Genetics and Health

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Genetics and Health

• Chapter 12

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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)

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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

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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?

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A single chromosome
A set of 23 paired chromosomes of the body
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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)

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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

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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

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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

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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

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Pedigrees
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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.

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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?

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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