype (PP, Pp,
or pp)
 PP and pp is considered homozygous (all one allele
type)
 Pp is considered heterozygous (two different allele
types)
The outward physical appearance for a gene is called
the phenotype (purple or white), which is based on its
genotype
PUNNETT SQUARE
is a diagram that is used to
predict an outcome of a particular
cross or breeding experiment.
P = purple
p = white
What are the chances of having
the white phenotype? ¼ or 25
%
What are the chances of carrying
the white allele? ½ or 50 %
What is the chance of having a
heterozygous genotype? ½ or
LETS DO SOME PRACTICE PROBLEMS!
50 %
PRACTICE!
TT x tt
Tt
100 % offspring = ____
Tt x Tt
25%
TT = ____
Offspring?
50% tt = ____
25%
Tt = ____
Bb
BB
Bb
Bb
Bb
bb
Today’s Goal
 I can complete a Punnett Square
 I can describe how mutations occur
Homework Finish DR How does Evolution occur
AND Study for vocab quiz TOMORROW
Warm-up:
5 minutes
DNA CODE AND MUTATIONS
• The DNA Sequence shows
how a species changes over time
• If a mutation (typo) occurs
within the DNA sequence, genes
can change causing alleles and
traits to change
• Over time as more mutations
accumulate the species changes
•Normal DNA
(gene):
A
A
A
G
G
G
•Let’s say that “AAAGGG” means that you can break down a
chemical in milk called phenylalanine
•The same sequence is copied to make egg (female) or sperm
(male):
A
A
A
G
G
G
•All egg or sperm cells will have the same sequence of
“AAAGGG” so all offspring will be able to break down milk
A
A
A
G
G
G
•Unless something goes wrong when the gene is copied:
A
A
A
C
G
G
•Now this egg or sperm cell is carrying a mutation of the
gene. Offspring who are born with this gene cannot break
down phenylalanine from milk, which causes brain
damage when it builds up in the body.
THIS MUTATION HAS LED TO 2 DIFFERENT
VARIATIONS WITHIN THE POPULATION:
Some babies will be disease free and can break
down phenylalanine in milk
 Some babies will have a disease (called
Phenylketonuria) and cannot break down this
protein in milk

HUMAN GENOME (2001)
• All living things are made of genetic
information
• We have similarities in our DNA to all
animals including dogs and fruit flies.
• The more closely related two species
are to each other the more similar their
DNA code (genome)
• Find out your genetic code
• 23andMe (was $999, now $99)
• Visit: www.23andMe.com
• Other: deCODE; Navigenics