Lecture 25

Question 1

Before Mendel, what was the proposed mechanism? What was known?

Answer 1

blending inheritance
known that offspring resemble parents

Question 2

Why were garden peas a good model organism?

Answer 2

easy to grow, many distinct traits, can self-fertilize or cross-pollinate manually, large number of offspring, clear, visible phenotypes

Question 3

What was the easiest garden pea phenotype to observe?

Answer 3

seeds

Question 4

What are the male and female parts of the pea plant called?

Answer 4

stamen

carpel

Question 5

What did Mendel do with the peas?

Answer 5

used pure breeding parental lines

counted offspring

noted repeatable ratios

proposed a model to explain ratios

tested his model

Question 6

What did Mendel’s first experiment show?

Answer 6

flower colour

pure purple x pure white -> all purple F1

reciprocal cross game same results (sex doesn’t matter)

dominant vs recessive established

Question 7

What were the big ideas from Mendel’s model?

Answer 7

traits are controlled by genes (each trait has two version, in alleles)

individuals have 2 alleles (one from each parent)

dominance

segregation (each gamete gets only one allele of each gene)

equal segregation (50% chance for each allele to enter gamete)

random fertilization

Question 8

A good model is what?

Answer 8

simple

can explain data

makes testable predictions

Question 9

What did Mendel’s second experiment show?

Answer 9

seed colour (yellow vs green)

F1 all yellow but carry hidden green allele

shows genes exist in pairs and segregate

yellow allele is dominant

Question 10

What did Mendel’s third experiment show?

Answer 10

1:1 test cross

F1 heterozygote x recessive homozygote

1 yellow : 1 green

confirmed existence of hidden (recessive) alleles

Question 11

What did Mendel’s fourth experiment show?

Answer 11

two traits considered at once

9:3:3:1 di-hybrid ratio

two independent 3:1 ratios combined, led to law of independent assortment (alleles for different genes separate independently during gamete formation)

Question 12

What did later Mendel work discover?

Answer 12

law of segregation, law of independent assortment, Punnett

Question 13

When was Mendel work published and rediscovered?

Answer 13

1866

1900