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Chapter 8: Genetics: The Code of Life

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Title: Chapter 8: Genetics: The Code of Life


1
Chapter 8 Genetics The Code of Life
  • Name five of your own traits
  • Describe how traits are passed from one
    generation to the next
  • Define genes and chromosomes
  • Explain how genetics can help farmers improve
    their crops

2
Chapter 8 Genetics Vocabulary
  • Breeding Producing offspring Raising plants or
    animals, especially to get new or better kinds
  • Chromosomes Thread-like parts of a cell nucleus
    made up of DNA and genes
  • Crossbreeding Combining the sex cells of
    organisms with different traits to create new
    traits
  • Fertilization The joining of a sperm cell with
    an egg cell
  • Gene A part of a chromosome that controls the
    development of individual traits

3
  • Heredity The passing of traits from parents to
    offspring
  • Hybrids The offspring of crossbreeding
  • Mutation A change in the genetic code of an
    organism
  • Traits Characteristics, which may be inherited,
    that identify organisms as individuals

4
I. Traits
  • All the ways your look and act are called traits
  • The color of your skin, hair, eyes, size, and
    shape are traits
  • You have personality traits

5
II. What is Heredity?
  • All living things reproduce new organisms called
    offspring
  • Offspring get their traits directly from their
    parents
  • Heredity is the passing down of traits from
    parents to offspring
  • Genetics is the scientific study of heredity

6
III. Beginning of Genetics
  • Genetics started in the mid 1800s
  • Gregor Mendel (Father of Genetics)
  • Mendel was breeding pea plants
  • Breeding is the producing of offspring or new
    breeds
  • Mendel studied how traits were passed from parent
    to offspring.
  • Mendel studied traits like short, tall, white
    flower, red flower, wrinkled or smooth.
  • He studied these traits to see if they were
    passed onto their offspring

7
  • Mendel used crossbreeding to study heredity
  • 1. Crossbreeding is the combining the sex cells
    of organisms with different traits to create new
    traits
  • 2. Mendel created hybrids
  • a. Hybrids are the offspring of crossbreeding

8
  • Mendels Finding
  • Crossed tall and short plants, always got tall
    plants
  • Crossed pink-and white- flowered plants, he
    always got pink flowered plants
  • Crossed round-seeded plants with wrinkled-seeded
    plants, he always got round seeds
  • Found that a strong trait from one parent may
    hide the weaker trait in the other
  • Stronger traits called dominant traits
  • Weaker traits are called recessive traits

9
  • Mendels Further investigation
  • Intitially thought traits may be lost.
  • He found that traits that disappeared showed up
    in later offspring.
  • Dominant trait always shows up over a recessive
    trait.
  • Recessive trait will show up only when both
    parents pass on the recessive trait.
  • Punnet Square is used to determine gene pairing.
  • Lower case is a recessive gene
  • Upper case is a dominant gene

10
  • Homozygous are parents that have two genes that
    are both dominant or both recessive
  • Heterozygous are parents that have genes where
    one is recessive and one is dominant.
  • Practice
  • 1. Let's say that in seals, the gene for the
    length of the whiskers has two alleles.  The
    dominant allele (W) codes long whiskers the
    recessive allele (w) codes for short whiskers.
  • a)  What percentage of offspring would be
    expected to have short whiskers from the cross of
    two long-whiskered seals, one that is homozygous
    dominant and one that is heterozygous? b) If one
    parent seal is pure long-whiskered and the other
    is short-whiskered, what percent of offspring
    would have short whiskers?
  • http//www.borg.com/lubehawk/psquprac.htmAnswer
    20to20Q1

11
IV. Chromosomes and Genes
  • Traits are controlled by DNA
  • Chromosomes are the thread-like parts of a cell
    nucleus made up of DNA and genes
  • Genes are part of a chromosome that controls the
    development of individual traits
  • Genes are the basic building blocks of heredity
  • All chromosomes come in pairs (23 pairs, or 46
    chromosomes)
  • 1. Half from their mom (23) and half from their
    dad (23)

12
www.windows.ucar.edu/.../ genetics_intro.html
13
V. How an Organism Gets its Gene
  • Most cells reproduce by division
  • A single cell divides into 2 cells copying its
    nucleus exactly
  • Many organisms (including humans) begin with 2
    special kinds of cells
  • Sex Cells
  • Sperm cell is the male sex cell
  • Egg is the female sex cell
  • When they reproduce themselves they only get half
    of their chromosomes
  • Fertilization is when an egg and sperm join
  • The rejoin their chromosomes to get the full
    number of chromosomes again, half from mom and
    half from dad

14
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15
Mutationshttp//www.biology-online.org/2/8_mutati
ons.htm
  • New Traits suddenly appear in organisms.
  • Cat born without a tail.
  • Flower giving offspring with a different color
    flower not known in that flower.
  • This is caused by a change in a gene or
    chromosome.
  • This change in genetic code is called a mutation.
  • Happens when sperm and egg cells hook up just a
    little bit differently.
  • This also accounts for some parts of evolution
    found in life on Earth.
  • Some mutations are harmful and kill the organism
    not allowing the new traits to be passed on.
  • Some mutations are beneficial and allow an
    organism to survive when it normally would not
    allowing this new trait to be passed on.

16
What are some mutations that have occurred to
help us be who we are today?
17
VII. Plant and Animal Breeding.
  • Breeding is the producing offspring Raising
    plants or animals, especially to get new or
    better kinds.
  • Breeding is used to control the traits of
    offspring.
  • Breed two different plants together to produce
    offspring with desired characteristics.
  • Where would this be helpful?

18
VIII. Environments and Traits.
  • Traits control a lot about you but not
    everything.
  • Traits can also be formed by environment.
  • Suppose a person has the genes to be a great
    runner.
  • What about if that person has a poor diet and
    never exercises.
  • Suppose a tomato plant was the offspring of
    plants that were big and juicy.
  • This tomato plant should be big and juicy.
  • What if it was put in poor soil and not watered
    enough.
  • http//genealogy.about.com/cs/geneticgenealogy/a/n
    ature_nurture.htm
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