Transcript Inheritance - Glen Rose FFA

Inheritance
Chapter 7
Inheritance: the way genes are passed down.
• If a father
doesn’t have
a leg does
that mean his
children will
be born with
out a leg????
Hundreds of years ago people knew that somehow
certain traits would be passed on to their children.
Gregor Mendel was the first to predict the outcome
of inheritance. The study of inheritance is Genetics.
• Mendel did
several
different
experiments
on pea plant.
• This is an
example of
wrinkled and
smooth seeds.
Genes and Alleles
• A gene is a specific
piece of DNA.
• You have two genes
that code for the
same thing (ex.
Height). Each of
those two genes is
called an allele.
• So if something had
the genes Aa one
allele would be “A”
the other would be
“a”).
Why two alleles for every gene?
• Because organisms get
2 sets of chromosomes
……….one from the
mother and one from
the father.
Phenotype
• Is the physical
characteristics of the
trait.
• In most cases it is
what we can “see”.
• Example: Freckles,
dimples, attached
earlobes etc.
Genotype
• Is the actual alleles that make up the trait.
• In most all cases this is represented by 2
letters.
• Example: AA, Aa, aa
Dominant
– A dominant trait is a trait
that covers or hides the
other trait of an allele.
• For example, dark colors in hair
usually overshadow the other
allele.
• In this class Dominant will
always be represented with a
capital letter.
• Example: Say “D” is the allele
for black hair and “d” is the
allele for blond. The if an
animal had Dd then it would
have black hair.
Recessive
• A recessive trait is the
trait that is hidden by
the dominant trait.
• In an animal with Dd
for hair color the
recessive allele is “d”.
• The animal carries a
gene for blond hair but
you can’t tell by
looking at it.
Heterozygous
• This is the term given
two different alleles.
• For example, Aa is
heterozygous.
• It may contain one
gene for brown
eyes(A) from the
mother and one gene
for blue(a) eyes from
the father.
Homozygous
• This is the term given
to the two same
alleles.
• For example, AA or aa
• A person may contain
2 genes for -brown
eyes – one from each
parent (AA) or 2 for
blue (aa).