Chapter 4 Section 1: Living Things Inherit Traits in Patterns Objectives: 1. I can explain how traits are passed from parent to offspring. 2. I can describe how genes are distributed in sexual reproduction. 3. I can understand that some traits are dominant and others are recessive. 4. I can design a model to determine genotype and phenotype.

Parents and Offspring are Similar Everyone has a unique combination of characteristics. These characteristics are also known as traits. Many of your traits may resemble your parents traits. Examples: Hair color, Eye Color, Blood Type These traits or characteristics are called inherited traits.

Parents and Offspring are Similar The inheritance of traits happens through sexual reproduction A cell containing genetic information from the mother and a cell containing genetic information from the father combine into a completely new cell. That cell then becomes the offspring.

Parents and Offspring are Similar Some traits are acquired, not inherited. An acquired trait is one that is developed during your life. Learned behaviors are one type of acquired trait. Examples: Reading, Writing, Riding a Bike

Genes are on Chromosome Pairs A gene is a unit of heredity that occupies a specific location on a chromosome and codes for a particular product. Heredity is the passing of genes from parents to offspring. These genes code for the expression of traits Cells contain pairs of chromosomes, with one chromosome coming from each of the parents. Chromosome pairs are called homologs.

Genes are on Chromosome Pairs The various form of the same gene are called alleles. Ex.–The gene that determines height is located at site A on a pair of homologs. Though both homologs have the gene for height at site A, the genes may not be indentical. Each species has a characteristic number of chromosomes. Humans have 23 pairs, for a total of 46 Chrom. The 23rd pair of chomosomes in humans is the sex(gender) chromosome

Genes are on Chromosome Pairs In humans, the sex chromosomes are called the X-chromosome and the Y-chromosome A human female has 2 X-chromosomes, while a human male has 1 X-chromosome and 1 Y-chromosome.

Gregor Mendel Made Some Important Discoveries About Heredity The first major experiments investigating heredity were performed by a monk named Gregor Mendel Mendel worked with 7 different traits Mendel realized that each plant must have 2 factors for each possible trait, 1 factor from each parent Some factors (traits) could be masked, such as dwarf height.

Phenotype and Genotype An organisms phenotype describes the actual characteristics that can be observed. Ex. – Eye color, height, feet size, etc. Genotype is the name for the genes an organism has.

Dominant and Recessive Alleles A dominant allele is one that is expressed in the phenotype even if only one copy is present in the genotype. A recessive allele is one that is expressed in the phenotype only when two copies are present in the genotype. If a dominant allele is paired with a recessive allele, then the dominant trait will appear in the phenotype.