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MED 109- BIOLOGY II > 12. HUMAN DISORDERS DUE TO CHROMOSOMAL ALTERATIONS > Flashcards

12. HUMAN DISORDERS DUE TO CHROMOSOMAL ALTERATIONS Flashcards

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1
Q
  1. What are some serious disorders caused by?
A
  • alterations of the chromosome number and structure
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2
Q
  1. Do all types of aneuploidy upset the genetic balance to the same severity?
A
  • NO
  • some types of aneuploidy upset the genetic balance
    less than others
  • this is why some individuals are able to survive to birth
    and beyond
  • these individuals will have a set of symptoms
  • this is known as a syndrome
  • it is characteristic of the type of aneuploidy they have
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3
Q
  1. What are the 3 types of common human autosomal trisomies?
A
  1. Trisomy 21
    (Down Syndrome)
  2. Trisomy 18
    (Edwards Syndrome)
  3. Trisomy 13
    (Patau Syndrome)
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4
Q
  1. Name 3 typical symptoms of an individual with Autosomal Trisomy?
A
  1. Birth Defects
  2. Intellectual Disability (Mental Retardation)
  3. Shortened Life Expectancy
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5
Q
  1. What is Down Syndrome?
A
  • this is an aneuploid condition
  • it results from 3 copies of Chromosome 21
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6
Q
  1. How many children born are affected with Downsyndrome?
A
  • 1 out of every 700
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7
Q
  1. What increases the frequency of Down Syndrome?
A
  • the frequency of Down Syndrome increases with the
    age of the mother
  • a mother having children over the age of 35 will greatly
    increase the chance of her child having a chromosomal
    abnormality
  • the sperm of older males also has a decreased
    chromosomal quality
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8
Q
  1. What are the phenotypic symptoms of Down Syndrome?
  • = very important
A
  1. Growth Failure
  2. Flat back of head (*)
  3. Abnormal Ears
  4. Many loops on the fingers
  5. Palm Crease
  6. Special skin ridge patterns
  7. Diminished muscle tone
  8. Broad Flat face
  9. Slanting eyes
  10. Epicanthic eye fold
  11. Short nose
  12. Short and broad hands
  13. Big wrinkled tongue
  14. Bog toe is spaced widely apart from the others
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9
Q
  1. What are the non-visible symptoms of Down Syndrome?
  • = very important
A
  1. Mental Retardation (*)
  2. Unilateral or Bilateral absence of one rib
  3. Intestinal Blockage
  4. Umbilical Hernia
  5. Abnormal Pelvis
  6. Diminished Muscle Tone
  7. Small, arched palate
  8. Dental anomalies
  9. Congenital Heart disease (*)
  10. Enlarged Colon
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10
Q
  1. What does the nondisjunction of sex chromosomes produce?
A
  • it produces a variety of aneuploid conditions

SUCH AS:
- XXY males
- XYY males
- XXX females
- XXXX females
- XO females

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11
Q
  1. What is Klinefelter Syndrome?
A
  • this is found in XXY individuals
  • these are males with an extra X chromosome
  • these are males with additional female characteristics
  • they have developmental abnormalities
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12
Q
  1. What are some symptoms of Klinefelter Syndrome?
A
  • Gynecomastia (breast development)
  • Frontal baldness is absent
  • Tendency to grow fewer chest hairs
  • Female type pubic hair pattern
  • Small testicular size
  • Poor beard growth
  • Narrow shoulders
  • Wide hips
  • Long legs
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13
Q
  1. What is Turner Syndrome?
A
  • this is known as Monosomy X
  • it happens in XO females
  • this makes then infertile and sterile
  • it is the only known viable Monosomy in humans
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14
Q
  1. What are some of the symptoms of Turner Syndrome?
A
  • Short Stature
  • Low Hairline
  • Shield-shaped Thorax
  • Widely spaced nipples
  • Shortened Metacarpal IV
  • Small fingernails
  • Brown Spots (nevi)
  • Characteristic facial features
  • Fold of skin by the neck
  • Constriction of the Aorta
  • Poor breast development
  • Elbow deformity
  • Underdeveloped Gonadal structures
  • No menstruation
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15
Q
  1. What causes Cri du Chat Syndrome?
    (Cry of the cat)
A
  • this is caused by the deletion of part of Chromosome 5
  • it is a chromosome structure abnormality
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16
Q
  1. What symptoms does a child born with Cri du Chat Syndrome have?
A
  • these children are severely mentally retarded
  • they have a cat like cry
  • they usually die in infancy or early childhood
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17
Q
  1. Which is more severe, a chromosomal abnormality or a genetically inherited disorder?
A
  • a Chromosomal Abnormality
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18
Q
  1. What causes Chronic Myelogenous Leukaemia
    (CML) ?
A
  • this is a type of cancer
  • it is caused by the translocation of chromosomes
  • the type of translocation that takes place is called a
    Reciprocal Translocation
  • this is the exchange of fragments between non-
    homologous chromosomes
19
Q
  1. There are two normal exceptions to Mendel’s standard chromosomal theory of inheritance.
    What are they?
A
  1. The inheritance of nuclear genes
  2. The inheritance of genes located outside the nucleus
20
Q
  1. What is an example of the Inheritance of Nuclear genes?
A
  • Genomic Imprinting
21
Q
  1. What kind of genes are an example of genes located outside the nucleus?
A
  • extranuclear genes
  • cytoplasmic genes

SUCH AS:
- organellar genes
- mitochondrial genes
- chloroplast genes
- these have their own DNA and genes
- they do not follow Mendelian genetics

22
Q
  1. What is Genomic Imprinting?
A
  • this is known as a kind of silencing
  • this is when either the maternal or paternal allele of a
    certain gene are inactivated
  • this happens at the beginning of development
  • this process inhibits the expression of that specific
    allele
23
Q
  1. What does Genomic Imprinting result in?
A
  • variation in the phenotype of the offspring
  • this is dependent on which parent passed along the
    alleles for certain mammalian traits
24
Q
  1. What does the silencing of certain genes involve?
A
  • it involves the stamping of the allele
  • it is stamped with an imprint during gamete
    production
  • this process is known as Methylation
25
Q
  1. What is Methylation?
A
  • this is the addition of a CH3 to the allele
  • this only happens with Nuclear genes

NB:
- this only affects a small fraction of mammalian genes
- 1% to be exact

26
Q
  1. What are most imprinted genes critical for?
A
  • Embryonic Development
27
Q
  1. What is Igf2?
A
  • this is a growth factor
  • it is essential for embryonic and foetal development
28
Q
  1. Can Igf2 also be imprinted in human beings?
A
  • yes
  • it is inactivated in humans
  • it is the maternal allele that is usually silenced by
    Methylation
29
Q
  1. What is Beckwith-Wiedemann Syndrome (BWS)?
A
  • this is the abnormal activation of the maternal Igf2
    allele
  • this happens during egg formation and early
    development
  • this leads to the overstimulation of the growth factor
30
Q
  1. What are the symptoms of the Beckwith-Wiedemann Syndrome (BWS)?
A
  • overgrowth
  • increased risk of childhood cancer
  • it affects 1 in every 15 000 births
31
Q
  1. Where are Extracellular and Cytoplasmic genes found?
A
  • they are found in organelles in the cytoplasm

SUCH AS IN THE:
- Mitochondria
- Chloroplasts (Chlorophyll)
- Chromoplasts (other pigments)
- Amyloplasts (starch)
- other plant plastids

32
Q
  1. What can be said about the DNA of mitochondria, chloroplasts and other plastids?
A
  • these organelles carry small circular DNA molecules
  • these contain genes
33
Q
  1. How are Extracellular genes inherited?
A
  • they are inherited maternally
  • this is because the zygote’s cytoplasm comes from the
    egg
34
Q
  1. How did the first evidence of Extranuclear genes come about?
A
  • it comes from studies on the inheritance of yellow or
    white patches on the leaves of green plants
35
Q
  1. What kind of DNA does Mitochondria carry?
A
  • Mitochondrial DNA
  • this carries genes that code for the cellular respiratory
    process
36
Q
  1. Does this diagram make sense?
A
  • yes
37
Q
  1. What are the results of having a defect in the Mitochondrial genes?
A
  • this can prevent cells from making enough ATP
  • this is known as an ATP synthase disorder
  • this results in serious neuromuscular disorders
  • this is because the brain and the muscles use up most
    of the ATP in the body
38
Q
  1. Provide 2 examples of Mitochondrial gene (synthase) disorders?
A
  1. Mitochondrial Myopathy
  2. Leber’s Hereditary Optic Neuropathy
39
Q
  1. What does Myopathy mean?
A
  • muscle deterioration
40
Q
  1. What does Neuropathy mean?
A
  • nerve deterioration
41
Q
  1. What does Encephalopathy mean?
A
  • brain deterioration
42
Q
  1. How can we prevent Mitochondrial Disorders?
A
  • we can use a Three Person IVF Procedure
43
Q
  1. What is a Three Person IVF Procedure?
A
  • this is when we do an IVF with a healthy embryo from 2
    mothers
  • the child now has 3 parents
  • the 2 eggs enables women with Mitochondrial DNA
    disorders (mtDNA) to have healthy children
  • the mothers usually have functional nuclear DNA and
    abnormal Mitochondrial DNA

MED 109- BIOLOGY II (90 decks)

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