Download GENETICS The Science of Heredity

GENETICS
The Science of Heredity
Mrs. Brunner
Science
7th Grade
 I. Gregor Mendel
A. Mendel’s Pea Experiments - 1851
 1. Monastic monk
 2. While growing peas, he noticed purebred plants…
 3. He cross pollinated purebred plants tall peas with
purebred short peas and got…
 4. parent generation = P generation, filial = F1
 5. big idea –
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a. pairs of factors control inherited traits(1male, 1female)
b. genes
c. 1 allele is dominant, 1 is recessive
d. dominate allele always ‘masks’ the recessive allele
 6. hybrid –
 7. What happens when plants have…
• a. 2 dominant alleles for tall stems…
• b. 1 dominant allele for tall,
1 recessive for short stems ...
• C. 2 recessive alleles for short stems…
 B. Symbols used
 1. parent generation –
 2. filial –
 3. dominant allele – upper case
 4. recessive allele – lower case
http://www.promotega.org/UGA06003/genetic_crosses.htm
http://www2.edc.org/weblabs/WebLabDirectory1.html
II. Probability and Genetics
A. Probability – likelihood that a certain event
will occur, events are independent of each other
B. Mendel was first to figure out…
C. Punnett Squares
1. chart that shows all possible outcomes of genetic
cross, each possible combination of alleles
2. predicts genetic possibilities
3. make sure you can read a Punnett Square! If
unsure, check pgs. 90-91
PUNNETT SQUARES
http://users.adelphia.net/~lubehawk/BioHELP!/psquare.htm

Baby Steps through Punnet Squares.url
D. Phenotypes and Genotypes
1. phenotype – physical appearance, trait, ex….
2. genotype – genetic makeup, allele combination,
ex….
a. homozygous alleles – both alleles are the same, TT
b. heterozygous alleles – alleles are different, Tt
E. Codominance
1. some alleles are not dominant or recessive
2. both alleles are expressed in offspring
3. codominant alleles are are written with a
superscript, for example…go to pg. 93
F. Meiosis
 1. 1903, Walter Sutton…
 2. sex cells – specialized cells that join together to form a
new organism,
 3. they only have ½ the number of chromosomes so that
when they join together…
 4. meiosis – process by which the number of
chromosomes is reduced by ½ to form sex cells
 5. similar to mitosis b/c chromosomes copy, line up on
spindle fibers, form new cells and separate
 6. different to mitosis b/c there are 2 divisions that result
in only ½ the number of chromosomes
 7. what/where is a gene?