Cell Cycle and DNA Structure

This page delves into the cell cycle, mitosis, and the structure of DNA. It provides a comprehensive overview of how cells divide and the organization of genetic material.

The cell cycle is explained, highlighting the different phases:

1. G1 - Everyday life of the cell
2. S - DNA synthesis and creation of sister chromatids
3. G2 - Preparation for mitosis
4. Mitosis - Cell division

Vocabulary: Chromatin is the loosely packed form of DNA in the nucleus, while chromosomes are the condensed form visible during cell division.

The guide then explores the organization of genetic material, from the organism level down to individual atoms. It introduces the concept of DNA as the "code of life" and explains its double helix structure.

Definition: The genome is all the DNA contained in one cell, which includes the complete set of instructions to create a whole new organism.

The Human Genome Project is mentioned as a significant achievement in genetics, having spelled out every nucleotide in the entire human genome.

Highlight: Genes are segments of DNA that code for proteins. A mutated gene has an incorrect sequence of nucleotides, which can lead to changes in protein structure and function.

DNA Structure and Replication

This section provides a detailed look at the structure of DNA and the process of DNA replication. It explains the components of DNA and how it serves as the blueprint for life.

Vocabulary: Nucleotides are the building blocks of DNA, consisting of a sugar, a phosphate group, and one of four nitrogenous bases: Adenine $A$, Thymine $T$, Cytosine $C$, or Guanine $G$.

The guide illustrates the molecular model of DNA, showing its anti-parallel strands and the complementary base pairing $A-T and C-G$. It then explains the process of DNA synthesis, which creates sister chromatids during cell division.

Example: DNA replication involves three main enzymes:

1. Helicase: Unwinds the DNA double helix
2. DNA Polymerase: Adds complementary nucleotides to create new strands
3. Ligase: Seals gaps in the newly synthesized DNA strands

The concept of leading and lagging strands in DNA replication is introduced, explaining why the lagging strand is synthesized in short fragments.

Highlight: The origin of replication $Ori site$ is a specific DNA sequence where helicase begins unwinding the double helix, initiating the replication process.

Protein Synthesis and RNA

This page focuses on the process of protein synthesis, explaining how the information in DNA is used to create proteins through transcription and translation.

Definition: Protein synthesis is the process by which cells build proteins based on the genetic information encoded in DNA.

The guide compares DNA and RNA, highlighting their structural and functional differences:

• DNA: Double-stranded, uses A, T, C, G bases, contains deoxyribose sugar
• RNA: Single-stranded, uses A, U, C, G bases, contains ribose sugar

Vocabulary: mRNA $messenger RNA$ carries genetic information from DNA to ribosomes, tRNA $transfer RNA$ brings amino acids to the ribosome, and rRNA $ribosomal RNA$ is a component of ribosomes.

The two main steps of protein synthesis are explained in detail:

1. Transcription: Copying a gene to create mRNA in the nucleus
2. Translation: Using mRNA instructions to build a protein at the ribosome

Example: During translation, codons $sequences of three RNA nucleotides$ are read by tRNA molecules, which bring the corresponding amino acids to build the protein chain.

The guide also introduces the concept of mutations, explaining how changes in the DNA sequence can affect protein structure and function.

Genetic Engineering and Gene Therapy

The final section of the study guide introduces concepts related to genetic engineering and gene therapy. It briefly touches on advanced topics in genetics research and application.

Definition: Gene therapy is a form of genetic engineering that aims to treat or prevent diseases by making edits to the human genome.

The guide mentions different types of mutations that can occur in DNA:

• Substitution
• Insertion
• Deletion
• Codon repeat

Highlight: Gene splicing, also known as genetic engineering, involves inserting favorable genes into an organism's genome to achieve desired traits or treat genetic disorders.

While the section is brief, it provides a foundation for understanding more advanced topics in genetics and biotechnology. These concepts are crucial for students interested in pursuing further studies in genetics or considering careers in fields such as genetic counseling or biomedical research.

Page 6: Mutations and Gene Therapy

This page explores various types of genetic mutations and introduces gene therapy concepts.

Definition: Gene therapy involves making targeted changes to the human genome to treat genetic conditions.

Vocabulary: Gene splicing refers to the process of inserting desired genes into an organism's genome.

Highlight: Multiple types of mutations can occur, including substitution, insertion, deletion, and codon repeat.

Gene Therapy and Splicing

This section explores modern genetic engineering techniques.

Definition: Gene therapy involves editing the human genome to treat medical conditions.

Highlight: Gene splicing allows the insertion of favorable genes into an organism's genome.

Example: Bacterial gene splicing involves extracting, cloning, and inserting genes using bacterial plasmids.

CRISPR Technology

This section details the revolutionary CRISPR-CAS9 gene editing system.

Definition: CRISPR-CAS9 is a precise gene editing tool that can modify specific DNA sequences.

Vocabulary: Guide RNA helps target specific DNA sequences for editing.

Highlight: CRISPR technology enables precise genetic modifications at exact locations in the genome.

Sex-Linked Disorders and Inheritance Patterns

This section explores the basics of sex-linked disorders and inheritance patterns. It explains the difference between male and female chromosomes and how this affects the inheritance of certain traits.

Definition: Sex-linked disorders are genetic conditions caused by mutations in genes on the sex chromosomes, particularly the X chromosome.

The guide discusses hemophilia as an example of an X-linked recessive disorder. It explains how males are more prone to X-linked disorders due to having only one X chromosome.

Example: In hemophilia inheritance, females can be carriers $XhX$ or affected $XhXh$, while males can be normal $XY$ or affected $XhY$.

The section also introduces the concepts of incomplete dominance and codominance, providing examples to illustrate these inheritance patterns.

Highlight: In incomplete dominance, neither allele is fully dominant, resulting in a blended phenotype in heterozygous individuals. This is exemplified by the petal color in 4 O'clock flowers.

Example: Codominance is illustrated using cat coat colors, where black $HBHB or HBh$ and rust $HRHR or HRh$ are both expressed in heterozygous individuals $HBHR$, resulting in a calico pattern.