Download Hybrid pink and white azalea (Rhododendron sp., fam. Ericaceae)

GENETICS: PATTERNS
OF INHERITANCE
ALLELE
• One of the
two or more
forms of the
gene for a
specific trait
• Represented
by letters
S – Smooth seed
s – wrinkled seed
AUTOSOMES
The first 22 sets of of
chromosomes are called
autosomes.
CHROMOSOME
A strand of DNA carrying
many different genes.
CODOMINANCE
Case in which both alleles
contribute to the
phenotype of the
offspring
Hybrid pink and white azalea
(Rhododendron sp., fam. Ericaceae)
CROSSING-OVER
Homologous chromosomes
within the tetrad
exchange portions of their
chromatids, occurs during
Prophase 1
DIPLOID
• Two sets of chromosomes
DIHYBRID CROSS
(Two-Factor Cross)
A genetic cross in which
two pairs of contrasting
traits are studied.
DOMINANT
The trait that hides the
expression of another
trait.
T
F1 GENERATION
The first filial generation
that results from a cross
between two purebred
parents.
F2 GENERATION
When flowers of the F1
generation were allowed
to self-pollinate, their
offspring became the
second filial generation
or F2 generation
GAMETE
Sex cells (egg or sperm)
GENE
A unit of DNA that
produces a specific trait
in an individual.
GENETICS
The scientific study of
heredity
GENOTYPE
The genetic makeup of an
organism
TT
GREGOR MENDEL
• Austrian monk who studied
mathematics and science
• As a boy he could predict the
possible types of flowers and fruits
that would result from
crossbreeding two plants in his
father’s garden
GREGOR MENDEL
cont’d
• Curiosity about the connection between
the color of a pea flower and the type of
seed that same plant produced inspired
him to begin experimenting with garden
peas in 1856.
• Made careful use of scientific methods,
which resulted in the first recorded study
of how traits pass from one generation to
the next.
HAPLOID
• One set of chromosomes
HETEROZYGOUS
Having two different
alleles for a trait.
HOMOZYGOUS
Having two identical
alleles for a trait.
HOMOLOGOUS
CHROMOSOMES
Human Chromosomes
Humans have 46 pairs of
chromosomes:
23 from the father
+ 23 from the mother
HYBRID
An individual that is
heterozygous for a
specific trait.
INCOMPLETE
DOMINANCE
Cases in which one allele
is not completely
dominate over another;
the offspring will have a
phenotype between that
of its parents
MEIOSIS
• The process of cell
division that leads to
gamete formation
• During meiosis, the
number of chromosomes
per cell is cut in half.
MONOHYBRID CROSS
(One-Factor Cross)
A genetic cross in which
only one pair of
contrasting traits is
studied
NONDISJUNCTION
• During nondisjunction, the
chromosomes fail to divide
properly during meiosis.
• Abnormal numbers of
chromosomes may find
their way into gametes.
PEDIGREES
• A “family tree”
• Constructed by
studying the
phenotypes of family
members from one
generation to the next.
EXAMPLE OF A
PEDIGREE
P GENERATION
The parental generation
with two pure-bred
parents
PHENOTYPE
The physical traits that
appear in an organism as a
result of it genes.
White
hair
Principle of Dominance
The principle of
dominance states that
some alleles are
dominant and others are
recessive.
Principle of Independent
Assortment
The principle of
independent assortment
states that genes for
different traits can
segregate independently
during the formation of
gametes.
Principle of Probability
The principles of
probability can be used
to predict the outcomes
of genetic crosses.
PROBABILITY
The likelihood that a
particular event will occur
PUNNETT SQUARE
A diagram used to predict the
probability that certain traits
will be inherited by offspring
RECESSIVE
• The trait that is hidden
• Recessive traits only
appear when
homozygous.
t
SEGREGATION
The separation of alleles
during gamete formation
SEX CHROMOSOMES
The last pair of
chromosomes in the
karyotype are called sex
chromosomes because
they determine a
whether a person will be
male (xy) or female (xx).
TEST CROSS
A genetic cross between an
unknown genotype for a
trait and a homozygous
recessive genotype for the
same trait; the phenotypes
of the resulting generation
reveal the unknown
genotype.
TETRAD
The pairing of homologous
chromosomes, occurs during
Prophase 1
TRAIT
A genetically determined
characteristic, such as
eye color.
Mendel’s 7 garden pea traits.
TRUE-BREEDING
Plants that when crossed
produce offspring
identical to themselves
every time.