Chapter 2: Transmission Genetics

Question 1

Describe the characteristics of mendels experiments?

Answer 1

• Dichotomous traits
• traits controlled by a single gene pair
• simple dominance
• no X-linkage
• Genes not linked

Question 2

What are dichotomous traits?

Answer 2

two different phenotypes, no intermediate (no heterozygote)

Question 3

Why was the common garden pea helpful for mendels experiments?

Answer 3

• easily handled and crossbred
• can self fertilize
  -has male and female parts already

Question 4

What is a monohybrid cross?

Answer 4

inheritance of ONE trait

Question 5

Describe mendels monohybrid cross (purple x white flower)

Answer 5

-begins with P generation : pure-breeding purple flower x pure-breeding white flower

-creates F1 generation: Purple flower progeny plants (all DOMINANT phenotypes)

-F1 is self fertilized

-creates F2 generation: 3:1 ratio

Question 6

What is a reciprocal cross?

Answer 6

when it doesnt matter which parent expresses which phenotype…. you get the same results either way

ex: (Female white x male purple) = purple
(male white x female purple) = purple

Question 7

What is the law of segregation?

Answer 7

-occurs during formation of gametes (meiosis)

• 2 alleles for each trait separate (segregate)
• each allele has an equal probability for inclusion in gamete…

Question 8

describe the stem length trait in mendels pea plants?

Answer 8

• the gene Le was determined to control the varition in stem length that mendel saw as tall and short in plants
• Le gene produces an enzyme called gibberellin 3B-hydroxylase
• 3B-hydroxylase catalyzes one step in the bio-chemical pathway synthesizing the plant growth hormone giberellin
• tall plants produce sufficient gibberellin to grow tall
  -mutation in recessive allele results in a low level of gibberellin production, leads to short stems