Basic Principles of Heredity
Week 15.2
Supplemental Instruction
Iowa State University
Leader: Natalie
Course: BIOL/GEN 313
Date: 12/3
Chapter: 3
1. Do mitosis and/or meiosis produce genetic variation? If so, explain what events bring about
variation.
Only meiosis: independent assortment and crossing over.
2. What is the difference between Meiosis 1 and Meiosis 2? (hint: What are other names for these
processes?)
Meiosis 1: reductional division- chromosome number is reduced by half
Meiosis 2: equational division- chromatids separate
3. Is either process above similar to mitosis?
Meiosis 2
4. How many combinations of chromosomes in gametes are possible if the haploid number for a
particular organism is 5?
Formula 2^n
2^5= 32
5. What is homologous recombination? Where can a chiasma be found?
Crossing over: DNA exchange between nonsister chromatids
Chiasma- the area of crossing over
6. What are two ways to predict progeny for multiple traits?
Branching Method
Punnett Squares
7. What is the multiplication rule? Pg 52
Multiplication rule- the probability of two independent traits occurring together can be
calculated by multiplying their independent probabilities
8. What is a testcross and why is it used?
Cross a homozygous recessive organism with another unknown organism to determine the
genotype of the unknown parent
9. What is Mendel’s first law and during what stages can it be observed?
Law of Segregation- summarized in table 3.2 pg 49
1. Each individual organism possesses two alleles encoding a trait (Before meiosis)
2. Alleles separate when gametes are formed (Anaphase 1)
3. Alleles separate in equal proportions (Anaphase 1)