Mendelian Inheritance I

Question 1

What was the most widely favored explanation for passing of traits in the 1800s?

Answer 1

“blending”: hypthesis that genetic material from the two parents blends

Question 2

What contradicts the blending hypothesis?

Answer 2

1. Examination of populations contradicts this hypothesis
2. Reappearance of traits, after skipping a generation, also contradicts this hypothesis

Question 3

Why did Mendel use peas for his pea experiment?

Answer 3

1. Many varieties with well-described characters
2. Mating of plants can be controlled
3. Easy to grow (short generation time, large number of offspring)

Question 4

Mendel’s Pea Experimental Design

Answer 4

-ONLY chose to track characters that varied in an “either-or” manner
-used varieties that were “true breeding”

Question 5

true breeding

Answer 5

plants that produce offspring of the same variety when they self-pollinate

Question 6

Hybridization

Answer 6

mating two contrasting, true-breeding varieties

Question 7

P (F0) generation

Answer 7

the generation of the true-breeding parents

Question 8

F1 generation

Answer 8

the generation of hybrid offspring that stems from matings in the P generation

Question 9

F2 generation

Answer 9

the generation that is produced when F1 individuals self-pollinate

Question 10

Mendel’s Experiment

Answer 10

1. P: Crossed parents that differed in an obvious character (purple pea flowers x white pea flowers)
2. F1: One parent’s character disappeared (all plants had purple flowers)
3. F2: The “lost” character reappeared in the next generation (purple and white flowers)

Question 11

What did Mendel deduce from his results?

Answer 11

1. Only the “purple flower factor” was affecting flower color in the F1 hybrids
2. Called the purple flower color a dominant trait and white flower color a recessive trait
3. “heritable factors” = genes
4. “Particulate” hypothesis

Question 12

What is the “particulate” hypothesis?

Answer 12

idea that parents pass on discrete heritable units (genes)

Question 13

Alleles

Answer 13

alternative versions of genes account for variation in inherited characters

Question 14

Heterozygous

Answer 14

an organism that has two DIFFERENT alleles (at a locus on homologous chromosomes) for a gene

Question 15

Homozygous

Answer 15

an organism w/ two IDENTICAL alleles (at a locus on homologous chromosomes) for a gene

Question 16

Law of Segregation (1st law of Inheritance)

Answer 16

the two alleles for a heritable character separate during gamete formation and end up in different gametes

Question 17

phenotype

Answer 17

physical appearance

Question 18

genotype

Answer 18

genetic makeup

Question 19

Monohybrid cross

Answer 19

following one character

Question 20

Dihybrid cross

Answer 20

following two characters

Question 21

Law of Independent Assortment (2nd Law of Inheritance)

Answer 21

Each pair of alleles segregates independently of other pairs of alleles during gamete formation
-ONLY applies to genes on different chromosomes