Term
What was the "Blending of Traits" model that existed before Mendel? What does this model propose about variation?.
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Definition
| There was no coherent model to explain patterns of heredity. Before the 20th century, two concepts provided the basis for most thinking about herdity. 1.) Heredity occurs with in species.. and 2.) traits are transmitted directly from parents to offspring. But this led to a variation paradox; if no variation enters a species from outside, and if the variation blends with every generation than all memebers of a species should soon have the same appearence. this does not happen. |
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Term
| What is an experimental "hybridization"? |
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Definition
| The mating of unlike parents. Such as different strains of tobacco. |
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Term
| What does it mean for traits to seperate? |
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Definition
| The process by which alternative forms of traits are expressed in off spring rather than blending each trait. |
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Term
| Why was the garden pea a good model for Mendels expiriments? |
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Definition
- Many earlier investigators had produced hybrid peas, so he knew he could expect to observe segregation og traits among offspring
- A large number of pure varieties of peas were available
- Pea plants are small and easy to grow
- Both male and female sexual organs are enclsed within the each pea flower
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Term
| What are the three stages of expirimental design Mendel used and their purpose? |
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Definition
- Mendel aloud plants of a given variety to self cross for multiple generations to assure himself that the traits he was studying were indeed true-bredding, that is, transmitted unchanged from generation to generation.
- Mendel then performed crosses between true-breeding varieties exhibiting alternative forms of traits. He also performed reciprocal crosses: using pollen from a white-flowered plant to fertilize a purple-flower plant, then using pollen from a purple flowered plant to ferilize a whie-flowered plant.
- Finally, Mendel permitted the hybrid offspring produced by these crosses to self-fertilize for several generations, allowing him to observe the inheritance of alternative forms of a trait. Most important, he counted the numbers of offspring exhibiting each trait in each suceeding generation.
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Term
| Distinguish between self-fertilization, cross-polination and cross-fertilization: |
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Definition
| Self-fert is the union of egg and spermproduced by a single hermaphordilic organism. Cross-polin is when the male part is removed before fertilization occurs, then they introduce pollen from a different strain, thus performing cross pollination that results in cross-fertilization. |
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Term
| What is a monohybrid cross? |
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Definition
| It is a cross that follows only 2 variations on a single trait, such as white and purple colored flowers. |
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Term
| Distinguish between a F1 first filial generation and an F2 second filial generation: |
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Definition
| The offspring resulting from a cross between parental generation, cross between memebers of the F1 generation. |
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Term
| Explain Mendels principle of segregation: |
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Definition
| The two allels for a gene segregate during gamete formation and are rejoined at random, one from each parent during fertalization. |
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Term
| Compare the segregation of allels with the behavior of homologoues in meiosis: |
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Definition
| The physical basis for allel segregation is the behaviour of chromosomes during meiosi. as you saw in chapter 11, homologues for each chromosome disjoin during anaphase I of meosis. The 2nd meiotic division then produces gametes that contain only one homologue for each chromosome. |
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Term
| Distinguish between a genotype and a phenotype: |
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Definition
| Genotype total set of alles that an individual contains. Phenotype is the physical appearence or other observable characteristics of that individual, which results from allel expression |
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Term
| Mendels five element model |
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Definition
- traits do not transmit physiological traits directly to offspring
- each individual recieves one copy of each gene from each parent
- not all copies of a gene are identical
- 2 allels remain descrete -- neither blend or alter each other
- the presence of a particular allel does not ensure that the trait it encodes will be expressed
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Term
| Distinguish between a diploid organism that is homozygous and one that is heterozygous: |
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Definition
| 2 haploid gametes containg the same allel fuse together during fertalization, when gametes contain different allels its heterozygous |
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Term
| What is a Punnett square? How is it used? What is one the outside of the Punnett square? What is on the inside? |
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Definition
| F2 possibilities may be visualized in a simple diagram |
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Term
| What is a pedigree? How is it used? |
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Definition
| The organized methology we use is a pedigree, a consistent graphical representation of matings and offspring over multiple generations for a particular trait. |
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Term
| What is a dihybrid cross? |
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Definition
| 2 different traits in a single cross |
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Term
| Explain Mendel's principle of Independent Assortment: |
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Definition
| It is a dihybrid cross, the genes of each allel assort independently. The segregation of different allel pairs is independent. |
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Term
| Compare segregation of allels for different genes with the behavior of different homologoues in meiosis: |
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Definition
| The independent alignment of different homologus chromosome pairs during metaphase I leads to the independent segregation of the different allel pairs. |
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Term
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Definition
| An individual with unknow genotype is crossed with the homozygous recessive genotype, that is the recessive parental variety |
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Term
| What is the polygenic inheritance? |
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Definition
| Describes a mode of inheritance in which more than one gene affects a trait such as height in human beings |
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Term
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Definition
| occurs when one gene influences multiple, seemingly unrelated phenotypic traits. An example being phenylketonunia, which is human disease that effects multiple systems but is caused by one gene. |
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Term
| Distinguish between incomplete dominance and codominace. |
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Definition
| I.D. The heterozygotes is intermediate in appearence between the two homozygotes. Codominace can be distinguished from I.D. by the appearence of the heterozygote. |
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Term
| How are ABO blood types in humans an example of one gene having more than two allels? |
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Definition
| The gene that encode has three common allels |
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Term
Mendel's understanding of the inheritance of traits in peas, expressed in modern language, included all of the following except:
A.) Parents transmit information encoded in factors (genes)
B.) Each individual contains two factors (genes) for each trait.
C. ) Not all genes are identical; alternative factors (allels) exist
D. ) If a given allel is present, its effects will be seen in the individual |
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Definition
| D. ) If a given allel is present, its effects will be seen in the individual |
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Term
| Albinism is caused by the lack of melanin production in cells, resulting in little or no pigmentation in the skin, hair, and irises of an individual. One relatively commin form of Albinism humans stems from processing two mutated OCA genes. Individuals that are heterozygous, have one functioning allele and produce pigment. How would you describe the mutated OCA gene -- dominant or recessive? Explain your reasoning |
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Definition
| Recessive because heterozygous individuals still are able to produce pigment showing that the OCA is a dominat allel masking the recessive |
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Term
| An organism that has a different sequence of DNA nucleotides at a particular location on a pair of homologous chromosomes is said to have different ________ for that trait. |
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Definition
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Term
| Mendel carried out his expiriments in what model organsim? |
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Definition
| 3 Genotypes, 2 Phenotypes |
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Term
| The principle of independent assortment: |
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Definition
| Occurs because of the random arrangment of chromomes during metphase I. |
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Term
| A testcross is performed in order: |
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Definition
| Determine the genotype of an individual |
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Term
| Cystic fibrosis (CF) is a recessive condition. If a man with CF has a child with a woman who is a carrier (heterozygous), what is the chance that their first child will have the condition? |
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Definition
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Term
| What are the possible gametes of an individual with the genotype AaBb? |
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Definition
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Term
| Marfan syndrome is an autosomal dominant disease caused by a mutation in collagen formation. Symptoms of Marfan syndrome include skeletal, optical, and cardiovascular abnormalties. Which of the following terms best describes this phenomenon of multiple effects of a single allel? |
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Definition
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Term
| Why does the book say the 3:1 ratio is actually 1:2:1? |
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Definition
| !/4 true breeding dominant individuals, 1/2 not-true breeding dominate individuals, and 1/4 true-breeding recessive individuals. |
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Term
| Why do traits in a dihybrid corss have to behave independently? |
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Definition
| Because when a organism shows dominant and recessive traits. |
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Term
| What does the 9:3:3:1 ratio refer to? |
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Definition
| 16 rather than 4 possible outcomes |
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