Chapter 14: Mendel and the Gene Idea

Question 1

Mendel

Answer 1

discovered the basic principles of inheritance by breeding pea plants and cross-pollinating them

Question 2

True Breeding

Answer 2

plants or animals that produce the same variety when self-pollinating

Question 3

Hybridization

Answer 3

mating 2 contrasting, true-breeding varieties; combining genes from 2 breeding groups

Question 4

Alleles

Answer 4

alternate versions of a gene
Example:
pea color:
-purple
-white

Question 5

Law of segregation

Answer 5

2 alleles for a heritable character separate during gamete formation (during meiosis one) and end up in different gametes (meiosis 2)

Question 6

Homozygote/Homozygous

Answer 6

2 of the same alleles, either both dom or both recessive

Question 7

Heterozygote/Heterozygous

Answer 7

2 different alleles, dom and recessive

Question 8

Phenotype

Answer 8

the way a gene presents physically

Question 9

Genotype

Answer 9

genetic make-up

Question 10

Monohybrid

Answer 10

heterozygous for one character (flower color, seed smoothness)

Question 11

Dihybrid

Answer 11

the offspring of 2 true-breeding parents, with 2 different characters

Question 12

Law of independent Assortment

Answer 12

each pair of alleles segregate independently of any other pair of alleles during gamete formation

Question 13

Complete dominance

Answer 13

when phenotypes of the heterozygote and the dominant homozygote are identical

Question 14

Pleiotropy

Answer 14

genes have multiple phenotypic effects, show themselves physically multiple ways (responsible for multiple symptoms of hereditary diseases like Cystic Fibrosis and Sickle Cell Disease)

Question 15

Epistasis

Answer 15

one gene affects the phenotype of another due to the interaction of their gene products

Question 16

Polygenic inheritance

Answer 16

multiple genes that affect a single trait (like height or skin color)

Question 17

Pedigree

Answer 17

family tree that describes the interrelationship of parents and children across generations

Question 18

Multifactorial inheritance

Answer 18

traits that depend on multiple genes combined with environmental influences

Question 19

Carrier

Answer 19

heterozygous individuals who carry the recessive gene but are phenotypically normal

Question 20

Consanguineous matings

Answer 20

between close relatives (like in-breeding); increases the chance that both parents carry the same rare allele

Question 21

What are the limitations to Mendell’s experiments?

Answer 21

Mendel only experimented on the characters of only 2 distinct alternative forms. He only experimented with true-breeding plants, on only 1 character. Chose only characteristics in 2 alternate forms, and only chose objects that were true-breeding. Meaning they were homozygous plants. He didn’t experiment, initially, with heterozygous plants until F1.

Question 22

Describe the four models of heredity proposed by Mendell

Answer 22

Hypothesis of 3:1 model in F2 offspring. Mendel observed this 3:1 ratio of inheritance.

1. Alternate versions of genes account for variations in characters
   - gene for color exists in 2 versions (purple, white) aka Alleles, reside at specific locus on gene
2. Each character: 2 alleles from each parent
3. If 2 alleles differ, then the dominant allele denotes appearance, and the other (recessive) has no effect
4. law of segregation- 2 alleles for a heritable character separate during gamete formation (during meiosis one) and end up in different gametes (meiosis 2)

Question 23

What three situations deviate from simple mendellian patterns of inheritance

Answer 23

When alleles are not completely dominant or completely recessive
When a gene has more than 2 alleles
When a gene produces multiple phenotypes

Question 24

Give example of multifactorial disorders

Answer 24

Heart disease, cancer, alcoholism. These are disorders that are somewhat genetic but also influenced by the environment. Eating a diet heavy in sugar and fat leads to an increased risk of CAD, increasing your risk of heart attack and stroke. Sugar feeds cancer. Alcoholism destroys your liver.

Question 25

How is polygenic inheritance different from pleiotropy?

Answer 25

Polygenic inheritance: multiple genes independently affect a single trait. There are many genes that go into eyecolor, skin color, height. These genes are inherited independently but work together to produce one trait.

Pleiotropy: genes have multiple phenotypic effects. In cases of hereditary diseases, like cystic fibrosis or sickle cell disease, there are multiple symptoms that can be observed because of the single CF or SC trait