Warm Up Things that are changed in an experiment are called the ___________________.

Chapter 14 Section 1: Human Heredity

Human Chromosomes Normal number of chromosomes –46 23 from haploid sperm 23 from haploid egg –2 are sex chromosomes Determine sex –Females 2 X chromosomes –Males 1 X and 1 Y –44 are autosomes All other chromosomes

Pedigree A pedigree is made to study inheritance of traits –A chart that shows relationships within a family

Standard Symbols Used in Pedigrees male female marriage/mating offspring individual showing trait being studied

Human Traits Genotypes in Pedigree chart –Can analyze offspring to determine genotype of parents… Recessive Disorder –Person with the disorder will be lowercase - rr Dominant Disorder –Person with the disorder will be either - Rr or RR

Blood Types Determined by three alleles (A, B and o) –A and B are: Codominant –O is: Recessive Produces no antigens Produces blood type O

Cystic Fibrosis Common genetic disease –Especially among people of Northern European descent Affects children: –Serious digestive problems –Produce thick mucus that clogs lungs and air passage Most cases caused by deletion of 3 bases in gene –Causes protein fold improperly

Sickle Cell Disease Common genetic disease: –Especially among people of African descent Red blood cells have a bent and twisted shape –Blood gets stuck in capillaries –Blood stops flowing –Causes damage to cells, tissues and organs Symptoms: –Physical weakness –Damage to the brain, heart and spleen Caused by substitution mutation

Sickle Cell Disease Malaria is common in Africa –Serious parasitic disease Heterozygote healthy –Resistant to malaria

Warm Up The alleles A and B are ______________. –A. Incomplete Dominant –B. Co-dominant –C. Dominant –D. Recessive

Sex-Linked Genes Special pattern of inheritance for genes located on sex chromosomes – Many more genes on X than on Y

Colorblindness Gene on X chromosome recessive If males (XY) have X chromosome with CB gene on it, they will be colorblind Most common form- –red green colorblindness (1 in 10 males) –Rare (1 in 100) in females

Hemophilia Genes for clotting found on X chromosome Cannot control bleeding, can bleed to death from a small cut Recessive Fails to make protein necessary to clot blood Affects 1 in 10,000 males

Duchenne Muscular Dystrophy Progressive weakening Loss of skeletal muscle 1 out of 3000 males affected Produces defective muscle protein

X-Chromosome Inactivation Multi-colored cats Females - XX chromosomes Males - XY chromosomes Females turn off one X chromosome –In cats In females, chromosomes in one part of the cat has gene for black spots and another part has gene for orange spots In males only have one X chromosome, so will have black spots or orange spots, not both

Chromosomal Disorders Meiosis works most of time –Sometimes things go wrong Nondisjunction –Chromosomes fail to separate Trisomy –3 copies of chromosome instead of 2

Down Syndrome Trisomy of chromosome 21 Affects one in 800 babies Produces mild to severe mental retardation Increased susceptibility many disease and other birth defects

Sex Chromosome Disorders Turner’s Syndrome –Female –One X chromosome –Sterile Klinefelter’s Syndrome –Male –Multiple X and one Y chromosomes –Usually sterile XYY can also occur No know instances of individuals born without X chromosome

Testing for Alleles If couple decides that they want to have children, and think that they may have genes for a genetic disorder they may elect to have genetic testing –Test for defective base sequences –Available for hundreds of disorders

Searching for Genes Only small part of genome is made up of genes –Only about 35,000 total Technique for finding genes: –Find promoters (where RNA polymerase binds) Indicates beginning of a gene –Just after promoter there is an open reading frame Produces mRNA sequence This sequence codes for amino acids

Gene Therapy Information from Human Genome Project can be used to cure genetic disorders –Gene therapy Changing the gene that causes a genetic disorder by replacing faulty gene with normal, working gene Not known how long the beneficial effects will last –Cystic fibrosis gene therapy last only a short while Uses viruses to insert the working gene into the DNA

Warm Up Which sex chromosome contains the sex linked disorders?