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Genetics and Health

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Title: Genetics and Health


1
Genetics and Health
  • Chapter 12

2
Structures of DNA
  • Can you roll your tongue? Can you bend back your
    thumb? These are just some of the characteristics
    that can be inherited from one generation to the
    next. Diseases and disorders can also be
    inherited
  • Genetics is the study of how these
    characteristics or traits are passed from parent
    to offspring
  • Where is DNA found?
  • Your body contains about 10 trillion cells, each
    cell has a NUCLEUS that contains CHROMOSOMES,
    each chromosome contains double-helix shaped
    molecules called DNA, DNA is divided into
    segments called GENES, it is these genes that
    control the traits that you inherit (eye color,
    hair color, genetic disorders, etc)

3
Structure of DNA
  • DNA has a double helix shape (Twisted latter)
  • Chemical compounds called BASES attach to 2
    sugar-phosphate backbones
  • Only certain bases can pair up with each other
    Adenine (A) and Thymine (T) can pair with each
    other, while Guanine (G) and Cytosine (C) can
    pair with each other
  • When a cell splits, one half of the DNA goes to
    the next cell and hence genes are passed on.
  • Different genes have different base pair
    arrangements/sequences, this is what determines
    the traits that you inherit

4
Chromosomes
  • The human body contains 46 chromosomes arranged
    in 23 pairs that hold all of the genetic
    information in your body
  • One chromosome of each pair comes from the
    mother, the other chromosome comes from the
    father
  • There are two types of sex chromosomes, X and Y
  • Y chromosome is ONLY found in males.
  • Males are XY
  • Females are XX
  • Does figure 12.2 show the chromosomes from a male
    or female? How do you know?

5
A single chromosome
A set of 23 paired chromosomes of the body
6
Inheritance and Genetics
  • Half of your genetic make-up comes from your
    mother, the other comes from your father
  • BUT, then why dont you look exactly like your
    brother, sister, mom or dad?
  • The answer is HEREDITY the passing of
    characteristics from parents to offspring
  • In the mid-1800s, Gregor Mendel, an Austrian monk
    experimented with pea plants to show that traits
    do not happen by accident. He genetically crossed
    tall and short pea plants to see how height would
    be affected. After looking at the results of many
    generations of pea plants, he found that height
    was an inherited trait and that tall plants
    appeared more often because the tallness was a
    dominant trait (it was more likely to be passed
    on) compared to shortness, which was a recessive
    trait (not likely to be passed on)

7
Mendels Experiment
  • Mendel took a tall plant purebred (SS) and short
    plant purebred (ss) and mated them, he then took
    the hybrid offspring (Ss) and mated 2 of them.
    Finally he looked at the offspring produced and
    found that 75 of the offspring were tall, hence
    tallness was the dominant trait. Anytime a big
    S was in the genetic makeup the plant came out
    tall. Only if the plant was ss then would it be
    short

8
Recording Inherited Traits
  • Chromosomes come in pairs. Genes for traits also
    come in pairs
  • Many traits are controlled by only one pair of
    genes, others are controlled by two or more pairs
  • For traits controlled by one pair of genes,
    geneticist use 2 letters to represent the
    genotypecombination of genes
  • Capital letters represent the dominant gene
  • Lowercase letters represent recessive genes
  • During reproduction, a chromosome separates and
    only one chromosome is passed on to the child
    (from both mother and father), dominant or
    recessive. The final combination in the child
    will determine what you inherit
  • Punnett Squares help geneticists determine the
    probability that offspring will inherit certain
    traits

9
Punnett Squares
  • Punnett Squares tell you genotypes genetic
    combinations
  • Punnett Squares also tell you phenotypes
    appearances
  • For example, all of the offspring will appear
    RED, since the gene A is dominant, so anytime it
    is in a pairing it will produce a bird that is
    RED, the recessive blue trait will only give a
    blue bird if it is found as aa
  • Problem Do a Punnett Square of two Aa birds
    mating and give the offspring

aa
  • AA

X

10
Pedigrees
  • A family tree or pedigree is used to trace traits
    in a family
  • A pedigree is a diagram that shows the history of
    a trait from generation to generation
  • Breeders often use pedigree charts to increase
    the likelihood of breeding an animal with
    desirable traits
  • Doctors use pedigree charts to determine the
    likelihood of inheriting deadly diseases from
    your relatives

11
Pedigrees
12
Genetic Changes
  • Most of the time the processes of cell
    reproduction and copying genes works well, BUT
    mistakes do happen during reproduction.
  • Most of the time the body cells do a pretty good
    job of correcting mistakes and errors found in
    DNA, but occasionally the body cells do not
    repair the errors and the mistakes are passed on
    generation to generation
  • Changes in genetic information can result in an
    abnormal gene called a mutation.
  • Mutations can be due to environmental
    conditions/factors such as UV light, chemicals
    like PCBs (which are found in cigarettes),
    nuclear radiation, and drugs. These factors that
    cause mutations are called mutagens
  • Mutations can lead to genetic disorders such as
    sickle-cell anemia.

13
Issues in Genetic Research
  • The Human Genome Project The mapping of the
    complete set of chromosomes that make up the
    human body. The genome is the genetic
    instructions of what makes you who you are
  • Scientists have mapped where each gene belongs on
    the 46 chromosomes
  • This is truly a powerful thing! BUT, With Great
    power comes great responsibility.
  • Pros with the new knowledge scientists can
    transfer out mutated genes from your genome
    Genetic Engineering. Genetic disorders can be
    elimniated. See pg. 223, Table 12.2 on Genetic
    Research
  • Cons Its not natural, Ethical concerns arise
    about who should be able to have genetic
    alterations done, cloning,
  • Cloning process of creating an identical copy of
    an original organism
  • What do you think are some pros and cons of
    cloning?

14
Genetic Research
Dolly first animals, what is next, humans?
Gene Therapy and Genetic Counseling -Genetic
counsellors gather medical information about an
individuals family and analyzes a his/her
chromosomes to help predict the chances of that
person developing a particular disorder
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