Genetics
Genetics is the field of science that studies heredity, which is the passing on of
________________________________ from parent to offspring.
Every single one of your cells (with two exceptions) contains ____________________________ that came
from your parents.
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The two exceptions are the sperm and the egg (ovum) = sex cells = _________________________
Your cells have 23 pairs of chromosomes. The pairs are called __________________________
___________________________. These
chromosomes contain
_________________________
____________________________________.
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Your genetic information
(__________________________)
determine the traits that will appear in
your offspring. Your genetic information
was inherited from your parents!
A _________________ is an inherited characteristic or a feature.
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tall/short plants
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purple/yellow flowers
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green or brown eyes
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Red hair/brown hair
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Can taste/can’t taste cilantro
Genes are arranged next to each other in a sequence along a chromosome
Homologous chromosomes contain the SAME genes
(example: your hair color) but one chromosome may
code for _________ hair and the other may code for
_________ hair. These are alternate forms of the hair
color gene.
An __________________is one of two or more
alternative forms of the same gene.
Alleles of the same gene occupy the same site of the homologous chromosomes
When the sperm and the egg (gamete) fuse together during ____________________, the traits and
characteristics of diploid organisms are determined by the ________________________
___________________________________.
Alleles that we see in genetics come from gametes (sex cells)!
During sexual reproduction, the allele that contains the trait is generated randomly.
Alleles can be either ____________________________
or ____________________________.
Gregor Mendel observed the breeding of pea-plants. His early work with pea plants explains how traits are
passed on from one generation to the next. He looked at many traits and how they changed from one
generation to the next as he self-fertilized plants.
Each of the traits that Mendel studied had two different forms (alleles) - these are generated randomly during
sexual reproduction.
Pairs of alleles are designated as Homozygous or Heterozygous:
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________________________ = 2 identical alleles for a trait (TT or tt)
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________________________ = 2 different alleles for a trait (Tt)
Generations of Pea Plants
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P = parent generation
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F1 = First generation offspring
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F2 = Second generation offspring
Mendel’s Experiment
TT x tt
________________ pea plant crossed
with a ________________ pea plant.
The Law of Segregation states that the 2 alleles _______________________ during meiosis.
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Each gamete will only receive one allele because the alleles are on separate homologous
chromosomes.
The principle of dominance states that ________________________________________ even if only one
dominant allele is present.
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Ex: Tall allele (T) is dominant, short allele is recessive (t)
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F1 generation = All plants were tall even though Tt.
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Conclusion = both TT and Tt plants are ________________
Recessive traits will only be shown if __________________ recessive alleles are present.
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Conclusion = only tt plants are ____________________.
We can use the Principle of Dominance to explain why genotype differs from phenotype.
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_______________ = the genetic material passed on between generations (TT or Tt or tt) (What genes
are in the organism)
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_______________ = the observable characteristics or traits of an organism (Tall or Short plant)
(What we see in an organism - example: blonde hair, brown eyes etc.)