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Heredity
Next Generation: HS.LS3.2 HS.LS3.2

Heredity

Description:

This lesson will introduce several basic genetic terms as well as examine some basic concepts of heredity.

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Tutorial

What's Covered

This lesson will cover the basics of heredity by looking at:

  1. Heredity
  2. Dominant and Recessive Traits

1. Heredity

Heredity is the passing of traits from parents to offspring. Gregor Mendel is considered the father of genetics because he did a lot of work with heredity and examined how information is passed through generations from parent to offspring. Mendelian inheritance is a term that was coined due to his research on pea plants. It describes how genes are passed from parents to offspring. Genes are found on chromosomes and are passed from parents to offspring. They contain information about specific traits. Some different types of inheritance include:

  • Autosomal dominant
  • Autosomal recessive
  • X-linked inheritance
  • X-linked dominant

Terms to Know

    • Heredity
    • The passing of traits from parents to offspring.
    • Gregor Mendel
    • Dubbed the "father of modern genetics" and arguably modern biology, Mendel was an Austrian monk who studied heredity and inheritance in plants.
    • Inheritance
    • Receiving genetic characteristics from parents, the manner in which genes are passed down to offspring.
    • Gene
    • A genetic unit of heredity; a specific section of DNA that codes for a specific protein.

Homologous chromosomes are chromosomes found within your cells that contain variations of the same information and are the same size and shape. A person will have one chromosome of this type from their mother and one from their father. A human has 46 total chromosomes in their body, 23 from each parent. Alleles are different versions of a gene, and you have two alleles for each trait, one on each homologous chromosome. The combination of alleles that you inherit will determine the outcome of that trait. A locus is a location on a chromosome where a trait will be located.

Example An example of a trait a person’s genes decides is their hairline. A person can have a straight hairline or they can have a widow's peak. This person has a pair of alleles at a specific locus, and each allele is a form of the gene for hairline.

Term to Know

    • Locus
    • The term used to describe the specific location of a gene/DNA sequence on a chromosome; variations of these genes are referred to as alleles.
    • Allele
    • Variation in a gene, an example would be eye color; there is a gene for eye color but there are different versions of genes that allow for different eye colors.

2. Dominant and Recessive Traits

Traits can be either dominant or recessive and recessive traits are only expressed when a dominant allele is not present. If a recessive allele is in the presence of a dominant allele, the dominant allele will always rule. There are three ways the mix of dominant and recessive alleles can present:

  • When there are two dominant alleles together, this is called homozygous dominant.
  • When there are two recessive alleles, this is homozygous recessive.
  • A person with both a recessive and dominant allele is heterozygous.

The prefix ‘homo’ means ‘“the same” and the prefix hetero means “different”

Terms to Know

    • Dominant Alleles
    • When one allele masks the expression of another on the same locus, this is seen at the phenotype level.
    • Recessive Allele
    • An allele that is masked by a dominant allele, recessive alleles are only expressed when they are found in homozygous pairs.
    • Homozygous
    • An organism with two identical alleles of a gene.
    • Heterozygous
    • An organism with two different alleles of a gene.
IN CONTEXT
In genetics letters are used to represent the combinations of alleles. A capital letter is used to represent an allele that is dominant, and a lowercase letter to represent a recessive allele. Assume that the gene for having a widow’s peak is dominant. Now, there are two parent that both have heterozygous alleles for a widow’s peak. What are the possible phenotypes, or the physical manifestation of the genes you inherit, for each genotype going to be?Genes.pngIf you have two parents that are both heterozygous, they could have children that are homozygous dominant, heterozygous, or homozygous recessive.

Terms to Know

    • Genotype
    • A trait or characteristic expressed at the genetic level, that is, the genetic makeup of an organism.
    • Phenotype
    • An observable characteristic of someone’s traits, examples: eye color, skin color, height, gender etc.

Summary

Heredity is the passing of traits from parents to offspring. Genes are the genetic information on chromosomes passes from parent to child, and alleles are the different versions of a gene. You inherited one from your mom, and one from your dad. Alleles can cause either dominant or recessive traits to be expressed. A dominate trait will always show if a person has the dominate allele. If a person is homozygous recessive, then the recessive trait will determine a person’s phenotype.

Keep up the learning and have a great day!

Source: SOURCE: THIS WORK IS ADAPTED FROM SOPHIA AUTHOR AMANDA SODERLIND

TERMS TO KNOW
  • Gene

    A genetic unit of heredity; a specific section of DNA that codes for a specific protein.

  • Allele

    Variation in a gene, an example would be eye color; there is a gene for eye color but there are different versions of genes that allow for different eye colors.

  • Locus

    The term used to describe the specific location of a gene/DNA sequence on a chromosome; variations of these genes are referred to as alleles.

  • Homozygous

    An organism with two identical alleles of a gene.

  • Heterozygous

    An organism with two different alleles of a gene.

  • Genotype

    A trait or characteristic expressed at the genetic level, that is, the genetic makeup of an organism.

  • Phenotype

    An observable characteristic of someone’s traits, examples: eye color, skin color, height, gender etc.

  • Dominant Alleles

    When one allele masks the expression of another on the same locus, this is seen at the phenotype level.

  • Recessive Allele

    An allele that is masked by a dominant allele, recessive alleles are only expressed when they are found in homozygous pairs.

  • Heredity

    The passing of traits from parents to offspring.

  • Gregor Mendel

    Dubbed the "father of modern genetics" and arguably modern biology, Mendel was an Austrian monk who studied heredity and inheritance in plants.

  • Inheritance

    Receiving genetic characteristics from parents, the manner in which genes are passed down to offspring.