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Key to
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ACT
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Interactive
activity |
GA |
Gray's Anatomy |
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Animation |
pp |
PowerPoint
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FIG
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Figure |
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Define,
pronounce |
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Structure of DNA
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Nucleotide is the subunit, made of
three components:
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Sugar (ribose in RNA;
deoxyribose in DNA)
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Phosphate
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Nitrogen base
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Different types of nitrogen
base: cytosine,
guanine, adenine,
thymine (DNA only),
uracil (RNA only) |
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First letters are used as abbreviations: C, G, A,
T, U |
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Bases may link C-G or G-C
and T-A or A-T (in RNA, U-A or A-U)
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This
rule is complementary
or obligatory "base-pairing"
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Nucleotides
combine to form a double helix
structure
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Every three bases make up one
"word" or codon in genetish
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Each different codon represents
a different amino acid
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Amino acids combine to form
polypeptides or proteins |
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A sequence of codons containing
the information needed to make one polypeptide/protein is
called a gene (gene = "recipe" for one protein)
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Genes are found at various
locations along a DNA molecule (chromatin/chromosome)
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All genes on all chromosomes is
a set of information called the genome
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This
table is a type of "phrasebook" for the language of "genetish"
--showing the meaning of different possible codons. The
small-case letters are abreviations for amino acids (e.g. leu
= leucine, ala = alanine) |
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Click here to
see Ben Fry's easier-to-read version of this classic table!
Ben constructed this as a student at MIT.
This version is similar to that found in your textbook. |
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Function of DNA
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Master code for proteins made by
the cell
ANIM
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Proteins perform functions that
regulate the cell, make up parts of the cell, and regulate the
synthesis (and breakdown) of other types of molecules (lipids,
carbohydrates, so on)
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In humans, temporary "working
copies" of specific genes from DNA are in the form of RNA
(review Cell
Structure & Function)
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rRNA -
ribosomal RNA
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Forms ribosomes
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mRNA - messenger RNA
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Unfolded strand contains gene
(code for one polypeptide)
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tRNA - transfer RNA
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Brings specific amino acids
to ribosome and places them according to code on mRNA
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nuclear DNA
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"Master" genetic
code in the nucleus
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mDNA or mtDNA - mitochondrial
DNA
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Additional genetic code in
the mitochondrion
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Replication of DNA
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DNA helix "unzips" and
nucleotides with bases complementary to those in each exposed DNA
strand "fill in" and make a new side
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Results in two identical
"daughter molecules" of DNA
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Semiconservative (half is new;
half is old)
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Facilitated by enzymes (isn't
everything?)
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Transcription of RNA
ANIM
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mRNA is a "transcribed"
copy of one gene in DNA
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DNA unzips at one gene, and other
side "fills in" with RNA nucleotides with bases that
complement the exposed bases of the DNA strand
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Promoter - sequence of bases
that tells the cell where to start transcribing the gene
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RNA polymerase - enzyme that
facilitates formation of mRNA strand
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mRNA is edited
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Introns - parts of sequence
that are deleted ("nonsense")
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Exons - parts of sequence the
remain in the final mRNA molecule |
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A structure called the
spliceosome forms on the mRNA, facilitating the splicing of
transcript (removal of introns, gluing together of exons)
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Other forms of RNA made in similar
manner; usually fold into complex shapes
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mRNA leaves nucleus via nuclear pores
Translation of RNA (protein
synthesis)
ANIM
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Initiation - mRNA associates with
rRNA of ribosome
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Elongation - tRNA brings amino
acids into place (anticodons on tRNA complement codons on mRNA)
elongating string of amino acids
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Termination - protein is released
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Mutations
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Chromosomal mutations - additions,
deletions to chromosome
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Point mutations - change in one or
few nucleotides in a gene sequence
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Regulation of
gene expression
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Chromosome level
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Packing - DNA wraps around
histone
proteins, forming "beads" called nucleosomes
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Packing can prevent certain
genes from being activated (transcribed)
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Transcription level
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Master genes turn on a group of
other genes
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Enhancer genes change the rate
of transcription of other genes
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Regulatory chemicals, such as
steroid hormones, may activate certain genes
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mRNA can be edited in different
ways (exons can be linked in different ways)
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mRNA can be "made ahead of
time" and then "masked" until needed later
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This Mini Lesson may be
updated or improved at any time.
Check back frequently or use the
link to the right to inform you of changes. |
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© 1988-April, 2007 Kevin
Patton
ALL rights
reserved
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04/01/07.
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