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Flashcards in Kaplan Biochem Ch 4 Deck (100)
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1

stop codon

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

2

start codon; what does it code for?

AUG; codes for methionine
- protein synthesis starts with methionine in eukaryotes and fmet (formylmethionine) in prokaryotes
- therefore the first AA at the amino end (N end) is always Met

3

How many codons are there?

There are 64 codons, 61 code for AA; so there are 61 tRNAs

4

most common inherited form of mental retardation

fragile X

5

Diseases caused by trinucleotide Repeat Expansion

- myotonic dystrophy
- spinobulbar myotonic atrophy aka kennedy syndrome
- Friedrich's ataxia

6

A transition mutation

- a point mutation that replaces a purine-pyrimidine base pair with a different purine-pyrimidine base pair.
- ex) an A-T base pair becomes a G-C base pair

7

silent mutation and effect on protein

- new codon specifies the same amino acid --> no effect on protein
- silent mutation usually in 3rd position: "Wobble effect"
- if you mutate the 3rd nucleic acid in a codon it's usually a silent mutation

8

missense mutation and effect on protein and examples

- new codon specifies different amino acid
- effect on protein: possible decrease in function of protein; variable effects
- ex) sickle cell, PKU, Becker's MD

9

a transversion mutation

- a point mutation that replaces a purine-pyrimidine base pair with a pyrimidine-purine base pair
- ex) an A-T base pair becomes a T-A or C-G base pair

10

Nonsense mutation and effect on protein and examples

- new codon is stop codon
- effect on protein: shorter than normal; usually nonfunctional
- ex) DMD (dystrophin), Hemophilia (Factor VIII)
- "Stop the nonsense"

11

frameshift/in-frame mutation and effect on protein

- addition or deleting of base(s)
- effect on protein: loss of function; shorter than normal or entirely missing

12

large segment deletion
- cause
- effect on protein

- usually occurs via unequal crossover in meiosis
- effect on protein: variable effects ranging from addition or deletion of a few AA to deletion of an entire exon

13

triplet repeat expansion

- Expansions in coding regions cause protein product to be longer than normal and unstable
- disease often shows anticipation in pedigree (disease gets worse with each generation)

14

What will the first 3 AA be in the coding strand?

Coding strand = DNA copy of mRNA except U = T.
- So AUG = start codon --> first 3 AA in DNA will be ATG

15

purpose of meiosis I

- crossover or recombination between homologous chromosomes is a normal part of meiosis I that generate genetic diversity in reproductive cells (sperm and eggs) with a largely beneficial result.
- normally, homologous maternal and paternal chromosomes exchange equivalent segments so no information is lost from ether one

16

cause and consequence of alpha-thallasemia

- unequal crossover (in meiosis I) has deleted one or more alpha-globin genes from chromosome 16

17

Cri-du-chat
- symptoms
- cause

- mental retardation, microcephaly, wide-set eyes, and characteristic kitten-like cry
- results from terminal deletion on the short arm of chromosome 5 (results from unequal crossover in meiosis I)

18

symptoms of hunting tons
- genetic inheritance
- mean age of onset
- juvenile onset

- AD disorder
- mean age of onset: 43-48
- Sx: mood disturbance, impaired memory, hyperreflexia (are often first signs)
- followed by abnormal gait, chorea (loss of motor control), dystonia, dementia, and dysphagia
- juvenile onset: (

19

diseases where the expansion of the trinucleotide repeat of the mutant allele is in the coding region

- huntington's disease
- spinobulbar muscular atrophy

20

Normal huntington allele has

5 tandom repeats of CAG in the coding region

21

family members affected with Huntington's have

30-60 CAG tandem repeats in the coding region

22

Normal protein vs someone who has Huntington's

- The normal protein contains 5 adjacent glutamine residues, whereas the proteins encoded by the disease-associated alleles have 30 or more adjacent glutamates
- the long glutamine tract makes the abnormal proteins extremely unstable

23

diseases where the expansion of the trinucleotide repeat of the mutant allele is in an untranslated region of the gene

- fragile x
- myotonic dystrophy

24

Amino Acid Activation

- each type of AA is activated by a different aminoacyl tRNA syntheses
- no proofreading during translation to detect if correct AA is bound to correct tRNA
- 2 high-energy bonds from an ATP are required
- the high-energy bond linking the AA to its cognate tRNA will later supply energy to make a peptide bond linking the AA into a protein

25

peptide bonds occur between

between the carboxyl group of one AA and the amino group of another

26

During translation, the AA are attached to the ____ ends of their respective ____

During translation, the AA are attached to the 3' ends of their respective tRNAs

27

the aminoacyl-tRNAs are situated in the __ and ___ sites of the ribosome.

- the aminoacyl-tRNAs are situated in the P and A sites of the ribosome.
- P stands for Peptide site
- A stands for acceptor site

28

Aminoacyl-tRNA synthetase

- class of enzyme that recognizes and pairs specific tRNA with their corresponding AA
- each AA is activated by a different aminoacyl-tRNA synthetase
- aa-tRNA synthetase transfers the activated AA to the 3' end of the correct tRNA
- have self-checking functions to prevent incorrectly paired aa-tRNAs from forming. If, however, one does release an incorrectly paired product, there is no mechanism during translation to detect the error and an incorrect AA will be introduced into some protein!

29

the peptide bond forms between the ____ of the amino acid (or growing peptide) in the __ site and the ___ of the next amino acid at the __ site

- the peptide bond forms between the carboxyl group of the amino acid (or growing peptide) in the P site and the amino group of the next amino acid at the A site
- this reaction gives off h20

30

Proteins are synthesized from the ___ to the _____

proteins are synthesized from the amino to the carboxy terminus