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babaghannouj
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what is DNA
- deoxyribonucleic acid
- hereditary molecule passed from parents to offspring
- common to all living organisms
- serves as the instruction manual for how to build an individual
- makes up chromosomes
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where is DNA found
- nucleus of eukaryotic cells
- cytoplasm of prokaryotic cells
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what is a chromosome
- consists of a single DNA molecule wrapped around proteins
- humans have 23 pairs
- one chromosome from each pair is inherited from the mother and one from the father
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types of chromosomes
- autosomes (n=22)
- sex chromosomes (n=1) - sex chromosomes determine gender : XX=female XY=male
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karyotype
image of an individual's complement of chromosomes arranged by size, length, shape, and centromere location
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DNA structure
- sugars and phosphates form the outside "backbone" of the helix
- the bases form the internal "rungs" like steps on a twisting ladder
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who discovered the helical nature of DNA
rosalind franklin
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who was credited for discovering the structure of DNA
james watson and francis crick were given franklin's info about the helical nature by maurice wilkins
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describe DNA replication
- hydrogen bonds that hold base pairs together are broken to unwind DNA
- DNA polymerase adds complementary nucleotides using the rules of base pairing
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DNA replication is semi-conservative
- at the end of DNA replication, 2 copies of the original DNA molecule exist
- each molecule consists of an original and a new strand
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complementary base pairing and the base pairing rule
- A always pairs with T
- C always pairs with G
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steps of DNA replication
- 1. DNA is complementary
- 2. DNA is unwound
- 3. DNA polymerase brings in nucleotides
- 4. DNA ligase fills in gap
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gene
- sequence of DNA that contains the in formation to make at least one protein
- expressed when the cell uses the DNA instructions to make proteins
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genotype
genetic make-up of an organism
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phenotype
physical attributes of an organism
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chromosomes
- contain gene sequences that code for proteins
- consist of many genes along their length
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DNA has coding and noncoding regions
- not all sequences of DNA serve as instructions for making proteins
- DNA sequences that do not hold instructions to make cellular proteins are called noncoding regions
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regulatory sequence
the part of a gene that determines the timing, amount, and location of protein produced
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coding sequence
- the part of a gene that specifies the amino acid sequence of a protein
- this sequence determines the identity, shape and func tion of proteins
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allele
alternative versions of the same gene that have different nucleotide sequences
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gene expression
the process of using DNA instructions to make proteins
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2 stages of gene expression
- 1 transcription - cells produce molecules of mRNA from the instructions encoded within genes
- 2 translation - mRNA codes for joining amino acids to make protein
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where do the 2 stages of gene expression occur
- transcription - prokaryotes: cytoplasm ; eukaryotes - in the nucleus
- translation - prokaryotes: ribosomes in the cytoplasm; eukaryotes: ribosomes on the rough ER
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mRNA
the RNA copy of an original DNA sequence made during transcription
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steps of transcription
- 1 RNA polymerase binds to the regulatory sequence just ahead of the gene's coding region. The DNA strands unwind, exposing the coding sequence of the gene.
- 2 RNA polymerase moves along the DNA strand. As it moves it "reads" the DNA coding sequence and synthesizes a complementary mRNA strand according to the rules of base pairing except that in RNA adenine pairs with uracil
- 3 as the mRNA strand is formed, it detaches from the DNA sequence. the DNA reforms its double-stranded helix
- 4 once the mRNA molecule is complete, it leaves the nucleus. the gene remains part of the chromosome in the nucleus where it can be used again in transcription
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translation
- uses the mRNA sequence to assemble the appropriate amino acid sequence of the protein
- mRNA - specifies for amino acids
- rRNA - make up ribosomes
- rRNA - brings in amino acids
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rRNA
type of RNA that make up ribosomes
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codon
sequence of 3 mRNA nucleotides that specifies a particular amino acid
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steps of translation
- 1 newly transcribed mRNA associates with a ribosome
- 2 as the ribosome moves along the mRNA, it "reads" the mRNA sequence in groups of 3 nucleotides called codons. each codon specifies a particular amino acid, which is b4rought to the ribosome by tRNA, which uses its anticodon sequence to find a matching mRNA codon
- 3 when the correct tRNA is in place, the specified amino acid is added to the growing chain. the ribosome moves on the the next codon.
- 4 the finished amino acid chain detaches fromt he ribosome and folds into its 3D shape
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tRNA
type of RNA that helps ribosomes assemble chains of amino acids during translation
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anti-codon
- the part of a tRNA molecule that binds to a complementary mRNA codon
- tRNAs bring the amino acid based on the anti-codon
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what can affect phenotype
- different alleles
- mutations
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what happens when DNA is mutated
may affect the proteins shape and function
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properties of amino acids
- 1 hydrophobic
- 2 polar
- 3 acidic
- 4 basic
- 5 special
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PCR (polymerase chain reaction)
- lab technique used to replicate a specific DNA ssegment
- scientists add nucleotides, DNA polymerase, and primers (short segments of DNA that show the section to which the DNA polymerase should bind)
- during each round of PCR, the 2 nucleotide strands separate. each strand is used as a template for complementary base pairing
- continues at an exponential rate
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genome
one complete set of genetic instructions encoded in the DNA of an organism
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noncoding regions of DNA
- coding sequences of DNA are extremely similar from person to person, but noncoding sequences vary much more
- provide a genetic fingerprint
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STR (short tandem repeat)
- sections of a chromosome in which DNA sequences are repeated
- everyone has STRs in the same places along our chromosomes, but the exact length varies from person to person
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steps of making a DNA profile
- 1 collect cells and extract DNA from crime scene evidence
- 2 use PCR to amplify multiple STR regions
- 3 separate STRs using gel electrophoresis
- 4 the gel shows the results of amplifying 3 different STR regions. the separated segments of DNA create a specific pattern of bands that is visible under fluorescence and unique to each person
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gel electrophoresis
- lab technique that separates fragments of DNA by size
- utilizes electric current to make DNA migrate through gel
- shorter fragments move further, whereas longer fragments remain near the top
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gene therapy
- type of treatment that aims to cure disease by replacing defective genes with functional ones
- requires knowing the gene of interest and inserting the gene into the genome for proper gene expression
- takes years (~20) to develop so other biotech methods are used to generate drugs/treatment
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steps of making of a transgenic goat
- 1 create hybrid gene - goat regulatory sequence and human antithrombin coding sequences are cut out of donor cell chromosomes and joined together using special enzymes
- 2 microinjection and embryo transfer
- 3 purify antithrombin from transgenic milk
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