DNA Structure and Extraction

Structure of DNA

• DNA is stored in the nucleus and controls all cellular activities
• A gene is a DNA segment coding for a specific protein, located on a chromosome
• The genome comprises the complete genetic instructions for an organism
• Chromosomes consist of tightly wound and packaged DNA; humans have 46 chromosomes (23 from each parent)
• DNA, or deoxyribonucleic acid, is a double helix structure that provides instructions for building proteins
• A double helix consists of two chains twisted together, with base pairs forming the rungs

Bases and Nucleotides

• Four bases: Adenine, Cytosine, Guanine, and Thymine, joined in pairs by hydrogen bonds
• A nucleotide includes deoxyribose sugar, phosphate, and a nitrogen base

DNA Extraction Steps

• Crushing strawberries helps break open cell walls, releasing DNA-containing nuclei
• Detergent breaks down fatty and nuclear membranes, releasing DNA into solution
• Salt causes DNA molecules to stick together and separate from proteins
• Gauze retains strawberry cell debris, cell membranes, and cell walls with DNA
• Ethanol precipitates DNA because DNA is insoluble in alcohol, inhibiting enzyme activity

Karyotypes and Homologous Pairs

• A karyotype is a photograph of all chromosomes arranged in homologous pairs including autosomal and sex chromosomes
• Homologous pairs are chromosomes with the same length/banding pattern carrying genes for the same characteristics at a particular location or locus

DNA Replication and Cell Division

• The cell cycle is the repeated process of cell growth and division
• Helicase unwinds and unzips DNA by breaking hydrogen bonds between base pairs and rewinds the double helix after replication
• DNA polymerase links new complementary nucleotides to form new DNA strands
• The centromere is the central point of a chromosome that holds sister chromatids together during cell replication
• Mitosis produces identical cell copies for body growth, tissue repair, and cell replacement, generating two diploid daughter cells
• During interphase, the cell functions normally and duplicates DNA, resulting in two copies of each chromosome
• Meiosis produces gametes through fertilization, where two gametes from two parents fuse to form a zygote

Introduction to Genetics

• An allele is a version of a gene that codes for a specific characteristic
• Autosomal inheritance transmits traits located on autosomal chromosomes
• X-linked inheritance transmits traits via the sex chromosome
• An amino acid is a small molecule that forms proteins, the building blocks of cells
• The genotype is a pair of alleles influencing a particular trait's appearance
• The phenotype is the collection of observable traits in an organism
• Mutation is a permanent change in the base sequence of a gene

Discovery of DNA and the Human Genome Project

• Rosalind Franklin's X-ray diffraction images were crucial in understanding DNA's structure
• James Watson and Francis Crick, using Franklin's data and Maurice Wilkins' work, proposed the double helix structure in 1953.
• The human genome project aimed to sequence all four bases in the entire human genome

Ethical Considerations of the Human Genome Project

• Publicly accessible genome data raises privacy and discrimination risks for job enrollment and health insurance
• Interpreting genetic test results can be difficult because cancer gene mutation presence may only indicate risk
• Incidental findings in research can uncover unrelated health problems during whole-genome analysis

Bioinformatics and Genetic Testing

• Bioinformatics stores and analyzes vast amounts of DNA sequence data using software and supercomputers
• This facilitates rapid data analysis and global accessibility, promoting faster treatment development
• Genetic testing is used for early diagnosis and allows informed decisions about reproduction and disease prevention

Pros and Cons of Genetic Testing

• Pros include early diagnosis, informed reproduction decisions, and achieving personal goals
• Cons include potential depression, discrimination, and relationship struggles

Pre-Implantation Genetic Diagnosis (PGD)

• PGD uses IVF to fuse sperm and egg outside the body in a controlled environment
• Embryos grow in the lab for a few days, then a cell is removed for genetic testing without harming the remaining cells
• Genetic analysis detects chromosomal abnormalities before implantation
• Healthy or desired trait embryos are selected for implantation, while others are discarded

Recommendations for PGD

• Either or both partners carrying gene mutations to avoid passing serious genetic diseases e.g. cystic fibrosis or spinal muscular atrophy
• Either partner has a chromosome rearrangement (translocation) leading to miscarriage or health problems in offspring
• A previous pregnancy has been affected by a chromosomal mutation
• Advanced maternal age (over 38 years old), recurrent miscarriage, or repeated IVF failure
• PGD prevents genetic diseases like cystic fibrosis, Down syndrome, Alzheimer's, and Huntington's

Benefits of PGD

• PGD Prevents suffering, allows parents to give their child a healthy life and can increase human life span up to 30 years
• Preventing genetic diseases saves family and government money on diagnosis and treatment
• The embryos could be accidentally terminated (killed) if the process is not done carefully
• The technology used is not 100% safe yet
• Children are already engineered by parents in many ways. Prenatal supplements, education, religion and morals
• Taking folate during pregnancy reduces risk of a a child developing autism, and it is considered ethically acceptable
• A complete ban will increase the demand and send people to unauthorized biologists or overseas to receive the same treatment that US is capable of