ESSENTIAL QUESTION: HOW ARE TRAITS INHERITED? Chapter 9 Lesson
1
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Main Idea: Living things inherit traits from their parents.
Examples: eye color, freckles, face shape They acquire other traits
from their environment. Examples: riding a bicycle, reading,
swimming
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Heredity: process through which traits are passed from parents
to offspring. Human traits that are passed by heredity are called
_______________. Examples: inherited traits eye color, hair color,
face shape, blood type An inherited trait can also be a behavior,
such as the way a spider spins a web.
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Not all traits are passed through heredity; some are picked up
along the way, or acquired. Acquired Trait: Traits that an organism
develops after its born. Some acquired traits come from the
____________ and some are ____________. Examples: environment
learned reading, riding a bicycle, playing baseball
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How does an organism inherit certain traits? DNA: molecule
found in the nucleus of a cell shaped like a double-helix
associated with the transfer of genetic information looks like a
twisted ladder Your DNA contains your genetic information which
determines your inherited traits.
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How do I get my parents DNA? Molecules of DNA are passed from
parent to child during reproduction. A copy of the DNA molecules
must be made. This is called DNA replication. New DNA molecules are
identical to the original. As a cell gets ready to divide, the
strand of DNA wind up tightly and form shorter, thicker strands of
DNA called chromosomes.
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chromosome: short thick coils of DNA Human cells have 46
chromosomes. Where do these come from? _________ from male and
______ from female 23 gene: short segment of DNA that determines an
organisms inherited traits One chromosome has hundred of genes in
it.
http://www.youtube.com/watch?v=V9BZ3zx8b8I&feature=player_detailpagewww.youtube.com/watch?v=V9BZ3zx8b8I&feature=player_detailpage
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Uh oh! Something goes wrong! Mutation
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If an error occurs during DNA replication, the change is called
a mutation. Error (Mutation)
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Mutations can be harmful because it change the organisms
chances for survival Some mutations are neither harmful or helpful.
Many mutations are caused by chance. Others are caused by
environmental factors called mutagens. For example: UV radiation
from the Sun or certain chemical such as pesticides
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Some human disease are inherited because they result from
mutations. DisorderDescription Cystic Fibrosis makes mucus extra
thick and sticky; clogs lungs and digestive track Hemophilia
prevents blood from clotting, resulting in uncontrolled bleeding
Muscular Dystrophy prevents body from making protein for muscle
cells, resulting in muscle weakness Sickle Cell Anemia creates red
blood cells shaped like sickles. These sickle cells block other
cells and do not carry as much oxygen.
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WHY ARE SOME TRAITS VERY COMMON? Chapter 9 Lesson 2
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Main Idea Over many generations, species develop traits that
help them to survive
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How Traits Are Passed Asexual Reproduction Offspring is
produced by one parent. exact copy of DNA is passed from parent to
offspring Examples: bacteria, many fungi & plants Regeneration
is a form of asexual reproduction.
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Sexual Reproduction Offspring is produced when a female gamete
joins with a male gamete. Half of the offsprings chromosomes comes
from the female and the other half from the male Examples: animals,
flowering plants
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Which trait will be seen? An offspring inherits traits from
both parents through chromosomes. Chromosomes are in pairs one from
mom and one from dad. What shows up? That depends on dominant or
recessive genes.
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Dominant stronger form of a trait; shows up in the offspring
Recessive weaker form of a trait; does not show up in the offspring
Example: Red color is the dominant color of a flower. A bee carries
pollen from a red to a yellow flower. If the offspring, gets a red
gene and a yellow gene for flower color, what color will the flower
be? RED
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Dominant Gene Parent Gene Other Parent Gene Gene That Will Show
Up Red Yellow RedYellow Flower Color Red Yellow
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Purebred organism that has two of the same genes for a trait.
They may be two dominant genes or two recessive genes. Hybrid
organism that has two different genes for the same trait. Offspring
of hybrids may show traits that neither of its parents has. Why
might the traits of offspring of hybrids be difficult to
predict?
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Selective breeding breeding plants and animals for useful
traits; genes in offspring are planned. Example: Cross a rose plant
with large, sweet-smelling flowers with a rose plant that does not
have sharp thorns. Result? A rose plant with large, sweet-smelling
flowers with no thorns
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Dairy cows are bred to produce milk. Beef cows are bred to
produce beef. Farmers and ranchers also use chemicals to make
plants and animals better. Hens can lay more eggs. Cows can produce
more milk.
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In nature, useful traits are not always traits the people would
prefer. They are usually the traits that help an organism survive.
Adaptations Adaptation: a trait or characteristic that helps an
organism survive in its environment Examples: beak shape spines,
stingers, & thorns camouflage mimicry warning colors
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Beak Shape pelican long deep beak that helps a pelican scoop up
fish hummingbird long thin beak that reaches nectar deep inside
flowers parrot - short and thick beak, which helps it crack and
open seeds.
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Camouflage Allows organism to hide in the environment Example:
Bees collect honey in areas with shadows. Their black strip looks
like shadows.
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Mimicry When a organism looks like another organism A king
snake is not poisonous but looks like a poisonous coral snake so
predators will stay away.
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Warning colors Bright colors means an organism is
poisonous.
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Main Ideas How can two red flowers produce an offspring that is
yellow? The flower is a hybrid. Each flower carries the recessive
gene of yellow. REDYELLOW RED RRRY YELLOWYRYY Flower 1 Flower
2
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What adaptation is his animal demonstrating? Camouflage
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Reproductive cells contain only 46 chromosomes. Where do these
chromosomes come from? 23 = mom 23 = dad Put these in order
smallest to largest: chromosome gene nucleus cell