
Chromosomes contain multiple genes

Genes that are located close to each
other on the same chromosome are said
to be linked

Linked genes usually travel together
during gamete formation

Linkage of genes on a chromosome
results in an exception to Mendel’s law of
independent assortment because linked
genes usually do not segregate
independently

However, scientists concluded that
linked genes can separate during
crossing over.

Crossing over occurs more frequently
between genes that are far apart

Polyploidy is having one or more extra
sets of all chromosomes. Example:
Triploid organism 3n, Polyploidy  6n,
8n

Polyploidy is always lethal in humans

Polyploidy usually occurs most frequently
in plants

Polyploidy plants usually have increased
vigor and size

We use Punnett Squares to predict the
possible offspring of a cross between two
know genotypes
Homozygous both alleles for a trait are
the same
 Heterozygous if the alleles for a trait
are different

A yellow-seed plant could be homozygous
(YY) or heterozygous (Yy).

Genotype an organism’s allele pairs
YY or Yy

Phenotype the expression of the allele
pair, the way an organism looks or behaves
blue eyes, brown hair, attached ear lobes,
etc.
Phenotype Physical appearance
Cross a homozygous dominant tall pea
plant with a heterozygous pea plant. T=
tall and t = short
 a. What percentage will be short?
 b. What percentage will be tall?
 c. What are the genotypes and
phenotypes?


In purple people eaters, one-horn is
dominant (H) and no horns (h) is
recessive. Draw a punnett square
showing the cross of a purple people
eater that is heterozygous with a purple
people eater that does not have horns.
Summarize the genotypes and
phenotypes of the possible offspring.
SpongeBob’s aunt and uncle,
SpongeWilma and SpongeWilbur, have
the biggest round eyes in the family.
Wilma is believed to be heterozygous for
her round eye shape, while Wilbur’s
family brags that they are a pure line.
Complete the punnett square to show
the possibilities that would result if
SpongeWilma and SpongeWilbur had
Children.
 Give the genotype for each person.
 Complete the punnett square…

List the possible genotypes and
phenotypes for the kids
 What is the probability that the kids
would have round eyes?
 What is the probability that the kids
would be oval eyes?
