Human Genetics & Genetic Engineering Notes CP BIOLOGY MS. MORRISON

Human Chromosomes Karyotypes = picture of chromosomes lined up by size and grouped in pairs (use cells in mitosis since this is only time can see individual chromosomes)

Human Chromosomes 46 chromosomes = 23 pairs Pairs 1-22 = autosomes Pair 23 = sex chromosomes, determine individual’s gender XX = female, XY = male 50%/50% chances of female/male zygotes

Human Chromosomes XX XXX YXY

Pedigree Charts Shows the relationship within a family Used to study how a trait is passed from one generation to the next Often used to track diseases or genetic disorders in a family

Pedigree Charts

Males shown as squares Females shown as circles Individuals with trait of interest are shaded Heterozygous individuals have only half of square or circle shaded Horizontal lines connect mating couples Vertical lines connect to their offspring Oldest generation is the top level

Types of Genetic Disorders Recessive – must have both recessive genes to have disorder, ex. PKU, Tay Sachs, cystic fibrosis Dominant – only need one dominant allele, ex. dwarfism, Huntington’s Codominant – both alleles expressed, ex. Sickle-cell

Sex-Linked Traits/Disorders Sex-linked genes = genes located on the sex chromosomes Y chromosome much smaller than X so many genes only found on X Males express all X-linked alleles since they have only one X chromosome – even recessives Ex. Color blindness, hemophilia

Chromosomal Disorders Result when chromosomes do not separate correctly during meiosis Most common error = nondisjunction – chromosomes do not separately properly and results in abnormal number of chromosomes in gametes Ex. Down syndrome = Trisomy 21, have 3 copies of chromosome 21

Genetic Engineering Earliest types – selective breeding – allowing only certain plants or animals to breed in order to pass on desired traits Today – involves recombinant DNA technology which means altering genes in a living organism to produce organisms with new genotypes

Types of Genetic Engineering Techniques DNA extraction – opening cell to separate DNA from rest of cell parts Restriction enzymes – used to cut DNA at specific points to make small fragments Gel electrophoresis – used to separate DNA fragments on the basis of their length

Benefits of Gel Electrophoresis Compare genomes of different organisms Compare genes of different individuals (forensics and paternity) Locate and identify particular gene

PCR (Polymerase Chain Reaction) Process used to amplify or clone very small samples of DNA so enough of DNA to study

DNA Sequencing Read base sequence of a DNA fragment Once know sequence – then amino acid sequence is known for protein it codes for Known DNA sequences can be compared among individuals of same species and of different species

Recombinant DNA Used to transform the DNA of a cell (often a bacterium) so that it takes in a piece of DNA from outside the cell and incorporates it into its DNA

Reasons for using Genetic Engineering Genetically modify bacteria to produce chemicals for medical or industrial applications, ex. Human insulin, growth hormone Alter the characteristics of organisms, ex. Long-life tomatoes, disease- resistant crops Gene therapy – insert gene to replace missing or defective gene