Download GENETICS NOTES – X BIOLOGY

GENETICS NOTES
Genetics : _________________________________________________________
Heredity: __________________________________________________________
Gregor Mendel - _____________________________________________________
 Austrian __________ who did experiments with _____ plants.
 Developed three laws of _______________________:
1. Law of ___________________ : some forms of a trait are dominant to other forms.
________________________ = form of a trait
Ex/ For plant height (the trait), there are two forms : _______ and _________
o Mendel’s first experiment: Parental (P) cross: ________ X _________
When Mendel crossed (took pollen from one plant and put it onto flower of
another) a pure-bred tall with a pure bred short plant, he saw that all of
the offspring were ___________________.
o Offspring of the P cross are called the _____ (first filial) generation &
were all ______. Because they were offspring of two pure-breeding plants,
he called these plants ________________________. Because of these
results, Mendel said that the tall __________ was ________________
to the short allele, and therefore he said that the short allele was
_____________________.
o Mendel’s second experiment: F1 cross: ____________ X ____________
o Offspring were ¾ tall and ¼ short, so he said that somehow the short allele
was preserved in the hybrids.
o For every trait, an individual has ____ alleles, one from each __________
o If an individual has two dominant alleles they are called: ______________
o If an individual has two recessive alleles they are called: _____________
o If an individual has one dominant and one recessive : ________________
o Therefore we can represent individuals genetically and by their physical
appearance:
Genotype = _________________ Phenotype = ___________________
Three possible genotypes for height:
Two possible phenotypes for plant height:
2. Law of __________________________: During gamete formation
(___________) the two alleles for a trait become separated into different
gametes.
Ex/ Heterozygous tall (________) pea plant can produce two types of sperm cells:
Punnett Square: _____________________________________________________
Homozygous Tall X Homozygous short (Mendel’s _____ cross):
Genotypic Ratio:
Phenotypic Ratio:
Heterozygous Tall X Heterozygous Tall (Mendel’s _____ Cross):
Genotypic Ratio:
Phenotypic Ratio:
3. Law of _______________________________________: During gamete
formation (___________), genes for _______________________________ are
inherited separately.
EX/ In Mendel’s pea plants, genes for height are inherited independently from genes
for flower position.
This law is best demonstrated when looking at _________-____________ crosses:
crossing two traits of two individuals.
_________________ cross: when two individuals are ___________________ for
two traits.
EX/
Plant Height
T = tall
t = short
Flower Position
A = axial (in middle of branch)
a = terminal (at end of branch)
Cross two heterozygous tall, heterozygous axial pea plants:
Genotypes of parents: _________________ X ____________________
Possible Gametes:
Square:
Cross a heterozygous tall, heterozygous axial with a short, terminal plant:
Genotypes of parents: _________________ X ____________________
Possible Gametes:
Square: