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
