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81 Cards in this Set

  • Front
  • Back
What type of polarity do DNA strands have?
5' to 3'
What is DNA composed of?
deoxyribose (a 5 carbon sugar), a phosphate group and a base (A, T, G, C)
How many H bonds are between A and T?
Two
How many H bonds are between G and C?
Three
What unwinds DNA by breaking the H bonds?
Helicase
How many RNA primers are used by the leading strand?
One
How many RNA primers are used by the lagging strand?
numerous, which form Okasaki fragments
What is transcription?
DNA is translated into RNA
What direction are nucleotides added?
5' to 3'
What happens to the 5' end of eukaryotic RNA?
it is capped
What happens to the 3' end?
a poly (A) tail is added
Through what does the mRNA leave the nucleus?
Nuclear pore
Where does the RNA polymerase bind on DNA?
promoter (at or close to the TATA box)
What type of energy does translation use?
GTP
Where does translation occur?
cytoplasm
What delivers amino acids to the ribosomes?
tRNA
What type of bond exists between amino acids?
peptide bond
Name some examples of post-translational modification?
-3-D folding
-addition of a carbohydrate, lipid or phosphate group,
-cleavage of signal sequences
Base substitution
one base is substituted for another
Transition
substitution of a pyrimidine by another pyrimidine

substitution of a purine by another purine
Transversion
pyrimidine by a purine
purine by a pyrimidine
Deletion
one or more nucleotides is lost from the sequence
Insertion
nucleotides inserted somewhere
UV light can cause what type of formation
formation of thymine dimers
Ionizing radiation can cause what?
double strand breaks
Direct repair
reverses DNA damage without cutting the deoxyribose phosphate backbone (removing a methyl group to restore the original base)
Base excision repair
used when inncorrect bases are present in the DNA

-the damaged base is recognized by glycosylase and is hydrolytically removed from the deoxyribose phosphate backbone, this leaves an apurinic or apyrimidic site where the correct base is then inserted and sealed with DNA ligase)
Mismatch repair
used to remedy incorrect pairings of the normal bases
Nucleotide excision repair
removes thymine dimers and bulky adducts
Exonuclease
can remove bases
Post replication repair
repairs double breaks in the strands
Nucleosome
-the most basic unit
- consists of 8 histone proteins
-DNA is wound almost twice around this protein core to produce a "bead-like" structure
30- nm Chromatin Fiber
-nucleosomes are joined by linker DNA and coiled into 30 nm fiber which is organized into loops
-this structure is maintained by histone H1 protein that is attatched to linker DNA
Loop-Scaffold Complex
provides the compact structures seen in metaphase chromosomes
Euchromatin
-single copy, genetically active DNA
Heterochromatin
repetitive stuctures that are genetically inactive
Centromeres
essential for proper chromosome segregation and the site of kinetochore formation
Telomeres
-cap the ends of chromosomes
-
In meiosis, crossing over occurs between what?
homologous chromosomes
Constitutional chromosome abnormality
found in all cells of the body
Somatic chromosomal abnormality
the abnormality is found only in cells or tissues
Numerical chromosomal abnormality
the gain or loss of complete chromosomes
Structural chromosomal abnormality
formation of abnormal chromosomes through the mispair of chromosome breaks or a malfunction in recombination
Aneuploidy
- one or more chromosomes are present or missing than the normal number
- this normally results from nondisjunction
Nondisjunction
failure of paired chromosomes to separate during anaphase (MI)
Monosomy
-loss of one chromosome
-autosomal monosomy is always lethal
Monosomy of sex chromosome X can result in what?
Turners syndrome (45, X)
Trisomy
gain of an extra chromosome
What is Trisomy 21?
Down Syndrome
Tetrasomy
gain of an extra pair of homologous chromosomes
Euploidy
an extra complete set of chromosomes is present or missing
Polyploidy
more than two sets of chromosomes are present
Monoploidy
a complete set of chromosomes is missing
(lethal)
Mosaicism
two or more genetically different cell lines within a single individual derived from a single zygote
Chimerism
two or more gentically different cell lines within a single individual derived from different zygotes
Robertsonian translocation
the short arm of two chromosomes breaks off and the two long arms are fused together
T/F

Autosomal monosomy is always lethal.
True
Negative control
some repressor protein binds to DNA to keep transcription from happening
Positive control
some protein helps to initiate transcription
T/F

The transcription of multiple genes into a primary transcript occurs only in prokaryotes.
True
Polycistronic RNA is found in?
Prokaryotes
PCR is used for what?
to amplify DNA
What do you need to add to the reaction vial when doing PCR?
-DNA to be amplified
-primase
-DNA ligase
-DNA polymerase
- dNTP's
Why do you heat the DNA in the first step of PCR?
to allow the DNA strands to denature (separates the two DNA strands)
What do you call the second step in PCR?
annealing
How is DNA sequencing different than PCR?
The reactions in DNA sequencing are run in the presence of dideoxynucleotides, (ddNTP's) which lack a hydroxyl group at the 3' position
-this means that whenever a ddNTP is added replication stops
-the reaction is run in polyacrilimide gel and then allow one to see the order fo the sequence
Mitochondrial genome
consists of very short portion of triple stranded circular DNA
Null mutation
complete loss of function
Leaky mutation
partial loss of function
Epigenic modifications
result loss of function without altering the DNA function
Founder effect
a disease is typically only seen only within a certain population which shows that only the founders had the disease
T/F

Mutations that produce a new function for a gene are rare among inherited disease but common in cancer
True
Mutational homogeneity
the same phenotype typically only results from one or two specific mutations
What is the most lethal genetic disease in the US?
Cystic fibrosis
If one does not have cystic fibrosis, what does the normal gene code for?
a membrane protein that transports chloride ions in and out of cells

(defect results in build-up of airway secretions)
What are phenotypic manifestations of Huntington's disease?
-uncontrolable movements
-personality alterations
-memory loss
From what does Huntington's disease result?
a gain of function mutation that produces and autosomal dominant disorder characterized by neurodegeneration
When is the typical onset of Huntington's disease?
35-40
Proto-oncogenes
non-mutant versions of genes that control cell proliferation
What do most gene therapies focus on?
insertion of a normal gene into the genome to replace a nonfunctional gene
Proto-oncogene
original version of the oncogene