Life Science Ch.5: Heredity
Section 5-1: What is Genetics? (p.124-130)
What have you inherited?
- Eye color, nose shape, and other physical features may
be inherited from your parents
- Heredity – the passing of traits from parent to offspring
- Each sex cell ends up with one form of a gene for each
trait an organism shows (for example – hairline)
Alleles – different forms a gene may have for a trait
The Father of Genetics
-Genetics – the study of how traits are inherited
- Gregor Mendel (1822) – first recorded genetics study
In Mendel’s Garden
- Used ordinary garden peas
- Purebred – an organism that always produces the same
traits in its offspring
-Dominant and Recessive Factors
o Dominant –the trait that seemed to dominate
o Recessive – the trait that seemed to disappear
-Predictions Using Probabilitiy
o Probability – a branch of mathematics that helps
predict the chance that something will happen
o Scientific research baed on repeatable results
o See table 5-1 Traits Compared by Mendel
Using a Punnett Square
- Punnett Square – a tool used to predict results in
Mendelian genetics
o Dominant (capital) and recessive (lowercase)
alleles represented by letters
o The letters show the genetic makeup or genotype
-Alleles Determine Traits
o Homozygous – organism with 2 alleles for a trait
that are exactly the same (TT or tt)
o Heterozygous – organism that has 2 different
alleles for a trait (Tt)
o Phenotype – the physical trait that shows as a
result of a particular genotype (Tt=tall)
-Determining Genotypes and Phenotypes
o Letters representing 2 alleles from one parent are
written along the top of the square
o Letters representing 2 alleles from the other
parent are placed along the side of the square
o See p.129 Using Punnett Squares
Mendel’s Success
- Mendelian Inheritance
1. Traits are controlled by alleles on chromosomes
2. An allele may be dominant or recessive in form
3. When a pair of chromosomes separates during
meiosis, the different alleles for a trait move into separate
sex cells
Life Science Ch.5: Heredity
Section 5-1: What is Genetics? (p.124-130)
What have you inherited?
- Eye color, nose shape, and other physical features may
be inherited ______________________________________
- Heredity – the passing of traits from parent to _________
- Each sex cell ends up with _____________ of a gene for
each trait an organism shows (for example – ___________)
-Alleles – different forms a gene may have for a _________
The Father of Genetics
-Genetics – _______________________________________
- Gregor Mendel (1822) – first recorded ________________
In Mendel’s Garden
- Used ordinary garden _________
- Purebred – an organism that always produces the _______
traits in its ___________
-Dominant and Recessive Factors
o Dominant –the trait that seemed to ____________
o Recessive – the trait that seemed to ____________
-Predictions Using Probabilitiy
o _________________ – a branch of mathematics
that helps predict the chance that something will
happen
o Scientific research based on repeatable _________
o See table 5-1 Traits Compared by Mendel
Using a Punnett Square
- Punnett Square – a tool used to predict results in
____________________________
o Dominant (_________) and recessive
(___________) alleles represented by letters
o The letters show the genetic makeup or
___________
-Alleles Determine Traits
o Homozygous – organism with 2 alleles for a trait
that are exactly the ________ (TT or tt)
o Heterozygous – organism that has 2 ____________
alleles for a trait (Tt)
o Phenotype – the physical trait that __________ as
a result of a particular genotype (Tt=tall)
-Determining Genotypes and Phenotypes
o Letters representing 2 alleles from one parent are
written along the ________ of the square
o Letters representing 2 alleles from the other
parent are placed along the _______ of the square
o See p.129 Using Punnett Squares
Mendel’s Success
- Mendelian Inheritance
1. Traits are controlled by ________________________
2. An allele may be _____________________________
3. When a pair of chromosomes separates during
meiosis, the different alleles for a trait move into
_________________________________
Life Science Ch.5: Heredity
Section 5-2: Genetics Since Mendel (p.132-136)
Incomplete Dominance
- the production of a phenotype that is intermediate to
those of the two homozygous parents
- Example: crossing of a red flower (RR) with a white flower
(R’R’) produces a pink flower (RR’)
Multiple Alleles
- many traits are controlled by more than two alleles
- Example: blood type in humans
-1900 one scientist found 3 human blood types: A, B and O
- A and B alleles are dominant
- if a person inherits both A and B, both are expressed
- phenotype A has genotype AA or AO
- phenotype B has genotype BB or BO
- phenotype AB has genotype AB
- phenotype O has genotype OO
Multiple Genes
- eye color is a trait produced by a combination of genes
- polygenic inheritance – occurs when a group of gene pairs
act together to produce a single trait
- combinations produce a wide variety
- Examples: height, weight, body build, skin color, hair color,
shape of eyes, lips and ears
- polygenic inheritance is not limited to human traits (egg
production, color of wheat)
Life Science Ch.5: Heredity
Section 5-2: Genetics Since Mendel (p.132-136)
Incomplete Dominance
- the production of a phenotype that is intermediate to
those of the
____________________________________________
- Example: crossing of a red flower ( ) with a white flower (
) produces a pink flower ( )
Multiple Alleles
- many traits are controlled by more than
__________________
- Example: blood type in humans
-1900 one scientist found 3 human blood types:
_______________
- A and B alleles are ____________
- if a person inherits both A and B, both are ____________
- phenotype A has genotype ___________
- phenotype B has genotype ___________
- phenotype AB has genotype ______
- phenotype O has genotype _______
Multiple Genes
- eye color is a trait produced by a combination of ________
- polygenic inheritance –
_________________________________________________
- combinations produce a wide variety
- Examples:
_________________________________________________
- polygenic inheritance is not limited to human traits
(___________________________________)