Patterns of Heredity 4.1 Living things inherit traits in patterns. 4.2 the BIG idea In sexual reproduction, genes are passed from parents to offspring in predictable patterns. 4.1 Living things inherit traits in patterns. 4.2 Patterns of heredity can be predicted. 4.3 Meiosis is a special form of cell division.

Living things inherit traits in patterns. sexual reproduction sexual reproduction A type of reproduction in which male and female reproductive cells combine to form offspring with genetic material from both cells. gene heredity gene The basic unit of heredity that consists of a segment of DNA on a chromosome. heredity dominant The passing of genes from parents to offspring; the genes are expressed in the traits of the offspring. recessive

Living things inherit traits in patterns. dominant sexual reproduction gene A term that describes the allele that determines the phenotype of an individual organism when two different copies are present in the genotype. heredity allele phenotype recessive genotype A term that describes an allele that is not expressed when combined with a dominant form of the gene. dominant recessive

Patterns of heredity can be predicted. 4.2 Patterns of heredity can be predicted. Punnett squares show possible outcomes of heredity. Punnett square Ratios and percentages can be used with Punnett squares to express the probability of particular outcomes. ratio probability percentage B b B = black fur b = brown fur BB Bb bb

Meiosis is a special form of cell division. 4.3 Meiosis is a special form of cell division. • At the beginning of meiosis I, the parent cell has two copies of each chromosome pair. gamete • During meiosis I, the homologs of the chromosome pair separate; there are two cells, each with two copies of one homolog from each pair. egg sperm • During meiosis II, the two copies of each homolog separate; each daughter cell has one homolog. fertilization meiosis Meiosis I 1n Meiosis II

gamete A sperm or egg cell, containing half the usual number of chromosomes of an organism (one chromosome from each pair), which is found only in the reproductive organs of a plant or animal. egg A female reproductive cell (gamete) that forms in the reproductive organs of a female and has just a single copy of the genetic material of the parent. sperm A male reproductive cell (gamete) that forms in the reproductive organs of a male and has just a single copy of the genetic material of the parent.

fertilization meiosis Part of the process of sexual reproduction in which a male reproductive cell and a female reproductive cell combine to make a new cell that can develop into a new organism. meiosis A part of sexual reproduction in which cells divide to form sperm cells in a male and egg cells in a female. Meiosis occurs only in reproductive cells.

4.1 Living things inherit traits in patterns. I. Living things inherit traits in patterns. sexual reproduction A. Parents and offspring are similar. gene B. Genes are on chromosome pairs. heredity C. Gregor Mendel made some important discoveries about heredity. allele phenotype 1. One Example genotype dominant 2. Mendel’s Conclusions recessive D. Alleles interact to produce traits. 1. Phenotype and Genotype CHAPTER RESOURCES 2. Dominant and Recessive Alleles KEY CONCEPT SUMMARY

Patterns of heredity can be predicted. 4.2 Patterns of heredity can be predicted. II. Patterns of heredity can be predicted. Punnett square A. Punnett squares show possible outcomes for inheritance. ratio probability B. Ratios and percentages can express the probability of outcomes. percentage CHAPTER RESOURCES KEY CONCEPT SUMMARY

Meiosis is a special form of cell division. 4.3 Meiosis is a special form of cell division. III. Meiosis is a special form of cell division. gamete A. Meiosis is necessary for sexual reproduction. egg B. Cells divide twice during meiosis. sperm 1. Meiosis I fertilization 2. Meiosis II meiosis C. Meiosis and mitosis differ in some important ways. CHAPTER RESOURCES KEY CONCEPT SUMMARY

X Y XX XY