Chapter 9 - Biochemical Genetics

Question 1

• 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

Answer 1

biochemical genetics

Question 2

where is biochemical genetics used

Answer 2

define metabolic diseases

Question 3

• 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

Answer 3

Metabolic disease

Question 4

compound acted upon by an enzyme in a chemical reaction

Answer 4

substrate

Question 5

Archibald Garrod’s Hypothesis

Answer 5

one gene - one enzyme

Question 6

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

Answer 6

Archibald Garrod’s Hypothesis

Question 7

• 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

Answer 7

metabolic pathways

Question 8

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

Answer 8

inborn errors of metabolism

Question 9

what is the result of homozygous recessive state on metabolic pathways

Answer 9

serious physiological consequences

Question 10

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

Answer 10

inborn errors of metabolism

Question 11

who proved Garrod’s hypothesis

Answer 11

• Beadle
• Tatum

Question 12

when did Archibald Garrod propose the relationship between genes and proteins

Answer 12

1908

Question 13

what disease did Archibald Garrod study

Answer 13

Alkaptonuria

Question 14

where is Alkaptonuria common

Answer 14

children of first-cousin marriages

Question 15

• 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

Answer 15

Alkaptonuria

Question 16

How to recognize metabolic disorder

Answer 16

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

Question 17

history

Answer 17

• timing of onset of symptoms
• response to therapies

Question 18

• 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

Answer 18

Galactosemia

Question 19

what is deficient in people with Galactosemia

Answer 19

Galactose-1-Phosphate Uridyltransferase

Question 20

Effects of Galactosemia

Answer 20

1. enlarged liver
2. mental retardation
3. slow growth

Question 21

Therapy of people with Galactosemia

Answer 21

newly born is given galactose-free diet

Question 22

what is a must in people with Galactosemia

Answer 22

early detection

Question 23

What is damaged in people with Galactosemia

Answer 23

1. liver
2. eyes
3. kidneys
4. brain

Question 24

• absence of enzyme phenylalanine hydroxylase
• resulting in inability to hydroxylate phennylalanine to tyrosine
• phenylalanine converted to phenylpyruvic acid (PPA) which is released in urine

Answer 24

Phenylketonuria (PKU)

Question 25

what enzyme is absent in people with Phenylketonuria (PKU)

Answer 25

phenylalanine hydroxylase

Question 26

PPA

Answer 26

phenylpyruvic acid

Question 27

Effects of Phenylketonuria (PKU)

Answer 27

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

Question 28

Therapy for Phenylketonuria (PKU)

Answer 28

diet therapy

Question 29

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

Answer 29

Alkaptonuria

Question 30

what enzyme is absent in people with Alkaptonuria

Answer 30

homogentisate 1,2-dioxygenase

Question 31

what activity is absent in people with Alkaptonuria

Answer 31

homogentisic acid oxidase activity

Question 32

where does homogentisic acid also accumulate

Answer 32

cartilaginous tissues

Question 33

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

Answer 33

ochronosis

Question 34

Homogentisic acid accumulation leads to darkening of what?

Answer 34

- nose - eyes - ears

Question 35

what is the effect of Alkaptonuria in the joints

Answer 35

benign arthritis

Question 36

- absence or reduciton or melanin - autosomal recessive trait - absence of enzyme tyrosinase needed in the production of melanin

Answer 36

albinism

Question 37

what enzyme is absent in albino people

Answer 37

tyrosinase