Download Genetics

Genetics
&
Heredity
Who was Gregor Mendel?
Who was Gregor Mendel?
• Austrian monk who studied
mathematics and science
• As a boy he experimented with
pea plants
• Made careful use of scientific
methods, which resulted in the
first recorded study of how
traits pass from one generation
to the next.
What is GENETICS?
What is GENETICS?
The study of how traits are
inherited through the
interactions of genes.
Genetic Material
• The nucleus of a cell
contains genetic
material
– DNA
• Chromosomes
– Genes
www.kent.edu/projects/cell/page7.htm
Genes
• Genes are short
sections of
chromosomes
• Genes come in
pairs and
offspring
inherit one copy
of each gene
from each
parent
http://www.accessexcellence.org
Genes come in pairs
• Since
chromosomes
come in pairs
(one from mom,
one from dad)
Genes come in
pairs
http://anthro.palomar.edu/biobasis/ima
ges/karyotype_male.gif
Define the following terms:
• Heredity
• Allele
• Trait
Define HEREDITY
The passing of traits from
parent to offspring
Allele
• Alleles are
different
versions of a
gene
• Every gene has
two or more
alternatives
http://library.thinkquest.org
Define TRAIT
• Characteristic or a way of
looking, thinking, or being
• Traits that are genetic
are passed down through
the genes from parents to
offspring
Describe RECESSIVE
Describe RECESSIVE
• A trait that is covered
over, or dominated, by
another form of that
trait and seems to
disappear
• Shown with a lower-case
letter
• Example: c, d
What is HOMOZYGOUS?
What is HOMOZYGOUS?
• Both alleles [forms of the gene]
are the same
• When offspring inherit two
dominant genes, (one dominant gene
from each parent) they are said to
be homozygous dominant (BB)
• When offspring inherit two
recessive genes, (one recessive
gene from each parent) they are
said to be homozygous recessive
(bb)
What is HETEROZYGOUS?
What is HETEROZYGOUS?
• When alleles occur in different
forms
• When offspring inherit one
dominant gene and one recessive
gene, they are said to be
heterozygous (Bb)
• Since the dominant gene will be
expressed, they are said to be
heterozygous dominant
Describe DOMINANT
Describe DOMINANT
• A trait that covers over,
or dominates, another
form of that trait
• Trait that always shows
up, even when only one of
the two alleles is in the
dominant form
• Shown by a capital letter
Define GENOTYPE
Define GENOTYPE
An organism's genetic makeup
Or the letters
Example: Bb, bb, BB
Define PHENOTYPE
Define PHENOTYPE
Outward physical appearance
and behavior of an organism
Example: black hair
What is a PUNNETT SQUARE?
What is a PUNNETT SQUARE?
• A tool to predict the probability of
certain traits in offspring that shows
the different ways alleles can
combine
• A way to show phenotype & genotype
• A chart that shows all the possible
combinations of alleles that can
result when genes are crossed
What is a PUNNETT SQUARE?
• Letters stand for dominant and
recessive alleles
• An uppercase letter stands for a
dominant allele
• Lowercase letters stand for
recessive alleles
Read More About Punnett
Squares Here:
http://www.borg.com/~lubehawk/p
square.htm
List the 3 Principles of
Heredity
List the 3 Principles of
Heredity
• Traits are controlled by alleles on
chromosomes
• An allele’s effect is dominant or
recessive
• When a pair of chromosomes
separate during meiosis the
different alleles for a trait move
into separate sex cells
What is meant by MULTIPLE
ALLELES?
What is meant by
MULTIPLE ALLELES?
• A trait that is controlled by
more than two alleles is said to
be controlled by multiple alleles
• Traits controlled by multiple
alleles produce more than
three phenotypes of that trait
What is meant by MULTIPLE
ALLELES?
For Example:
The alleles for blood types in humans
are called A, B, and O
The O allele is recessive to both the A
and B alleles
What is meant by MULTIPLE
ALLELES?
When a person inherits one A
allele and one B allele for
blood type, both alleles are
expressed
The person has the blood
phenotype AB
What is meant by MULTIPLE
ALLELES?
A person with phenotype A
blood inherited an A and an
O allele (AO)
~OR~
an A and an A allele (AA)
What is meant by MULTIPLE
ALLELES?
Someone with phenotype B
blood has the genotype BB or
BO
This person inherited either a
B and an O allele
~OR~
Two B alleles
What is meant by MULTIPLE
ALLELES?
A person with phenotype O
blood has the genotype OO
What is POLYGENIC
INHERITANCE?
What is POLYGENIC
INHERITANCE?
• Occurs when a group of gene
pairs acts together to produce a
trait
• The effects of many alleles
produces a wide variety of
phenotypes