HeredityHeredity

Objective 8Objective 8Describe the function of Describe the function of

chromosomes.chromosomes. Identifying genes as parts of Identifying genes as parts of

chromosomes that carry genetic chromosomes that carry genetic traits.traits.

In the past, traits were thought In the past, traits were thought to be carried by the blood.to be carried by the blood.

We now know what genes are We now know what genes are responsible for certain traits and responsible for certain traits and that the genes are in every cell.that the genes are in every cell.

We have used this information We have used this information and completed the Human and completed the Human Genome project. The mapping Genome project. The mapping out of the human DNA.out of the human DNA.

Pass it onPass it onEvery organism requires Every organism requires a set of instruction for a set of instruction for specifying its traits. specifying its traits. Heredity is the passage of Heredity is the passage of these instruction from one these instruction from one generation to another.generation to another.

HeredityHeredity

The passing The passing of traits from of traits from parent to parent to offspring.offspring.

Let’s consult with Tim and Let’s consult with Tim and Moby.Moby.

Heredity film.Heredity film.

Heredity information is Heredity information is contained in genes, contained in genes, located in the located in the chromosomes of each chromosomes of each cell. cell.

Each gene carries a Each gene carries a single unit of single unit of information. information.

ChromosomesChromosomesThey are composed of They are composed of genes that provide the genes that provide the instruction for making instruction for making all the proteins in an all the proteins in an organism.organism.

During cell division, During cell division, the duplicated the duplicated chromosomes separate chromosomes separate so that one copy of so that one copy of each chromosomes is each chromosomes is present in the two new present in the two new cells.cells.

This photomicrograph shows a specialized This photomicrograph shows a specialized type of giant chromosomes called polytene type of giant chromosomes called polytene chromosomes. Polytene chromosomes chromosomes. Polytene chromosomes occur in many species of two-winged flies. occur in many species of two-winged flies.

Homologous chromosomesHomologous chromosomes

Chromosomes that Chromosomes that have the same have the same sequence of genes sequence of genes and have the same and have the same structure.structure.

Down syndrome is Down syndrome is often called often called Trisomy 21 Trisomy 21 because most because most people with this people with this condition have condition have three copies of the three copies of the number 21 number 21 chromosome. chromosome. Down syndrome Down syndrome almost always almost always results in mental results in mental retardation, retardation, though the though the severity of the severity of the retardation varies. retardation varies.

GenesGenesSegments of DNA that Segments of DNA that carry hereditary carry hereditary instructions and are instructions and are passed from one parent passed from one parent to offspring; located on to offspring; located on the chromosome.the chromosome.

Let’s watch Tim and Moby give Let’s watch Tim and Moby give information about Genes.information about Genes.

AllelesAllelesDifferent forms Different forms of a single gene of a single gene or Alternate or Alternate forms of a gene. forms of a gene.

Alleles exampleAlleles exampleFor example, a mother might pass on For example, a mother might pass on

a gene for blue eyes to her offspring, a gene for blue eyes to her offspring, and the father might pass on a gene and the father might pass on a gene for brown eyes. Each parent passes for brown eyes. Each parent passes on one allele to the offspring. Each on one allele to the offspring. Each offspring has two alleles for each trait offspring has two alleles for each trait such as eye color. The expression of such as eye color. The expression of physical characteristics depends on physical characteristics depends on the genes contributed by both parents the genes contributed by both parents for that particular characteristic.for that particular characteristic.

An inherited trait of an An inherited trait of an individual can be individual can be determined by one or by determined by one or by many genes, and a singles many genes, and a singles gene can influence more gene can influence more than one trait. A human cell than one trait. A human cell contains many thousands of contains many thousands of different genes.different genes.

TraitsTraitsinherited inherited characteristic: characteristic: a quality a quality or characteristic that is or characteristic that is genetically determined.genetically determined.

Dominant TraitDominant Trait

The trait observed The trait observed when at least one when at least one dominant allele for a dominant allele for a characteristic is characteristic is inherited.inherited.

Recessive TraitRecessive TraitA trait that is apparent A trait that is apparent only when two only when two recessive alleles for the recessive alleles for the same characteristic are same characteristic are inherited.inherited.

Albinism, the Albinism, the lack of normal lack of normal pigmentation, pigmentation, occurs in all occurs in all races. A rare races. A rare condition, condition, albinism occurs albinism occurs when a person when a person inherits a inherits a recessive allele, recessive allele, or group of or group of genes, for genes, for pigmentation pigmentation from each from each parent. parent.

Human Genome ProjectHuman Genome ProjectCCompleted in 2003, the Human ompleted in 2003, the Human

Genome Project (HGP) was a 13-year Genome Project (HGP) was a 13-year project coordinated by the U.S. project coordinated by the U.S. Department of Energy and the Department of Energy and the National Institutes of Health. National Institutes of Health.

Project Project goals were to were to

identifyidentify all the approximately 20,000-25,000 all the approximately 20,000-25,000 genes in human DNA, genes in human DNA,

determinedetermine the sequences of the 3 billion the sequences of the 3 billion chemical base pairs that make up human chemical base pairs that make up human DNA, DNA,

storestore this information in databases, this information in databases, improveimprove tools for data analysis, tools for data analysis, transfertransfer related technologies to the private related technologies to the private

sector, and sector, and addressaddress the ethical, legal, and social issues the ethical, legal, and social issues

(ELSI) that may arise from the project. (ELSI) that may arise from the project.

What are some practical What are some practical benefits to learning about benefits to learning about

DNA?DNA?Knowledge about the effects Knowledge about the effects

of DNA variations among of DNA variations among individuals can lead to individuals can lead to revolutionary new ways to revolutionary new ways to diagnose, treat, and someday diagnose, treat, and someday prevent the thousands of prevent the thousands of disorders that affect us. disorders that affect us.

The endThe end