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Biology 105
Ch. 14 Study Guide ?'s: Mendel and the Gene Idea
| Question | Answer |
|---|---|
| Define true breeding. | organisms that produce offspring of the same variety (as the parent plant) over many generations of self-pollination.---homozygous dominant or recessive parents |
| Define Hybridization. | the crossing of two true breeding varieties. (PPxpp) |
| What is Mendel's law of segregation? How can this law be explained by the behavior of chromosomes during meiosis? | Definition: two alleles for a heritable character segregate (separate from each other) during gamete formation and end up in different gametes. ////Explained by meiosis because alleles are segregated due to the splitting of the sister chromatids |
| What is Mendel's law of independent assortment? How can this law be explained by the behavior of chromosomes during meiosis? | Law: two or more genes assort independently during gamete formation////explained in meiosis due to the random orientation of chromosomes when they line up in metaphase I and II |
| What is incomplete dominance? Give and example. | When the phenotype of heterozygotes is in between the phenotypes of individuals homozygous for either allel. Example: Red flower x white flower= pink flower |
| Explain how phenotypic expression in the heterozygote differs with complete dominance, incomplete dominance, and co-dominance. | Complete: only dominant trait is shown. Incomplete: phenotype is somewhere between the dominant and recessive phenotypes. Co-dominance: both phenotypes are shown. (AB blood type) |
| What is pleitropy? Give an example. | Definition: when a mutation in one gene effects many phenotypic characteristics. Ex: gene for pea color also affects gene for color of outside of pod. |
| What is epistasis? Give an example. | a form of gene interaction in which the expression of a gene at one locus alters the expression of a second gene. (work on the same biochemical pathway) Ex.: yellow--->green--->red, with enzymes in between. absence of one enzyme has big influence |
| Describe a simple model for polygenic inheritance and explain why most polygenic characters are described in quantitative terms. | Skin color(AaBbcc has 2 dark pigment genes). 2 or more genes effect a single phenotypic trait. Quantitative because characters vary along a continuum that we can measure. |
| How can environmental conditions influence the phenotypic expression of a character? | Climate of tree location=change in phenotype(leaf size)...Acidity of soil affects flower color. Experiences=differences |
| Why are studies of human inheritance not as easily conducted as Mendel's work with peas? | Humans only produce few offspring, and the generation span is very long. Also, we can't purposefully ask two parents of specific genotypes to breed. |
| How can a lethal recessive allele be maintained in a population? | If the effects of the recessive disease don't become apparent until later in adult life, the adult may have had kids before they realize the child is at risk. Also, people can be just carriers. |
| Explain the inheritance and expression of cystic fibrosis. | Autosomal, Recessive disease. A transport protein doesn't work properly, causing thick mucus to be in the individuals body( in pancreas, lungs, etc.) which could cause infections |
| Explain the inheritance and expression of Sickle-cell disease. | Autosomal. Recessive. mutation in hemoglobin protein causes blood cells to be sickle-shaped. carriers still have some sickle-shaped cells |
| Explain why lethal dominant genes are much rarer than lethal recessive diseases. | If an individual has a lethal dominant disease, he/she will most likely die, and his/her genes will not be passed on. |
| Give an example of a late-acting lethal dominant in humans and explain how it may escape elimination by natural selection. | Ex: Huntington's Disease: a degenerative disease of the nervous system. Escapes natural selection because symptoms don't appear until after reproductive age, and affected individual may have already passed trait onto kids. |
Created by:
lrumberger