biology unit 12 + 15.1

}}The Work of Gregor Mendel (Father of Genetics): The scientific study of biological inheritance is called ==genetics==. Mendel worked with pea plants because they are small and easy to grow and because they can produce many offspring. Male and female reproduction cells join in a process known as ==fertilization== to produce a new cell. Pea plants self-fertilize. A ==trait== is a specific characteristic. True-breeding plants is to reproduce with another plant. The offspring of crosses between parents with different contrasting characteristics are called ==hybrids==. An individual’s characteristics are determined by [==genes==] that are passed from one parental generation to the next. Different forms of a single gene are called ==alleles==. This ==principle [of dominance]== states that some alleles are dominant and others are recessive. The ==segregation== of alleles occur during the formation of ==gametes==, or reproductive cells.}}

[[Applying Mendel’s Principles: %%Probability%% is the likelihood that a particular event will occur. Organisms that have two identical alleles for a particular gene are %%homozygous%%. Organisms that have two different alleles for the same gene are %%heterozygous%%. A %%phenotype%% is the particular physical traits. A %%genotype%% is the genetic makeup. A %%Punnett square%% is the best way to predict genotypes and phenotypes. The principle of %%independent assortment%% states that genes for different traits can segregate independently during the formation of gametes. Mendel’s principles of heredity are: 1. The inheritance of biological characteristics is determined by individual units called genes, which are passed from parents to offspring. 2. Where two or more forms (alleles) of the gene for a single trait exist, some alleles may be dominant and others may be recessive. 3. Each adult organism has two copies of each gene. They segregate during gamete form. 4. Alleles for different genes usually segregate independently of each other. Thomas Hunt Morgan used fruit flies to advance the study of genetics.[[

<<Other Patterns of Inheritance:<< <<$<strong>Incomplete Dominance</strong>$<< <<is a case in which one allele is not completely dominant over another. For example, when crossing an RR(Red) flower with a rr (white) flower you would get 4 Rr(pink) flowers.<< <<$<strong>Codominance</strong>$<< <<is a situation in which the phenotypes produced by both alleles are clearly expressed. For example, when crossing a black (BB) chicken with a white (WW) chicken, you would get 4 black and white (BW) chickens. A gene with more than two alleles has<< <<$<strong>multiple alleles</strong>$<<<<. An example of this would be the variety of bunny coat colors (CC, c^hc^3, cc).<< <<$<strong>Polygenic traits</strong>$<< <<are controlled by two or more genes. Eye color would be an example of one. The phenotype of an organism is only partly determined by its genotype. Environmental conditions can affect gene expression and influence genetically determined traits.<<

{{A ^^genome^^ is the full set of genetic information that an organism carriers in its DNA. ^^Chromosomes^^ are bundles of DNA and protein found in nuclei. Many alleles for human genes display codominant inheritance. A ^^sex-linked gene^^ is located on a sex chromosome. A ^^pedigree^^ shows the presence or absence of a trait according to the relationships among parents, siblings, and offspring. A pedigree can be used to infer genotypes and predict future outcomes.{{

Vocabulary

12.1

Genetics-

Fertilization-

Trait-

Hybrid-

Gene-

Allele-

Principle of Dominance-

Segregation-

Gamete-

12.2

Probability-

Homozygous-

Heterozygous-

Phenotype-

Genotype-

Punnett Square-

Independent Assortment-

12.3

Incomplete Dominance-

Codominance--

Multiple Alleles-

Polygenic Traits-

15.1

Sex Chromosome-

Autosome-

Sex-Linked gene-

Pedigree-