Heredity/Mendel Guided Notes
Name_____________________________________ per____
Heredity: The passing of ______________________characteristics onto the offspring
___________________: is the branch of biology that studies heredity
Gregor Mendel
Considered the ______________________ of genetics
Was an Austrian monk that used ________ _____________________ to study heredity
Pea plants usually self pollinate so their genetic information can be ____________________
By carefully ___________________________ his data he made some great findings
Mendel Crossed Plants with different _____________________ or characteristics
Mendel crossed a __________ pea plant with a _________________ pea plant to see what
would happen
The result was that the offspring (___________________) were all tall
However when crossed the second generation, ¼ were _________________
Mendel repeated these crosses for 7 different variations
He discovered that in the 2nd generation (______)that the trait that had disappeared in
the first generation (________) reappeared again, always.
Genetic generation abbreviations
P1= _________________________
F1= _________________________
F2=_________________________
Mendels findings
1. Mendel concluded that each organism has 2 factors called ________________ that control
each trait
_________________ are different gene forms that determine the different form of the trait
For example the gene for _____________ has an allele for tall and another for small
Typically we use upper and lower case letters to identify these ____=tall allele and
_______=short allele
Genes can either be homozygous or heterozygous
______________________ has the same 2 alleles ie TT or tt
______________________ has different alleles ie Tt
2. Principle of Dominance = some alleles are dominant and will ____________ a recessive allele
So ______ or ____________ will both be tall, whereas tt will be short
Dominant genes are represented by upper case letters and recessive (non-dominant) by
lower case
3. Noticed that alleles segregate when forming gametes
Also noticed alleles segregate independently of each other – ____________________
_________________________
Monohybrid crosses illustrate Mendel’s findings
A monohybrid cross is one that looks at only ____________
specific trait and how it segregates
Easy to do this using the _____________________ square
method
Determining Genotype and Phenotype
Genotype refers to the allele _____________ of a gene, the actual gene alleles
For example the genotype of the punnett square is ¼ TT, ½ Tt, and ¼ tt
This gives a genotypic ratio of _______________
Phenotype refers to the trait the is expressed by the organism or what it __________ ________
Since both TT and Tt are tall, the phenotype of the punnett square is ¾ tall and ¼ short
The phenotypic ratio is ______________
Dihybrid crosses
Dihybrid crosses look at _______ different traits passed on from parents
Ex: In peas, seed shape & seed color
R = round
Y = yellow
r = wrinkled
y = green
Dihybrid Cross Example
One Parent is RRYY (__________________________)
The other is rryy (___________________________)
So RRYY X rryy
Step 1: find all possible gamete _____________________by
using FOIL (First Outer Inner Last)
There will always be ________ different combinations
in dihybrid Crosses
Possible gametes: RY RY RY RY x ry ry ry
Step 2: Set up ___________ punnett square and put possible gametes from parents on top
and side, then fill in squares for possible offspring
All offspring are heterozygous for both seed shape and seed color - RrYy, what is their
phenotype and genotype?
Now cross two F1 plants.
RrYy x RrYy
Possible gametes: ____ ____ ____ ____ x
____ ____ ____ ____
Phenotypic Ratio for a Dihybrid Cross:
For this cross, find the number of each - round yellow : round green : wrinkled yellow :
wrinkled green
___/16 round yellow
(R_Y_)
___/16 round green
(R_yy)
___/16 wrinkled yellow (rrY_)
___/16 wrinkled green
(rryy)
Phenotypic Ratio = ___ : ____ : ____: ____