Biochem Comlex Review

Front 1

Characteristics of Gene Expression

Back 1

Produces all the proteins an organism requires
Transcription of a section of DNA
Translation of RNA leads to protein synthesis
Occurs throughout interphase
Transcription in nucleus
Translation in cytoplasm

Front 2

Characteristics of DNA Replication

Back 2

duplicates the chromosomes before cell division
DNA copy of entire chromosome
Occurs during S phase
Replication in nucleus

Front 3

G1 Phase of Cell Cycle

Back 3

period of cellular growth preceding DNA synth

Front 4

S phase of cell cycle

Back 4

period of time where DNA replication occurs.
At the end of this phase each chromosome has doubled its DNA content and is composed of 2 identical sister chromatids linked at the centromere

Front 5

G2 phase of cell cycle

Back 5

period of cell growth after DNA synthesis but preceding mitosis

Front 6

B DNA conformations

Back 6

right handed, double helical hydrogen bonded base pairs stacked in center of molecule, 10 base pairs per complete turn helix

Front 7

Z DNA conformation

Back 7

rare, left handed, G-C rich sequences, exact function unknown

Front 8

DNA Plolymerases

Back 8

enzymes that synthesize nucleic acids by forming phosphodiester bonds

Front 9

Nucleases

Back 9

-enzymes that hydrolyze phosphodiester bonds
-Exonuclease remove nucleotides from either the 5' or 3' ends of a nucleic acid
Endonucleases cut within the nucleic acid and release nucleic acid fragments

Front 10

Prokaryotic Cell Replication Steps

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1) Recognition of origin of replication (dna A protein)
2) Unwinding of DNA double helix (Helicase, requires ATP)
3) Stabilization of unwound templete strands (single stranded DNA binding protein, SSB)
4) Synthesis of RNA primers ( Primase)
5) Synthesis of DNA leading and lagging strands (DNA Polymerase III)
6) Removal of RNA primers ( DNA polymerase 1, 5'-3' exonuclease)
7) Replacement of RNA with DNA (DNA polymerase I)
8) Joining of Okazaki fragements (DNA ligase, requires NAD)
9) Removal of positive supercoils ahead of advancing replication forks (DNA topoisomerase II, DNA gyrase)

Front 11

DNA replication Steps in Eukaryotic cells

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1) Recognition of origin of replication
2) Unwinding of DNA double helix ( Helicase, requires ATP)
3) Stabilization of unwound template strands ( Single stranded DNA binding protein)
4) Synthesis of RNA primers ( Primase)
5) Synthesis of DNA leading strand (DNA polymerase delta) and lagging strand (DNA polymerase alpha)
6) removal of RNA primers
7) Replacement of RNA with DNA
8) Joining of Okazaki fragments (DNA ligase, requires ATP)
9) Removal o fpositive supercoils ahead of advancing replication forks (DNA topoismerase II)
10 ) Synthesis of telomeres (Telomerase)

Front 12

Damage to DNA Thymine dimers

Back 12

Caused by UV radiation, recognized/removed by Excision endonuclease, repaied by DNA polymerase and DNA ligase

Front 13

Enzyme deficient in Xeroderma pigmentosum

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Excision endonuclease

Front 14

Damage to DNA Cytosine deamination

Back 14

Can be due to spontaneous mutation or caused by chemicals. Damaged recognized by Uracil glycosylase and removed by AP endonuclease. Repaired by DNA polymerase and DNA ligase

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Damage to DNA Apurination or aprymidination

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Can be spontantous or due to heat. Recognized and removed by AP endonuclease. Damage repaired by DNA polymerase and DNA ligase

Front 16

Mismatched Base Pairs

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Caused by DNA replication errors. Repaired by DNA polymerase and DNA ligase

Front 17

When does DNA replication occur in a prokaryotic cell

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prior to cell division

Front 18

when does DNA replication occur in a eukaryotic cell

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during S phase

Front 19

Ribosomal RNA (rRNA)

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-most abundant type of RNA in cell
- used as a structural component of the ribosome, associates with the ribosomal proteins to forma the complete functional ribosome

Front 20

Transfer RNA (tRNA)

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second most common type, function is to carry amino acids to the ribosomes where they will be linked together during protein synthesis

Front 21

Messenger RNA (mRNA)

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carries the information specifying the amino acid sequence of a protein to the ribosome, is only type of RNA that is translated

Front 22

heterogenous nuclear RNA (hnRNA)

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aka Pre-mRNA, found only in the nucleus of enkaryotic cells, precursor of mRNA and is formed during its post-transcriptional processing

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Small nuclear RNA (snRNA)

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only found in nucleus of eukaryote, major function is to participate in splicing mRNA

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Ribozymes

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RNA molecules with enzymatic activity

Front 25

Three stages of processing eukaryotic mRNA

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Capping, Addition of Poly-A tail, splicing

Front 26

Mutations in splice sites can cause?

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Abnormal proteins

Front 27

What is a silent mutation and what is it's effect on proteins?

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Its a new codon that specifies the same amino acid. Has no effect on protein function

Front 28

Missense Mutation and its effects

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Its a new codon that specifies a different amino acid. It can cause a possible decrease in function with variable effects

Front 29

Nonsense mutation

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New codon creation is a Stop codon. It makes the protein shorter than normal and the new protein is usually non functional

Front 30

Frameshift mutation

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Is a deletion or addition of a base, produces a protein that is usually non functional and often shorter than normal

Front 31

Large segment deletion

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Is an unequal crossover in meiosis and produces a loss of function. The protein produced is shorter than normal or entirely missing

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Splice donor or acceptor

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Variable effects ranging from addition or deletion of a few amino acids to deletion of an entire exon

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Triple repeat expansion

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Expansions in coding regions causes protein product to be longer than normal and unstable. Disease often shows anticipation in pedigree

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What are proteasomes

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large cytoplasmic complexes that have multiple protease activities capable of sequentially digesting damaged proteins, may play a role in proding antigenic peptides for presentation by Class I MHC molecues

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Lysosomes

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Organelles whose major function is to digest materials that the cell has ingested by endocytosis. Organelle contain mulitple enzymes that digest carbs, fats and proteins. They are found in every cell, with PMN's and macrophages having the highest concentration. Missing lysosomal enzymes can allow the buildup of the undigested substrate in the cell causing serious consequences

Front 36

Cause of Scurvy

Back 36

deficient hydroxylation secondary to Vit C deficiency

Front 37

Cause of Osteogensis Imperfectia

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mutations in collagen genes

Front 38

Cause of Ehlers-Danlos syndromes

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mutations in collagen genes and lysine hydroxylase gene

Front 39

Cause of Menkes disease

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Deficient cross-linking secondary to functional copper deficiency

Front 40

Attenuation (premature termination of transcription)

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Occurs in prokaryotic cells only, requires simultaneous transcription and translation, two potential transcription termination signals