Science test 2

Understanding Heredity Notes

Understanding Heredity

One generation passes information to the next.

Lambs resemble their parents because of heredity.

People selectively bred plants and animals so their offspring would have valuable traits.

Mendel’s Research

He conducted careful experiments over many years.

He was a bright student, but his family did not have money to send him to the university.

He concluded that parent plants have a factor that transfers traits to their offspring.

Discovery of Chromosomes

By the 1880s, scientists were able to observe the nucleus of a cell.

They named these structures chromosomes.

The new pair of chromosomes is a mixture of the chromosomes of their parents.

A Remarkable Molecule

DNA was first extracted from the nuclei of cells in 1869.

Scientists concluded that the DNA molecule is a complex double strand of molecules.

Scientists use the term double helix to describe the twisted-ladder shape of a DNA molecule.

Genes and Heredity

On a chromosome, sections of DNA called genes contain coded instructions to make molecules called proteins.

Humans have thousands of different proteins.

Watson and Crick’s model of DNA helped describe how heredity works.

Vocabulary

Generation

Offspring that are at the same stage of descent from a common ancestor.

Heredity

The passing of traits from parent to offspring.

Inheritance

The passing on of genetic traits from parents to offspring.

Variation

The range of expression of a trait within a population.

Chromosome

A structure made of coiled DNA that transfers hereditary information to the next generation.

Gene

The basic unit of heredity carried by the chromosome; codes for proteins.

Protein

A molecule that performs the tasks of a cell, is part of cells and cell structures, and helps determine the traits of an organism.

Genotype

An organism’s particular genetic makeup.