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Chapter 3
General Genetics- Exam 1
| Question | Answer |
|---|---|
| Theories that have been proposed to explain the transmission of hereditary traits | Theory of pangenesis Theory of preformationism |
| What is the blending theory? | Factors that control hereditary traits are maleable They can blend together generation after generation |
| What experiment refuted blending theory? | Gregor Mendel's pioneering experiments with garden peas refuted all of the above |
| Why was Mendel was successful when others were not? | Mendel was successful when his predecessors were not because he chose a suitable organism, took time to ensure pure breeding, concentrated on one or a few discontinuous characters at a time, adopted quantitative form of analysis |
| Describe Mendel's Experimental System | Used pure-breeding lines of garden peas Selected 7 traits to study, each of which had two distinguishable appearances He carefully designed his experiments and gathered mathematical data |
| What is cross fertilization? | Pollen and egg are derived from different plants |
| What is self-fertilization? | Pollen and egg are derived from the same plant |
| What is a monohybrid cross? | A single-factor cross |
| What is the parental generation in Mendel's experiment? | Pure bred lines |
| What is the first filial generation in Mendel's experiment? | Offspring of cross-fertilization of parentals |
| What is the second filial generation in Mendel's experiment? | Offspring of self-fertilization of F1 plants |
| What is the third filial generation in Mendel's experiment? | Offspring of self-fertilization of F2 plants |
| What was the result of Mendel's experiment? | 1. The F1 generation showed only one of the two parental traits 2. The F2 generation showed an ~ 3:1 ratio of the two parental traits 3. Reciprocal crosses yielded similar results |
| What did Mendel's results refute? | Refuted a blending mechanism of heredity The data suggested a particulate theory of inheritance |
| What did Mendel postulate? | A pea plant contains two discrete hereditary factors, one from each parent these factors (alleles) The two factors may be identical or different Segregation Random fertilization |
| Define homozygous | When the alleles are identical |
| Define heterozygous | When the alleles are different |
| What happens when the two factors differ in the Mendel's results? | The dominant are expressed while recessive hidden |
| What is segregation? | During gamete formation, the factors separate randomly, so half the gametes receive each factor |
| What is random fertilization? | Male and female gametes randomly unite, reestablishing the paired factors |
| What is a genotype? | The specific allelic composition of an individual With respect to plant height, a pea plant may have 3 different genotypes |
| What is a phenotype? | The physical appearance of an individual With respect to plant height, a pea plant may have 2 different phenotypes |
| What is an example of different phenotypes that can be present? | Tall; dwarf |
| The phenotype is a product of what? | The phenotype is a product of the genotype and the environment |
| What is a punnett square | A grid that enables one to calculate the results of simple genetics crosses |
| What is the genotypic ratio? | 1: 2: 1 |
| What is the phenotypic ratio? | 3: 1 |
| How did Mendel verify his principles of segregation? | By performing a test-cross |
| What happens in a test-cross? | In a test-cross an organism with known phenotype but unknown genotype is crossed with an organism that has the recessive phenotype (and hence is homozygous recessive) |
| What is a dihybrid cross? | A two-factor cross |
| What is the law of independent assortment? | During gamete formation, the segregation of any pair of hereditary determinants is independent of the segregation of other pairs |
| How was the law of independent assortment verified? | By performing a test cross |
| What are modern geneticists often interested in? | Modern geneticists are often interested in the relationship between the molecular expression of genes and the outcome of traits |
| What approach do modern geneticists use? | Identify an individual with a defective copy of the gene Observe how this copy will affect the phenotype of the organism |
| What are loss-of-function alleles? | The defective copies of genes Commonly inherited in a recessive manner |
| What is alternative method to the Punnet square? | The forked line method |
| Steps to the fork line generation | Treat each gene separately Consider phenotypic (or genotypic) differences |
| If n= # of heterozygous gene pairs involved | Number of possible parental gametes= 2^n Number of different genotypes in zygotes= 3^n Number of different phenotypes in zygotes= 2^n Proportion of homozygous recessive in F2= 1/4^n |
| Propability formula/range | # of favorable cases/total number of cases Ranges from 0 - 1 |
| If an even has a probability of p, what is the probability of all alternative events | q |
| Rules for combing probabilite | Product rule Sum rule Binomial expansion equation (binomial theorem) |
| What is the product rule? | The probability of the occurrence of independent events is the product of their respective probabilities |
| Probability of rolling a 3 AND then a 4 with a die? | P(3 and 4) = P(3) X P(4)= 1/6 X 1/6= 1/36 |
| What is the sum rule? | The probability of the occurrence of one of several mutually exclusive events is the sum of their respective probabilities |
| Probability of rolling a 3 OR a 4 with a die? | P(3 or 4) = P(3) + P(4) = 1/6 + 1/6 = 1/3 |
| If the 2 events are not mutually exclusive, then.... (related to sum rule) | P(A or B) = P(A) + P(B) - [P(A) X P(B)] |
| Probability of drawing an ace or a heart from a deck of cards | P(A or ♥) = P(A) + P(♥) – [P(A) X P(♥)] = 4/52 + 13/52 – (4/52 X 13/52) = 17/52 – (1/52) = 16/52 |
| What is the binomial expansion equation (definition)? | The probability of the occurrence of unordered mutually exclusive events is defined by the binomial theorem |
| What is the binomial expansion equation (formula)? | P = ((n!)/(x!(n-x)))p^x(q^n-x) where p = probability that the unordered number of events will occur n = total number of events x = number of events in one category p = individual probability of x q = individual probability of the other category |
| Two heterozygous brown-eyed (Bb) individuals have five children. What is the probability that two of the couple’s five children will have blue eyes? | 26% of the time, a heterozygous couple’s five children will contain two with blue eyes and three with brown eyes |
| Why do we use chi-square analysis? | Independent assortment/random fertilization are chance events, they are subject to random fluctuations To minimize the possibility that chance deviation will significantly alter the outcome |
| What is the chi-square analysis test used for? | The chi-square test is a statistical method used to determine “goodness of fit” This refers to how close the observed data are to those predicted from a hypothesis |
Created by:
KristenR2025