Download Genes and Traits Handout

Genes and Traits
Name:
Date:
Part 1: Genetics:
Fill in the blanks from viewing the presentation.
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Genetics is the study of how traits are inherited in offspring.
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Gene: Segment of chromosome (DNA) that codes for a trait
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Allele: Different form of the same gene.
Example: Skin Color (Color, Albino)
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Humans normally have two alleles for each gene.
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Dominant allele: A (Capitol Letter)
Recessive allele: a (Lowercase Letter)
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Dominant: Trait that gets expressed from dominant allele.
Recessive: Trait only gets expressed when there are no dominant alleles.
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Phenotype: Observable physical or behavioral trait
Genotype: Genes (Alleles) that code for a trait
Part 2: Corn Planting and Observations
Follow directions from your teacher for planting corn.
Problem: How are traits inherited in corn?
Observation: Some corn is yellow, some corn is white.
Predict: Which is the dominant trait? Albino or normal color? _______________________
Complete a Punnett Square below to find the answer:
Pd:
Genes and Traits part 2
Name:
Date:
Pd:
Part 1: Basic Genetics part 2:
Fill in the blanks from viewing the presentation.
Homozygous: having the same forms (alleles) for a gene on both chromosomes.
Also said to be purebred.
Homozygous Dominant = AA
Homozygous Recessive = aa
Heterozygous: having different forms (alleles) for a gene on both chromosomes.
Also said to be hybrid.
Heterozygous = Aa, or aA
Monohybrid Crosses
Gene: Albinism
Dominant Allele: A = normal skin color
Recessive Allele: a = albino
Cross a heterozygous individual with a heterozygous individual: Aa X Aa
A
a
A
AA
Aa
a
Aa
aa
Cross a homozygous dominant individual with a homozygous recessive individual: AA X aa
a
a
A
Aa
Aa
A
Aa
Aa
Test Cross: Cross a homozygous recessive individual with an unknown (homozygous dominant or
heterozygous): aa X A?
A
A
a
Aa
Aa
a
Aa
Aa
A
?
a
Aa
a?
a
Aa
a?
A
a
a
Aa
aa
a
Aa
aa
The outcome determines the offspring. If half of the offspring are albino, then the unknown is
heterozygous (Aa). If all of the offspring have normal skin color, then the unknown is homozygous
dominant.