Bio Exam 2

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62 Terms
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Nucleotide Structure
Has a sugar molecule, either a ribose in RNA or deoxyribose in DNA attached to a phosphate group and a nitrogen containing base
Complementary Nucleotides
how bases match on opposite DNA strands through hydrogen bonding on their nitrogenous bases
Semi-Conservative DNA Replication
one strand from each parent is conserved and remains intact after replication has taken place
unzips the two strands of DNA, breaks through H-bond that bolds the bases together
makes the primer that allows DNA polymerase to figure out where to go, is make of DNA
DNA ligase
helps glue together DNA fragments
DNA Polymerase
replicates DNA molecules to build new strand of DNA, cannot figure out where to start without primer
split DNA strands in order to relive stress, untangle replicating DNA
Leading Strand
DNA replication occurs continuously
Lagging Strand
DNA synthesis restarts many times as the helix unwinds which results in Okazaki fragments
an enzyme that adds extensions to the template strand where RNA primer can bind , found at the end of each chromosome
Advantages of mRNA
- can make many mRNAs from one gene and can also make many proteins from one mRNA - can change whether or not to make mRNA from DNA and how much
Transcription Unit
a region of DNA used as a template for type of mRNA
Promoter DNA
where the RNA polymerase and cofactors bind and transcriptions begins, recognized and bound by proteins
Terminator DNA
where transcription ends, has specific nucleotides that are recognized and bound by proteins
Difference between replication and translation
replication requires a primer to begin, translation does not
- spliceosomes, proteins and small nuclear RNAs (snRNAs) removes introns - snRNAs bind, recognize specific nucleotides at exon-intron junctions
- transfer RNAs, small stable RNAs w/ 70-80 nucleotides - each type binds to a specific type of amino acid - each type has 3 different nucleotides which is an anticodon
Start Codon
first codon of mRNA transcript translated by a ribsome
Stop Codon
a sequence of three nucleotides in DNA or mRNA that signals a halt to protein synthesis in the cell
Point Mutations
single base is added, deleted, or changed
Silent Mutations
base substitutions that result in no change of the amino acid or amino acid functionality when the altered mRNA is translated
Missense Mutation
a single base pair substitution alters the genetic code in a way that produces an amino acid that is different from the usual amino acid at that position; wrong amino acid
Nonsense Mutation
a sequence change gives rise to a stop codon rather than a codon specifying an amino acid
Frameshift Mutation
deletion or insertion of anything other than 3n (3, 6, 9, etc. ) nucleotides
Gene Expression in Prokaryotes
control of gene expression is mostly at the transcriptional level
Gene Expression in Eukaryotes
regulation of gene expression can occur at all stages in the process
Lac operon mRNA
makes proteins that help import the disaccharide lactose and break it down
DNA methylation
makes a chromosome more tightly packed because it makes DNA more attracted to itself and that limits gene expression
Histone acetylation
when amino groups are added to histone proteins, decreasing the attraction and making them unwind more, gene are more likely to be expressed more
Diploid Cell
2n, have pairs of homologous chromosomes
Haploid Cell
1n, have only one of each homologue, also gametes (eggs, sperm)
Sister chromatids
copies made by replication from one copy
Homologous chromosomes
not copies of each other, each inherited from a different haploid gamete
stretch of DNA that determines a certain trait, genes mutate and can take two or more alternative forms
one of the forms of genes
Meiosis I
meiotic spindle lines up homologous chromosomes next to each other, separates homologous chromosomes and sister chromatids stay together
Meiosis II
halves the amount of DNA, sister chromatids separate
Steps increasing genetic diversity
- Crossing over - Random assortment of chromosomes - Random fusion of gametes from different parents
Mendel's Law of Segregation
the two alleles in the parent "segregate" from each other during the formation of gametes
Independent Assortment
two alleles of two or more different genes get sorted into gametes independently of one another
Incomplete Dominance
a mixture of the alleles in the genotype is seen in the phenotype.
both alleles in the genotype are seen in the phenotype.
errors in chromosome separation during meiosis
a specific gene that is not on a sex chromosome
traits that are influenced by genes carried on the sex chromosome
Polygenic Traits
characteristic like height or skin color that is influenced by two or more genes, does not follow the pattern for Mendelian inheritance
Quantative phenotype
measurable phenotype that depends on the cumulative actions of many genes and the environment
Complex Epistasis
interactions of genes that are not alleles, the suppression of one such gene by the other, complex interactions between genes and traits
where non-sister chromatids remain physically connected at points of exchange, can result in the exchange of alleles
happens during prophase I when homologous chromosomes become connected
Crossing Over
exchange of genetic material and produces new allele combinations on chromosomes
errors in chromosome separation during meiosis
person has three copies of one of the chromosomes instead of two (47 instead of 46)
person is missing one chromosome in the pair (45 instead of 46)
Barr body
inactivated, condensed X chromosome found in female cells, essential to regulate the amount X-linked gene product being transcribed
SRY gene
located at the distal region of the Y chromosome, is necessary for determining male sex determination
process whereby the DNA sequence in a gene is copied into mRNA; the process whereby a base sequence of messenger RNA is synthesized on a template of complementary DNA
parts of pre-mRNA (introns) are chopped out and remaining pieces (exons) are stuck back together
sequence of DNA containing a cluster of genes under the control of a single promoter
upstream sequence to which RNA polymerase binds
segment of DNA to which repressor protein binds