KARYOTYPES & THE HUMAN GENOME

KARYOTYPES & THE HUMAN GENOME

To analyze chromosomes, scientists photograph cells while they are undergoing mitosis when the chromosomes are fully condensed & easy to see.

They then cut out the chromosomes from the photographs & arrange them together in homologous pairs.

KARYOTYPES & THE HUMAN GENOME

A picture of chromosomes arranged in this way is called a karyotype, like the picture at left.

KARYOTYPES & THE HUMAN GENOME

To review, humans have 46 chromosomes in each of our body cells & 23 in each of our sex cells.

Recall that the 23rd pair of chromosomes are called sex chromosomes & they determine a person’s gender.

Mutations can occur on any of our 23 pairs of chromosomes.

KARYOTYPES & THE HUMAN GENOME

Karyotypes play an important role in identifying genetic disorders, as they can give doctors a preview to the genome of an unborn child & help diagnose a disorder in someone who has physical or mental signs that there is something wrong with them.

GENETICISTS

A geneticist is a scientist that works in the laboratory doing molecular research or collecting and analyzing family histories and counseling families on genetic diseases & disorders.

They have the opportunity to discover new genes & can possibly help cure genetic disorders.

SEX-LINKED TRAITS

There is a special pattern of inheritance for genes located on the X and Y chromosomes.

Because their chromosomes determine one’s gender, genes located on these chromosomes are called sex-linked genes.

SEX-LINKED TRAITS

SEX-LINKED TRAITS

More than 100 sex-linked genetic disorders have now been mapped to the X chromosome.

The Y chromosome is much smaller than the X chromosome & appears to contain only a few genes.

SEX-LINKED TRAITS Males have only one

X chromosome, therefore all X-linked alleles are expressed in males, even if they are recessive traits.

Colorblindness, hemophilia and muscular dystrophy are considered sex-linked traits.

DNA ANALYSIS

Due to the great diversity of the human genome (all of the genes in a human’s body), we can be sure that no two individuals are exactly the same (except identical twins).

DNA ANALYSIS

DNA Fingerprinting is a specific form of genetic testing that analyzes sections of hair, blood, sperm or skin tissue to locate patterns of bands in the DNA that distinguishes one person from any other person in the world.

This often helps solve criminal cases or free someone who has been wrongfully accused and convicted of a crime.

DNA ANALYSIS

HUMAN GENOME PROJECT

This project is an ongoing effort to analyze the human genome in order to map genes & determine what causes certain diseases, to give us clues to some of the properties of life and to find information that may be useful in developing drugs & treatments for disease.

ETHICAL ISSUES

Many ethical issues exist in the advancement of genetics.

Scientists have determined that some cells (stem cells) can be manipulated with the hopes of one day curing diseases & disorders, however many people fear that cloning, harvesting stem cells from fertilized cells and other such genetic manipulations will result in a self-engineered society.

ETHICAL ISSUES