Human Genetics

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Human Genetics
Human Genetics
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I. Mutations changes in DNA

• a. Germ Cell Mutations
• occurs during meiosis takes place in sex cells
• b. Somatic Mutations -
• take place in the body cells
• c. Mutations increase the amount of variation
  among offspring.

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II. Gene MutationChanges in Nucleotides of DNA

• a. Point Mutations (2 types)
• 1.Base pair substitutes
• may have no effect,
• change amino acid
• or change to stop codon

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• Frameshift Mutations
• Base-pair insertion
• or deletion
• Result is a nonfunctional protein
• Alters the reading frame of mRNA triplets

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III. Chromosome Mutations

• Deletion removal of a chromosomal segment
• Duplication repeats a chromosomal segment
• Inversion segment reversal in a chromosome
• Translocation movement of a chromosomal segment
  to another non-homologous chromosome

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IV. Causes of Mutations

• A. Chance
• B. Mutagen environmental factor damages DNA
• Ex. UV light (sun skin cancer), cigarette tar,
  asbestos, virus, radiation

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V. Karyotypes

• Shows chromosomes paired by size, shape, and
  appearance in metaphase.
• Cells are treated, photographed, sorted and
  arranged by homologous pairs.
• Chorionic villi sampling, and amniocentesis can
  be used to diagnose chromosomal abnormalities.

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VI. Changing Chromosome Number

• Nondisjunction failure of chromosomes to
  separate during Prophase I of meiosisaddition or
  loss of a chromosome
• B. Monosomy occurs when only one of a pair is
  present (45)
• C. Trisomy occurs when three of a particular type
  of chromosome is present (47)

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• D. Nondisjunction Abnormalities
• Many trisomies and nearly all monosomies are
  fatal.
• XYY males (Jacob syndrome)- tall, acne, not
  overly aggressive
• XO females (Turner syndrome)- short, webbed neck,
  no puberty.

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Turner syndrome affects approximately 1 out of
every 2,500 female live births worldwide. It
embraces a broad spectrum of features, from major
heart defects to minor cosmetic issues. Some
individuals with Turner syndrome may have only a
few features, while others may have many. Almost
all people with Turner syndrome have short
stature and loss of ovarian function, but the
severity of these problems varies considerably
amongst individuals.
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• Trisomy Extra chromosomes (47)
• Klinefelter Syndrome XXY male, some
  retardation, low fertility (rare cases
  (48,XXXY) or (49,XXXXY)
• Triple X Female (XXX) no physical abnormalities
• Fragile X Syndrome X chromosome broken males
  hyperactive or autistic, delayed speech
• Down Syndrome extra 21st chromosome mental
  retardation, fold of skin above eyes, weak muscles

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VII. Sex Determination

• A. Thomas Hunt Morgan
• Experiments with Drosophila (fruit fly)
• Sex Chromosomes Determine Gender
• B. Autosomes are non-sex chromosomes
• C. Sex chromosomes differ between males and
  females.
• Human female is XX
• Human male is XY.

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• D. Sex chromosomes carry genes for traits
  unrelated to sex.
• E. Single, recessive allele on X expressed
• F. Males express sex-linked alleles more

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G. Example of Sex Link Traits

• Color Blindness
• Hemophilia blood doesnt clot
• x x normal x y normal
• x x normal x y hemophelia
• XhXh hemophelia

H
h
H
H H
h
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VIII. Human Genetics Traits

• A. Single Allele Traits
• 1. Sickle Cell Anemia
• a. Sickle shaped red cells
• b. Clump block arteries, lack 02,
• pain, weakness, death
• c. AA normal cell
• AA both kinds protected from
• malaria
• AA sickle cells

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2. Huntingtons Disease

• Cause by one dominant allele
• Brain cells degenerate no muscle control death
• Occurs at 30 -40 passed to child 50 of time

H h
h h
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3. Tays-Sacs, Cystic Fibrosis, Phenylketonuria,Dw
arfism
Tays Sachs Disease is an inherited incurable
disease of the central nervous system.
Its symptoms first appear when a baby is about 6
months old. The baby stops smiling and
developing through the normal developmental
stages. Blindness and paralysis follow within
the next four years
resulting in the child's death by the age of five
years. Most babies die within the first two
years.
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B. Polygenic Traits

• 2 or more genes control trait
• 1.Skin color - 4-7 genes with additive effect of
  amount of melanin
• 2. Eye Color blue (light melanin), brown (lot
  of melanin)
• 3. Height

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C. Multiple Allele Traits

• Trait with 3 or more alleles only get 2
• 1. ABO Blood group system types A, B, AB, O
• 2. AA type A AO type A OO type O
• BB type B BO type B AB type AB
• A,B codominant Both dominant to O

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D. Sex Influenced Traits

• not a sex chromosomes influenced by sex
  hormones
• BBaldness dominant in males and
  recessive in females
• BBbald females and males
• BB female will not lose her hair
• BB male will lose hair

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IX. Studying Humans

• A. Population Sampling
• select a number to represent
• whole population
• B. Twin Studies
• environment vs. genetics
• C. Pedigree Studies
• family chart of traits

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D. DNA fingerprinting study the patterns of
bands obtained from electrophoresis 1.
Gel electrophoresis process to separate DNA
fragments by size of charge
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