Chapter 14: Mendel and the Gene Idea

Question 1

Character

Answer 1

Observable heritable feature that may vary among individuals

Question 2

True-Breeding

Answer 2

Referring to organisms that produce offspring of the same variety over many generations of self-pollination

Question 3

Hybridization

Answer 3

In genetics, the mating, or crossing, of two true-breeding varieties

Question 4

P Generation

Answer 4

True-breeding (homozygous) parent individuals from which F1 hybrid offspring are derived in studies of inheritance

Question 5

F1 Generation

Answer 5

First filial, hybrid (heterozygous) offspring arising from a parental cross

Question 6

F2 Generation

Answer 6

Offspring resulting from interbreeding (or self-pollination) of the hybrid F1 generations

Question 7

Allele

Answer 7

Any of the alternative versions of a gene that may produce distinguishable phenotypic effects

Question 8

Dominant Allele

Answer 8

Allele that is fully expressed in the phenotype of a heterozygote

Question 9

Recessive Allele

Answer 9

Allele whose phenotypic effect is not observed in a heterozygote

Question 10

Law of Segregation

Answer 10

• Mendel’s first law

- States that the two in a pair segregate into different gametes during gamete formation

Question 11

Punnett Square

Answer 11

Diagram used in the study of inheritance to show the predicted genotypic results of random fertilization in genetic crosses between individuals of known genotype

Question 12

Homozygous

Answer 12

Having two identical alleles for a given gene

Question 13

Heterozygous

Answer 13

Having two different alleles for a given gene

Question 14

Phenotype

Answer 14

• Observable physical and physiological traits of an organism
• Determined by genetic makeup

Question 15

Genotype

Answer 15

Genetic makeup, or set of alleles, of an organism

Question 16

Testcross

Answer 16

• Breeding an organism of unknown genotype with a homozygous recessive individual to determine the unknown genotype
• Ratio of phenotypes in the offspring reveals the unknown genotype

Question 17

Monohybrid

Answer 17

Organism that is heterozygous with respect to a single gene of interest

Question 18

Monohybrid Cross

Answer 18

Cross between two organisms that are heterozygous for the character being followed (or the self-pollination of a heterozygous plant)

Question 19

Dihybrid

Answer 19

Organism that is heterozygous with respect to two genes of interest

Question 20

Dihybrid Cross

Answer 20

Cross between two organisms that are heterozygous for both of the characters being followed (or self-pollination of a plant that is heterozygous for both characters)

Question 21

Law of Independent Assortment

Answer 21

• Mendel’s second law
• States that each pair of alleles segregates, or assorts, independently of each other during gamete formation
• Applies when two genes for two characters are located on different chromosomes

Question 22

Multiplication Rule

Answer 22

Rule of probability stating that the probability of two or more independent events occurring together can be determined by multiplying their individual probabilities

Question 23

Addition Rule

Answer 23

Rule of probability stating that the probability of any one of two or more mutually exclusive events occurring can be determined by adding their individual probabilities

Question 24

Complete Dominance

Answer 24

Situation in which the phenotypes of the heterozygote and dominant homozygote are indistinguishable

Question 25

Incomplete Dominance

Answer 25

Situation in which the phenotype of heterozygotes is intermediate between the phenotypes of individuals homozygous for either allele

Question 26

Codominance

Answer 26

Situation in which the phenotypes of both alleles are exhibited in the heterozygote because both alleles affect the phenotype in separate, distinguishable ways

Question 27

Tay-Sachs Disease

Answer 27

- Human genetic disease caused by a recessive allele for a dysfunctional enzyme - Leads to an accumulation of certain lipids in the brain - Seizures, blindness, and generation of motor and mental performance usually manifest a few months after birth - Death within a few years

Question 28

Pleiotropy

Answer 28

Ability of a single gene to have multiple effects

Question 29

Epistasis

Answer 29

Type of gene interaction in which one gene alters the phenotypic effects of another gene that is independently inherited

Question 30

Quantitative Character

Answer 30

Heritable feature that varies continuously over a range rather than in an either-or fashion

Question 31

Polygenic Inheritance

Answer 31

Additive effect of two or more genes on a single phenotypic character

Question 32

Multifactorial

Answer 32

Referring to a phenotypic character that is influenced by multiple genes and environmental factors

Question 33

Pedigree

Answer 33

Diagram of a family tree showing the occurrence of heritable characters in parents and offspring over multiple generations

Question 34

Carrier

Answer 34

- In genetics, an individual who is heterozygous at a given genetic locus for a recessively inherited disorder - Heterozygote is generally phenotypically normal for the disorder but can pass the recessive allele to offspring

Question 35

Cystic Fibrosis

Answer 35

- Human genetic disorder caused by a recessive allele for a chloride channel protein - Characterized by an excessive secretion of mucus and consequent vulnerability to infection - Fatal if untreated

Question 36

Sickle-Cell Disease

Answer 36

Recessively inherited human blood disorder in which a single nucleotide change in the beta-globin gene causes hemoglobin to aggregate, changing red blood cell shape and causing multiple symptoms in afflicted individuals

Question 37

Huntington's Disease

Answer 37

- Human genetic disease caused by a dominant allele - Characterized by uncontrollable body movements and degeneration of the nervous system - Usually fatal 10 to 20 years after the onset of symptoms

Question 38

Amniocentesis

Answer 38

- Technique of prenatal diagnosis - Amniotic fluid, obtained by aspiration from a needle inserted into the uterus, is analyzed to detect certain genetic and congenital defects in the fetus

Question 39

Chorionic Villus Sampling (CVS)

Answer 39

- Technique associated with prenatal diagnosis - Small sample of the fetal portion of the placenta is removed for analysis to detect certain genetic and congenital defects in the fetus