Name: ________________________
Period: _______
HEREDITY NOTES – December 11, 2014
Heredity: the ________________________________ from parents to offspring.
Trait: A ____________________ or ___________________________ that describes an organism (Ex: height; eye color;
endurance)
Importance of Gregor Mendel
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Austrian botanist ______________
Mid ____________________
Formed the _______________________________________
His work laid the ___________________ to the study of heredity
Mendel is referred to as “_________________________.”
______________________ = study of genes, heredity, and genetic variation.
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Mendel studied _______________________.
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Observed differences in multiple traits over ________________________________, because pea plants
______________________________, and have _________________________________ such as: plant height,
seed color, pod color, seed shape, pod shape
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Mendel noticed that some plants always produced offspring that had a form of a trait exactly like the parent
plant (he called these “___________________”).
Example: Purebred short plants always produced __________ offspring and purebred tall plants always
produced ___________ offspring.
Mendel’s First Experiment:
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Mendel crossed __________________ plants with _______________________ of a trait.
Example: Purebred _______ plants were crossed with purebred _________ plants.
Mendel observed that ____________________________________________________________________.
None resembled the short parent.
P stands for “________________” and F# stands for “______________” (son).
Mendel’s Second Experiment:
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Mendel then crossed _____________________________________________ produced from his _________
experiment.
Offspring ratio in F2 generation = __________ tall and ___________ short
To his surprise, Mendel observed that this generation had a _________________________________, even
though ____________ of the F1 parents were short!
Mendel’s first law, the Law of Segregation, has three parts.
From his experiments, Mendel concluded that:
1. Traits are handed down through “____________________________” in the _________________________.
2. Because offspring obtain hereditary factors from both parents, each organism must contain
__________________________________________.
3. The factors in a pair segregate (____________________) during the formation of sex cells, and each sperm
or egg _______________________________________ of the pair.
Dominant and Recessive Alleles
One factor (gene) in a pair may ________________, or hide, the other factor.
Example: When he crossed a purebred tall plant with a purebred short plant, ___________________________
_______________________ even though all the F1 offspring should have both tall and short factors. (The
tallness factor masked the shortness factor.)
Genes: a _____________________________ that determines a ____________.
Alleles: the _____________________________ of a gene.
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Alleles are abbreviated with a ___________________.
Example:
T = allele for “tall” height
t = allele for “short” height
Every gene has _____________________ (1 from mom & 1 from dad).
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Alternative versions of genes (different alleles) result in __________________________ in inherited traits.
Example: The gene for flower color in pea plants exists in two versions, one for __________________
flowers and the other for _________________ flowers.
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Each ___________ resides at a ____________________________ on a ______________________________
(remember that there are multiple chromosomes)
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If the two alleles for a gene are different, the ______________________________ will determine the organism’s
appearance and “mask” the other allele.
- Dominant alleles are shown with a ___________________.
- Dominant alleles are “___________________.”
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The _____________________________ will only determine the organism’s appearance if both alleles on the
gene are recessive.
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Recessive alleles are shown with a _____________________.
Recessive alleles are “__________________.”
Mendel observed a variety of dominant alleles in pea plants other than the tall allele. For instance, a plant that is
heterozygous (Yy) for seed color will always have ________________ seeds (even though both color alleles are present).
However, a plant that is a heterozygous for pod color (Gg) always displays the _____________________ allele (even
though both color alleles are present).
In addition, round seeds are dominant over wrinkled seeds, and smooth pods are dominant over wrinkled pods.
Homozygous Genes
We know now that Mendel’s “purebred” plants had __________________________________ for a particular gene. The
modern scientific term for “purebred” is ___________________________.
Homozygous: having the ________________________ for a particular gene (NN or nn).
Example:
A homozygous tall plant has two tall alleles (_______) and will
only contribute a tall allele (T).
A homozygous short plant has two short alleles (_______) and
will only contribute a short allele (t).
Heterozygous Genes
When the two types of homozygous plants were crossed the offspring received ________________________ and
__________________________ from the parent plants.
All offspring contained both alleles (1 tall allele and 1 short allele).
Heterozygous: possessing _____________________________________________, one inherited by each parent (Nn).
Although the offspring have both a tall and a short allele, only the tall allele is expressed (the tall allele is
________________________ and “_____________” the short allele).
Genotype vs. Phenotype
Genotype: the ____________________ that an organism has for a trait.
(Example: AA, Aa, aa)
Phenotype: the _____________________ that the organism shows or “_____________________”.
(Example: Does the butterfly look dark or light in color?)
Law of Independent Assortment: Each pair of ___________________________________ of each other in the
production of __________________ (egg or sperm).
Example: Each sex cell will have only ______________________________________ (haploid). The plant will
donate either a yellow or green seed allele, or a wrinkled or a smooth pod shape. If the plant donates the
yellow seed allele it does not mean that it will also donate the wrinkled pod allele.
The donation of one allele from each pair is ___________________________________________.
Remember:
1) There are ___________________ for every ____________.
2) __________________ alleles are “stronger” and Capitalized.
3) __________________ alleles are “weaker” and lower-case.
4) Recessive traits will only be shown if both alleles are ______________________.
What are the possible allele combinations for these 2 plants?
Dominant trait: ____________________
Allele: ____
Recessive trait: ____________________
Allele: ____
Possible genotype combinations: _________________________
Possible phenotype combinations: ________________________