Scnm Board Review - Genetics

Front 1

Which nucleotide bases make up the purines and which are the pyrimidines? Which are used in DNA and which in RNA?

Back 1

Purines: Adenine, Guanine (Pure As Gold)
Pyrimidines: Cytosine, Uracil, Thymine (CUT the PYe)

DNA: A, G, C, T
RNA, A, G C, U

Front 2

Nucleotide A pairs with ___ and C pairs with ___ in a DNA strand.

Back 2

A with T
C with G

Front 3

Gene transcription begins in the ____ of the cell with the creation of what?

Back 3

Nucleus; mRNA

Front 4

What is the enzyme that pries the 2 strands of DNA apart and transcribes one strand into mRNA?

Back 4

RNA polymerase

Front 5

RNA polymerase attaches and initiates transcription at the ____ of the DNA strand.

Back 5

Promoter

Front 6

What regulates whether a section of DNA gets transcribed into mRNA?

Back 6

Transcription factors

Front 7

In DNA replication, the nucleotides are added:
A: 5' to 3'
B: 3' to 5'
C: Both

Back 7

5' to 3'

Front 8

What organ(s) does most of the synthesis of the purines and pyrimidines?

Back 8

Mainly liver, but also brain. The liver creates nucleosides that enter the bloodstream and travel to other tissues to get converted into nucleotides.

Front 9

What is the hexose monophosphate shunt? What is the key enzyme involved? What is the other name for pathway?

Back 9

It is an alternate pathway for glucose 6-phosphate to enter to create ribose 5-phosphate which can then be used for purine and pyrimidine nucleotides.

The main enzyme is Glucose-6-P Dehydrogenase; it's a rate-limiting step and the products are CO2, 2 NADPH, and Ribulose 5-P.

Pentose Phosphate Pathway

Front 10

From Ribose 5-phosphate, what is the pathway to manufacture A, T, C, G and U?

Back 10

Ribose 5-P conerts to PRPP. For purine synthesis (A, G), PRPP gets converted to IMP and then to AMP and GMP. This process requires glycine, aspartate, glutamine and THF (TetraHydroFolate).

For pyrimidine synthesis, the PRPP is joined with orotic acid to form UMP. The orotic acid is formed from carbomoyl phosphate and aspartate.

Note that carbomoyl phosphate is also used in the urea cycle.

Front 11

What's the difference between a nucleoside and nucleotide?

Back 11

Nucleoside = base + ribose

Nucleotide = base + ribose + phosphate; they're linked together by phosphodiester bonds

Front 12

What are purines catabolized to? What are pyrimidines catabolized to?

Back 12

Purine degradation generates uric acid.

Pyrimidines degrade into CO2 and urea.

Front 13

What is the enzyme that is used in the degradation of the purines?

Back 13

Xanthine oxidase.

Guanine is degraded directly to xanthine. Adenine is degraded to hypoxanthine and then xanthine. Xanthine oxidase is used in both the oxidation process of hypoxanthine to xanthine and the xanthine to uric acid.

Front 14

Where does translation occur?

Back 14

In the cytoplasm

Front 15

Where does transcription occur?

Back 15

In the nucleus

Front 16

What does it mean when we say our genetic code is unambiguous and redundant?

Back 16

Each codon specifies only 1 amino acid and more than 1 codon may code for the same amino acid.

Front 17

What is the start codon?

Back 17

AUG

Front 18

What are the stop codons?

Back 18

UGA - U Go Away
UAA - U Are Away
UAG - U Are Gone

Front 19

What 3 things occur to the mRNA before it's transported out of the nucleus?

Back 19

1) 5' cap
2) Polyadenylation on 3' end (approx 200 A's)
3) Splicing out of introns (remember: EXons EXit and are EXpressed)

Front 20

What is attached to defective proteins to tag them for breakdown?

Back 20

Ubiquitin

Front 21

What is used in the cytoplasm to create a protein?

Back 21

Ribosome (2 subunits come together: 40S + 60S for eukaryotes)

mRNA - This is the strand that gets translated

tRNA - brings in the appropriate amino acid that's bound to its 3' end

rRNA - transfers growing polypeptide to amino acid in "A" site of ribosome

Front 22

What is a point mutation in DNA?

Back 22

Single base pair alteration in DNA leading to a single amino acid change in a protein.

Front 23

What type of genetic mutation is Sickle Cell Anemia?

Back 23

Point mutation

Front 24

What type of genetic mutation is fragile X syndrome? What type is Huntingtons?

Back 24

They are both trinucleotide repeats. Fragile X syndrome is CGG repeats in X chromosome leading to mental retardation.

Huntington's is CAG repeats in chromosome 4.

Front 25

What are the odds that an affected person with an autosomal dominant disorder will have a child with the disorder?

Back 25

50%

Front 26

What are the odds that an affected person with an autosomal recessive disorder will have a child with the disorder?

Back 26

25%

Front 27

X-linked dominant traits would show up how?

Back 27

If the mother had it, there's a 50% chance a son or daughter would get it. If the father had it, the sons would not get it, the daughters would all get it.

Front 28

What type of genetic inheritance is Hemophilia A and Duchenne's muscular dystrophy?

Back 28

X-linked recessive