Download Chapter 3 Genetics

Chapter 3 Genetics
3-1
Examples:
Traits=
Purebred=
Alleles=
Recessive allele=
Heredity =
Genes=
Dominant allele=
Hybrids=
Gregor Mendel: a priest who studied how physical characteristics were passed down to
offspring in pea plants.
-his work/ideas formed the foundation of genetics.
-he is known as the Father of Genetics
Experiment:
Mendel crossed purebred plants (Parental or P generation) with opposite traits to see what the
offsprings’(first filial generation F1) traits would be.
Mendel’s results:
- he saw the same results in all the experiments
- he crossed purebred plants which had opposite traits
-in first filial generation, one trait was evident and the other had disappeared
- in the second filial generation (F2), one trait showed up in ¾ of the offspring, and the
other trait reappeared but only in ¼ of the offspring.
Conclusion:
- individual factors must control the inheritance of traits, the traits exist in pairs with
each parent contributing one of the pair. (Later called genes.)
-one factor can mask or hide another factor. (Dominant can cover the recessive allele)
Helpful Tip:
Geneticist use symbols to represent alleles in genetic crosses. Capital letter for the dominant
allele and lower case for the recessive allele.
-ex: TT means two dominant alleles; tt means two recessive alleles;
Tt means one dominant allele and one recessive allele
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Examples:
Probability=
Punnett square =
Phenotype =
Genotype =
Homozygous =
Heterozygous =
Codominance =
Mendel was the first scientist to recognize that the principles of probability can
be used to predict the results of genetic crosses.
Punnett Squares:
-used to show all the possible outcomes of a genetic cross and to determine the
probability of a particular outcome.
- possible alleles from one parent across the top, the alleles from the other parent
on the side.
-boxes represent all the possible combinations.
PRACTICE: