DNA structure, genes, proteins

• 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

• nucleus of eukaryotic cells
• cytoplasm of prokaryotic cells

• 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

• autosomes (n=22)
• sex chromosomes (n=1) - sex chromosomes determine gender : XX=female XY=male

image of an individual's complement of chromosomes arranged by size, length, shape, and centromere location

• sugars and phosphates form the outside "backbone" of the helix
• the bases form the internal "rungs" like steps on a twisting ladder

rosalind franklin

james watson and francis crick were given franklin's info about the helical nature by maurice wilkins

• hydrogen bonds that hold base pairs together are broken to unwind DNA
• DNA polymerase adds complementary nucleotides using the rules of base pairing

• at the end of DNA replication, 2 copies of the original DNA molecule exist
• each molecule consists of an original and a new strand

• A always pairs with T
• C always pairs with G

• 1. DNA is complementary
• 2. DNA is unwound
• 3. DNA polymerase brings in nucleotides
• 4. DNA ligase fills in gap

• 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

genetic make-up of an organism

physical attributes of an organism

• contain gene sequences that code for proteins
• consist of many genes along their length

• 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

the part of a gene that determines the timing, amount, and location of protein produced

• 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

alternative versions of the same gene that have different nucleotide sequences

the process of using DNA instructions to make proteins

• 1 transcription - cells produce molecules of mRNA from the instructions encoded within genes
• 2 translation - mRNA codes for joining amino acids to make protein

• transcription - prokaryotes: cytoplasm ; eukaryotes - in the nucleus
• translation - prokaryotes: ribosomes in the cytoplasm; eukaryotes: ribosomes on the rough ER

the RNA copy of an original DNA sequence made during 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

• 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

type of RNA that make up ribosomes

sequence of 3 mRNA nucleotides that specifies a particular amino acid

• 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

type of RNA that helps ribosomes assemble chains of amino acids during translation

• the part of a tRNA molecule that binds to a complementary mRNA codon
• tRNAs bring the amino acid based on the anti-codon

• different alleles
• mutations

may affect the proteins shape and function

• 1 hydrophobic
• 2 polar
• 3 acidic
• 4 basic
• 5 special

• 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

one complete set of genetic instructions encoded in the DNA of an organism

• coding sequences of DNA are extremely similar from person to person, but noncoding sequences vary much more
• provide a genetic fingerprint

• 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

• 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

• 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

• 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

• 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