Patterns of Heredity

CHAPTER

the BIG ideathe BIG idea

CHAPTER OUTLINE

In sexual reproduction, genes are passed from parents to offspring in predictable patterns.

Living things inherit traits in patterns.4.14.1

Patterns of heredity can be predicted.4.24.2

Meiosis is a special form of cell division.4.34.3

VOCABULARY

KEY CONCEPT CHAPTER HOME

4.14.1

SECTION OUTLINESECTION OUTLINE

Living things inherit traits in patterns.

gene

sexual reproduction

heredity

allele

phenotype

genotype

dominant

recessive

Offspring inherit alleles, which are forms of genes, from their parents. Alleles come on chromosome pairs and can be dominant orrecessive.

alleles

a gene

The alleles you have are your genotype; the observable characteristics that come from your genotype are your phenotype.

VOCABULARY

KEY CONCEPT CHAPTER HOME

Patterns of heredity can be predicted.4.24.2

SECTIONOUTLINESECTIONOUTLINE

ratio

Punnett square

B b

B

b

BB Bb

Bb bb

B = black furb = brown fur

Punnett squares show possible outcomes of heredity.

Ratios and percentages can be used with Punnett squares to express the probability of particular outcomes.

percentage

probability

VOCABULARY

KEY CONCEPT CHAPTER HOME

4.34.3

SECTIONOUTLINESECTIONOUTLINE

Meiosis is a special form of cell division.

egg

gamete

sperm

• At the beginning of meiosis I, the parent cell has two copies of each chromosome pair.• During meiosis I, the homologs of the chromosome pair separate; there are two cells, each with two copies of one homolog from each pair.• During meiosis II, the two copies of each homolog separate; each daughter cell has one homolog.

Meiosis I

Meiosis II

fertilization

meiosis

1n

1n

1n

1n

VOCABULARY

KEY CONCEPT CHAPTER HOME

I. Living things inherit traits in patterns.

A. Parents and offspring are similar.

B. Genes are on chromosome pairs.

4.14.1

KEY CONCEPTSUMMARYKEY CONCEPTSUMMARY

Living things inherit traits in patterns.

1. One Example

C. Gregor Mendel made some important discoveries about heredity.

2. Mendel’s Conclusions

gene

sexual reproduction

heredity

allele

phenotype

genotype

dominant

recessive

1. Phenotype and Genotype

D. Alleles interact to produce traits.

2. Dominant and Recessive Alleles

VOCABULARY

KEY CONCEPT CHAPTER HOME

II. Patterns of heredity can be predicted.

B. Ratios and percentages can express the probability of outcomes.

4.24.2

KEY CONCEPTSUMMARYKEY CONCEPTSUMMARY

A. Punnett squares show possible outcomes for inheritance.

Patterns of heredity can be predicted.

ratio

Punnett square

percentage

probability

VOCABULARY

KEY CONCEPT CHAPTER HOME

III. Meiosis is a special form of cell division.

A. Meiosis is necessary for sexual reproduction.

1. Meiosis I

B. Cells divide twice during meiosis.

4.34.3

KEY CONCEPTSUMMARYKEY CONCEPTSUMMARY

Meiosis is a special form of cell division.

2. Meiosis II

egg

gamete

sperm

fertilization

meiosis

C. Meiosis and mitosis differ in some important ways.