1. Patterns of Heredity 4.1 Living things inherit traits in patterns. 4.2
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Patterns of Heredity
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.
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2. 4.1 Living things inherit traits in patterns.
alleles
a gene
Offspring inherit alleles, which are forms of genes, from their parents. Alleles come on chromosome pairs and can be dominant or
recessive.
sexual reproduction
gene
heredity
allele
The alleles you have are your genotype; the observable characteristics that come from your genotype are your phenotype.
phenotype
genotype
dominant
recessive
SIMULATION
Try a virtual version of Mendel’s experiment.
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3. 4.1 sexual reproduction Living things inherit traits in patterns.
gene
heredity
A type of reproduction in which male and female reproductive cells combine to form offspring with genetic material from both cells.
allele
phenotype
genotype
dominant
recessive
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4. 4.1 gene Living things inherit traits in patterns.
sexual reproduction
gene
gene
heredity
The basic unit of heredity that consists of a segment of DNA on a chromosome.
allele
phenotype
genotype
dominant
recessive
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5. 4.1 heredity Living things inherit traits in patterns.
sexual reproduction
heredity
gene
heredity
The passing of genes from parents to offspring; the genes are expressed in the traits of the offspring.
allele
phenotype
genotype
dominant
recessive
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6. 4.1 allele Living things inherit traits in patterns.
sexual reproduction
allele
gene
heredity
An alternate form of a gene for a specific trait or gene product.
allele
phenotype
genotype
dominant
recessive
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7. 4.1 phenotype Living things inherit traits in patterns.
sexual reproduction
phenotype
gene
heredity
The observable characteristics or traits of an organism.
allele
phenotype
genotype
dominant
recessive
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8. 4.1 genotype Living things inherit traits in patterns.
sexual reproduction
genotype
gene
heredity
The genetic makeup of an organism; all the genes that an organism has.
allele
phenotype
genotype
dominant
recessive
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9. 4.1 dominant Living things inherit traits in patterns.
sexual reproduction
dominant
gene
heredity
A term that describes the allele that determines the phenotype of an individual organism when two different copies are present in the genotype.
allele
phenotype
genotype
dominant
recessive
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10. 4.1 recessive Living things inherit traits in patterns.
sexual reproduction
recessive
gene
heredity
A term that describes an allele that is not expressed when combined with a dominant form of the gene.
allele
phenotype
genotype
dominant
recessive
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11. 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
SIMULATION
Predict offspring traits with virtual Punnett squares.
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12. 4.2 Punnett square Patterns of heredity can be predicted.
ratio
A chart used to show all the ways genes from two parents can combine and be passed to offspring; used to predict all genotypes that are possible.
probability
percentage
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13. 4.2 ratio Patterns of heredity can be predicted.
Punnett square
ratio
ratio
A comparison between two quantities, often written with a colon, as 3 : 4.
probability
percentage
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14. 4.2 probability Patterns of heredity can be predicted.
Punnett square
probability
ratio
The likelihood or chance that a specific outcome will occur out of a total number of outcomes.
probability
percentage
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15. 4.2 percentage Patterns of heredity can be predicted.
Punnett square
percentage
ratio
A ratio that states the number of times an outcome is likely to occur out of a possible 100 times.
probability
percentage
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16. 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
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Meiosis II
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17. 4.3 gamete Meiosis is a special form of cell division.
egg
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.
sperm
fertilization
meiosis
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18. 4.3 egg Meiosis is a special form of cell division.
gamete
egg
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
fertilization
meiosis
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19. 4.3 sperm Meiosis is a special form of cell division.
gamete
sperm
egg
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.
sperm
fertilization
meiosis
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20. 4.3 fertilization Meiosis is a special form of cell division.
gamete
fertilization
egg
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.
sperm
fertilization
meiosis
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21. 4.3 meiosis Meiosis is a special form of cell division.
gamete
meiosis
egg
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.
sperm
fertilization
meiosis
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22. 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
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2. Dominant and Recessive Alleles
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23. 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
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24. 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.
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SIMULATION
Try a virtual version of Mendel’s experiment.
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Predict offspring traits with virtual Punnett squares.
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