Transcript Chapter 4 - Fort Bend ISD

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.