19 - Simple Mendelian genetics: genes and alleles

Question 1

Gene

Answer 1

A discrete unit of hereditary information consisting of a specific nucleotide sequence in DNA (or RNA, in some viruses)

Question 2

Allele

Answer 2

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

Question 3

Genotype

Answer 3

The genetic makeup, or set of alleles, of an organism

Question 4

Phenotype

Answer 4

the observable physical and physiological traits of an organism, which are determined by its genetic makeup

Question 5

Homozygote

Answer 5

An organism that has a pair of identical alleles for a gene (encoding a character)

Question 6

Heterozygote

Answer 6

an organism that has two different alleles for a gene (encoding a character)

Question 7

Homozygous recessive

Answer 7

refers to having two copies of the same RECESSIVE gene for a particular trait

Question 8

homozygous dominant

Answer 8

refers to having two copies of the same DOMINANT gene for a particular trait

Question 9

gamete

Answer 9

A haploid reproductive cell, such as an egg or sperm, that is formed by meiosis or is the descendant of cells formed by meiosis. Gametes unite during sexual reproduction to produce a diploid zygote.

Question 10

Test cross

Answer 10

Breeding of an organism of unknown genotype with a homozygous recessive individual to determine the unknown genotype. The ratio of phenotypes in the offspring reveals the unknown genotype.

Question 11

P (parental) generation

Answer 11

the TRUE BREEDING (homozygous) parent individuals from which F1, hybrid off-spring are derived in studies of inheritance. (P stands for parental)

Question 12

F1 generation

Answer 12

The first filial, hybrid (heterozygous) offspring arising from a parental (P generation) cross

Question 13

F2 generation

Answer 13

The offspring resulting from interbreeding (or self-pollination) of the hybrid F1 generation

Question 14

Dominant allele

Answer 14

An allele that is fully expressed in the phenotype of a heterozygote

Question 15

Recessive allele

Answer 15

An allele whose phenotypic effect is not observed in a heterozygote

Question 16

law of segregation

Answer 16

Mendel’s first law, stating that the two alleles in a pair segregate (separate from each other) into different gametes during gamete formation

Question 17

True-breeding

Answer 17

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

Question 17

Law of independent assortment

Answer 17

Mendel’s second law, stating that each pair of alleles segregates, or assorts, independently of each other pair during gamete formation; applies when genes for two characters are located on different pairs of homologous chromosomes or when they are far enough apart on the same chromosome to behave as though they are on different chromosomes

Question 17

Multiplication rule

Answer 17

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

Question 18

Addition rule

Answer 18

A 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 19

Monohybrid cross

Answer 19

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

Question 20

Dihybrid cross

Answer 20

A cross between two organisms that are each heterozygous for BOTH of the character being followed (or the self-pollination of a plant that is heterozygous for both characters)