14 Mendel and the Gene

Question 1

Polymorphic

Answer 1

a species that has two or more distinct phenotypes in the same interbreeding population at the same time

Question 2

Self-fertilization

Answer 2

the fusion of two gametes produced by the same individual to form offspring

Question 3

Gene

Answer 3

a hereditary factor that influences a particular trait

Question 4

Allele

Answer 4

a particular form of a gene

Question 5

Genotype

Answer 5

combination of alleles of particular genes in an individual

Question 6

Phenotype

Answer 6

an individual’s observable traits

Question 7

Homozygous

Answer 7

having two of the same allele

Question 8

Heterozygous

Answer 8

having two different alleles

Question 9

Dominant allele

Answer 9

an allele that produces its phenotype in heterozygous and homozygous genotypes

Question 10

Recessive allele

Answer 10

an allele that produces its phenotype only in homozygous genotypes

Question 11

Pure line or pure breeding

Answer 11

individuals of the same phenotype that, when crossed, always produce offspring with the same phenotype; parents are homozygous for the gene in question

Question 12

Hybrid

Answer 12

offspring from crosses between homozygous parents with different genotypes; heterogenous for one or more specific genes

Question 13

Reciprocal cross

Answer 13

a cross in which the phenotypes of the male and female are reversed compared with a prior cross

Question 14

Testcross

Answer 14

a cross of a homozygous recessive individual and an individual with the dominant phenotype but unknown genotype in order to infer the unknown genotype from phenotypes seen in the offspring

Question 15

X-linked

Answer 15

referring to a gene located on the X chromosome

Question 16

Y-linked

Answer 16

referring to a gene located on the Y chromosome

Question 17

Autosomal

Answer 17

referring to a gene located on any non-sex chromosome (an autosome)

Question 18

Chromosome theory of inheritance

Answer 18

the principle that genes are located on chromosomes and that patterns of inheritance are determined by the behavior of chromosomes during meiosis

Question 19

Principle of segregation

Answer 19

each pair of hereditary elements (alleles on homologous chromosomes) separate from each other during the formation of offspring in anaphase of meiosis I

Question 20

Principle of independent assortment

Answer 20

alleles of different genes separate into gametes independently because pairs of homologous chromosomes have two equally likely ways of lining up before segregating during metaphase of meiosis I

Question 21

Linkage

Answer 21

tendency of alleles of particular genes to be inherited together (do not assort independently); seen when two or more genes are on the same chromosome

Question 22

Multiple allelism

Answer 22

the existence of more than two alleles of the same gene

Question 23

What does the physical distance between genes determine?

Answer 23

how frequently crossing over occurs between them

Question 24

Recombination frequency

Answer 24

how often genes recombine due to crossover during meiosis

Question 25

What is the relationship between the distance between a pair of genes and the probability that crossing over will take place?

Answer 25

the shorter the distance between a pair of genes, the lower the probability that crossing over will take place between them

Question 26

Dihybrid cross

Answer 26

a mating between two individuals who are heterozygous for two traits

Question 27

Dependent assortment

Answer 27

transmission of one particular allele would depend on the transmission of another

Question 28

Wild type

Answer 28

the most common phenotype(s) seen in a wild population

Question 29

Mutation

Answer 29

any permanent change in the hereditary material of an organism or the nucleotide sequence that is the only source of new alleles in populations

Question 30

Mutant

Answer 30

an individual with a new or rare phenotype due to a mutation

Question 31

Sex-linked inheritance

Answer 31

inheritance patterns observed in genes carried on sex chromosomes; females and males have different numbers of alleles of a gene, often creating situations where a trait appears more in one sex

Question 32

Autosomal inheritance

Answer 32

inheritance patterns that occur when genes are located on autosomes

Question 33

What is the difference between linkage and sex-linkage?

Answer 33

Linkage refers to two or more genes located on the same chromosome while sex-linkage can refer to a single gene located on a sex chromosome and says nothing about the relative location of genes

Question 34

What are the three possible dominance relationships between different alleles?

Answer 34

complete, incomplete (heterozygotes have an intermediate phenotype), and codominance (heterozygotes have phenotypes of both alleles)

Question 35

Mode of transmission

Answer 35

type of inheritance observed as a trait is passed from parent to offspring; describes a trait as autosomal or sex-linked and the type of dominance e.g. autosomal recessive, autosomal dominant, X-linked recessive

Question 36

Pedigree

Answer 36

family tree of parents and offspring, showing inheritance of particular traits of interest

Question 37

Carrier

Answer 37

a heterozygous individual carrying a normal allele and a recessive allele for an inherited trait who does not display the phenotype of the recessive trait but can pass the recessive allele to offspring

Question 38

Autosomal recessive traits

Answer 38

(1) individuals with the trait must be homozygous (1) if the parents of the affected individual do not have the trait, both parents are heterozygous (3) trait often skips generations

Question 39

Autosomal dominant trait

Answer 39

(1) individuals who are homozygous or heterozygous for it have the dominant phenotype (2) affected offspring have at least one affected parent and are heterozygous if only one parent is affected (3) trait does not skip generations

Question 40

Why do males exhibit X-linked recessive traits more often than females do?

Answer 40

Males have only one copy of the X chromosome so any X-linked allele will determine the phenotype in a male

Question 41

What causes mutations?

Answer 41

errors during dna replication and dna repair

Question 42

What are the possible associations between genotype and phenotype?

Answer 42

(1) Many genes can influence one trait (2) Many traits can result from a single genotype (3) A single gene can influence more than one trait

Question 43

What factors influence the expression of genetic traits?

Answer 43

epigenetic factors and environmental factors (e.g. cell type and diet); the same genotype could result in very different phenotypes depending on these factors

Question 44

Epigenetic factors

Answer 44

heritable changes in gene function that do not involve changes to the DNA sequences

Question 45

Are alleles inherently dominant or recessive?

Answer 45

No, dominance depends on the relative influence of each allele on a specific phenotype under specific environmental conditions

Question 46

Non-dominance

Answer 46

either incomplete dominance or codominance; the heterozygotes show a different phenotype than either homozygote

Question 47

Which of the sex chromosomes in humans is smaller?

Answer 47

Y chromosome

Question 48

X chromosome

Answer 48

contains many genes that are essential for development, especially the development of intelligence and social cognition

Question 49

Y chromosome

Answer 49

carries a few genes that are essential for the expression of male-specific traits

Question 50

Gender

Answer 50

socially constructed roles, behaviors, expressions and identities of girls, women, boys, men, and gender diverse people (continuum)

Question 51

Sex

Answer 51

set of biological attributes primarily associated with physical and physiological features including chromosomes, gene expression, hormone levels and function, and reproductive/sexual anatomy (continuum)

Question 52

Sexual orientation

Answer 52

direction of romantic, sexual, and emotional feelings (continuum)