AP Bio Hereditary

Law of Segregation

Refers to the segregation of alleles to individual gametes. During gamete formation, each gamete receives one allele for each gene, ensuring offspring inherit one allele from each parent.

Law of Independent Assortment

The independent assortment of alleles. During gamete formation, genes for different traits segregate independently from one another, resulting in genetic variation in offspring.

Complete Dominance

A form of inheritance where the dominant allele completely masks the effect of the recessive allele in a heterozygous genotype, resulting in the appearance of the dominant trait.

Incomplete Dominance

A genetic scenario where the phenotype of heterozygous individuals is intermediate between the phenotypes of the two homozygous parents. This results in the blending of traits in the offspring.

Codominance

A form of inheritance where both alleles in a heterozygous genotype are fully expressed, resulting in offspring with a phenotype that displays both traits simultaneously.

Linked Genes

Genes that are located close to each other on the same chromosome tend to be inherited together during meiosis, leading to reduced recombination frequencies.

Crossing Over

The process during meiosis where homologous chromosomes exchange genetic material, leading to genetic variation in the resulting gametes.

Nondisjunction

The failure of homologous chromosomes or sister chromatids to separate properly during meiosis results in gametes with an abnormal number of chromosomes.

Polyploidy

Occurs if all the chromosomes undergo meiotic nondisjunction and produce gametes with twice the number of chromosomes. This results in organisms with more than two complete sets of chromosomes, often seen in plants.

Point Mutations

Occurs when a single nucleotide in the DNA of a gene is incorrect. This can occur because of substitution, deletion, or insertion of nucleotides, leading to potential changes in the protein produced.

Sickle-Cell disease (result of point mutation)

Caused by nucleotide substitution, results in the production of defective hemoglobin, the oxygen-carrying protein in red blood cells.

Tay-Sachs Disease

Caused by nucleotide insertion, results in lysosomes that lack the functional enzyme to break down certain fats (glycolipids).

Aneuploidy

A genome with extra or missing chromosomes, mostly caused by nondisjunction.

Down Syndrome

Occurs when an egg or sperm with an extra copy of chromosome 21 fuses with a normal gamete.

Turner Syndrome

Results when there is nondisjunction of the sex chromosomes. It is characterized by a female having only one X chromosome, leading to various developmental issues and a lack of secondary sexual characteristics.

Duplications

Occur when a chromosome segment is repeated on the same chromosome

Inversions

Occurs when chromosome segments are rearranged in reverse orientation on the same chromosome; this doesn’t really have a drastic effect.

Translocations

Occurs when a segment of a chromosome is moved to another chromosome or to a different location on the same chromosome. This can lead to genetic imbalances and various disorders.

Environmental effects on Phenotypic Expression

Nutrition, Temperature (affects sex determination in reptiles, and also influences the color of animal fur), Seasonal changes in daylight length influence the expression of hair color, and UV rays affect skin, Soil PH can influence flower color, expression of one’s genes is sometimes dependent upon chemicals in the environment.

Maternal inheritence

Refers to the transmission of genetic information from the mother to offspring, primarily through the mitochondria, which is inherited solely from the maternal lineage.