Genetic Inheritance – Chapter 4 Review

Fill-in-the-blank flashcards covering key definitions, Mendelian ratios, deviations from Mendelian inheritance, sex-linked and linked genes, and genetic mapping concepts.

The alternative forms of a gene that occupy the same locus on homologous chromosomes are called __.

alleles

A segment of DNA that acts as a unit of hereditary information is a __.

gene

The specific physical location of a gene on a chromosome is known as its __.

locus

The genetic makeup of an individual, written as a pair of alleles (e.g., PP, Pp), is its __.

genotype

The observable traits of an organism, influenced by genotype and environment, constitute its __.

phenotype

An organism that has two identical alleles for a gene is __ for that gene.

homozygous

An organism that possesses two different alleles for a gene is __ for that gene.

heterozygous

An allele that is fully expressed in the phenotype even in the presence of another allele is called a __ allele.

dominant

An allele whose phenotypic effect is masked in a heterozygote and expressed only when homozygous is termed __.

recessive

A cross in which the male and female gametes come from the same individual is a __.

self-cross

A cross between an individual of dominant phenotype and a homozygous recessive individual to determine the unknown genotype is a __.

test cross

Mendel’s First Law, the Law of __, states that the two alleles for a heritable character separate during gamete formation.

Segregation

Mendel’s Second Law, the Law of __, states that each pair of alleles segregates independently of any other pair during gamete formation.

Independent Assortment

In a monohybrid F₂ generation, the expected phenotypic ratio is __.

3 : 1

In a monohybrid F₂ generation, the expected genotypic ratio is __.

1 : 2 : 1

A monohybrid test cross (Pp × pp) yields an F₂ phenotypic ratio of __.

1 : 1

A dihybrid F₂ generation gives the classic phenotypic ratio of __ for two unlinked genes.

9 : 3 : 3 : 1

A dihybrid test cross (YyRr × yyrr) produces an F₂ phenotypic ratio of __.

1 : 1 : 1 : 1

Mendel chose pea plants partly because they have a short life cycle and __ pollination can be easily controlled.

pollination

True-breeding individuals are always __ at the gene(s) of interest.

homozygous

A diagram used to predict allele composition of offspring, with parental gametes on axes, is a __ square.

Punnett

When both alleles in a heterozygote are fully and separately expressed, the relationship is called __ (e.g., MN blood group).

codominance

In the MN blood group, the F₂ genotypic ratio of LᴹLᴹ : LᴹLᴺ : LᴺLᴺ is __.

1 : 2 : 1

When neither allele is completely dominant and the heterozygous phenotype is intermediate, the inheritance is __ dominance (e.g., Snapdragon).

incomplete

Snapdragon F₂ phenotypic ratio for red : pink : white flowers is __.

1 : 2 : 1

The ABO blood group exemplifies __ alleles because three alleles (Iᴬ, Iᴮ, i) exist at one locus.

multiple

Traits such as human skin colour, controlled by many genes each with additive effects, illustrate __ inheritance.

polygenic

Genes located on sex chromosomes are called __ genes.

sex-linked

The recessive, X-linked disorder characterized by slow blood clotting is __.

hemophilia

In hemophilia crosses, a male is affected if his single X chromosome carries the __ allele.

recessive (h)

Genes located close together on the same chromosome that tend to be inherited together are called __ genes.

linked

Because linked genes do not assort independently, a dihybrid test cross of linked genes gives many __-type offspring and few recombinants.

parental

Crossing over during prophase I of meiosis produces __ offspring, increasing genetic variation.

recombinant

The percentage of recombinant offspring divided by total offspring, multiplied by 100, gives the __ frequency.

recombination

One map unit (centiMorgan) corresponds to a __ % recombination frequency.

1

Genetic __ is an ordered list of loci on a chromosome based on recombination data.

mapping

If 44 recombinants are observed among 270 total offspring, the genetic distance between the two genes is __ cM (round to two decimals).

16.30 cM

In gene ordering, the greatest recombination value identifies the genes that are farthest apart, helping place the genes in __ along the chromosome.

sequence

In Drosophila, the alleles G (grey body) and N (normal wings) written as GN/gn indicate they are on the same __ of a homologous pair.

chromosome

Environmental factors such as sunlight can influence polygenic traits like human __ colour.

skin

Alleles Iᴬ and Iᴮ are __ to each other in the ABO system; both antigens appear in heterozygous (IᴬIᴮ) individuals.

codominant

An organism with genotype YYRR is crossed with yyrr to produce F₁ generation YyRr, demonstrating that yellow seed colour (Y) and round seed shape (R) are __ dominant.

both

A male is said to be __ for X-linked genes because he has only one copy of the X chromosome.

hemizygous

Crossing over of linked genes occurs between __ chromatids of homologous chromosomes.

non-sister