Biology DNA Profiling and tRNA Functions

Transfer RNA (tRNA)

• tRNA is produced in the nucleolus and assembled in the cytoplasm.
• It transports specific amino acids from the cytoplasm to ribosomes for protein synthesis.

DNA Profiling

• A unique pattern, or profile, is created from an individual's DNA to distinguish it from others.
• DNA is extracted from cells (e.g., blood, semen) by breaking the cell membrane.
• Polymerase Chain Reaction (PCR) amplifies DNA when initial quantities are low.
• Restriction enzymes cut DNA at specific sequences, often in non-coding regions known as junk DNA.
• Gel electrophoresis separates DNA fragments using an electric current; smaller fragments travel faster.
• DNA fragments are transferred to a nylon membrane and visualized using radioactive DNA markers, forming a bar-code-like pattern on X-ray film.
• Applications include identifying criminals in forensic contexts and determining paternity.

Genetic Screening

• Genetic screening detects the presence of specific alleles or genes in an individual's DNA.
• A DNA segment with a matching sequence, marked with radioactive or fluorescent labels, is hybridized to the person's DNA.
• Positive binding indicates the presence of the targeted gene, aiding in the diagnosis of inheritable diseases like cystic fibrosis and hemochromatosis.

Heredity and Gene Expression

• Heredity is the transmission of traits from one generation to the next through genes.
• Genes are DNA sequences on chromosomes that code for proteins or determine characteristics.
• Gene expression involves producing a feature or protein based on genetic information; dominance determines phenotypic outcomes (e.g., brown eyes are dominant over blue).

Chromosome Structure

• Each gene occupies a specific location called the locus on a chromosome.
• Genes have two forms, known as alleles, which can be dominant or recessive.
• Chromosomes consist of two chromatids connected by a centromere, condensing into visible structures before cell division.
• Chromatin refers to the relaxed form of chromosomes, made of DNA and histone proteins.

Structure of Deoxyribonucleic Acid (DNA)

• Discovered by James Watson and Francis Crick in 1951, DNA is a polymer of repeating units.
• DNA's structure is a double helix with sides made of alternating deoxyribose sugar and phosphate groups.
• Complementary bases (A-T and G-C) form the rungs of the helix, held together by hydrogen bonds.

Nucleotides

• Nucleotides are the building blocks of DNA, composed of a sugar, phosphate group, and a nitrogen base.

DNA Replication

• Occurs in the nucleus during interphase of mitosis and meiosis, requiring ATP and DNA polymerase.
• The DNA double helix unwinds and unzips to provide templates for new strands.
• Free nucleotides pair with existing strands, resulting in two identical DNA molecules, each consisting of one old and one new strand.
• DNA replication ensures accurate transmission of genetic information across generations.

Structure of Ribonucleic Acid (RNA)

• RNA differs from DNA: it contains ribose sugar instead of deoxyribose, uses uracil in place of thymine, and is typically single-stranded.
• Three types of RNA include:
  • Messenger RNA (mRNA): Carries genetic information from DNA to ribosomes for protein synthesis.
  • Ribosomal RNA (rRNA): A key structural component of ribosomes.

This quiz covers the functions of transfer RNA (tRNA) in the cytoplasm and the process of DNA profiling. Learn how tRNA collects amino acids for protein assembly and the unique patterning of DNA for individual identification. Test your understanding of these essential biological concepts.