Exam 2 review summary (chapter 7) PDF

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chapter 7 summary and take home message...

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Chapter 7

Genes and In Inheritance heritance Chapter Outline 1 Why d do o off offspring spring resemble their pa parents? rents? 7.1 Family resemblance: Your mother and father each contribute to your genetic makeup. TAKE-HOME MESSAGE 7.1: Offspring resemble their parents because they inherit genes— instruction sets for biochemical, physical, and behavioral traits, some of which are responsible for diseases—from their parents. 7.2 Some traits are controlled by a single gene. TAKE-HOME MESSAGE 7.2: Some traits are determined by instructions an individual carries on a single gene, and these traits exhibit straightforward patterns of inheritance. 7.3 Mendel learned about heredity by conducting experiments. TAKE-HOME MESSAGE 7.3: In the mid-1800s, Gregor Mendel conducted studies that helped us understand heredity. He focused on easily observed and categorized traits in garden peas and applied methodical experimentation and rigorous hypothesis testing to determine how traits are inherited. 7.4 Segregation: You’ve got two copies of each gene but put only one copy in each sperm or egg. TAKE-HOME MESSAGE 7.4: Each parent puts a single set of instructions for building a particular trait into every sperm or egg it makes. This instruction set is called a gene. The trait observed in an individual depends on the two copies (alleles) of the gene it inherits from its parents. 7.5 Observing an individual’s phenotype is not sufficient for determining its genotype. TAKE-HOME MESSAGE 7.5: It is not always possible to determine an individual’s genetic makeup, known as its genotype, by observation of the organism’s outward appearance, known as its phenotype. For a particular trait, an individual may carry a recessive allele whose phenotypic effect is masked by the presence of a dominant allele. Much genetic analysis makes use of clever experiments and careful record-keeping, often using Punnett squares, to determine organisms’ genotypes.

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Probabilit Probability y and chance play centr central al roles in geneti genetics. cs. 7.6 Chance is important in genetics. TAKE-HOME MESSAGE 7.6: Probability plays a central role in genetics. In segregation, each gamete that an individual produces receives only one of the two copies of each gene the individual carries in its other cells, but it is impossible to know which allele goes into the gamete. Chance plays an important role in fertilization, too: all of the sperm or eggs produced by an individual are different from one another, and any one of those gametes may be the gamete involved in fertilization. 7.7 A test-cross enables us to figure out which alleles an individual carries.

TAKE-HOME MESSAGE 7.7: In a test-cross, an individual that exhibits a dominant trait but has an unknown genotype is mated with an individual that is homozygous recessive. The phenotypes of the offspring reveal whether the unknown-genotype individual is homozygous dominant (all of the offspring exhibit the dominant trait) or heterozygous (half of the offspring show the dominant trait and half show the recessive trait). 7.8 We use pedigrees to decipher and predict the inheritance patterns of genes. TAKE-HOME MESSAGE 7.8: Pedigrees help scientists, doctors, animal and plant breeders, and prospective parents determine the genes that individuals carry and the likelihood that the offspring of two individuals will exhibit a given trait.

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How are genot genotypes ypes translated into p phenotypes? henotypes? 7.9 Incomplete dominance and codominance: the effects of both alleles in a genotype can show up in the phenotype. TAKE-HOME MESSAGE 7.9: Sometimes the effects of both alleles in a heterozygous genotype are evident in the phenotype. With incomplete dominance, the phenotype of a heterozygote appears to be an intermediate blend of the phenotypes of the two homozygotes. With codominance, a heterozygote has a phenotype that exhibits characteristics of both homozygotes. 7.10 What’s your blood type? Some genes have more than two alleles. TAKE-HOME MESSAGE 7.10: In multiple allelism, a single gene has more than two alleles. Each individual still carries only two alleles, but in the population, more than just two alleles exist. This is the case for the ABO blood groups in humans. 7.11 Multigene traits: how are continuously varying traits such as height influenced by genes? TAKE-HOME MESSAGE 7.11: Many traits, including continuously varying traits such as height, eye color, and skin color, are influenced by multiple genes. 7.13 Why are more men than women colorblind? Sex-linked traits differ in their patterns of expression in males and females. TAKE-HOME MESSAGE 7.13: The patterns of inheritance of most traits do not differ between males and females. However, when a trait is coded for by a gene on a sex chromosome, such as color vision on the X chromosome, the pattern of expression differs for males and females.

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Some genes are link linked ed together together.. 7.16 Most traits are passed on as independent features: Mendel’s law of independent assortment. TAKE-HOME MESSAGE 7.16: Genes tend to behave independently, such that the inheritance pattern of one trait doesn’t usually influence the inheritance of any other trait. 7.17 Red hair and freckles: genes on the same chromosome are sometimes inherited together. TAKE-HOME MESSAGE 7.17: Sometimes, having one trait influences the presence of another trait. This is because the alleles for two genes are inherited and expressed almost as a package deal when the genes are located close together on the same chromosome....