Mitosis and Meiosis

• Mitosis is a process where one cell divides into two identical cells, also known as cell reproduction or cell division.
• Mitosis is essential for growth and repair in organisms.
• DNA replication during mitosis ensures each new cell receives all the necessary genetic information to function correctly.
• The original cell undergoing mitosis is called the parent cell.
• The two new cells produced through mitosis are called daughter cells, and they are identical to each other and the parent cell.
• Meiosis is a process that produces sex cells, where male and female cells combine to create a unique offspring.
• Meiosis occurs for the purpose of creating new organisms.
• Karyotypes are organized displays of an individual's chromosomes, used to study chromosomal abnormalities.
• Haploid refers to having half the usual number of chromosomes, typically in sex cells.
• Diploid refers to having the full, or doubled, set of chromosomes, typical in somatic cells.
• DNA is stored in the form of chromosomes.
• Chromosomes exist in pairs called homologous chromosomes.
• "Homo" means "same," indicating that homologous chromosomes carry the same types of genes.
• Chromosome pairs 1-22 are autosomes, or non-sex chromosomes.
• Pair 23 determines sex, with XX for females and XY for males.
• A karyotype provides an image of an individual's chromosome pairs.
• Non-disjunction mutations occur when chromatids fail to separate during cell division, leading to cells with an incorrect number of chromosomes.
• Aneuploidy means a cell has an abnormal number of chromosomes.
• Monosomy indicates a missing chromosome.
• Trisomy indicates an extra chromosome.

Mutations

• Mutations are mistakes that happen during DNA replication, such as the addition or deletion of a nucleotide.
• Mutations can be either spontaneous or induced.
• Spontaneous mutations are random errors in DNA replication during cell division with no identifiable cause.
• Induced mutations are errors in DNA replication caused by exposure to mutagens like x-rays, ultraviolet radiation, viruses, and certain chemicals.
• Altering the genetic code through mutations can change the protein a gene creates, with potential effects being beneficial, harmful, or neutral.
• Mutations in sex cells are passed down to offspring, while those in somatic cells are not inherited.
• All alleles, or variations of genes, originate from mutations.
• Three types of mutations exist: substitution, insertion, and deletion.
• Substitution involves adding the wrong nucleotide.
• Insertion involves adding an extra nucleotide.
• Deletion involves missing a nucleotide.

DNA, Genes, and Chromosomes

• DNA (deoxyribonucleic acid) is a complex polymer carrying the genetic code.
• It acts as instructions on how to make a body.
• DNA consists of two strands intertwined into a double helix.
• The strands have a sugar-phosphate backbone.
• The "rungs" of the DNA ladder are nitrogenous bases, also known as nucleobases.
• A strand of DNA is a long chain of connected nucleotides.

Nitrogenous Bases

• There are four nitrogenous bases: adenine, thymine, guanine, and cytosine.
• Adenine pairs with thymine.
• Guanine pairs with cytosine.
• DNA is structured within a double helix, made of two strands with a sugar-phosphate backbone.
• The 'rungs' within the DNA are nitrogenous bases (Adenine, Thymine, Guanine, Cytosine)
• The base pairing rule dictates that adenine pairs with thymine, and guanine pairs with cytosine.

Genes

• A gene is a segment of DNA that contains instructions and code for creating protein and passing down traits.
• A gene is typically one section/segment of a DNA.
• A gene is code for one trait; e.g. eye colour

Human Chromosomes

• Humans typically have 46 chromosomes, with 23 from the sperm cell and 23 from the egg cell.
• Chromosomes dictate sex, with x and y chromosomes being respective to biological sex
• Female humans have two X chromosomes
• Male humans have two Y chromosomes.

Dominant and Recessive Traits

• Alleles are variations of genes that code for the same trait.
• Individuals receive two copies of every gene, one from each parent.
• Homozygous means having two identical alleles for a trait.
• Heterozygous means having two different alleles for a trait.
• Dominant alleles always show in the phenotype, masking other alleles.
• Dominant alleles are represented with a capital letter
• Recessive alleles only show in the phenotype if there are no dominant genes
• Recessive alleles are represented with a lower case letter.

Complete Dominance, Co-dominance, and Incomplete Dominance

• Complete dominance is where one gene is completely dominant over the other.
• Co-dominance occurs when both alleles are expressed equally.
• Incomplete dominance means that heterozygous alleles result in a phenotype between two traits.