Chapter 14: Mendel and the Gene Idea
Supplemental Instruction
Iowa State University / SI Leader: / Kelsey
Course: / Bio 211 (5)
Date: / 10-22-09
Instructor: / Dr. Holscher
1. Describe the procedure of Mendel’s experiment. (What did he cross? Why?)
He crossed 2 true breeding plants to see what traits their offspring had. He then crossed the offspring (F1) to see the characteristics of their offspring (F2).
2. Explain Mendel’s 2 laws:
· Law of Segregation: the alleles for a character segregate during gamete formation and end up in different gametes. When an individual produces gametes, the copies of a gene separate so each gamete gets one copy
· Law of Independent Assortment: gametes are separated independently from each other and don’t come as “packaged units”. Alleles assort independently of each other (ex. hair color isn’t related to or dependent on height).
3. What is an allele?
An alternate version of a gene
4. What is the name for the specific place an allele is located?
locus/loci
5. A ______homozygous______organism has 2 identical alleles.
6. A ____heterozygous______organism has 2 different alleles.
7. After crossing two cats, you notice its offspring are orange, denoted as Rr.
· “Orange” is the cat’s ___phenotype______
· Rr is the cat’s ___genotype______
8. Pretend you have a snake with blue skin, and you know that blue skin is recessive in snakes. What must the snake’s genotype be?
bb
9. What is the purpose of a testcross?
To determine the genotype of something with a dominant phenotype. Example: purple flower, Pp or PP?
10. Describe the three different types of dominance:
· complete: one trait completely overpowers another
· codominance: 2 alleles affect phenotype in different distinguishable ways
· incomplete dominance: phenotype of F1 is a mix between two parent phenotypes
11. Explain epitasis:
Some species (especially mammals) have different alleles for fur color, but also a gene that must be present for pigmentation to even be expressed. “gene at one locus alters phenotypic expression of gene at a second locus”
12. What is the purpose of a testcross?
13. Describe the three different types of dominance (other than complete).
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14. Explain epistasis.