bio chapter 13-duhon

Gregor Mendel

Gregor Mendel

Discovered that inherited traits are specified in units by keeping detailed records of how pea plant traits passed from one generation to the next

Monohybrid crosses

pairs of homologous chromosomes separate and end up on different gametes

Dihybrid crosses

genes of a pair segregate into gametes independently of other gene pairs.

Original theory for hereditary material

that hereditary material was a fluid, with fluids from both parents mixing at fertilization

DNA

The hereditary material, was not proven to be the hereditary material until the 1950's

Gene

Each ______ occurs at a specific location/locus, on a particular chromosome

Somatic cells

diploid cells that form parts of an organism's body (In most cases, both genes of a pair are expressed)

Breeding true

When organisms breed true for a trait because they carry identical alleles of genes governing that trait.

Homozygous

An organism with two identical alleles of genes for a certain trait.

Heterozygous

An organism with two different alleles of genes for a certain trait.

Hybrid organism

An organism that has two different alleles for a trait

Genotype

The set of alleles an organism carries.

Phenotype

An organisms observable traits.

Dominant alleles

An allele who's effects mask those of a recessive allele.

Recessive alleles

An allele who's effects are masked by those of a dominant allele.

Gametes formed during meiosis

Only carry one of their original alleles.

Testcross

cross between an organism with an unknown genotype and an organism with a recessive phenotype

Monohybrid cross

A cross between heterozygous organisms who share a trait.

F1

First generation.

F2

Second generation.

The phenotypic ratio

Organisms have a 3:1 chance of receiving a dominant allele.

Dihybrid cross

A cross between two individuals, concentrating on two definable traits

dihybrid phenotypic ratio

9:3:3:1

law of independent assortment

the law that states that genes separate independently of one another in meiosis

Linkage group

all genes on a chromosome

# of linkage groups in humans

23

Codominance

when two nonidentical alleles of a gene are both fully expressed in heterozygotes, so neither is dominant or recessive

multiple allele system

genes with three or more alleles in a population

incomplete dominance

when one allele is not completely dominant over it's partner

polygenic inheritance

when alleles of 2 or more genes determine 1 single trait

Pleiotropy

When one gene influences multiple traits

Continuous variation

range of small differences in a shared trait

Heterozygous Organism

An organism that has two different alleles for a trait

phenotypic ratio in F2 offspring

1:2:1

epistasis

one gene affects the expression of another gene

pleiotropic genes

A gene that affects multiple traits

genotype+environment=

phenotype

short tandem repeats

sections of a chromosome in which DNA sequences are repeated