Gene Expression/ Inheritance Patterns

High School Biology

Mr. Walker

Objective 6: Explain how the environment can influence the expression of traits.

Students will be able to:

1) Explain how and why genes are expressed.

2) Provide examples of internal factors which can influence gene expression.

3) Provide examples of external factors which can influence gene expression.

4) Describe how a cell uses different genes to function.

5) Describe how one gene can produce several different types of proteins.

Genes: 1) Explain how and why genes are expressed.

• Genes are segments of DNA that code for a protein or are the instructions on how to build an organism.
• Exons are expressed DNA. They are the genes which are the code or blueprint of every organism.
• Introns are internal DNA which isn’t used as a code or blueprint. They are leftover genetic code from mutations.
• Genes get expressed by transcription and translation. (How)
• Genes get expressed because our bodies produce proteins called enzymes which will bind to the gene and build the proteins which they are the code for. (Why)

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Genes (Dominant/Recessive)

• Expressed genes can be dominant or recessive
• Dominant genes can stop recessive genes from being expressed.
• Individuals can have 2 dominant genes which are trying to be expressed.

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Incomplete dominance

• The phenotype of the offspring is a mix between the two genotypes of the parents. Example: a red flower x a white flower= a pink flower

Codominant Alleles

• Causes the offspring to have both genotypes which are equally expressed. Example: a Black rooster x a white chicken= a checkered rooster.

Polygenic Inheritance

• The pattern controlled by two or more genes.
• Example: height in humans, Skin color.

• Traits can have more than 1 allele.
• Example is blood type
• 4 types of blood

Multiple alleles

Why do muscle cells differ from skin cells?�4) Describe how a cell uses different genes to function

-All body cells have ALL the chromosomes. They have ALL the DNA. They have ALL the genes.

-Each cell type (skin, muscle, nerve, etc) expresses genes that they need.

-Cells can have all the DNA but not express all the different genes.

-With the expression of specific genes, our cells can build the structures which they need to function properly.

Influences in Gene Expression

2) Provide examples of internal factors which can influence gene expression.

3) Provide examples of external factors which can influence gene expression.

• Internal Factors:
• Proteins, mRNA, organelles, and other substances are not evenly distributed in cells. These regulate gene expression differently and can create different types of cells.
• Cells communicate with each other by sending/receiving messages in the form of molecules. These molecules can turn genes on and off.
• Examples of internal factors which influence gene expression include, the period of development, age, hormones being released, gender.
• External Factors:

-The environment around the organism can influence the genotype. Example: Arctic Fox

-The presence of drugs and chemicals can change gene expression (depression medicines etc)

-The amount of light can affect the color of butterflies when they develop as caterpillars

-The outside temperature can turn off the genes for dark fur color and turn on light fur color in some organisms.

5) Describe how one gene can produce several �different types of proteins.

• Proteins are chains of amino acids. These chains are put together in a specific shape at a ribosome. Each combination and each new shape makes a different protein.
• One amino acid change can be shaped into hundreds of different types of proteins, even if they have the same amino acid sequence.

Protein 1:

Protein 2:

Protein 3: