Chapter 9 - Biochemical Genetics Flashcards

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1
Q
  • science concerned with the chemical and the physical nature of genes and the mechanism by which they control the development and maintenance of the organism
  • use to define metabolic diseases
A

biochemical genetics

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2
Q

where is biochemical genetics used

A

define metabolic diseases

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3
Q
  • an inherited enzyme deficiency leading to the disruption of normal body metabolism
  • accumulation of a toxic substrate
  • impaired formation of a product normally produced by the deficient enzyme
A

Metabolic disease

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4
Q

compound acted upon by an enzyme in a chemical reaction

A

substrate

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5
Q

Archibald Garrod’s Hypothesis

A

one gene - one enzyme

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6
Q

Genes act through the production of enzymes, with each gene responsble for producing a single enzyme that in turn affects a single step in a metabolic pathway

A

Archibald Garrod’s Hypothesis

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7
Q
  • highly contrlled sequences making up the biochemical reactions that continually occur in the body
  • produce crucial chemicals such as pigments, enzymes for the digestion of food and the breakdown of various body wastes
A

metabolic pathways

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8
Q

inability to produce a certain enzyme, thus interrupting a metabolic pathway

A

inborn errors of metabolism

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9
Q

what is the result of homozygous recessive state on metabolic pathways

A

serious physiological consequences

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10
Q

what did Garrod reffer to inherited diseases that reflect a patient’s inability to make a particular enzyme

A

inborn errors of metabolism

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11
Q

who proved Garrod’s hypothesis

A
  • Beadle
  • Tatum
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12
Q

when did Archibald Garrod propose the relationship between genes and proteins

A

1908

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13
Q

what disease did Archibald Garrod study

A

Alkaptonuria

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14
Q

where is Alkaptonuria common

A

children of first-cousin marriages

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15
Q
  • a patient with this disorder produces urine that when exposed to air turns distinctively dark
  • these people lack the enzyme found in normal individuals who are able to convert the reddening agent to another substance
A

Alkaptonuria

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16
Q

How to recognize metabolic disorder

A
  1. index of suspicion
  2. family history
  3. history
  4. physical examination
  5. laboratory examination
17
Q

history

A
  • timing of onset of symptoms
  • response to therapies
18
Q
  • unable to metabolize galactose because of deficiency in enzyme Gal-1-Puridyl transferase
  • person with genotype gg
  • blocks a step in the reaction chain and galactose accumulates in the bloodstream
A

Galactosemia

19
Q

what is deficient in people with Galactosemia

A

Galactose-1-Phosphate Uridyltransferase

20
Q

Effects of Galactosemia

A
  1. enlarged liver
  2. mental retardation
  3. slow growth
21
Q

Therapy of people with Galactosemia

A

newly born is given galactose-free diet

22
Q

what is a must in people with Galactosemia

A

early detection

23
Q

What is damaged in people with Galactosemia

A
  1. liver
  2. eyes
  3. kidneys
  4. brain
24
Q
  • absence of enzyme phenylalanine hydroxylase
  • resulting in inability to hydroxylate phennylalanine to tyrosine
  • phenylalanine converted to phenylpyruvic acid (PPA) which is released in urine
A

Phenylketonuria (PKU)

25
Q

what enzyme is absent in people with Phenylketonuria (PKU)

A

phenylalanine hydroxylase

26
Q

PPA

A

phenylpyruvic acid

27
Q

Effects of Phenylketonuria (PKU)

A

excess PPA inhibits conversion of tryptophan to serotonin in brain and spinal cord

28
Q

Therapy for Phenylketonuria (PKU)

A

diet therapy

29
Q
  • absence of homogentisic acid oxidase activity
  • inherited as a single gene recessive trait
  • causes pigmentation called ochronsois of the ear and eyes
A

Alkaptonuria

30
Q

what enzyme is absent in people with Alkaptonuria

A

homogentisate 1,2-dioxygenase

31
Q

what activity is absent in people with Alkaptonuria

A

homogentisic acid oxidase activity

32
Q

where does homogentisic acid also accumulate

A

cartilaginous tissues

33
Q

bluish-black discoloration of certain tissues, such as the ear

A

ochronosis

34
Q

Homogentisic acid accumulation leads to darkening of what?

A
  • nose
  • eyes
  • ears
35
Q

what is the effect of Alkaptonuria in the joints

A

benign arthritis

36
Q
  • absence or reduciton or melanin
  • autosomal recessive trait
  • absence of enzyme tyrosinase needed in the production of melanin
A

albinism

37
Q

what enzyme is absent in albino people

A

tyrosinase