Ch. 14 The Human Genome

Ch. 14 Outline

14-1: Human Heredity Human Chromosomes Human Traits Human Genes From Gene to Molecule

Ch. 14 Outline

14-2: Human Chromosomes Human Genes and Chromosomes Sex-linked Genes X-Chromosome Inactivation Chromosomal Disorders

14-3: Human Molecular Genetics Human DNA Analysis The Human Genome Project Gene Therapy Ethical Issues in Human Genetics

Human Chromosomes

Karyotypes: A picture of chromosomes arranged by

homologous pairs Humans have 23 pairs (46 total) chromosomes. Two of the 46 chromosomes are called sex

chromosome because they determine and individual’s sex. In Human’s:

Female – Male –

Human Chromsomes

Autosomes: the remaining 44 chromosomes. They do not determine the sex of the organism.

All Human egg cells carry a single X chromosome.

Half of all sperm cells carry an X chromosome and half carry the Y. This is why the ratio of males to females

is 50/50.

Human Traits

Scientists use a pedigree chart to help study how a trait is passed from one generation to the next. Pedigree: chart that shows the

relationships within a family.

How to read a pedigree

A circle represents a female.

A square represents a male.

A horizontal line connecting a male and female represents a marriage.

A vertical line and a bracket connect the parents to their children.

A half-shaded circle or square indicates that a person is a carrier of the trait.

A completely shaded circle or square indicates that a person expresses the trait.

A circle or square that is not shaded indicates that a person neither expresses the trait nor is a carrier of the trait.

Pedigrees

These Charts are used to infer the genotypes of family members. They can reveal if traits are sex-linked, dominant or recessive.

Human Genes

Blood Group Genes Knowing a person’s blood group is

important during transfusions. Two blood groups:

Rh groups ABO groups

The Rh Blood Group

The Rh blood group is determined by a single gene with two alleles: Positive and negative Rh+ is dominant to Rh-

The Rh factor is named after the Rhesus Monkey where the factor was first isolated

Very important for females to know during pregnancies.

ABO Blood Groups

There are three alleles for the ABO Blood Group: IA, IB, I

“i” is the recessive allele. ii type O blood

IAIB are codominant type AB blood IAIA or IAi type A Blood IBIB or IBi type B Blood

ABO Blood Groups

Phenotype(Blood Type Genotype

Antigen on Red Blood Cell

Safe Transfusions

To From

Antigens and Blood

Disorders in Humans

Genetic Disorders may be caused by: Recessive Alleles

Ex. CF, PKU, Tay-Sachs Dominant Alleles

Huntington’s Disease Codominant Alleles

Sickle Cell Anemia

Concept Map

caused by

includeincludeinclude

AutosomolDisorders

Recessive alleles

Dominant alleles Codominant alleles

Albinism Galactosemia Tay-Sachs disease

Huntington’s disease

Sickle cell disease

Cystic fibrosis

Phenylketonuria Achondroplasia Hypercholes-terolemia

Sex-Linked Genes

Sex-linked genes: Genes Located on the sex chromosomes Many genes are located on the X

chromosome Sex-linked disorders are caused by

genes on the X or Y chromosome Colorblindness, Hemophilia

X-Chromosome Inactivation

Females have two X chromosomes but males only have one. How do females cells “adjust” to having an extra X if males can survive with just one? One of the X chromosomes in female cells

are randomly switched off. Those are called Barr bodies.

Chromosomal Disorders

Nondisjunction: failure of chromosomes to separate correctly in meiosis This leads to an abnormal number of

chromosomes in gametes Ex: Down Syndrome (3 copies of

chromosome 21 “trisomy”)

Nondisjunction

Homologous chromosomes fail to separate

Meiosis I:Nondisjunction

Meiosis II

The Human Genome Project

A research project to sequence (identify in order) all the bases in Human DNA ~3.2 BILLION pairs!

Some discoveries: A large amount of DNA does not code for

proteins Humans only have 30,000-40,000 genes

(scientists expected 100,000)

The Human Genome Project Website http://www.genome.gov/ Really interesting Information about the

Human Genome Project. It might help you understand stuff better.

EDUCATE YOURSELF!

Gene Therapy

Information about the human genome might be used to cure genetic disorders though the use of gene therapy.

Gene therapy: the process of changing a gene that causes a genetic disorder It replaces the faulty gene with a normal,

working gene

Ethical Issues

If Human cells can be manipulated to cure disease, should biologists try to engineer people with specific traits?

What will happen to the human species if we design our own bodies?

Should we clone humans?