Chapter 2 Flashcards
What are two examples of pre-Mendelian hypotheses of inheritance?
Pangenesis and blending hypothesis
This theory of inheritance was proposed by Hippocrates in 400 BC
Pangenesis
In this theory of inheritance, “seeds” are produced by all parts of the body, collect in the reproductive organs and are transmitted to offspring at conception
Pangenesis
Who proposed the theory of pangenesis?
Hippocrates
What are the two main ideas of the blending hypothesis of inheritance?
- Factors that control hereditary traits are malleable; 2. Factors that control hereditary traits can blend together from generation to generation
Who is considered to be the father of genetics?
Gregor Johann Mendel
Mendel’s meticulously accurate records of his experiments included this type of analysis
Quantitative analysis
Mendel published this work in 1866
Experiments on Plant Hybrids
Was Mendel’s 1866 paper given attention right away by the scientific community?
No
What are two reasons why Mendel’s work went ignored in his lifetime?
- Title did not capture importance of work; 2. Lack of understanding of chromosome transmission
Mendel’s work was independently rediscovered in 1900 by these three scientists
Hugo de Vries (Holland); Carl Correns (Germany); Erich von Tschermak (Austria)
Mendel chose this species to study the natural laws governing plant hybrids
Garden pea (Pisum sativum)
What are two reasons why the garden pea plant was advantageous for Mendel to study?
- It existed in several varieties with distinct characteristics; 2. Its structure allowed for easy crosses and parental choice
What two types of breeding experiments did Mendel carry out?
Self-fertilization and cross-fertilization
This type of fertilization naturally occurs in pea plant because of isolation of the plant’s reproductive structure
Self-fertilization
This type of fertilization requires removing and manipulating the anther of the pea plant
Cross-fertilization
How many true-breeding characteristics did Mendel study in pea plants?
7
These are the observable characteristics of an organism
Characters
This term describes the specific properties of a character
Trait (or variant)
This is a variety of an organism that produces the same trait over several generations
True-breeder
What are the seven characters of pea plants that Mendel studied?
- Height; 2. Flower color; 3. Flower position; 4. Seed color; 5. Seed shape; 6. Pod color; 7. Pod shape
What two variants of the height character in peas did Mendel observe?
Tall and dwarf
What two variants of the flower color character in peas did Mendel observe?
Purple and white
What two variants of the flower position character in peas did Mendel observe?
Axial and terminal
What two variants of the seed color character in peas did Mendel observe?
Yellow and green
What two variants of the seed shape character in peas did Mendel observe?
Round and wrinkled
What two variants of the pod color character in peas did Mendel observe?
Green and yellow
What two variants of the pod shape character in peas did Mendel observe?
Smooth and constricted
Did Mendel have a hypothesis to explain hybrids?
No
Mendel believed that quantitative analysis of crosses may provide these that govern hereditary traits
Mathematical relationships
This approach, used by Mendel, is used to deduce empirical laws
Empirical approach
Mendel’s first experiments involved crossing these
Two variants of the same character
This is the term for crossing two variants of the same character to observe that character
Single-factor cross
What was the result for the F1 generation across all 7 single-factor crosses that Mendel performed?
All one variant
What was the ratio of the F2 generation across all 7 single-factor crosses that Mendel performed?
3:1
Mendel’s results refuted this mechanism of heredity
Blending
This variant’s effect can be seen in the F1 generation of a single-factor cross
Dominant
This variant’s effect cannot be seen in the F1 generation of a single-factor cross
Recessive
Mendel’s results supported this type of inheritance theory, that suggests traits are inherited as discrete units
Particulate theory of inheritance
This Mendelian law states that two copies of a gene segregate from each other during the process that gives rise to gametes
Law of Segregation
What ratio is consistent with Mendel’s Law of Segregation?
3:1
This is a grid that helps predict the outcome of simple genetic crosses
Punnett square
The Punnett square was proposed by this English geneticist
Reginald Punnett
What are the two possible patterns of inheritance for two-factor crosses?
Linked assortment or independent assortment
The occurence of these in the F2 generation of two-factor crosses contradicts the linked assortment model
Nonparentals (offspring with novel combinations of traits)
What is the predicted phenotypic ratio of an independently assorted F2 generation?
9:3:3:1
This Mendelian law states that two different genes will randomly assort during gamete formation
Law of Independent Assortment
Why are some genes linked?
They are close together on the same chromosome
This is when an offspring receives a combination of alleles that differs from the parental generation
Genetic recombination
What are two causes of genetic recombination?
Independent assortment and crossing over
The Punnett square becomes cumbersome when involving this many independently assorting genes
3 or more
These are two alternative methods to the Punnett square for predicting crosses involving 3 or more independently assorting genes
Forked-line method and multiplication method
Modern geneticists are often interested in the relationship between this and the outcome of traits
Molecular expression of genes
What two-step approach do modern geneticists use to examine the outcome of traits based on gene expression?
- Identify individual with defective copy of gene; 2. Observe how this copy affects the organism’s phenotype
These are defective copies of genes
Loss-of-function alleles
Are loss-of-function alleles commonly inherited as dominant or recessive alleles?
Recessive
This is used to determine the pattern of inheritance of traits in humans
Pedigree analysis
Pedigree analysis is commonly used to determine the inheritance pattern of these
Human genetic diseases
Is cystic fibrosis a recessive or dominant disorder?
Recessive
About what percent of Caucasian people carry the gene that causes cystic fibrosis?
3%
This protein that regulates ion transport across the cell membrane is altered by a mutant allele in individuals with cystic fibrosis
Cystic fibrosis transmembrane conductance regulator (CFTR)
What is the formula for the probability of an event?
Probability = # of times an event occurs/total # of events
This deviation between observed and expected outcomes is large for small samples and small for large samples
Random sampling error
To compute probability, these two mathetmatical operations are used
Product rule and binomial expansion equation
This rule states that the probability that two or more independent events will occur is equal to the product of their respective probabilities
Product rule
These are events in which the occurrence of one does not affect the probability of another
Independent events
In this genetic disease, affected individuals cannot perceive extreme sensations as painful
Congenital analgesia
This is a statistical method used to determine the goodness of fit
Chi Square Test
This refers to how close the observed data are to those predicted from a hypothesis
Goodness of fit
Can the chi square test prove that a hypothesis is correct?
No
What is the general formula for the Chi Square Test?
χ² = ∑ (O - E)²/E
What does O stand for in the Chi Square Test formula?
Observed data in each category
What does E stand for in the Chi Square Test formula?
Expected data in each category based on the experimenter’s hypothesis
What does ∑ stand for in the Chi Square Test formula?
Sum of calculations for each category
The calculated chi square value can be used to obtain these from a chi square table
P values
These probabilities determine the likelihood that observed deviations are due to random chance alone
P values
What do low chi square values indicate?
High probability that the observed deviations could be due to random chance alone
What do high chi square values indicate?
Low probability that the observed deviations are due to random chance alonee
If a chi square test results in a P value less than this, the hypothesis is rejected
0.05 (5%)
Before using a chi square table, these have to be determined
Degrees of freedom
This is a measure of the number of categories that are independent of each other
Degrees of freedom
What is the formula for degrees of freedom?
df = n - 1
What does n stand for in the formula for degrees of freedom?
Total number of categories
