GENETICSChapter 10, Section 1

GREGOR MENDEL Father of Genetics Mendel began to breed garden pea plants

so that he could study the inheritance of their characteristics

Genetics – the branch of biology that studies heredity

Heredity – the passing of characteristics from parents to offspring

Traits – Characteristics that are inherited

GREGOR MENDEL’S EXPERIMENTS Mendel studied pea plants because they

reproduce sexually. Plants contain both male and female sex cells.

Sex cells are called gametes. The male gamete is in the pollen grain. The female gamete is located in the pistil.

The transfer of the male pollen grains to the pistil of a flower is called pollination.

The joining of both male and female gametes is called fertilization.

MENDEL’S MONOHYBRID CROSS

“Mono” means one. Hybrid refers to the offspring of parents that have different forms of a trait.

Monohybrid Crosses are made of two parents that differ only by a single trait.

All of the characteristics he studied had only two forms, so all plants had either one form or the other: Either-or

THE RULE OF UNIT FACTORSA. Mendel concluded that each

organism has two factors that control each of its traits.

B. These factors are genes and are located in chromosomes.

C.Genes exist in alternative forms called alleles.

D.Alleles are inherited from parents.

THE RULE OF DOMINANCE

Mendel called the observed trait dominant. Dominant traits are represented with capital

letters. The trait that disappeared or was “masked” is called recessive. Recessive traits are represented with lower

case letters.

THE LAW OF SEGREGATION

Organisms inherit two copies of each gene, one from the female parent and one from the male parent.

Only one copy of a gene goes into an organism’s gametes. Meaning, the two copies of a gene

separate – or segregate – during gamete formation.

KEY TERMS Phenotype – is the way an organism

looks and behaves Genotype – is the genetic makeup of

an organism Homozygous – Two alleles for the trait

are the same Heterozygous – Two alleles for the trait

are different

1.Who is Gregor Mendel?2.What is a monohybrid cross?

3.Explain the Rule of Dominance.

4.Explain the Rule of Segregation.

5.Explain the Rule of Unit Factors.

6.What are the differences between genotype and phenotype?

Write the question and the answer.

REGINALD PUNNETT The Punnett Square is a grid system for predicting the

possible genotypes resulting from a cross.

The outside edges, or axes, of the grid represent the possible genotype of gametes from each of the parents.

The grid boxes show the possible genotypes of offspring from those two parents.

MONOHYBRID CROSSES Crosses that examine the inheritance of only one specific

trait – for example, flower color

Example: Homozygous dominant crossed with homozygous recessive

MONOHYBRID CROSSES Heterozygous crossed with heterozygous

MONOHYBRID CROSSES Heterozygous crossed with homozygous recessive

DIHYBRID CROSS Dihybrid crosses are crosses that examine the inheritance

of two different traits, example flower color and flower height

Example: Heterozygous crossed with heterozygous

PROBABILITY Probability is the likelihood, or chance, that a particular

event will happen. It predicts the average number of times something will

happen, not the exact number of times.

number of ways a specific event can occur

number of total possible outcomesProbability =