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.

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.