heredity

• the passing of traits from parents to offspring
• homozygous- having two identical alleles of a particular gene, e.g. BB, AA, aa, bb

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• heterozygous- having different alleles of the same gene, e.g. Bb, Aa, Ab, ab
• dominant allele- an allele that determines the trait that is expressed. only one copy has to be present (capital)
• recessive allele- an allele that does not determine the trait that is expressed unless both copies are present (lowercase)
• genome- the entire set of genetic material in an organism, including all the genes and the DNA that controls them
• alleles- alternative forms of a gene at a specific locus on a chromosome. basically like instructions that represent a trait (eg: AA for green eyes) one allele from each parent is passed on to the offspring. each gene has several different possible alleles
• gene- unit of inheritance
• trait- a characteristic or feature that an organism possesses and can be passed down from generations
• genetic inheritance- the transmission of genes from parents to offspring. biological traits are controlled by genes found on chromosomes. we have half genes from mother and half from father.(meiosis creates gametes, egg+ sperm fused during fertilization to create zygote)
• Gregor Mendel- Father of Genetics, studied pea plants, discovered that genes are inherited through 3 laws: law of dominance, law of segregation and law of independent assortment
• pure breeding plants: always produce the same kind of offspring (eg: tall plants when self pollinated produce tall offspring)
• Blending model: the most popular theory of inheritance before Mendel's experiments. suggested that the traits of the parents blend together in their offspring
• self pollination: plants fertilize themselves
• cross pollination: plants fertilize other plants
• Mendel's experiments: he started with pure breeding tall plants cross pollinated with pure breeding short plants. the result of the tall plant crossed with short plant was all the offspring were tall, leding to the discovery of dominant and recessive traits
• Punnett square: like a grid or tic tac toe board that helps predict the possible outcomes of a trait in offspring based on their parents. each parents genes are on either top or side of the grid

  
• Ratio: in genetics, ratios refer to the proportional relationship between different gene combinations or traits. (always reduced to lowest terms)
• law of dominance- in a pair of alleles (gene variants) for a particular trait, one allele may be dominant and the other recessive. the dominant alle determines the trait that is expressed in the phenotype, while the recessive allele is masked in the presence of the dominant allele

  
• law of segregation- explains how alleles segregate or separate during the formation of gametes(meiosis). each individual has two alleles for each trait, one inherited form each parent. during gamete formation, these alleles separate so that each gamete carries only one allele for each trait

  
• law of independent assortment: According to this law, the alleles for different traits segregate independently of each other during gamete formation. applies when considering the inheritance of two or more traits located on different chromosomes.

  
• genetic hybrids: offspring that differ from their parents in one or more traits (were all hybrids)
• interspecies hybrid: the union of two different species
• genotypic ratio: the ratio of offspring with each possible allele combination from a particular cross (eg: 2Rr: 2rr) number of times a characteristic of an organism will be seen in the offspring when genes for certain traits are crossed.
• phenotyic ratio (appearance): the ratio of offspring with a dominant trait compared to the recessive trait (eg: 1 round : 1 wrinkled)
• phenotype: observable characteristics of an organism, determined by the genotype(what an organism looks like eg: round, wrinkled, green. yellow)
• Genotype: the genetic makeup of an organism (eg: AA, Aa, aa) that determines the potential range of physical traits (phenotype). genotype is made of genes which carry the specific instructions for a specific trait