1. Unit 4 Genetics
Ch. 14 The Human Genome

2. Human Chromosomes
To analyze chromosomes, biologists photograph cells in mitosis
They then cut out the chromosomes from the photograph, & group them together in pairs

3. Human Chromosomes
Karyotype - a picture of chromosomes arranged in pairs

4. Human Chromosomes
Sex chromosomes - 2 of the 46 chromosomes, that determine an individual’s sex
Females: XX
Males: XY
Autosomes - remaining 44 chromosomes

5. Human Traits
Pedigree - chart that shows the relationships within a family

6. Human Traits
Remember that the phenotype of an organism is determined by its genotype
Also, that environmental effects on gene expression are not inherited, genes are

7. Human Genes
The human genome, our complete set of genetic information, includes 10’s of 1000’s of genes
The DNA sequences on these genes carry information for specifying many characteristics

8. Human Genes
Many genetic disorders are caused by autosomal recessive alleles

9. Human Genes
However, some genetic disorders may be caused by a dominant allele
Ex.) Dwarfism, Huntington’s Disease (loss of muscle control, & mental function until death occurs)

10. From Gene to Molecule
In cystic fibrosis, & sickle cell disease, a small change in the DNA of a single gene affects the structure of a protein, causing a serious genetic disorder

11. From Gene to Molecule
Cystic fibrosis is caused by the deletion of 3 bases in the DNA of a single gene
As a result, the body does not produce a protein needed to transport chloride ions
CF causes serious digestive & respiratory problems

12. Cystic Fibrosis

13. From Gene to Molecule
Sickle cell disease is common in African Americans
It is characterized by the bent & twisted shape of the red blood cells
The cells get stuck in the capillaries, damaging cells, tissues, & organs
It causes physical weakness, & damage to the brain, heart, & spleen (may be fatal)

14. Human Genes & Chromosomes
Genes located close together on the same chromosome are linked, so they tend to be inherited together
Linked genes may be separated, however, during crossing-over

15. Sex-Linked Genes
Sex-linked genes - genes located on the sex chromosomes
Males have 1 X chromosome, therefore, all X-linked alleles are expressed in males, even if they are recessive

16. Sex-Linked Genes
Ex. of sex-linked disorders: colorblindness, hemophilia, muscular dystrophy

17. Chromosomal Disorders
Nondisjunction - when homologous chromosomes fail to separate during meiosis
If it occurs, abnormal #’s of chromosomes could find their way into gametes, & a disorder of chromosome #’s may result

18. Chromosomal Disorders
Down Syndrome results when there is an error on chromosome 21

19. Human DNA Analysis
DNA Fingerprinting - (Gel Electrophoresis), analyzes sections of DNA that vary from one individual to another

20. DNA Fingerprinting

21. The Human Genome Project
Genome- the entire genetic makeup of an organism
The Human Genome Project is an ongoing effort to analyze the human DNA sequence
Biotechnology companies are rushing to find genetic info. that may be used
in developing new drugs &
treatments for diseases

22. Gene Therapy
In gene therapy, an absent or faulty gene is replaced by a normal, working gene
Viruses are often used because they can enter cells so easily

23. Ethical Issues in Human Genetics
The goal of biology is to gain a better understanding of the nature of life
As our knowledge increases, so does our ability to change the genetics of living things, including humans
What will happen to the human species if we design our bodies?