Transcript Notes: Inherited, learned Traits and punnett squares

Notes: Genetics and Heredity
Sci.7.10A & Sci.7.10C
What is Heredity?
Heredity is the passing along of traits from parent to
offspring or children.
Traits are the physical characteristics that an
organism contains. Example-hair color, eye color,
hair texture
Genetics is the study of heredity
Inherited Traits vs. Learned
Traits
Inherited traits are physical characteristics that
organisms inherit from their parents. They are
passed down from parents to offspring through
reproduction.
Learned traits are characteristics that are learned or
influenced by their environment. They are
behaviors.
Which of the following characteristics are inherited?
Which of the following characteristics are learned?
Having naturally curly hair
Obesity
Having a good singing voice
Having brown eyes
Being intelligent
Having attached ear lobes
What are some traits that this
family share?
DNA
Traits are found on DNA which stands for deoxyribonucleic
acid.
The DNA in every cell is located in rod like structures called
chromosomes within the nucleus of cells.
How would you describe the
shape of DNA?
Alleles
Genes come in two different called alleles.
A dominant allele is one whose traits are always physically
expressed in the organism when the allele is present.
A recessive allele is a masked or covered up whenever the
dominant allele is present. A recessive trait will only appear
when both alleles are recessive.
Dominant/Recessive Alleles
Remember alleles are two different forms of a trait.
Ex: Height is a trait. Tall is the dominant allelewritten as a “T”. Short is the recessive allele-written
as a “t”.
Dominant alleles are always written as capital
letters.
Recessive alleles are always written as lower-case
letters.
Phenotype vs. Genotype
Phenotype is the physical appearance
Ex: Hair color (blonde, brown, red or black) and Eye
color (blue, brown, green, grey)
Genotype is its genetic makeup or combination of
alleles. BB, Bb, bb
Which trait is dominant? Which trait is
recessive? How can you tell by looking at
genotype?
Phenotype
(physical appearence)
Genotype
(genetic makeup)
Tall
TT
Tall
Tt
Short
tt
What is the trait being
examined in the diagram?
Which trait is controlled by the dominant allele?
Which trait is controlled by the recessive allele?
What is the phenotype being
examined in the diagram?
Identify the dominant phenotype. Identify the
recessive phenotpye. How do you know?
Homozygous and heterozygous
An organism that has two identical alleles for a trait is said to
be homozygous.
Ex: A tall plant that has the alleles TT and a short plant with
the alleles tt are both homozygous.
An organism that has two different alleles for a trait is said to
be heterozygous.
Ex: A tall plant that has the alleles Tt is heterozygous.
Describing Genotype-Homozygous
dominant, homozygous recessive and
heterozygous
A homozygous dominant genotype is a combination of alleles where both
alleles are dominant.
Ex: TT for tall plants
A homozygous recessive genotype is a combination of alleles where both
alleles are recessive.
Ex: tt for short plant
Heterozygous is a combination of both dominant and recessive alleles.
The dominant allele is always written first followed by the recessive
allele.
Ex: Tt for tall plants
What is Carrie’s genotype?
What is Rusty’s genotype?
What percentage of the offspring are
heterozygous for tall?