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gene
unit of DNA that encodes info needed to produce proteins, cells, & entire organisms;
can be a few hundred to many thousands of nucleotides in length
locus
location of a gene on a chromosome
autosomes
non-sex chromosomes
homologous chromosomes
carry the same kinds of genes for the same characteristics
alleles
alternative versions of genes found at the same gene locus; formed by mutations
homozygous
homologous chromosomes carry same allele at gene locus
heterozygous
two homologous chromosomes carry different alleles at given locus; also called hybrid
Punnett Square Method
predicts offspring genotypes and phenotypes from combinations of parental gametes
1. Assign letters to the different alleles of the characteristic under consideration (dominant=uppercase, recessive=lowercase)
2. determine the possible gametes from both parents
3. write gametes from each parent along each side of 2x2 grid
4. fill in genotypes of each pair of combined gametes in the grid
5. determine genotypic ration based on outcome
6. based on dominant and recessive traits, calculate predicted phenotype
.Gregor Mendel
discovered patterns of inheritance and many essential facts about genes, alleles, and distribution of alleles during reproduction; used pea plants to see patterns in way plant characteristics were inherited
why did Mendel use pea plants?
has both carpel (female) and stamen (male) reproductive structures and naturally self-fertilize; was able to cross-fertilize
pollen from stamen transfers to carpel
key to Mendel's success
chose a simple design, studies one trait at a time and followed several generations
ex. white vs purple flowers
true breeding
homozygous for a characteristic
genotype
particular combination of the 2 alleles carried by an individual
phenotype
physical expression of the genotype (purple or while flowers)
test cross
used to deduce whether an organism w/ a dominant phenotype is homozygous or heterozygous
female sex chromosomes
two X chromosomes
male sex chromosomes
X chromosome and Y chromosome
incomplete dominance
when the heterzygous phenotype is intermediate btw the two homozygous phenotypes,
some alleles are incompletely dominant over others
blood type
single gene may have multiple alleles, produce types A,B,AB,O from 3 alleles, A,B,o
alleles A and B
code for enzymes that add different sugar molecules to the ends of glycoproteins that protrude from red blood cells
allele o
codes for nonfunctional enzymes that do not add any sugar molecules
codominance
when heterozygotes express the phenotypes of both the homozygotes (both A and B glycoproteins in AB blood type)
universal donor (type O)
lacks sugars and not attacked by antibodies, makes A & B antibodies
nondisjunction
incorrect separation of chromosomes in meiosis; causes gametes to have too many & too few chromosomes
nucleic acids
polymers of nucleotides linked together by dehydration synthesis reactions;
information storage and transmission
genes
units of heredity made of nucleic acid(DNA)
nucleotides
building block molecules of nucleic acid; composed of a sugar, phosphate group and nitrogenous base
nucleic acid backbone
sugar and phosphate groups structure
pyrimidines
nitrogenous bases characterized by a 6-membered ring made up of carbon and nitrogen atoms
purines
nitrogenous bases characterized by 5-membered ring fused to a 6-membered ring where both rings are made up of carbon and nitrogen atoms
Chargaff's rules
Adenine (A) = Thymine (T)
Guanine (G) = Cytosine (C)
Waton and Crick
discovered the double helix
Human Genome Project
revealed that 98.5% of DNA serves no purpose and does not encode for mRNA or any other RNA
mini-satellite sequences
single nucleotide differences btw individuals of the same species, account for fingerprint identification
forensic DNA analysis
commercially available in 1987; overturned over 200 rulings nicknamed "DNA 200"
recombinant DNA
combination of DNA from 2 or more organisms into a single DNA molecule; many important proteins such as insulin, HGH, and EPO are commercially produced this way
DNA tech in agriculture
1995, recombinant DNA used to insert bacterial gene in plant DNA to produce crystal spore that kills insects with no threat to plants or humans and pesticides were no longer used
DNA replication
requires 20+ enzymes and accessory proteins, extremely rapid and accurate
1. double helix unwinds & strands separate
2. each strand acts as a template
3. new strand winds up w/ old strand
each new DNA double helix is half old/parent strand and half new/daughter strand
helicase
enzyme that separates DNA strands to form a replication "bubble"; at each end is a replication fork where new strands are being made
replication fork
Y-shaped regions of replicating DNA where new strands are growing
DNA polymerase
enzyme that synthesizes new DNA strands
DNA ligase
enzyme that joins the small DNA segments of the lagging (daughter strand)
leading strand synthesis
DNA polymerase moves in the same direction as helicase, adds complimentary nucleotides in the 5' to 3' direction
lagging strand synthesis
DNA polymerase moves in the opposite direction of helicase
proteins
results from the instructions given by DNA
transcription
RNA is synthesized using DNA as an instruction template
mRNA (messenger RNA)
RNA that is synthesized from a gene coding for a protein; complimentary to DNA
4 bases of DNA
adenine
guanine
cytosine
thymine
4 bases of RNA
adenine
guanine
cytosine
thymine
translation
RNA directs the synthesis of a polypeptide protein;
converts language of nucleic acids (4 bases)into language of proteins (20 amino acids)
tRNA (transfer) and rRNA (ribosomal)
interpreters btw nucleotide mRNA and amino acid proteins
triplet
how many nucleotides code for one amino acid
codon
every 3 letters of mRNA nucleotides
how many possible codons can be many in a single DNA strand template?
4 nucleotides^3 codons = 64 possible codons
start codon
AUG (codes for methionine)
stop codons
UGA
UAG
UAA
JUST MEAN STOP
T/F: more than one codon can code for the same amino aid
TRUE
only 20 amino acids, but 64 possible codon combinations
transcription-initiation
RNA polymerase nbinds to the promoter region of DNA near beginning of gene, separates double helix near promoter
tells RNA where to "land"
T/F: enzymes get destroyed after use
FALSE
they get recycled
transcription-elongation
RNA polymerase travels along DNA and catalyzes addition of ribose nucleotides into RNA
transcription-termination
at end of gene, RNA polyemerase encounters sequence of DNA called a termination signal,
RNA polymerase detaches from DNA and releases RNA molecule
transcription result
after termination, DNA rewinds into double helix,
RNA molecule free to move from nucleus to cytoplasm for translation
RNA polymerase
enzyme that binds to promoter region of DNA and separates the double helix to begin catalyzing the addition of ribose nucleotides; may move to another gene and begin transcription or rebind to the same promoter & transcribe the same gene again
how does initiation begin?
RNA polymerase finds a promoter region and binds, causing the DNA double helix to unwind
translation
RNA-directed synthesis of proteins according to the genetic message of sequential codons in the mRNA
ribosome
where proteins are built; coordinates the pairing of tRNA anticodons w/ mRNA codons; composed of ribosomal RNA (rRNA) and protein
P-site
holds the tRNA w/ the polypeptide chain attached
A-site
holds the tRNA w/ the next amino acid to be added
where does protein synthesis occur?
on the ribosomes outside the nucleus
tRNA
interpreter btw nucleotide language of mRNA & amino acid language of proteins;
transfers correct amino acid from cytoplasmic pool of amino acids to ribosome for protein synthesis
initiation of translation
initiation complex binds to mRNA, start codon of mRNA pairs to anticodon base of tRNA
translation: elongation
tRNA occupies Asite and anticodon hydrogen bonds to codon of mRNA; peptide bond formation
methionine from initiator tRNA forms peptide bond w/ amino acid on tRNA at Asite, leaves tRNA at Psite w/ no amino acid and tRNA at Asite w/ dipeptide attached
translation: translocation
tRNA vacates Psite, ribosome moves one codon down mRNA; translocates tRNA (w/ growing peptide) from Asite to Psite
translation: termination
mRNA reaches stop codon (UAA, UAG, UGA)
mutations
permanent changes in DNA the can involve large chromosomal regions or single nucleotide pair
point mutations
mutations linked to one or two nucleotides in a single gene & can affect the function of a protein
substitution mutation
replacement of one base w/ another
insertion mutation
insertion of one or more nucleotide pairs into a gene
deletion mutation
deletion of one or more nucleotide pairs from a gene
evolution
change in the genetic makeup of a population over time as a result of natural selection
how did the idea of evolution develop?
explorers observed vast numbers of species where patterns emerged that seemed inconsistent w/ the idea that species were created fixed and unchanging by God;
fossils also revealed that life has changed over time especially through the layers of rock
fossils
preserved remains or traces of organisms that died long ago; petrified remains of bones, wood, shells, or impressions in mud mostly found in sedimentary rock
Charles Darwin and Alfred Russel Wallace
provided evidence of the occurrence of evolution and proposed the mechanism for how it occurs - natural selection
descent w/ modification
individuals in each generation differ slightly from the members of the preceding generation; over long periods of time, small genetic differences accumulate to produce major transformations
Principle 1 of Darwin/Wallace theory
individual members of a population are different from one another; variations arise by chance from random mutations in DNA and differences can be obvious in many physical characteristics
Principle 2 of Darwin/Wallace theory
at least some differences between members of a population are characteristics that may be passed from parent to offspring (mechanism of inheritance not understood yet)
Principle 3 of Darwin/Wallace theory
in each generation, some individuals in a population survive & reproduce successfully, some do not; observed that more individuals are born to survive than reproduce and some individuals have more offspring than others
Principle 4 of Darwin/Wallace theory
natural selection, in competition to survive and reproduce, winners are determined not by chance but by the traits the possess
natural selection
individuals w/ advantageous traits survive longest and produce the most offspring ; modifies populations over time even though it acts on individuals b/c the percentage of individuals inheriting favorable traits increases
which part of the pea plant contains ovaries.
carpels
how do we know that evolution occurred?
1. fossils provide evidence of evolutionary change overtime
2. comparative anatomy gives evidence of descent w/ modification
3. embryological similarity suggests common ancestry
4. modern genetic analysis reveal similarities in genes among diverse organisms
t/f only dominant phenotypes can be described as true breeding
FALSE
when Mendel crossed a true breeding purple and true breeding white, what were the results?
all purple flowers
________ is determined by __________
phenotype, genotype
in a test cross what type of phenotype is the unknown ALWAYS crossed with?
recessive bc of known genotype
which of the following determines sex of child in humans?
male gamete/X or Y sperm
is it possible for 2 curly haired parents to produce a wavy haired child?
NO
person w/ blood type AB can receive blood from...?
ANYONE
individual w/ down syndrome has 3 copies of which chromosome?
trisomy-21
which of these is a Pyrimidine?
cytosine, thymine (they have y's)