Chapter 15: Transmission of Genetic Information

Which of the following properties of the garden pea were advantageous for Mendel's studies of inheritance?

-Pea plants can be self-fertilized or cross-fertilized. -True-breeding strains were available. -Many varieties with different traits were available.

X-Y system X-O system haplodiploid system Z-W system $environmental

-X-Y system $presence or absence of the Y chromosome $humans -X-O system $ratio between X chromosomes and autosome sets $fruit fly -haplodiploid system $haploid or diploid set of chromosomes $bee -Z-W system $presence or absence of the W chromosome $bird $environmental alligator

In pea plants, yellow seeds are dominant to green seeds, and the yellow and green alleles are represented with Y and y, respectively. Match each genotype with the correct description of alleles. -YY -Yy -yy

-YY Homozygous for the yellow allele -Yy Heterozygous for the yellow and green alleles -yy Homozygous for the green allele

females males affected individuals unaffected individuals presumed heterozygotes

-females circles -males squares -affected individuals shaded -unaffected individuals not shaded -presumed heterozygotes half shaded

The three important ideas Mendel postulated concerning the transmission of traits from parents to offspring include:

-the two alleles of a gene separate during gamete formation so that each gamete receives a single allele per trait -an individual carries two variants of genes per trait -traits exist in two forms - dominant and recessive

Males inherit their X chromosome from their mother ... of the time.

100%

A cross that follows the simultaneous inheritance of two different characters is called a(n) ... ... cross.

2, factor

What ratio did Mendel observe in the F2 offspring in monohybrid crosses between true-breeding lines for dominant and recessive traits?

3 dominant : 1 recessive

A B C D E

A Female B Male C Unaffected individuals D Affected individuals E Carrier individuals

When two P generation individuals are crossed, the offspring constitute the

F1 generation.

Plants from two different true-breeding P generation lines are crossed to one another and produce offspring. These offspring are allowed to self-fertilize, which results in production of the:

F2 generation

True or false: In all animals that have a Y chromosome, the presence of the Y chromosome results in male development.

False

True or false: In dominant inheritance, affected parents always have affected offspring.

False

True or false: Inheritance is the acquisition of traits by their transmission from offspring to parent.

False

What type of experiment involves mating two individuals with different characteristics to each other? One individual provides females gametes, while the other provides male gametes.

Hybridization

Character

A general feature of an organism

Gene

A genetic determinant that is passed intact from one generation to the next

Trait

A specific variant of a feature of an organism

Allele

A variant form of a genetic determinant

... dominance involves an intermediate phenotype in the heterozygote.

Incomplete

What is represented in pedigree analysis?

Inheritance of an inherited trait over several generations in one family

The pattern of inheritance that deals with genes that segregate and assort independently is described by the term ... inheritance.

Mendelian

What type of inheritance involves genes that undergo segregation and independent assortment?

Mendelian inheritance

In pea plants, smooth pods are dominant to constricted pods, and the smooth and constricted alleles are represented with S and s, respectively. What genotype will have constricted pods?

Only ss

What type of plant did Mendel use for most of his work?

Pea

In pea plants, round seeds are dominant to wrinkled seeds, and the round and wrinkled alleles are represented with R and r, respectively. What genotypes will have round seeds?

RR and Rr

homozygous dominant

TT

If "T" is a dominant allele for "tall," which of these would phenotypically describe a heterozygote (Tt)?

Tall

What is pleiotropy?

The ability of a mutation in a single gene to have multiple effects on an individual's phenotype

What theory states that the inheritance patterns of traits can be explained by the transmission of chromosomes during meiosis and fertilization?

The chromosome theory of inheritance

What is the norm of reaction?

The phenotypic range displayed by individuals with a particular genotype under different environmental conditions

True or false: After several generations of self-fertilization of a true-breeding line, all of the offspring will have the same traits as the original parents.

True

True or false: In humans, both males and females receive an X chromosome from their mothers.

True

heterozygous

Tt

What type of allele is defined as the prevalent allele in a population?

Wild-type

Human males always inherit their ... chromosome from their mother.

X

In humans, most sex-linked genes are found on the ... chromosome.

X

Genes found exclusively on the X chromosome are called:

X-linked

The genotype of a human female is:

XX

The sex chromosome makeup of a human female is ... and the sex chromosome makeup of a male is ...

XX, XY

In what system does the Y chromosome determine maleness?

XY

The ... chromosome determines maleness in mammals.

Y

Which chromosome causes maleness in mammals?

Y

In a pedigree, parents are connected to their offspring by:

a vertical line

In recessive inheritance, two affected parents will:

always produce affected offspring

Most human genes are found on the paired chromosomes, called ..., which are the same in both sexes.

autosomes

The paired chromosomes that are the same in both sexes are called

autosomes

A general feature of an organism, such as plant height or flower color, is called a(n)

character

Flower color is an example of a(n) ... in pea plants. Purple and white flower colors are examples of ...

character, traits

The ... theory of inheritance states that inheritance patterns of traits can be explained by the transmission of chromosomes during meiosis and fertilization.

chromosome

Independent assortment of alleles of different genes can be explained by the random alignment of homologous pairs of ... during meiosis I.

chromosomes

Traits that appear in every generation and affect males and females equally are characteristic of:

dominant inheritance

When two true-breeding plants that differ in a single character are crossed, the monohybrids display the ... trait, and the ... trait is masked.

dominant, recessive

Mendel used the garden pea to study inheritance because the pea plants were:

easy to cross

The combination of alleles that an individual has for a particular gene is the individual's:

genotype

The combination of alleles that an individual possesses, such as Tt or TT, is the individual's

genotype

The term ... describes the genetic composition of an individual for a particular gene.

genotype

An individual with two identical alleles of a gene of a particular trait has a(n) ... genotype with respect to that gene.

homozygous

In a pedigree, a female and a male who mate are connected by a(n) ... line.

horizontal

Pedigree analysis is typically used for studying:

human traits that follow simple inheritance patterns

The offspring of hybridization experiments are referred to as

hybrids

After DNA replication in a heterozygote, the two sister chromatids on a single chromosome contain:

identical alleles

The acquisition of traits by their transmission from parent to offspring is called

inheritance

In an incomplete dominance pattern of inheritance, a heterozygous individual shows a(n) ... phenotype.

intermediate

The results of pedigree analysis are less definitive than breeding experiments because the small size of human families results in:

large sampling errors

It is ... common to find Y-linked genes as compared to X-linked genes.

less

A gene found on the X chromosome is designated as an X- ... gene.

linked

The sex chromosomes refer to a distinctive pair of chromosomes that vary between ... and ... individuals.

male, female

Recessive X-linked alleles affect

males more than females.

In a recessive pattern of inheritance, two unaffected parents:

may produce affected or unaffected offspring

Consider two true-breeding individuals that differ in a single character. If these mate, their offspring are

monohybrids

The offspring of two true-breeding parents that differ in a single character are called single-character hybrids, or

monohybrids

In humans, a male always receives an X chromosome from his ... and a Y chromosome from his ...

mother, father

Normal alleles become abnormal alleles through the process of

mutation

The difference between a normal allele and one that causes disease is the result of

mutation

The phenotypic range exhibited by individuals with a particular genotype under differing environmental conditions is called the ... of ...

norm, reaction

Mendel's work involved quantitative experiments and careful analysis of the ... of offspring carrying specific traits.

number

In genetic crosses, the term "hybrid" refers to:

offspring of a hybridization experiment

Individuals with a dominant disorder usually have:

one affected parent

Sex-linked genes are located on:

one sex chromosome but not the other

Most of Mendel's experiments were conducted using ... plants.

pea

A(n) ... analysis is the analysis of an inherited trait over several generations in one family.

pedigree

Human traits that follow simple Mendelian patterns are usually studied using:

pedigree analysis

In pea plants, the allele T codes for tall plants and the allele t codes for short plants. If a plant is short, this would be considered its:

phenotype

The phenomenon in which a mutation in a single gene leads to multiple effects on an individual's phenotype is called

pleiotropy

Mendel's proposed his laws of inheritance based on:

quantitative experiments

The ... alignment of chromosomes in meiosis I leads to the independent assortment of alleles on different chromosomes.

random

A trait that causes a disease will occur more frequently in males than females if the trait is

recessive and X-linked

A trait that appears to skip generations and is present at an equal frequency in males and females exhibits:

recessive inheritance

The limitations of pedigree analysis as compared to breeding experiments include:

sample size too small

The ... chromosomes are a pair of chromosomes that are different in males and females.

sex

Genes found on one sex chromosome but not the other are called ... ... genes.

sex linked

A cross in which only one character is studied is called a(n) ... ... cross.

single, factor

When a cell prepares to divide, the homologs replicate so that each homolog consists of a pair of ... chromatids.

sister

In Mendel's experiments, he observed a 3:1 ratio between dominant and recessive traits in

the F2 generation of monohybrid crosses.

If a true-breeding line is allowed to self-fertilize for several generations, the resulting offspring will have:

the same traits as the parents

A single-factor cross is one in which an experimenter follows

the variants of only one character.

A variant form of a character is called a(n) ..., and a variant form of a gene is called a(n) ....

trait; allele

homozygous recessive

tt

A two-factor cross is one in which an experimenter follows the inheritance of

two different characters.

An individual who is homozygous for a given gene carries:

two identical alleles of the gene

A hybridization experiment involves mating:

two individuals with different characteristics

Mendel proposed that each individual carries ... forms of a gene for a given character, which are called alleles, and that the alleles of a gene separate during gamete formation so that each gamete receives ... allele(s).

two, one

For any given gene, the allele encoding a protein that is made in the proper amount and functions normally is known as the ... ... allele.

wild type