Genes and Inheritance

1. Chromosome Trait Protein Gene Genes and Inheritance • Genes contain the information for the production of proteins, which specify traits. • Since genes are inherited, traits are also inherited.

2. Location of Genes Chromosome from egg (mom) Chromosome from sperm (dad) • In sexually reproducing organisms, cells have a homologous pair of chromosomes (one from each parent). • Chromosomes from a homologous pair have the same genes but can have different alleles. • Allele: different form of a gene • May be dominant or recessive. Homologous pair of chromosomes

3. Gregor Mendel: Father of Genetics • Genetics: branch of biology dealing with heredity • Gregor Mendel (1822-1884)was an Austrian monk who is regarded as the father of genetics. • Mendel used pea plants to study the inheritance patterns of many traits.

4. Parent A Parent A Parent B Parent B Offspring Offspring New Idea (Mendel) Inherited traits behave as discrete units Old Idea Blending of parental traits Mendel’s View of Inheritance

5. Seed color yellow dominant over green Seed shape round dominant over wrinkled Pod shape inflated dominant over constricted Pod color green dominant over yellow Mendel’s Pea Experiments • Mendel examined a small number of phenotypic characters or traits in peas. • Dominant alleles masked recessive alleles.

6. X Parents pp Pp PP Pp Pp Pp Offspring p P Gametes P Gametes p Using a Punnett Square: Monohybrid Crosses • Calculates outcomes of genetic crosses. • Important vocabulary: • Homozygous dominant • Heterozygous • Homozygous recessive Each parent provides two gametes for the grid

7. Genotype PP (homozygous) Pp (heterozygous) Pp (heterozygous) Phenotype Purple pp (homozygous) White Purple Purple Genotype and Phenotype • The genotype of an organism refers to its genetic make-up. • The phenotype of an organism refers to its observable features or traits.

8. Results of Mendel’s Experiments

9. Homologous pair of chromosomes, each has a copy of the gene on it (A or a) Gametes (sperm Or egg cells) Mendel’s Law of Segregation • Each pair of alleles is separated into different gametes and into different offspring. • Gametes contain only one copy of a gene since they only receive one chromosome from each homologous pair.

10. Genotype: AaBb Intermediate Cells Gametes Ab Ab aB aB Law of Independent Assortment • Alleles for different traits are sortedindependently of each other. • All combinations of alleles are distributed to gametes with equal probability.

11. Polydactylism is a dominant trait Free ear lobe Attached ear lobe Handedness Hitch-hiker’s thumb In this crowd of men, almost all show some degree of pattern baldness, a dominant trait. Selected Hereditary Traits

12. Dominant Recessive Human Tongue Roll • The ability to roll the tongue into a U-shape when viewed from the front is controlled by a dominant allele.

13. Punnett Square Practice 1. Brown hair (B) is dominant over lighter hair colors (b). If two heterozygotes for this trait mate, what are the: a. genotype frequencies b. phenotype frequencies of the offspring?

14. Punnett Square Practice 2. Dwarfism (D) is dominant over normal height (d). If a person of normal height and a dwarf who is homozygous dominant mate, what are the chances of having a child that is also a dwarf?

15. Punnett Square Practice 3. Polydactyly, or having extra digits (P) is dominant over having five digits on each limb (p). If a woman with polydactyly mates with a normal male, then: a. What are the possible genotypes of the woman? b. What is the genotype of the male? c. Create two Punnett Squares displaying their possible children.

16. Punnett Square Practice 4. Tallness in pea plants (T) is dominant to shortness (t). Round seeds (R) are dominant to wrinkled seeds (r). Set up a Punnett Square showing the mating results of two plants that are heterozygous for both traits.