How many chromosomes do humans have?

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How many chromosomes do humans have?
STUDY!

• Humans have 46 chromosomes.
• They occur in 23 pairs!

Do you remember what this is called?
A karyotype
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Pair 1 22 are known as autosomes.
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The 23rd pair are called sex chromosomes.
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• X Chromosome
• Y Chromosome
• Do you remember what combination codes for female
  and male?
• XX Female
• XY Male

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Sex Linked Genes

• Some genes are located on the X chromosome.
• These traits are called sex-linked traits and are
  controlled by the genes on the x chromosome.
• Females receive two alleles for these genes, but
  males only receive one, since they only get one X
  along with the Y.
• Because XX Female and XY Male
• Examples include color blindness, pattern
  baldness and hemophilia.

STUDY!
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Colorblindness

• Females who are heterozygous for a trait are
  known as carriers
• A female can be
• XBXB normal
• XBXb carrier
• XbXb - colorblind
• Males CANNOT be carriers because they only have
  one X chromosome
• A male can be
• XBY Normal
• XbY - colorblind

STUDY!
This PS shows a cross between a normal man and a
woman who is a carrier. (Notice that NO allele
is attached to the Y!)
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Sex-linked Problem

• A woman has normal color vision and is married to
  a man with normal color vision. One of their two
  sons has normal color vision but the other son is
  colorblind. How was this possible?
• First, figure out the genotypes of the parents.
• Mom XBXb because she has to be carrier
• Dad XBY because we know he is normal
• Will any of their daughters be colorblind? Will
  any of their daughters be carriers?
• Do the Punnett square to find out!!

STUDY!
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A pedigree is used to show genetic inheritance
within a family
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• Squares represent Males
• Circles represent Females
• Horizontal lines show marriages
• Vertical lines show offspring
• So, lets analyze this pedigree!

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• A pedigree is a graphic representation of genetic
  inheritance.
• In most instances, the shapes are either shaded
  or not.
• If the shape is shaded, then the individual has
  the particular trait.

STUDY!
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Celebration of Learning Moment! ?

• Pedigree Problem Worksheet

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Occasionally, problems occur at the chromosomal
level.
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We call these problems genetic disorders

• A genetic disorder is a disease that is caused by
  an abnormality in an individual's DNA.
• Abnormalities can range from a small mutation in
  a single gene to the addition or subtraction of
  an entire chromosome or set of chromosomes.
• There are various genetic disorders, some
  dominant, recessive, sex-linked, co-dominant.

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Well discuss the more frequently encountered
genetic problems human have.

• WARNING
• Some images may be explicit or hard to see.
• Use your knowledge of these disorders to be kind
  and compassionate to others!

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Dominant Allele Disorders

• What does it mean by dominant?
• Dominant dominates over the recessive allele.
• DD or Dd

• Examples
• Achondroplasia
• Huntington's Disease

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Achondroplasia

• Long bones do not develop properly
• Results in unusually short arms and legs, a large
  head and relatively long torso
• Only 1/8th of the children born with this
  condition inherited it from a parent.
• Most cases of achondroplasia occur spontaneously
  and are the result of a new mutation in an egg or
  sperm of one of the normal- appearing parents. 

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Huntington's Disease

• Progressive, degenerative disease
• Causes certain nerve cells in your brain to waste
  away
• Results in uncontrolled movements, emotional
  disturbances and mental deterioration.
• Huntington's disease is inherited as a dominant
  allele so if one parent has this disease, the
  offspring have a 50 chance of inheriting it.

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Recessive Allele Disorders

• What does it mean to be recessive?
• Dominated by dominant allele
• What HAS to be present to have a recessive
  phenotype?
• BOTH recessive alleles

• Examples
• Cystic Fibrosis
• Tay Sachs Disease
• Albinism

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Cystic Fibrosis

• Inherited recessive disorder resulting from a
  mutation of the gene that regulates the secretory
  glands, including mucus and sweat glands.
• The characteristics of cystic fibrosis are salty
  tasting skin, normal appetite but poor growth and
  poor weight gain, excess mucus production,
  frequent chest infections and coughing/shortness
  of breath.
• Both parents must carry the allele for the child
  to inherit the condition. 

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Tay-Sachs Disease

• Fatal genetic lipid storage disorder in which
  harmful quantities of a fatty substance build up
  in tissues and nerve cells in the brain.
• Infants with Tay-Sachs disease appear to develop
  normally for the first few months but as fatty
  material builds up, a relentless deterioration of
  mental and physical abilities occurs.
• The child becomes blind, deaf, and unable to
  swallow. Muscles atrophy and they can no longer
  swallow.
• Children with Tay-Sachs disease usually die by
  age 4.
• Both parents must carry the allele for a child to
  inherit the condition

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Albinism

• Recessive disorder that occurs when one of
  several genetic defects makes the body unable to
  produce or distribute melanin, a natural
  substance that gives color to your hair, skin,
  and iris of the eye.
• In one type of albinism, people have white or
  pink hair, skin, and iris color, as well as
  vision problems.
• Another type of albinism, called ocular albinism
  type 1 affects only the eyes. The person's skin
  and eye colors are usually in the normal range.
  However, an eye exam will show that there is no
  coloring in the back of the eye .

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Can you remember any of the genetic disorders
weve previously discussed?

• Klinefelters Syndrome Males with one extra X
  chromosome (XXY)
• Turner Syndrome Female disorder where girl only
  has only fully functional X chromosome
• Down Syndrome Trisomy of the 21 chromosome
• Sickle Cell Anemia Misshaped red blood cells

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Create an informative poster!

1. You and your partner will pick a genetic disorder
   and research it
2. Create a detailed AND creative poster to inform
   others about your chosen disorder.
3. This is the ONLY time you will be allowed to use
   your device. And, you should ONLY be
   researching!!!