Chapter 11: Patterns of Inheritance

inheritance

the process by which the traits of organisms are passed to their offspring

genes

segments of DNA that encode the info needed to make an organism; the units of inheritance

locus

a gene’s physical location on a chromosome

homologues

pairs of chromosomes in diploid organisms

mutations

changes in the sequence of nucleotides in the DNA of a gene; all alleles arose as this

homozygous

if both homologues carry the same allele at a given gene locus, the organism is _______

same flower

Mendel experimented on edible pea plants, in which male and female reproductive structures occur on the ____ _______

self fertilization

when an organism fertilizes its own eggs

cross fertilization

when sperm from one individual fertilize the eggs of another individual

hybrids

if cross fertilizing parents differ in at least one GENETICALLY determined trait, the offspring are called _______

true breeding

organisms that possess traits that are inherited by all offspring produced by self fertilization

parental

in one experiment, Mendel cross fertilized true breeding, white flowered plants with true breeding purple flowered plants; these plants were the ______ generation

filial

the offspring of the P generation are members of the first ______ generation (F₁)

second

in the ______(F₂) generation, Mendel observed a 3:1 ratio of plants with purple flowers to plants with white flowers

phenotype

observable property

phenotype

observable traits

dominant, recessive alleles

the inheritance of _______ and ______ ______ on homologous chromosomes explains the results of Mendel’s crosses

gene

distinct physical units that determine traits and come in pairs

law of segregation

homologous chromosomes separate from each other during meiosis; each gamete receives only one allele of each gene

diploid

true breeding _______ organisms have two copies of the same allele for a given gene and are homozygous for that gene

dominant, recessive

when two different alleles are present in an organism, the _______ allele may mask the _______ allele

heterozygous

all of the offspring from the F₁ cross were produced either when P sperm fertilized p eggs or vice versa, in both cases, the offspring were ________

law of uniformity

Because P is dominant over p, all the offspring were purple, this is referred to as the ___ __ _________

1. PP

2. Pp

3. pp

Mendel’s F₂ generation contained three types of offspring
1. (purple)
2. (purple)
3. (white)

phenotype

consists of its traits, including outward appearance, behavior, and any other observable feature

genotype

consists of the combination of alleles it carries

Punnett square method

can predict genotypes and phenotypes of offspring; also known as genetic bookkeeping

test cross

crossing an organism with a dominant phenotype but unknown genotype with a homozygous recessive organism

independently

Mendel hypothesized that traits are inherited __________

3, 1

mendel predicted that if the two traits were inherited independently, then _ quarters of the offspring would show the dominant phenotype and _ quarter would show recessive

law of independent assortment

the inheritance of two or more traits

meiosis

the physical basis for this independence is found in the events of _______

1. each trait is completely controlled by a single gene

2. only two possible alleles of each gene exist

3. one allele is completely dominant to the other allele

Mendel’s rules lead to the following conclusions of independent assortment:
1.
2.
3.

incomplete dominance

the phenotype of the heterozygotes is intermediate between the phenotypes of the homozygotes

multiple alleles

a single gene may have _______ ______, not just two; human blood types are an example of this

codominance

when a heterozygote expresses the phenotypes of both of the homozygotes

pleiotropy

a phenomenon where some genes often have multiple phenotypic effect

polygenic inheritance

many traits influenced by two or more genes

chromosomes

genes located on different _________ also sort independently; however, genes on the same one do NOT sort independently

gene linkage

GENES located on the same chromosome tend to be inherited together

genetic recombination

new combinations of alleles on both homologous chromosomes

sex chromosomes

in many animals, an individual’s sex is determined by its ___ __________

sex linked

genes that are located only on sex chromosomes

males

______ fully express all the alleles they have on their single X chromosome

inheritance

________ of sex linked traits differs for males and females

color vision deficiency

caused by certain defects in either of two genes located on the X chromosome

cones, red, green

the normal, dominant alleles of these genes encode proteins that allow one set of color vision cells in the eye, called _____, to be most sensitive to ___ and _____ light

colorblindness

________ is a sex linked recessive disorder

pedigrees

diagrams that show the genetic relationships between a set of related individuals

recessive

some human genetic disorders are caused by _______ alleles

carrier

a person who is heterozygous at a disorder locus

sickle cell anemia

inherited disorder that results in anemia, a low number of red blood cells and hemoglobin, a protein found in red blood cells that transports oxygen

huntington disease

an autosomal dominant disorder caused by a defective protein that kills cells in specific brain regions

hemophilia

a sex linked recessive disorder caused by a recessive allele on the chromosome that results in a deficiency in one of the proteins needed for blood clotting

this person has two different ALLELES at the locus for hair texture

a person is heterozygous for hair texture. what does this mean about the person’s DNA?