Chapter 4: Gene Function

Question 0

Disruptions of biochemical processes by genes can cause a build up of what?

Answer 0

• intermediate
  L> how much and what kind of build up depends on where the disruption occurs.
  L> disruptions occur via enzyme activity.

Question 1

Genes regulate ____.

Genetic Diseases affect _____.

Answer 1

• chemical events

- biochemical processes

Question 2

Who provided the first evidence of a relationship between genes and enzymes?
-What was it? (3)

Answer 2

• Garrod
• a step in the metabolic pathway may be blocked
• intermediate chemical accumulates
• inborn error of metabolism ( aka born with the genetic disorder)

Question 3

Phenylalanine hydroxylase is the enzyme that is rendered inactive with what genetic disorder?
L> recessive or dominant?
L> sex chromosome or not?

Answer 3

• Phenylkentonuria (PKU)
  L> autosomal recessive(2 copies of a defective gene)
  L> not sex chromosome related

Question 4

With PKU aside from getting the defective gene from both parents how else can one get this disorder.

Answer 4

• spontaneous mutation of one allele and the inheritance of another mutated allele.

Question 5

Symptoms of PKU?

Answer 5

L> low mental capabilities…hypotonia, skin, rashes, musty odor, fairer complexion

Question 6

Albinism is caused by the defect in what enzyme?

Answer 6

• Tyrosinase

L> normally breaks down tyrosine into DOPA which produces melanin ( pigment)

Question 7

Homogentisic Acid Oxidase enzyme is defective in what disorder?
L> causes?
L> recessive, not?
L> sex chromosome, not?

Answer 7

-Alkaptonuria
L> black urine disease
L> autosomal recessive

Question 8

Beadle and Tatum created what hypothesis?(1942)

L> describe it

Answer 8

• One gene- one enzyme
• gene mutation may result in loss of enzyme activity
  L> absence of end product and accumulation of precursors

Question 9

What was corrected about the one gene one enzyme hypothesis?

Answer 9

• its actually one gene- one polypeptide

Question 10

Phenylketonuria (PKU)

• ______mutation on what chromosome?
• What enzyme is involved, what does it normally produce?
• Excessive amounts of PHE are ____.
• it has ___ effects

Answer 10

• Chromsome 12 , recessive
• Phenylalanine hydroxylase
• tyrosine production
• harmful
• pleiotropic effects

Question 11

What are pleiotropic effects?

Answer 11

• when one gene influences multiple phenotypic traits (ex: PKU)
  L> that whole intermediate build up via enzyme not working concept.

Question 12

Phenylalanine hydroxylase comes from?

Answer 12

• dietary source

Question 13

Symptoms of PKU?

Answer 13

• severe delayed mental development
• slow growth rate
• early death
  L> can be teratogenic (cause malformations of an embryo or fetus )

Question 14

Screening for PKU: 
- What is the Guthrie Test? 
L> what is put on filter paper? 
L> its incubated with \_\_\_\_ and \_\_\_\_. 
L> Growth of the above is promoted by \_\_\_. 
L> whose it done on?

Answer 14

• blood drop on filter paper
• incubates with bacillus subtillis and B-2-thienylalanine
  L> growth is promoted by PHE (test comes up positive if present)
• new borns

Question 15

What is KUVAN?

Answer 15

• medication used to lower PHE levels for those with PKU

Question 16

Lesch-Nyhan Syndrome :

• Is the mutation on a sex Chromosome or not?
• recessive, dominant?
• What enzyme deficiency is linked to it?
• What is excessively produced?
• This disease is ultimately ____.

Answer 16

• It’s on the X Chromosome… recessive
• HGPRT: hypoxanthine guanine phosphotibosyl transferase : essential to purine usage
• purine is produced excessively…and converted to uric acid which accumulates
• fatal (before 20)

Question 17

Kartagener Syndrome:
- autosomal or sex mutation?
L> recessive or dominant?

Answer 17

• autosomal recessive

Question 18

Kartagener Syndrome:

- what are the three characterizations!

Answer 18

• sinus and lung abnormalities
• sterility
• dextrocardia (organs are mirror images of what they should be)

Question 19

Kartagener Syndrome:

- mutation is on what chromosome?

Answer 19

• chromosome 9

Question 20

Kartagener Syndrome:
-Genes affected code for proteins of the dynein motors of ___ and ___.
L> What does this have to do with the three characterizations of the disorder?

Answer 20

• cilia and flagella
• Lungs and sinus: mucous etc will not be moved properly etc
• Sterility: sperm cannot move…eggs don’t move
• Dextrocardia: normally cilia motion cells in embryo to the correct spot during development…but not in this syndrome. The embryonic fluid moves randomly instead of to the right.

Question 21

Cystic Fibrosis:
- autosomal or sex related?
L> recessive or dominant?

Answer 21

• autosomal recessive

Question 22

Cystic Fibrosis:

- located on what chromosome

Answer 22

• 7q31.2-q31.3

Question 23

Cystic Fibrosis:

• 1/ ___ births have this
• estimated carriers to be 1/__ people

Answer 23

• 2000

- 23

Question 24

Cystic Fibrosis: | -life expectancy??

Answer 24

- ~40 years

Question 25

Cystic Fibrosis: | - characterizations? (3)

Answer 25

- pancreatic, pulmonary, and digestive dysfunction in children and young adults!

Question 26

Cystic Fibrosis: | - Deletion of ____, a single __ is missing, affecting a ____.

Answer 26

- delta F508 - amino acid (3bases) - chloride channel M- protein

Question 27

Cystic Fibrosis: | - _/3 mutations are delta F508 but the rest are of the other ___ mutations that can cause it.

Answer 27

- 2/3 | - 999

Question 28

Cystic Fibrosis: -Where is the most common site of the CF mutation delta F508? ( think Cystic Fibrosis transmembrane conductance regulator diagram (CFTR) ) L> what does this cause?

Answer 28

- Most common site site affected by the deletion of the delta F508 sequence is a nucleotide binding fold (NBF) region that binds ATP L> the mutation causes excess Cl- to not be taken back and the sweat gland releases more in the sweat (aka higher Cl- concentration in sweat than normal person)

Question 29

What are the two types of genetic counselling?( fetal analysis)

Answer 29

- Amniocentesis | - Chorionic villus sampling

Question 30

``` Genetic Counselling: - Chorionic villus sampling ? L> time period? L> reliable? L> issues? L> results, fast?slow? ```

Answer 30

``` - sampling of placental tissue! L>10-12 weeks it can be done L>not very reliable L> due to cell mosaicism : presence of two or more populations of cells with different genotypes in one individual ( cells from mom and baby together) - results are made quick! ```

Question 31

``` Genetic Counselling: - Amniocentesis ? L> reliable, yes or no? L> time frame of use? L> results waiting period? L> safe? ```

Answer 31

- amniotic fluid is sampled which contains fetal tissue to culture. L> yes L> 16 weeks L> long waiting period...cells need to be cultured L> not 100%... 1/300 babies are lost via this