Chapter 4: Gene Function Flashcards Preview

Genetics > Chapter 4: Gene Function > Flashcards

Flashcards in Chapter 4: Gene Function Deck (32):

Genes regulate ____.
Genetic Diseases affect _____.

- chemical events
- biochemical processes


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

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


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

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


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

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


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

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


Symptoms of PKU?

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


Albinism is caused by the defect in what enzyme?

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


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

L> black urine disease
L> autosomal recessive


Beadle and Tatum created what hypothesis?(1942)
L> describe it

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


What was corrected about the one gene one enzyme hypothesis?

- its actually one gene- one polypeptide


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

-Chromsome 12 , recessive
- Phenylalanine hydroxylase
-tyrosine production
- pleiotropic effects


What are pleiotropic effects?

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


Phenylalanine hydroxylase comes from?

- dietary source


Symptoms of PKU?

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


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?

- 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


What is KUVAN?

- medication used to lower PHE levels for those with PKU


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 ____.

- 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)


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

- autosomal recessive


Kartagener Syndrome:
- what are the three characterizations!

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


Kartagener Syndrome:
- mutation is on what chromosome?

- chromosome 9


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?

- 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.


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

- autosomal recessive


Cystic Fibrosis:
- located on what chromosome

- 7q31.2-q31.3


Cystic Fibrosis:
- 1/ ___ births have this
- estimated carriers to be 1/__ people

- 23


Cystic Fibrosis:
-life expectancy??

- ~40 years


Cystic Fibrosis:
- characterizations? (3)

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


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

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


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

- 2/3
- 999


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?

- 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)


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

- Amniocentesis
- Chorionic villus sampling


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

- 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!


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

- 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