Biology Chapter 8

heredity
passing of traits form parents to offspring

genetics
branch of biology that studies heredity

monohybrid cross
a cross that considers one pair of contrasting traits

true-breeding
all the offspring only display one particular trait

P generation
first two individuals crossed in a breeding experiment

F1 generation
offspring of the P generation; first filial generation

F2 generation
offspring of the F1 generation; second filial generation

alleles
different versions of a gene

dominant
the expressed form of a trait

recessive
not expressed when the dominant form of the trait is present

homozygous
when the two alleles of a particular gene are the same

heterozygous
the alleles of a particular gene are different

genotype
set of alleles that an individual has

phenotype
physical appearance of a trait

law of segregation
the two alleles for a trait separate when gametes are formed

law of independent assortment
the alleles of different genes separate independently of one another during gamete formation

punnet square
diagram that predicts the outcomes of a genetic cross

test cross
cross of a homozygous recessive individual with an individual with a dominant phenotype of an unknown genptype

probability
the likelihood that a specific event will occur

pedigree
a family history that shows how a trait is inherited

sex-linked trait
trait whose allele is located on the X chromosome

polygenic trait
when several genes influence a trait

incomplete dominance
when an individual displays a trait that is intermediate between the two parents

codominance
two dominant alleles are expressed at the same time

multiple alleles
genes with three or more alleles

Gregor Mendel
person whose studies formed the basis of modern genetics

3:1
phenotypic ratio expected when crossing two individuals heterozygous for a trait

homozygous dominant
the genotype PP is an example

homozygous recessive
a genotype of an individual used in a test cross

T.A. Knight
performed breeding experiments on pea plants 200 years before Mendel did

genotype
an individual’s set of alleles

law of segregation
two alleles for a trait separate when gametes are formed

law of independent assortment
alleles for different genes separate independently of one another during gamete formation

genetic disorder
harmful effects produced by inherited genetic mutations

1 PP: 2 Pp: 1 pp
genotypic ratio expected when crossing two individuals heterozygous for a trait

F2
when two members of the F1 generation are crossed, the offspring are referred to as the __ generation

sex-linked
a trait that is determined by a gene found only on the X chromosome is said to be a __________ trait

Pp and pp
parents with the genotypes Pp and pp can produce offspring of genotypes __ ___ __

3:1
crossing two pea plants heterozygous for flower color should produce a phenotypic ratio of ___ in the offspring

recessive
In a pedigree, if two normal parents produce a child with a genetic disorder, the the disorder is caused by a _________ allele.

genetic counseling
providing medical guidance about genetic disorders that could affect parents or their offspring is called _______ __________

cross pollinate
Mendel removed stamens on pea flowers in order to _____-_________ two P generation plants that had contrasting forms of a trait

self pollinate
Mendel allowed each variety of garden pea to ____-_________

true breeding
This ensured that each plant in the P generation was ____-________ for a particular trait.

Mendel hypotheses
1. for every inherited trait the person has 2 copies of the gene
2. there are alternative forms of genes- alleles
3. 2 alleles occur together– 1 is obvious (dominant), other is not (recessive)
4. when gametes are formed the alleles for each gene separate independently

garden pea
four characteristics that make this good for testing:
-grow easily
-mature quickly
-produce many offspring
-2 different forms