Mol Lecture #22

Question 1

Mendelian Genetics Overview

Answer 1

• Thinking about the gene as a heritable unit that gives rise to some attribute. (ex. Height, eye color, etc.) (also gives rise to attributes that we cannot see)

Question 2

Gregor Mendel (This flashcard isn’t terribly important)

Answer 2

• Mathematician, chemist, and biologist
  Interested in inheritance

Question 3

What did Gregor test on, and what did it reveal?

Answer 3

• Pea plants- pisum sativum
• Character
• Trait

Question 4

Character

Answer 4

• specific heritable attribute (ex., flower color)

Question 5

Trait

Answer 5

• differences in a given character (ex., white or purple)

Question 6

Mendel’s single character crosses

Answer 6

• Usually self-fertilize or self-cross (mating ability)
  → (produce gametes and make a zygote in a single plant)
• Experimentalists can control crosses and force cross-pollination to cross different plants

Question 7

True-breeding strains

Answer 7

• Mendel’s first work uses true-breeding strains: plants that always look the same for a specific attribute (character- tall, short, purple, white)

Question 8

Gregor’s Experiment setup

Answer 8

• Parental generation (P)
• PxP→ F1 generation→ F1 generation self-crosses→ gives rise to F2 generation

Question 9

Mendel’s Results

Answer 9

• F1 generation showed only 1 of the parental traits for each character. (same mathematical outcome each time)
  →For any character, one of the traits wins out as dominant
  → Later on, the one that didn’t win out (recessive) will show itself in very specific ways

Question 10

Self-Cross

Answer 10

• After F1 self-crosses (heterozygous) always get, 3:1 ratio of parental traits where the 3 (of those 3:1) is showing the parental trait observed in the F1.

Question 11

Mendelian Genetic Findings

Answer 11

1) Evidence that genes exist in pairs in individuals
- Genes are the factors or units of character, and alleles of the same genes give rise to the different traits of a given character
2) Found that traits can be dominant (won out) or recessive (did not show up)
3) Evidence that gene pairs entered gametes individually to recombine at fertilization. (when we recombine, we’re going to be able to get the recessive trait back)

Question 12

Principle of segregation

Answer 12

• allele pairs separate or segregate during gamete formation and randomly unite at fertilization.

Question 13

Homozygote

Answer 13

• a true breeding individual with 2 like alleles for a gene (1 gamete type for this gene)

Question 14

Heterozygote

Answer 14

-an individual with two different alleles for a given gene (F1) (2 gamete types with respect to this gene)

Question 15

Monohybrid (heterozygote for a specific gene)

Answer 15

• offspring of parents that are true breeding for a specific character

Question 16

Phenotype

Answer 16

• the appearance of the individual (the physical manifestation of the attribute)

Question 17

Genotype

Answer 17

• the alleles of a given individual that produce the phenotype.

Question 18

Probability and Prediction in Mendelian Genetics

Answer 18

• Probability Rules→ 0-1 probability for any given thing
• Product Rule
• Sum Rule

Question 19

Product Rule

Answer 19

• What is the probability of this AND that happening together? - multiply

Question 20

Sum Rule

Answer 20

• What is the probability of this OR that happening? -add

Question 21

Probabilities in Crosses- Punnett Square

Answer 21

• Invented by: Reginald Punnett
• Invented a diagrammatic way to represent crosses and determine probability.

Question 22

Test Crosses (Setup & Purpose)

Answer 22

• For individuals showing a dominant trait for a given character, the genotype could be Pp (het) or PP (homozygous)
• In a Test Cross, we use a recessive true-breeding plant for a given character to determine the unknown genotype of the dominant trait plant.
• Mathematically determining the genotype of the parental.