Chapter 4:

Section IV: Introduction to Genetics

Intro to Genetics

• Genetic Material is contained in cells.

• Traits = physical characteristics that an organism can pass on to its offspring (parents to kids)– Example: hair color, eye color, straight or

curly hair

Parents to Offspring

• Organisims resemble their parents.

• Heredity = is the process in which traits pass from parents to offspring.

• The scientific study of heredity is called genetics.

The Role of Genes in Inheritance

• DNA = deoxyribonucleic acid– Genetic material that is passed on from parents to

offspring– Carries information– Blueprint of life

• Gene = section of DNA that controls a trait that is inherited by an organism– Is like a recipe, contains instructions for building and

running cells.

Asexual and Sexual Reproduction

• Asexual Reproduction = a reproductive process that involves only one parent.

• Remember “A” = One

– Example: bacteria = splits into two identical cells.

Asexual and Sexual Reproduction

• Sexual Reproduction = new organisms result from the combination of genetic material from TWO parent organisms– Sperm = MALE CELL– Egg = FEMALE CELL– The traits are determined by BOTH cells

Sexual Reproduction and Change

• Inherit genetic material from BOTH parents.– This is why we don’t look like just one parent.

• Children look more like their parents than their grandparents.

• Children look more like their grandparents than their great grandparents.

Changing Traits by Selective Breeding

• Selective Breeding = The process of selecting a few organisms with desired traits to serve as parents of the next generation. – Organisms that have certain desired traits are

mated to produce offspring with the desired traits of both parents.

– The desired traits are produced by the combination of genetic material that the offspring inherit from both of their parents.

Selective Breeding

• Santa Gertrudis Cattle were bred on the King Ranch in southeastern Texas – Mated Brahman cattle with shorthorn cattle

• Shorthorn cattle have tender and tasty beef • Brahman cattle thrive in the heat

• Generation after generation, Santa Gertrudis cattle pass the desirable characteristics on to their offspring.

Changing Traits in Nature

• Chemicals are used to kill insects– Kills almost all the insects in the field.– The remaining reproduce.– Offspring inherit genes from the parents that

make them immune to the chemical that was once used to kill them.

– Chemical = Pesticide, and eventually they will no longer work.

Changing Traits in Nature

• Selective breeding is planned and carried out by farmers.

• Traits of organisms can also change over generations naturally.