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Biochemistry Exam 2 > Leys Material > Flashcards

Leys Material Flashcards

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1
Q

Cells acquire nucleotides through what two processes?

A

De novo synthesis and salvage pathway

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2
Q

De novo synthesis of purines results in what?

A

Synthesis of inosine that can be converted into adenosine and guanosine

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3
Q

Atoms in newly synthesized purines are derived from what sources? (3)

A

Amino acids aspartate, glutamine, and glycine, methyl groups supplied by folic acid, and carbon dioxide

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4
Q

What two things regulate the de novo synthesis of purines at multiple points in the pathway?

A

ADP and GDP

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5
Q

Hypoxanthine and guanine can be recycled through the salvage pathway with what enzyme?

A

Hypoxanthine guanine phosphoribosyl transferase (HGPRT)

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6
Q

Xanthine oxidase catalyzes a hydroxylase type reaction leading to the formation of what?

A

Uric acid that can be excreted

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7
Q

What is the main cause of gout?

A

Excess uric acid

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8
Q

What are two main reasons one would have excess uric acid in their system?

A

Excess production or low levels of secretion

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9
Q

Crystallization of Sodium urate in the joints leads to what?

A

A localized inflammatory response

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10
Q

What is used to treat gout? Hint, it is a purine analog.

A

Allopurinol, that hint didn’t help at all did it…

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11
Q

What does allopurinol do during treatment?

A

This is used to treat gout and does so by inhibiting xanthine oxidase which prevents the formation of uric acid.

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12
Q

A HGPRT deficiency causes what syndrome?

A

Lesch-Nyhan syndrome that results in severe retardation, crippling gouty arthritis and self-mutilation

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13
Q

Lesch-Nyhan occurs in what sex and why?

A

Males only because the HGPRT gene is located on the X chromosome

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14
Q

The breakdown of purines can replenish intermediates used in what cycle?

A

TCA, through the production of fumarate

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15
Q

The atoms in a purine ring are derived from what?

A

Aspartate and carbamoyl phosphate

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16
Q

The first 3 enzymes in the synthesis of pyrimidines are located on the same protein which is what?

A

CAD protein

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17
Q

What pyrimidines can be interconverted?

A

U and C

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18
Q

dUMP is converted to TMP by what enzyme and what does it do?

A

Thymidylate synthase, an enzyme requiring the transfer of a methyl group from tetrahydrofolate

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19
Q

Inhibitors of tetrahydrofolate production are used as therapeutic agents for treating what?

A

Cancer and bacterial infections

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20
Q

Fluro substituted pyrimidine analogs that inhibit thymidylate synthase are used to as what?

A

Anticancer agents

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21
Q

Ribonucleotide reductase converts ribonucleotides to what?

A

Deoxyribonucleotides

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22
Q

What are the base pairs in DNA and RNA?

A

DNA: A-T; G-C
RNA: A-U; G-C

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23
Q

Homologous regions of DNA can be compared among different species to determine what?

A

Phylogenetic relationships

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24
Q

Closely related organisms contain similar DNA compliments, so what is the main genetic difference between them?

A

They are often arranged differently on the chromosomes of each species

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25
The living world is made up of what 3 divisions, or domains?
Bacteria, archaea and eukaryotes
26
What are the 4 main processes for generating change in a genome?
Intragenic mutation (single base change), gene duplication, DNA segment shuffling, horizontal transfer (from one cell to another).
27
Bacterial genes are usually clustered into groups called what?
Operons, that are then transcribed as a single unit
28
What are the noncoding parts of DNA called?
Introns
29
What are the coding parts of DNA called?
Exons
30
In a comparison of the same gene in several closely related species will the exons and introns be similar?
The exons will generally be very similar (conserved) but the introns will vary in size and content
31
Do bacterial genes have non coding portions?
No, it is very dense with coding information
32
Is most of the DNA in higher eukaryotes coding or noncoding?
Noncoding, most of the genome is repeated sequences that are mobile elements that can move around in the genome
33
Describe the general shape of bacterial chromosomes and eukaryotic chromosomes?
Bacterial is circular and eukaryotic is linear
34
Can metabolic pathways between organisms be compared through their genome?
Yes
35
Genes can be grouped into families based on what?
Similar (homologous) sequences found in different organisms
36
The phylogenetic relationships of different organisms can be compared by comparing what?
The DNA sequence of similar genes in the two organisms
37
What is the DNA dependent (uses DNA as a template) DNA synthesizing enzyme?
DNA polymerase
38
Is RNA polymerase DNA or RNA dependent?
DNA
39
What does RNA polymerase synthesize?
RNA
40
What is reverse transcriptase?
An RNA dependent DNA synthesizing enzyme
41
What is primase?
A DNA dependent RNA polymerase
42
What does primase do?
Primase synthesizes a small RNA “primer” that can be used by the DNA polymerase to elongate the chain
43
DNA polymerase minimizes the number of mistakes (mis-incorporated nucleotides) by doing what?
Using a 3’ to 5’ exonuclease (or proofreading) activity that is part of the same protein
44
DNA polymerase as well as all other nucleic acid polymerases synthesize DNA in what direction only?
5'-3'
45
The base component of each nucleotide is connected to the sugar at what carbon?
1' carbon
46
What carbon differs between DNA and RNA?
2' carbon
47
Bacterial chromosomes contain how many origins of replication?
One
48
In bacteria, can new rounds of DNA replication begin before the previous round is completed?
No
49
Eukaryotes contain how many origins of replication?
Many, and they may change during teh development of the organism
50
In eukaryotes, each entire chromosome is replicated how many times during each cell division?
Only once
51
During replication, when can new round of eukaryotic replication begin?
Until after the cell divides
52
What are the special structures that are placed at the end of linear eukaryotic chromosomes?
Telomeres
53
Telomeres are constructed with what enzyme?
Telomerase
54
How does telomerase work?
Uses an RNA template to synthesize a short repeated DNA sequence at the ends of chromosomes
55
What unwinds (separates) the 2 DNA strands before polymerization of the new strands?
Helicase
56
What do single stranded binding proteins do?
Keeps single strands of DNA from reforming a double helix
57
The polymerase on the leading strand moves (1)________ the replication fork and the polymerase on the lagging strand moves (2)_____ from it.
(1) toward | (2) away
58
The lagging strand is synthesized in short fragments called what?
Okazaki fragments
59
What initiates the synthesis of each Okazaki fragments?
Primase
60
Which DNA strand is created continuously?
The leading strand
61
What on the DNA signals that the DNA is unreplicated and is ready to be used as a template for the next round of synthesis?
Methylation
62
New or modified genes can be generated by one or a combination of what 4 events?
1) point mutations in the coding region that change the amino acid composition of the protein. 2) duplication of the entire gene. 3) Mixing of segments of one gene with segments of another gene – segment shuffling. 4) Acquisition of new activities by transfer of genes between two organisms -horizontal gene transfer
63
Breaks in the DNA (especially double stranded breaks) facilitate the initiation of what?
Recombination
64
A defect in DNA ligase, that affects joining together of adjacent segment of DNA on a chromosome, can cause what?
Abnormal amounts of recombination
65
What is the definition of genetic recombination?
The reciprocal exchange of genetic information
66
Recombination can be the result of what 4 things?
1) reciprocal exchange during cell division. 2) DNA damage, e.g. X-ray damage. 3) Introduction of foreign DNA. 4) Programmed recombination during the development or maturation of a cell type, e.g. antibody producing genes during B-cell maturation
67
What is gene conversion?
It is the non-reciprocal exchange of genetic information
68
Recombination between direct repeated sequences on the same chromosome causes what?
The loss of DNA that was between the two repeated segments
69
Circular DNA can be inserted in a chromosome by what method?
By recombination between a region on of circular molecule and an homologous region on the chromosome
70
X-rays and other agents that cause breaks in DNA induce what?
Recombination
71
Transposable elements are found in what species?
All
72
What do transposable elements do?
Move from one location in the DNA to another location within that cell
73
Transposable elements can cause changes in the DNA specifically where?
At the site of insertion
74
What are two major types of transposable elements?
One type that contains inverted repeated sequences at the ends and causes a short region of the genome to be duplicated at the site of insertion and a second type that is structurally similar to a retrovirus and transposes through an RNA intermediate
75
Unequal crossing-over is recombination that resulted from what?
Imprecise pairing of tandemly repeated sequences
76
Unequal crossing over results in what?
Loss or gain of gene copies
77
What are the two types of mutations?
DNA rearrangements and base substitutions
78
What are the two outcomes when there is damage to a nucleotide?
Can either be repaired or lead to a permanent mutation
79
Mutations can be caused by what?
Errors during replication or by injury to the DNA from chemicals or radiation
80
What percent of every genome is made up of segmental duplications or large regions of DNA that are present in more than one copy
A small percent, 3%
81
Gene amplification can result in what?
Resistance to drugs, transformation into cancerous cells or other changes in the cell phenotype

Biochemistry Exam 2 (1 decks)

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