2.1 Principles of Genetic Inheritance

Genetic inheritance is the foundation of human development. It's all about how traits are passed down from parents to children through DNA, genes, and chromosomes. Understanding these basics helps explain why we look and function the way we do.

Inheritance patterns like dominant and recessive traits determine which characteristics show up in offspring. Cell division processes like mitosis and meiosis are crucial for growth and reproduction, shaping how genetic information is passed on and mixed up between generations.

Genetic Basics

DNA, Genes, and Chromosomes

Top images from around the web for DNA, Genes, and Chromosomes

• 

  Chromosome Structure | Biology for Non-Majors I View original

  Is this image relevant?

• 

  The Nucleus and DNA Replication | Anatomy and Physiology I View original

  Is this image relevant?

• 

  Laws of Inheritance | Biology for Non-Majors I View original

  Is this image relevant?

• 

  Chromosome Structure | Biology for Non-Majors I View original

  Is this image relevant?

• 

  The Nucleus and DNA Replication | Anatomy and Physiology I View original

  Is this image relevant?

1 of 3

Top images from around the web for DNA, Genes, and Chromosomes

• 

  Chromosome Structure | Biology for Non-Majors I View original

  Is this image relevant?

• 

  The Nucleus and DNA Replication | Anatomy and Physiology I View original

  Is this image relevant?

• 

  Laws of Inheritance | Biology for Non-Majors I View original

  Is this image relevant?

• 

  Chromosome Structure | Biology for Non-Majors I View original

  Is this image relevant?

• 

  The Nucleus and DNA Replication | Anatomy and Physiology I View original

  Is this image relevant?

1 of 3

• DNA (deoxyribonucleic acid) contains the genetic instructions for the development, functioning, growth and reproduction of all known organisms
• DNA is made up of four chemical bases: adenine (A), guanine (G), cytosine (C), and thymine (T)
• Genes are segments of DNA that code for specific proteins and determine an organism's traits (eye color, height)
• Genes are located on chromosomes, which are thread-like structures located inside the nucleus of cells
• Humans have 23 pairs of chromosomes, for a total of 46 chromosomes

Alleles and Mutations

• Alleles are different versions of a gene that can result in variations in the trait controlled by that gene (brown eyes vs. blue eyes)
• Each individual inherits two alleles for each gene, one from each parent
• When the two alleles are different, one allele is expressed over the other (dominant vs. recessive)
• Mutations are changes in the DNA sequence that can lead to changes in gene function
• Mutations can be caused by errors during DNA replication or by environmental factors (UV radiation, chemicals)

Inheritance Patterns

Dominant and Recessive Traits

• Dominant traits are expressed when an individual has at least one dominant allele (brown eyes)
• Recessive traits are expressed only when an individual has two recessive alleles (blue eyes)
• Genotype refers to the genetic makeup of an individual, or the specific alleles they possess for a given trait (BB, Bb, bb)
• Phenotype refers to the physical expression of a trait, which is determined by the genotype (brown eyes, blue eyes)

Mendelian and Polygenic Inheritance

• Mendelian inheritance refers to the inheritance patterns first described by Gregor Mendel
• Mendel's laws state that traits are inherited in a predictable manner, with each parent contributing one allele for each trait
• Punnett squares can be used to predict the probability of offspring inheriting certain traits based on the genotypes of the parents
• Polygenic inheritance involves traits that are influenced by multiple genes (height, skin color)
• Polygenic traits often result in a continuous range of phenotypes rather than distinct categories

Cell Division

Mitosis and Meiosis

• Mitosis is the process by which a cell divides into two genetically identical daughter cells
• Mitosis is used for growth, repair, and asexual reproduction
• The stages of mitosis are: prophase, metaphase, anaphase, and telophase
• Meiosis is the process by which a cell divides into four genetically distinct daughter cells, each with half the number of chromosomes as the parent cell
• Meiosis is used for sexual reproduction and produces gametes (sperm and egg cells)
• The stages of meiosis are: meiosis I (prophase I, metaphase I, anaphase I, telophase I) and meiosis II (prophase II, metaphase II, anaphase II, telophase II)
• During meiosis, genetic recombination occurs, resulting in offspring with a unique combination of traits from both parents