Download GENETICS

GENETICS
The study of how hereditary
information is passed from parent
to offspring.
KARYOTYPE

A karyotype is a picture of the
chromosome pairs.
GENETIC DISORDERS
LIST OF GENETIC DISORDERS
Sickle Cell Anemia
 PKU
 Hemophilia
 Down Syndrome
 Tay Sachs
 Fragile X
 Color-blindness

PUNNETT SQUARES

Cross Male and Female
– (sex determination)
DOMINANT/RECESSIVE
If a gene is dominant, it shows-it is more
powerful. *T*
 If a gene is recessive, it may show-it is
weaker. *t*

GENOTYPE AND PHENOTYPE

Genotype
– What the genes (letters) say
 Ex. TT or Tt or tt

Phenotype
– How the genes appear (physically)
 Ex. Tall or Short
GENETICS

Gregor Mendel
– “father of genetics”
– Studied the inheritance of pea plants in the
1850’s
– Crossed (mated) pea plants with different
traits and helped develop the 3 laws of
genetics
 1. Law of Dominance
 2. Law of Segregation and Recombination
 3. Law of Independent Assortment
LAW OF DOMINANCE

Cross 2 pure/homozygous tall (TT) pea
plants.
– Ex.

Cross 2 pure/homozygous short (tt) pea
plants.
– Ex.
LAW OF DOMINANCE

Cross two hybrid/heterozygous pea plants.
– Ex.
CO-DOMINANCE or INCOMPLETE DOMINANCE
For some traits, there are TWO dominant
alleles (genes).
 Two things can happen:

– 1. Co-Dominance: Both alleles are expressed
– 2. Incomplete Dominance: Alleles blend
together
CO-DOMINANCE

Punnet Square
CO-DOMINANCE
INCOMPLETE DOMINANCE

When neither allele dominates-the result is
a new phenotype.
– Ex. 4 o’clock flower
INCOMPLETE DOMINANCE


Punnet Squares
Worksheet
MULTIPLE ALLELES

Sometimes there are more than two possible
alleles for a trait.
– Ex. Blood types

Rules for blood typing (three alleles).
–
–
–
–
1.
2.
3.
4.
Type
Type
Type
Type
A dominates Type O
B dominates Type O
O is recessive
A is CO-DOMINANT to Type B
BLOOD TYPES
Type
Genotype
Phenotype
BLOOD TYPE PUNNET SQUARE

Cross a homozygous Type A mother with
a homozygous Type O father.

Cross a homozygous Type A mother with
a heterozygous Type B father.
BLOOD TYPE PUNNET SQUARE

Cross two heterozygous Type A parents.
BLOOD GENOTYPES
Type
 Type
 Type
 Type

A- I I
B- I I
O- i i
AB- I I
LAW OF SEGREGATION AND RECOMBINATION
During meiosis, the two genes responsible
for each trait separate from each other.
 Each gamete contains only one gene for
each trait.

– Ex. Hybrid Tall
Tt
Pure Short
tt
SEGREGATION AND
RECOMBINATION
LAW OF INDEPENDENT
ASSORTMENT

If 2 traits are crossed at the same time
(dihybrid cross), each trait is inherited
randomly.
SEX LINKED DISORDERS

The X chromosomes carry some genes
that the Y chromosomes do not.
– Ex. Hemophilia (a recessive disorder)
 h is the gene for hemophilia
 H is the gene for non-hemophilia (normal)
 Genotypes
XY
XY
XX
XX
XX
 Cross a normal male with a hemophiliac female.
SEX LINKED DISORDERS

Cross a hemophiliac male with a carrier
female.

Cross a colorblind male with a normal
female.
GENE CHROMOSOME THEORY

Each gene is found in a specific place on a
chromosome (locus/loci).
LINKED GENES

Some traits are found on the same
chromosome and are usually inherited
together.
– Ex.
 Red hair and _____________
PEDIGREE CHART

Hemophiliac Story
PEDIGREE CHART
MUTATIONS

Some mutations can occur during meiosis.
– Ex. Non-disjunction causes Down Syndrome

Other mutations can be caused by
environmental factors.
– 1) Chemicals such as asbestos, pesticides and
industrial pollutants can cause genetic changes
(mutation).
– 2) Radiation
– 3) Natural conditions may influence which genes are
expressed. Ex. Cold temperatures change fur color.