Unit 4 Genetics Ch. 14 The Human Genome

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

Human Chromosomes Karyotype - a picture of chromosomes arranged in pairs

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

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

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

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

Human Genes Many genetic disorders are caused by autosomal recessive alleles

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)

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

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

Cystic Fibrosis

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)

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

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

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

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

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

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

DNA Fingerprinting

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

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

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?