Biology Exam 3

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202 Terms

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blending theory of inheritance
inheritance of traits from two parents produces offspring with characteristics that are intermediate between those of the parents
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continuous variation
inheritance pattern in which a character shows a range of trait values with small gradations rather than large gaps between them
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discontinuous variation
inheritance pattern in which traits are distinct and are transmitted independently of one another
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hybridization
process Mendel performed, mating two individuals that differ with the goal of achieving a certain characteristic in their offspring
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P0
the parental generation in a cross
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F1
first filial generation
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trait
variation in the physical appearance of a heritable characteristic (plant height, seed texture)
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reciprocal cross
a paired cross in which the respective traits of the male and female in one cross become the respective traits of the male and female in the other cross
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dominant traits
Traits that always show in a person even if only one gene of the pair is inherited for the trait, remain unchanged in hybridization
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recessive traitss
become latent, disappear in the offspring of a hybrid
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product rule of probability
The chance of two or more independent events occurring together is the product of their chance of occurring separately
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allele
gene variations that arise by random mutation and exist at the same relative locations on homologous chromosomes
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phenotype
observable traits expressed by an organism (appearance)
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genotype
underlying genetic makeup of an organism
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homozygous
Having two identical alleles for a particular gene
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Heterozygous
An organism that has two different alleles for a trait
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monohybrid
A cross between individuals that involves one pair of contrasting traits
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test cross
a cross between a dominant expressing individual with an unknown genotype and a homozygous recessive individual; the offspring phenotypes indicate whether the unknown parent is heterozygous or homozygous for the dominant trait
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incomplete dominance
in a heterozygote, expression of two contrasting alleles such that the individual displays an intermediate phenotype
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codominance
in a heterozygote, complete and simultaneous expression of both alleles for the same characteristic
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Example of incomplete dominance
red x white = pink
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Example of codominance
in certain varieties of chicken, the allele for black feathers is codominant with the allele for white making the chicken have speckled white and black feathers
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wild type
An individual with the normal (most common) phenotype.
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x-linked
A gene carried on the X chromosome. If a male inherits an X-linked recessive trait from his mother, he expresses that trait because the Y from his father has no counteracting gene. Females are more likely to be carriers of X-linked traits but are less likely to express them.
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hemizygous
the presence of only one allele for a characteristic, as in X-linkage; hemizygosity makes descriptions of dominance and recessiveness irrelevant
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recessive lethal
inheritance pattern in which an allele is only lethal in homozygous form, the heterozygote may be normal or have some altered, nonlethal phenotype
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dominant lethal
inheritance pattern in which an allele is lethal both in the homozygote and heterozygote, this allele can only be transmitted if the lethality phenotype occurs after reproductive age
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law of dominance
In many traits one allele is dominant over the other allele. The "weaker (recessive" allele is only expressed when it is paired with another recessive allele
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law of segregation
Mendel's law that states that genes segregate equally into gametes such that offspring have an equal likelihood of inheriting any combination of factors, reason we can use Punnett squares
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law of independent assortment
the law that states that genes separate independently of one another in meiosis, every combination of alleles is equally likely to occur
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linkage
phenomenon in which alleles that are located in close proximity to each other on the same chromosome are more likely to be inherited together
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epistasis
antagonistic interaction between genes such that one gene masks or interferes with the expression of another
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DNA transformation
process in which external DNA is taken up by a cell
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bacteriophage
A virus that infects bacteria
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Chargaff's Rule
Different species have equal amounts purines (A and G), and pyrimidines (C and T), Amount A = Amount T, Amount C = Amount G
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purines
Bases with a double-ring structure.
Adenine and Guanine
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pyrimidines
Cytosine and Thymine, single-ring structure
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In DNA, phosphate is connected to the ____ of the sugar
5' carbon
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In DNA, OH group is connected to the _____ end of the sugar
3' carbon
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Adenine and thymine form ________
2 hydrogen bonds
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Guanine and cytosine form ____
3 hydrogen bonds
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dideoxynucleotide
type of nucleotide used during DNA sequencing to terminate synthesis (ddNTPs)
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gel electrophoresis
technique used to separate DNA fragments of different sizes
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histones
protein molecules around which DNA is tightly coiled in chromatin, rich in amino acids
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heterochromatin
Eukaryotic chromatin that remains highly compacted during interphase and is generally not transcribed.
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semi-conservative method of replication
each of the two parental DNA strands acts as a template for new DNA to be synthesized. Post replication each double-stranded DNA has one old, one new strand
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dna polymerase
Enzyme in DNA that adds nucleotides one-by-one to the growing DNA strand that is complementary to the template strand
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nucleoside triphosphate (NTPs)
serve as the source of DNA nucleotides and the source of energy to drive polymerization
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DNA Polymerase 1
rocesses RNA primers during lagging-strand synthesis and fills small gaps during DNA repair reactions
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DNA polymerase 2
involved in DNA repair processes, catalyzes the repair of nucleotide base pairs
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DNA polymerase 3
remains in the replication fork on the template strand and continuously adds nucleotides to the new complementary strand as the fork progresses, DNA polymerase III adds DNA nucleotides to the primer(s), synthesizing the DNA of both the leading and the lagging strands.
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origins of replication
site where DNA replication begins
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DNA replication
The process in which DNA makes a duplicate copy of itself.
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helicase
An enzyme that untwists the double helix of DNA at the replication forks.
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replication forks
a Y-shaped point that results when the two strands of a DNA double helix separate so that the DNA molecule can be replicated
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sing;e-strand binding proteins
protein that binds to single-stranded DNA during replication, helps in keeping the two strands of DNA apart so they may serve as templates
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DNA Polymerase
Can only add nucleotides 5' to 3'. Requires a 3' OH group to which it can ad nucleotides
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RNA primase
synthesizes an RNA primer that is complementary to template DNA, primers DNA synthesis
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primer
a short stretch of RNA with a free 3' end, bound by complementary base pairing to the template strand and elongated with DNA nucleotides during DNA replication
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Topoisomerase
prevents overwinding of the DNA double helix ahead of the replication fork as the DNA is opening up, causes temporal nicks in DNA helix, then reseals it
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leading strand of DNA
strand that is synthesized continuously in the 5' to 3' direction, synthesized in the direction of the replication fork, can be extended from a single primer
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Okazaki fragment
DNA fragment that is synthesized in short stretches on the lagging strand, each require primer to start synthesis. New primer segments are laid down in the direction of replication fork but pointing away from it
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lagging strand of DNA
the strand that replicated in short fragments and away from the replication fork
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sliding clamp
ring-shaped protein that holds the DNA pol on the DNA strand
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ligase
An enzyme that connects two fragments of DNA to make a single fragment
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Primase
An enzyme that joins RNA nucleotides to make the primer using the parental DNA strand as a template.
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There are ______ origins of replication in eukaryotes while there's only one in prokaryotes
many
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How many DNA polymerases are there in eukaryotes compared to prokaryotes?
Eu= 14, pro=5
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telomere
DNA at the end of linear chromosomes, unpaired, ends get shorter as cells divide over generations
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Telomeres repeat
TTAGG
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Telomerase
enzyme that contains a catalytic part and an inbuilt RNA template, functions to maintain telomeres at chromosome ends
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mismatch repair
The cellular process that uses specific enzymes to remove and replace incorrectly paired nucleotides.
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nucleotide excision repair
A repair system that removes and then correctly replaces a damaged segment of DNA using the undamaged strand as a guide.
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induced mutations
result from an exposure to chemicals, UV, or other environmental agent
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spontaneous mutation
occur without exposure to any environ
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point mutations
changes in a single nucleotide pair of a gene
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transition substitution (mutation)
when a purine is replaced with a purine or a pyrimidine is replaced with another pyrimidine
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transversion substitution (mutation)
purine replaced by a pyrimidine, or pyrimidine replaced by a purine
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silent mutations
have no effect on the amino acid produced by a codon because of redundancy in the genetic code
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trinucleotide repeat expansion
a steady increase in the number of copies of a repeated DNA sequence of three nucleotide bases from generation to generation; responsible for genetic anticipation
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translocation mutation
mutation in which one part of one chromosome breaks off and attaches to another
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central dogma
theory that states that, in cells, information only flows from DNA to RNA to proteins
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degeneracy
redundancy of the genetic code; that is, most amino acids are encoded by several codons
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codon
A specific sequence of three adjacent bases on a strand of DNA or RNA that provides genetic code information for a particular amino acid
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reading frame
On an mRNA, the triplet grouping of ribonucleotides used by the translation machinery during polypeptide synthesis.
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nonsense codon
one of the three mRNA codons that specifies termination of translation
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plasmid
A small, circular section of extra DNA that confers one or more traits to a bacterium and can be reproduced separately from the main bacterial genetic code.
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transcription bubble (prokaryotic transcription)
region of locally unwound DNA that allows for transcription of mRNAs
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missense mutation
A base-pair substitution that results in a codon that codes for a different amino acid.
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nonsense mutation
A mutation that changes an amino acid codon to one of the three stop codons, resulting in a shorter and usually nonfunctional protein.
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nontemplate strand
the strand of DNA that is not used to transcribe mRNA; this strand is identical to the mRNA except that T nucleotides in the DNA are replaced by U nucleotides in the mRNA
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initiation site
nucleotide from which mRNA synthesis proceeds in the 5' to 3' direction; denoted with a "+1"
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upstream nucleotides
Before initiation site (-)
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downstream nucleotides
nucleotides following the invitation site (+)
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Transcription, translation, and mRNA degradation occur simultaneously in prokaryotes because
Prokaryotes don't have membrane-enclosed nuclei
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Core enzyme of RNA polymerase
Lacks the sigma subunit; responsible for catalytic function. Made up of two alpha units, Beta unit, and beta prime unit. Performs elongation
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two alpha subunits in core enzyme
necessary to assemble the polymerase on the DNA
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B subunit in core enzyme
bunds to ribonucleic triphosphate that will become part of the mRNA molecule
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B' subunit in core enzyme
binds the DNA template strand
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sigma (σ) subunit
involved only in transcription initiation, confers transcriptional specificity such that the polymerase begins to synthesize mRNA from an appropriate initiation site
Without σ, the core enzyme would transcribe from random sites and produce gibberish