Chapter 4 Section 1: Living Things Inherit Traits in Patterns

1. 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.

2. 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.

3. 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.

4. 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

5. 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.

6. 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 46Chrom. • The 23rd pair of chomosomes in humans is the sex(gender) chromosome

7. 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.

8. 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.

9. 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.

10. 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.