Page 165 - Science Course 3 (Book 1)

Mo4-L5b: What Influences Traits?

Let’s Begin During fertilization, the egg cell chromosomes and
the sperm cell chromosomes combine to form an
offspring with a full set of paired chromosomes.

Combining Genes
In sexual reproduction, an egg cell and a sperm
cell each contribute one gene for a trait.

XX
X =
Sperm female

XY
Y =
Sperm Male

Meiosis is the process during which sperm and
egg cells form.
Zygote

Prophase 1 Because each sperm cell and egg cell is unique, the
resulting offspring is also unique.

Metaphase 1 Influencing Traits

An organism’s complete set of genes is its genotype.

Anaphase 1 The phenotype of a trait is how the trait appears, or
is expressed.

Telophase 1

Prophase 2

Genotype = bb Genotype = Bb or BB
Metaphase 2 Phenotype = Blue eyes Phenotype = Green eyes

Anaphase 2 Phenotypes result from the interaction of an
organism’s genes and its environment.

Telophase 2 Nutrients and other physical factors can cause
dramatic changes in the phenotype of some
organisms.
Daughter Health
cells
Disease
During meiosis, four new reproductive cells are
formed, each with a single set of chromosomes.
Nutritional Phenotype
Medicine Behavior
Genes Environment
Diet
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