http://www.thetech.org
/genetics/zoomIn/inde
x.html

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
DNA is our genetic
“code”.
Our code is
located on our
chromosomes
inside the nucleus
of our cells.
One chromosome
is made up of
many genes.
One gene has
information for
one trait.

Karyotype – when we organize our
chromosome in pairs and organize them
from biggest to smallest. The last pair are
the sex chromosomes (determine sex). The
sex chromosomes are not organized by
size.
 Sex-linked
genes – Carried on the X or Y (sex
chromosomes) chromosome (usually the X), most
are recessive and usually seen only in males (ex:
balding).
B - normal hair
-
-
XX
Female
(with hair)
-
XY
Male(bald)
b – bald
Bb b
 Heredity
– Passing traits from parents to offspring.
 Genetics –The branch of biology that focuses on
heredity.
 Monohybrid Cross – a cross that involves only one
pair of contrasting traits.
 True-breeding – all of the offspring of a cross will
display only one form.
• An Austrian monk who carried out experiments
with pea plants to formulate theories on heredity.
• He was the first to establish rules that predict
patterns of heredity.
• Mendel crossed varieties of garden peas with
contrasting traits, counted the number of each
kind of offspring and collected data.
Cross means the breeding of 2
individuals
 Mendel
preformed monohybrid crosses using
pea plants.
On1 of the 2 colors is
P generation
in the F1 generation
(dominant form). The
other (recessively) will
reappear in the F2
generation (in a 3:1
ratio).
 Alleles
– the different versions
of a gene, each is inherited
from one parent. (so there are 2
alleles for each gene). There
can be dominant or recessive
alleles.
 Homozygous – when 2 alleles in
an individual are the same.
 Heterozygous – when the 2
alleles in an individual are
different.
 Genotype – the set of alleles
organism has
 Phenotype – physical
appearance of a character
 Punnett
square – used to predict the outcome of a
genetic cross.
The two colors of flower
(purple and white) Alleles
Both parents have 2
different alleles – (Bb)
Heterozygous
 Monohybrids
are
when we use
Punnett Squares to
compare only one
trait.
 Ratios
 Can
You Guess
what these are?

Two traits at a time
 Ratios
 The
traits will blend
together. This is
because once trait
cannot mask (cover)
the other trait.
 Each
allele is shown
to it’s fullest
abilities
 Law
of Segregation – two alleles for a gene
will separate when gametes are formed. (you
get one from each parent)

Meiosis


It’s like mitosis but it happens twice. When the cells
undergo PMAT for the second time they never have as
S phase where the chromosomes are copied. In the
end, the two cells (gametes) have only half the
number of organisms.
Remember it’s here where nondisjunction and
chromosomal mutations occur.
 Law
of Independent Assortment – two or
more pairs of alleles will separate
independently of one another during gamete
formation. For example a cat with brown
hair will not always have long hair

Traits are given independently



Hair
Eye Color
Height
 Genetic
variation
within a
population
 Caused by
mutations
 Anything that
changes the gene
pool results in
evolution.
 The
frequency of
an allele in a
stable population
will not vary.
 P+Q=1 or
P+PQ+Q=1
 Genotypes
will
tend to remain the
same
 Used to determine
recessive alleles
 Used to see
natural selection.
A
randomly mating population must be free from
mutations, migrations and natural selection
 Frequencies of alleles will not change over time
 And populations match the equation
P+PQ+Q=1
Remember mutations are a good thing too or else we
wouldn’t walk on two legs. It drives evolution.
Certain genes are more prevalent in a population than others
(because they are more helpful for the survival of an
organism) can’t survive - can’t reproduce