Download Understanding Biological Inheritance

Understanding Biological
Inheritance
GREGOR
MENDEL
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Word List
Dominant
Punnett square
Homozygous
Mendel
Recessive
Pea plants
Genotype
Hybrid
Phenotype
Gene
DNA
Allele
Heterozygous
Purebred
Carrier
Heredity
Chromosomes
Sex-linked trait
Yellow seed coat
Blue eyes
Brown hair
Gregor Mendel
Austrian monk & mathematician
“The Father of Genetics”
Experimented with garden peas
(Pisum sativum)
Grow & reproduce quickly
Matings can be controlled
Show a number of distinct traits that are easy to observe
Studied peas for 8 years!
Designed simple experiments and observed only one trait at a
time
Used math to formulate his conclusions – Mendel’s Laws
Traits that Mendel studied:
Mendel’s Big Idea!
Genes are found in pairs
Characteristics are controlled by unit factors
(genes) that exist in pairs in organisms and are
passed from parents to offspring
When two parents produce an offspring, each
parent gives one of the factors from each pair
Mendel’s garden
Mendel’s 1st Law
1. Law of Dominance:
In a cross of parents that are pure for
contrasting traits, only one form of the trait
will appear in the next generation. Offspring
that are hybrid for a trait will have only the
dominant trait in the phenotype.
One factor is dominant and the other is
recessive
Law of Dominance (cont)
Mendel’s 2nd Law
2. The Law of Segregation:
During the formation of gametes (eggs or
sperm) in meiosis, the two alleles (letters)
responsible for a trait separate from each
other. Alleles for a trait are then "recombined"
at fertilization, producing the genotype for the
traits of the offspring.
When hybrids are crosses, the resulting ratio of
phenotypes is 3 dominant : 1 recessive.
Mendel’s 3rd Law
3. The Principle of Independent
Assortment
Alleles for different traits are distributed to sex
cells (& offspring) independently of one
another.
This Law is easiest explained when setting up
dihybrid Punnett squares in 16 boxes
Independent Assortment (cont)
Dihybrid Set Up