Download Gene Mapping Linked traits can be unlinked if crossing over occurs

Patterns and Processes
of Inheritance
Classical Genetics
Pedigree Analysis
Technology
Sample Problems
Classical Genetics
Mendel’s Laws
Genetic Crosses
Modes of Inheritance
Sample Problems
Mendel’s Laws
•
Gregor Mendel experimented with
garden peas in an attempt to explain
the mechanism of inheritance of traits
• His data revealed the following rules
of inheritance:
1. Law of Dominance: Every trait is
coded for by a pair of factors (alleles)
one of which masks the effect of the
other
Sample Problems
Mendel’s Laws
2. Law of Segregation: During the
formation of gametes the alleles for a
trait separate so that each gamete has
one allele for each trait
3. Law of Independent Assortment: the
allele possessed by a gamete for one
trait has no influence on the allele for
any other trait
Sample Problems
Genetic Crosses
•
•
•
•
The phenotype of an individual can be
either heterozygous or homozygous for a
particular trait
Purebred individuals are homozygous for
the trait
Hybrid individuals are heterozygous for the
trait (also called carriers)
The mating of two individuals is called a
cross
Sample Problems
Genetic Crosses
•
•
•
•
Monohybrid crosses involve two
individuals both heterozygous for the trait
Dihybrid crosses involve two individuals
both heterozygous for each of two traits
A punnet square is a useful way to
determine the genotypes and phenotypes
from one and two trait crosses
A test cross is a method for determining
the genotype of an individual by crossing it
with a homozygous recessive individual
Sample Problems
Modes of Inheritance
•
There are 6 common modes of
inheritance
1. Autosomal Dominant
2. Autosomal Recessive
3. Incomplete Dominance
i. Codominace
ii. Intermediate Inheritance
4. Multiple Alleles
Sample Problems
Modes of Inheritance
5. X-Linked Dominant
6. X-Linked Recessive
7. Y-Linked
Sample Problems
Pedigree Analysis
Symbols
Analysis
Sample Problems
Symbols
•
•
A pedigree chart is a representation of
related individuals from several
generations
Standard pedigree chart symbols are
used in Biology 30
Sample Problems
Analysis
•
1.
2.
3.
4.
Certain modes of inheritance of some
traits can be determined from a
pedigree chart
Autosomal Dominant
Autosomal Recessive
X-linked Dominant
X-linked Recessive
Sample Problems
Technology
Selective Breeding
Genetic Counseling
Gene Mapping
Sample Problems
Selective Breeding
•
•
•
Selective breeding is the purposeful mating
of individuals with certain traits to alter the
population
Inbreeding increases the frequency of a
trait in a population so that individuals
become more alike (also called artificial
selection)
Outbreeding increases the variation within
a population so individuals become less
similar
Sample Problems
Genetic Counseling
•
•
Genetic counseling provides information
and support to families who have members
with birth defects or genetic disorders and
to families who may be at risk for a variety
of inherited conditions
Genetic counsellors would use pedigree
charts and genetic testing to determine the
probabilities of certain traits
Sample Problems
Gene Mapping
•
•
•
Gene mapping is the determination of
the location of genes on a
chromosome
To construct a gene map several
linked traits must be identified
Linked traits are traits that are due to
genes on the same chromosome
Sample Problems
Gene Mapping
•
•
•
Linked traits can be unlinked if
crossing over occurs
Crossing over results in unexpected
phenotypes resulting from genetic
crosses
The frequency of crossing over is
greater if linked genes are far apart on
the same chromosome
Sample Problems
Gene Mapping
•
•
By examining the offspring of genetic
crosses it is possible to determine the
frequencies of crossing over for
several traits
The crossover frequencies can be
used to construct a gene map
Sample Problems