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What are sex chromosomes?

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chromosomes that determine an organism's sex

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What are autosomes?

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all other chromosomes; do not directly affect an organism's sex

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How is a carrier different from a person who has a genetic disorder?

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a carrier does not show symptoms of a disorder but can pass the disorder to offspring

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Complete the two Punnett squares below to compare autosomal recessive disorders with autosomal dominant disorders. Fill in the possible genotypes for offspring, and write in the phenotype (no disorder, carrier, or disorder) for each Autosomal Recessive:

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Autosomal Recessive: DD, no disorder; Dd, carrier; Dd, carrier; dd, disorder.

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Complete the two Punnett squares below to compare autosomal recessive disorders with autosomal dominant disorders. Fill in the possible genotypes for offspring, and write in the phenotype (no disorder, carrier, or disorder) for each Autosomal Dominant

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Autosomal Dominant: DD, disorder; Dd, disorder; Dd, disorder; dd, no disorder

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4. What are sex-linked genes?

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genes that are located on the sex chromosomes

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Fill in the Punnett square below to show the pattern of inheritance for sex chromosomes. Sex Chromosome Inheritance

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Sex Chromosome Inheritance: XX, female; XX, female; XY, male; XY, male

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5. In humans, how does a gamete from a male determine the sex of offspring?

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A female can only pass on X chromosomes, but a male can pass on either X or Y chromosomes.

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6. For what are genes on the Y chromosome responsible?

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male characteristics

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7. How are sex-linked genes expressed differently in the phenotypes of males and females?

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Males show the phenotypes from all sex-linked genes; females exhibit phenotypes similarly to autosomal gene expression, except for X chromosome inactivation.

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8. The verb carry means "to transport." How is the everyday meaning of carry related to the meaning of the term carrier in genetics?

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A carrier is a person who "transports" a disease-causing allele to offspring.

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9. What is X chromosome inactivation?

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In females, one of the two X chromosomes in every cell is randomly "turned off."

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1. How is incomplete dominance different from a dominant and recessive relationship?

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In incomplete dominance neither allele is completely dominant and one allele is not hidden in a heterozygote. The heterozygous phenotype is somewhere between the homozygous phenotypes.

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2. How is codominance different from a dominant and recessive relationship?

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In codominance both alleles are completely expressed and the heterozygous phenotype contains the separate products of both alleles.

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3. What is a multiple-allele trait?

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a trait for which a gene has more than two alleles

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Describe how phenotypes appear in incomplete dominance

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Phenotype: third, distinct phenotype; neither of the homozygous parental phenotypes is seen Example: betta fish (green, steel blue, royal blue); 4 o'clock plant (white, red, pink)

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Describe how phenotypes appear in codominance.

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Phenotype: third phenotype that has both homozygous parental phenotypes Example: blood type (A, B, AB)

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Many genes may interact to produce one trait: Polygenic Traits

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Polygenic traits: traits produced by two or more genes; show continuous ranges of phenotypes; examples include height, eye color, skin color.

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Many genes may interact to produce one trait: Epistasis

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Epistasis: one gene affects the expression of other genes involved in a particular trait; examples include albinism

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8. Why is genotype not the only factor that affects phenotype?

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The environment can affect gene expression, which will influence phenotype.

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9. List and explain two examples of how environment and genotype can interact.

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Sex determination in sea turtles depends on both genes and the temperature at which sea turtle eggs mature. Human height is affected both by genes and such factors as nutrition and health care.

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10. The prefix in- means "not." How is the meaning of this prefix related to the meaning of incomplete dominance?

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neither allele is dominant

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11. The prefix co- means "together." How is the meaning of this prefix related to the meaning of codominance?

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both alleles are expressed together

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12. The prefix poly- means "many," and the term genic means "related to genes." How do these word parts combine to give the meaning of polygenic?

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Polygenic traits are traits produced by two or more genes.

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1. What is gene linkage?

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when genes are on the same chromosome and tend to be inherited together

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2. Why were fruit flies useful in Morgan's research?

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Many generations of fruit flies could be quickly and cheaply grown; fruit flies had easily observed traits.

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3. What is the difference between a wild type and a mutant type?

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Wild type is the most common phenotype; mutant type is a much less common phenotype.

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4. What did Morgan conclude from his research on fruit flies?

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Linked genes are on the same chromosome; chromosomes, not genes, assort independently during meiosis; homologous genes can be exchanged through cross-overs during meiosis.

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Mendel: Genes assort independently of one another.

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Punnet, Bateson: studied pea plants; suggested that some genes were linked Morgan: studied fruit flies; concluded that linked genes were on the same chromosome; chromosomes assort independently

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5. How is the distance between two genes related to the chance they are inherited together?

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The closer genes are, the more likely they will be inherited together; the farther apart they are, the more likely they are to be separated.

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6. What hypothesis was the basis of Sturtevant's research?

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the frequency of cross-overs during meiosis was related to the distance between genes

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7. What is a linkage map?

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a map of the relative locations of genes on a chromosome

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How are cross-over frequencies related to linkage maps?

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the percentage of cross-overs is converted into map units (a cross-over frequency of 1 percent is equal to 1 map unit), and gene locations are determined based on all cross-over frequencies for the genes being mapped

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9. What do linkage maps show about genes on a chromosome?

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relative locations and an estimate of physical distance between genes, but not actual physical distances

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Cross-over Frequencies: A-B 20% B-C 5% A-C 25% A-D 7% D-B 13% D-C 18%

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Linkage Map: A—7—D—13—B—5—C

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8. Complete the chart to follow the logic necessary to fill out a pedigree for a sex-linked gene. Use XD and Xd for the dominant and recessive X-linked genes, respectively.

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Tracing Sex-Linked Genes Phenotype must have Genotype Female, recessive phenotype must have XdXd Male, recessive phenotype must have XdY Female carrier must have XDXd

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9. What are two methods that are used to directly study human chromosomes?

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karyotypes and genetic testing (genetic screening)

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10. What does a karyotype show about chromosomes?

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It can show any large-scale changes in chromosomes.

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11. What is a karyotype?

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a picture of all of the chromosomes in a cell

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These are agents that carry diseases but do not express disease symptoms.

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Carrier

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Genes that are located on sex chromosomes

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Sex-linked gene

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The process by which femal X chromosomes are randomly deactivated.

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X-chromosome inactivation

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In this case, the heterozygous phenotype is somewhat in the middle as far a gene expression.

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Incomplete Dominance

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In this case, both dominant traits are expressed separately.

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Codominance

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These traits are produced by at least two genes.

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Polygenic traits

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A map that shows the loci, or general location of genes.

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Linkage Map

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These are shown on charts to help scientists trace the genotypes and phenotypes of families to help determine whether they have dominant or recessive alleles.

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Pedigree

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The ratio of body chromosomes to sex chromosomes in a cell.

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Karyotype

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Explain six mechanisms that add variation into a population

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Heredity plays a huge role in genetic diversity. Other factors may include migratory patterns of species entering the same community, even amongst single species. Mutations can also factor into genetic diversity, as they can be extremely potent if passed on to offspring. The passage of genetic diseases can drastically alter genetic diversity as well, even when organisms with different traits produce offspring, there can be a visible difference.

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Draw a Punnet square for a heterozygous tall pea plant and a homozygous short pea plant. Give percentages and ratios of genotype and phenotype of offspring

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Pp Pp Pp pp Ratio= 3:1:1 Percentage of dominance= 75%

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What were Mendel's conclusions that led to the Law of Segregation?

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Organisms inherit two copies of each gene, one from each parent. Organisms only donate one copy of a gene for their gametes. This the two genes segregate, or separate, from each other.

Chapter 7 Extending Mendelian Genetics – Flashcards

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