FINAL Flashcards
(165 cards)
1
Q
gene mutations are ____ and _________
A
rare and random
2
Q
mutations generate
A
new hereditary variety
3
Q
mutation rate is measured in two ways…
A
- Molecular level: number of mutations per base pair.
- Phenotypic level: number of mutations affecting a phenotype.
4
Q
Certain genes in specific genomes have elevated mutation rates. These genes are identified as being _______ ________
A
mutation hotspots
5
Q
Mutations that occur in germ-line cells, such as those giving rise to sperm and egg, can be passed from one generation to the next. These are identified as ___________ mutations.
A
germ-line
6
Q
_______ mutations can be passed to subsequent generations of cells in a cell lineage through mitotic cell division, but only the direct descendants of the original mutated cell carry the gene mutation.
A
somatic
7
Q
The most common kinds of gene mutations are those that substitute, add, or delete one or more DNA base pairs. These kinds of mutations are confined to a specific base pair or location in a gene and are called _____ mutations.
A
point
8
Q
base pair substitution mutations come in two types…
A
- Transition mutations, one purine replaces the other purine or one pyrimidine replaces the other pyrimidine.
- transversion mutations, where a purine is replaced by a pyrimidine or vise versa.
9
Q
A base-pair substitution producing an mRNA codon that specifies the same amino acid as the wild-type mRNA is known as a ___________ mutation (also known as a silent mutation).
A
synonymous
10
Q
A base-pair substitution that results in an amino acid change to the protein is a _______ mutation.
A
missense
11
Q
what are the consequences of a missense mutation?
A
Protein function may be altered by a missense mutation. The specific consequence of the protein change (i.e., whether it results in complete or only partial loss of protein function) depends on what kind of amino acid change takes place and where in the polypeptide chain the change occurs.
12
Q
A base-pair substitution that creates a stop codon in place of a codon specifying an amino acid is a ________ mutation
A
nonsense
13
Q
Insertion or deletion of one or more base pairs in the coding sequence of a gene leads to addition or deletion of mRNA nucleotides. This can alter the reading frame of the codon sequence, beginning at the point of mutation. The result would be a ________ mutation, in which the mutant polypeptide contains an altered amino acid sequence from the point of mutation to the end of the polypeptide.
A
frameshift
14
Q
what are the consequences of a frameshift mutation?
A
In addition to producing the wrong amino acids in a portion of the polypeptide, frameshift mutations commonly generate premature stop codons that result in a truncated polypeptide. For these reasons, frameshift mutations usually result in the complete loss of protein function and thus produce null alleles.
15
Q
__________ mutations, occur in noncoding regions of genes, such as promoters, introns, and regions coding specific segments of mRNA. None of these regions directly encodes amino acids, but mutations in these regions can lead to the production of abnormal or abnormal amounts of mRNAs that, in turn, produce mutant phenotypes.
A
regulatory
16
Q
Promoter consensus sequences direct the efficient initiation of transcription. Mutations that alter consensus sequence nucleotides and interfere with efficient transcription initiation are _______ mutations.
A
promoter
17
Q
what is a splicing mutation?
A
A mutation altering the normal splicing pattern of a pre-mRNA.
18
Q
Mutations occurring due to spontaneous events or changes involving nucleotides or nucleotide bases are called what?
A
spontaneous mutations
19
Q
what is forward mutation?
A
A mutation that alters a wild type and generates a mutant. Also known as mutation.
20
Q
reverse mutation or reversion does what?
A
converts a mutant to a wild-type or near wild-type form
21
Q
__________ mutations are called this because the second mutation, by restoring wild-type appearance, can be said to “suppress” the mutant phenotype generated by the first mutation.
A
supressor
22
Q
_________ Mutations and Cryptic Splice Sites can alter the product made and potentially produce a useless mRNA
A
splicing
23
Q
_____________ Mutations reduce normal mRNA production
A
Polyadenylation
24
Q
missense mutations do what?
A
change in encoded amino acid
25
nonsense mutations lead to what?
to an early stop codon
26
During DNA replication, a mutational event leading to increased or decreased numbers of repeating nucleotides in newly synthesized DNA and caused by slippage of DNA polymerase on the template strand or slippage of the newly synthesized strand on DNA polymerase. This is called what?
strand slippage
27
___________ is loss of an amino group from a base, which can result in a base substitution.
deamination
28
___________ needs to be repaired before DNA replication, and can result in a base substitution.
depurination
29
_________ mutations are caused by mutagens, agents that damage DNA
induced
30
____________ Mutagens specifically interact with DNA.
chemical
31
________ _____ ________ are similar to a DNA nucleotide and get incorporated into DNA strands. However, base analogs such as 5-BU can change forms (location of ring double bonds) leaning to mispairing.
nucleotide base analogs
32
what causes nucleotide base analogs to mutate?
a chemical mutagen
33
____________ Agents remove amino groups from bases leading to mispairing.
denanimating
34
_________ Agents add bulky side groups like methyl and ethyl distorting the helix.
Alkylating
35
_________ Agents add hydroxyl groups leading to mispairing
Hydroxylating
36
____ ___________ Agents fit between base pairs, distort the helix and can cause single strand breaks that are not well repaired, leading to frameshifts.
DNA intercalating
37
_________ Agents turn H groups into OH groups, or even carboxy groups leading to base substitutions and frameshifts.
oxidizing
38
Most lesions that occur are repaired. The repair processes that exist are partially redundant and fall into two broad categories...
1) direct repair and restoration of wild type
2) damage that allows replication to proceed past structural changes, but is error prone.
39
DNA polymerase ___________ detects and removes mismatches in replication
proofreading
40
____________ Repair uses the enzyme photolyase to bind to thymidine dimers, and the energy of visible light to break the dimer.
photoreactive
41
what is photoactive repair
repair of UV-induced photoproducts catalyzed by photolyase activated by visible light
42
what is base extension repair?
removal of an incorrect or damaged DNA base and repair by synthesis of a new strand segment
43
what is nucleotide extension repair?
removal of a strand segment containing DNA damage and replacement by new DNA synthesis
44
what is mismatch repair?
removal of a DNA base-pair mismatch by excision of a segment of the newly synthesized strand followed by resynthesis of the excised segment
45
___ exposure induces the formation of photoproducts that can inhibit DNA replication as well as lead to mutation.
UV
46
Detecting damage is paramount to protecting the genome and the cell. Multiprotein complexes constantly work to detect damage. The BRCA1 gene is one gene involved in this process. A second is ___, which activates the p53 repair pathway. These surveillance pathways can arrest a cell in G1 until repair is complete, or send the cell into apoptosis.
ATM
47
________________ _______ ______ is needed when both strands are damaged
double-strand break repair
48
There are two known processes for double-strand break repair...
1. Nonhomologus End Joining is an error-prone process. Bases are deleted by this mechanism.
2. Synthesis-Dependent Strand Annealing is an error-free process that uses the undamaged sister chromatid as a template. (this is only available at the end of S or during G2 phase of the cell cycle, and wouldn’t work in bacteria)
49
___________ recombination is the exchange of genetic material between homologous molecules of DNA.
homologous
50
do all organisms undergo homologous recombination?
YES
In bacteria, homologous recombination occurs during events such as conjugation and as a consequence of the repair of double-strand breaks.
Archaea undertake homologous recombination under circumstances similar to those in bacteria.
In eukaryotes, recombination between homologous chromosomes is essential in prophase I of meiosis, where it is initiated by controlled double-strand DNA breaks in a process that is reminiscent of synthesis-dependent strand annealing.
51
___________ _________ elements are DNA sequences of various lengths and sequence composition that have evolved the ability to move within the genome by an enzyme-driven process known as transposition.
Transposable genetic
52
what are the effects that transposable genetic elements have on genomes?
First, transposition can be a mutational event—one that has a biological basis as opposed to a chemical or physical (irradiation) cause.
Second, transposition can increase genome size through duplication of the transposable genetic elements.
53
Metastasize means to...
spread from the original tumor to one or more new locations
53
Cancer is not a single disease. Rather, it is two hundred or more different diseases, affecting almost all organ systems, tissues, and types of cells
TRUE OR FALSE
TRUE
54
the recognition of cancer as a genetic disease that usually results...
from the occurrence of multiple gene mutations in somatic cells of the body
55
list 4 ways in which cancer cells are different from normal cells
1. normal cells are specialized, cancer cells are differentiated
2. cancer cells have a higher rate of proliferation (they can divide and grow much more quickly than a normal cell)
3. cancer cells are larger than normal cells and have larger nuclei
4. cancer cells are poorly organized as they grow
56
what are the hallmarks of cancer?
1. Sustained Cell Proliferation
2. Evasion of Normal Growth Suppression
3. Resistance to Cell Death
4. Cellular Immortality
5. Angiogenesis Induction
6. Activation of Invasion and Metastasis
7. Reprogramming of Energy Metabolism
8. Immune System Avoidance
9. Tumor-promoting Inflammation
10. Genome Instability and Mutation
57
As a group, ______________ encode transcription factor proteins and cell-cycle regulating proteins.
proto-oncogenes
58
Proteins that fail to function or that function incorrectly owing to mutations of proto-oncogenes result in inappropriate progression of the cell cycle. The mutated versions of proto-oncogenes are called _____________
oncogenes
59
___________ ____ _________: Cancer cells are in a chronic state of growth and division, unlike normal cells that undergo controlled proliferation. Sustained proliferation can be produced by gene mutations that drive excessive growth.
Sustained Cell Proliferation
60
___________ __ _________ ________ ____________: Gene mutations that eliminate the function of growth-suppressing proteins or render cells insensitive to growth-control signals enable cancer cells to circumvent the protein signals and regulatory proteins that normally regulate cell proliferation.
Evasion of Normal Growth Suppression
60
_______ ___ ____ ________ : Normal cells are generated through mitotic division, age during their active phase, and then enter senescence and undergo a process known as apoptosis, during which they die. Cancer cells in contrast generally live much longer than normal cells, owing to gene mutations that, by interfering with the normal mechanisms and signals leading to apoptosis, enable cancer cells to delay or bypass cell death.
Resistance to Cell Death
61
_______ __________: In addition to bypassing induced cell death, cancer cells also live much longer than is normal for cells that do not undergo apoptosis. Many are effectively rendered immortal by mutations that stabilize cells or modify the indicators of cell aging in a manner that allows them to grow and divide perpetually.
Cellular Immortality
62
____________ __________: Angiogenesis is the development of new blood vessels. Malignant tumors require blood vessels to supply the growing tumor with oxygen and compounds needed for growth. A number of normal cell types are recruited by the tumor to form blood vessels. These are among of the cadre of normal cells that are part of a tumor.
Angiogenesis Induction
63
_______ __ ________ ___ _________: The growth of normal cells usually requires the presence of other cells, partly because contact with other cells exercises control over that growth, keeping each tissue confined to a limited area. In cancer, a succession of gene mutations alters normal growth restrictions, allowing tumors to grow in size and invade surrounding tissues. Additional gene mutations, coupled with cellular immortality, can enable single cancer cells to break away from the original tumor, plant themselves in a new location, and proliferate to produce a new malignant tumor. This is the process of metastasis.
Activation of Invasion and Metastasis
64
____________ __ ______ __________ : The active proliferation of malignant tumors requires a disproportionate amount of energy. Thus, in addition to stimulating angiogenesis to supply itself with oxygen, the tumor must reprogram its cellular metabolism to meet its energy needs.
Reprogramming of Energy Metabolism
65
__________ __________ __________: The immune system is responsible for detecting and eliminating foreign microbes and cells that may do harm to the body. In addition, the immune system monitors the body for abnormal cells and helps eradicate precancerous and cancer cells before they develop into tumors. For newly forming tumors to proliferate, it is now thought that they must evade immune system detection. This notion is related to another emerging theory that links inflammatory processes in the body to the proliferation of cancer cells and malignant tumor formation.
Immune System Avoidance:
66
_______________ ___________: Cancerous tumors attract immune system cells deployed by the immune system to attack and eradicate cancer cells. This causes an inflammatory reaction within tumors that, paradoxically, helps promote some aspects of tumor growth, such as angiogenesis. Inflammation can also help supply the tumor with growth factors that in turn promote growth and survival factors, helping cancer cells evade destruction.
Tumor-promoting Inflammation
67
______ _______ __ ____________: Cancer cells are highly unstable and rapidly acquire new mutations of various kinds. This frequently gives them a growth advantage that allows them to proliferate much faster than surrounding normal cells. Large numbers of individual gene mutations are present in cancer cells, and a great deal of research activity is devoted to identifying which of these mutations are “drivers” of cancer cell proliferation (i.e., which mutations actively promote tumor growth) and which mutations are “passengers” (i.e., mutated due to cancer cell genome instability but not essential for tumor growth). These mutations can be identified by cancer cell genome sequencing.
Genome Instability and Mutation
68
A general term for a cancerous condition or tumor is...
neoplasia
69
malignant tumors are not confined in growth and may metastasize
TRUE OR FALSE?
true
70
Before they become cancerous, cells begin to look abnormal and grow abnormally...
The abnormality can first appear as hyperplasia, meaning extra growth, and progress to dysplasia, meaning disorganized growth. Hyperplastic and dysplastic cells can form tumors, masses of abnormal cells, but in these early stages the tumors are classified as benign tumors, meaning they are noncancerous, are usually well encapsulated by surrounding tissues or membranes. Benign tumors are considered “precancerous.” They are composed of abnormal cells that can grow excessively, but they do not invade surrounding normal tissue. Dysplastic cells can progress, however, to neoplasia, a state of growth in which they are now cancer cells proliferating in large numbers and in a highly disorganized manner. In this state, the masses are classified as malignant tumors, which are not confined in their growth. If malignant tumor growth continues it can enter metastasis, a state in which the tumor invades normal tissues
71
__________ _________ ________ is the classical approach to genetic analysis whereby genes are first identified by mutant phenotypes caused by mutant alleles and the gene sequence is subsequently identified by recombinant DNA technologies.
Forward genetic analysis
72
__________ _________ is a genetic analysis that begins with a gene sequence, which is used to identify or introduce mutant alleles and subsequently to identify and evaluate the resulting mutant phenotype.
reverse genetics
73
what is a great strength of forward genetic screens?
they are unbiased; no prior knowledge of the molecular function of the encoded gene product is required.
74
forward genetic screens are designed to....
These screens are designed to create many mutant organisms, and then screen for the mutants of interest.
75
what are the reasons we are shifting toward the usage of reverse genetics in biology?
The enormous amount of genomic sequence available has increased by orders of magnitude the number of known gene sequences, and only a fraction of them have been assigned a function by forward genetics. Additionally, genomic sequencing and reverse genetic screens have uncovered a degree of gene duplication not previously suspected.
76
A dream of geneticists for many decades was to have the ability to “edit” the genome—precisely changing the nucleotide sequence at a specific chromosomal locus to any desired sequence. What is this called?
genome editing
77
what does CRISPR stand for?
clustered regularly interspaced short palindromic repeats
78
what does cas mean?
CRISPR-associated
79
the ___ genes encode a DNA endonuclease, either as a single protein or as a protein complex depending on the species.
cas
80
what does the CRISPR-cas system do?
the CRISPR–cas system acts as a defense mechanism against invading nucleic acids.
81
Often the goal of genome editing is not to make random mutations at a specific locus but rather to change the sequence of a single base pair. This can be accomplished by introducing a fragment of DNA containing the desired base change along with the CRISPR–Cas9 components...
A fraction of the time, the CRISPR–Cas9 complex will create a double-strand break in the DNA that will be repaired by homologous recombination using the supplied DNA fragment. The end result is a genome in which a single base pair has been edited.
82
what are some applications of CRISPR?
A) Applications in agriculture that modify the genotype and hence phenotype of domesticated plants and animals have the potential to accelerate creation of new breeds and varieties for specific purposes or for adaptation to changing climates.
B) The ability of CRISPR technology to create specific mutations in the genome of a live cell has revolutionized reverse genetic approaches to the study of gene function and given rise to a rapidly proliferation of applications. One obvious application is gene therapy, in which a mutant allele in the cells of an individual is “corrected” to a functional state.
83
A primary role of this gene-silencing RNA system is to silence repetitive ____.
DNA
84
double-stranded RNA (dsRNA) can act as a trigger for the degradation not only of the double-stranded RNA itself but also of any RNA molecules that are complementary to the double-stranded RNA.
TRUE OR FALSE
TRUE
85
____________ gene silencing acts as a genomic immune system to silence both repetitive DNA sequences and invading nucleic acids.
dsRNA-mediated
86
To take advantage of endogenous RNAi activity as a way of silencing genes, scientists utilize double-stranded RNA that is complementary in sequence to the target gene. Describe this...
The mRNA of the target gene will then be degraded through the action of Dicer and Argonaute enzymes, causing a loss-of-function phenotype of the target gene. The efficiency of silencing can approach that of a null allele, although often the phenotypes induced represent a range of partial loss-of-function phenotypes.
87
Loss-of-function phenotypes induced by RNAi can be heritable if the source of the dsRNA is a transgene integrated into the genome.
TRUE OR FALSE
TRUE
88
_______________ _____ can also be introduced directly into cells or organisms by injection of double-stranded RNA or indirectly by infection with a double-stranded RNA virus, and in these cases the effects are transient, disappearing when the source of the dsRNA is removed.
Double-stranded RNA
89
describe the usage of RNAi in C. elegans
Caenorhabditis elegans normally eats E. coli as food, and, remarkably enough, when C. elegans is fed E. coli that is producing double-stranded RNA, the double-stranded RNA will be taken up into C. elegans and will silence genes in many organs of the C. elegans body. Although in this case the RNAi-induced phenotype is not indefinitely heritable, the phenotypic effects can be seen in several subsequent generations produced by self-fertilization of the worm that was fed the E. coli. This persistence is due to the activity of RNA-dependent RNA polymerases that exist in C. elegans.
90
what are the advantages of RNAi?
The advantages of the RNAi approach to reverse genetics include the ease and rapidity of applying the method. It allows large-scale reverse genetic screens to be conducted in cell cultures and whole organisms without the laborious preparatory task of creating mutagenized populations. In addition, transient RNAi-mediated gene silencing offers an alternative means of applying reverse genetics in species for which stable transformation protocols do not exist, but for which techniques to introduce dsRNA are available.
91
With the ultimate goal of studying specific genes and their functions, biologists use recombinant DNA techniques to...
1) fragment DNA into easily managed pieces and then separate and purify these fragments;
2) create many copies of DNA molecules of identical sequence;
3) combine DNA fragments to construct recombinant DNA molecules;
(4) determine the exact sequence of specific DNA molecules;
(5) identify fragments of DNA containing complementary sequences;
(6) introduce specific DNA molecules into living organisms
(7) precisely edit the genomes of organisms
(8) assay the phenotypic effects of the genetic changes.
92
a palindrome has the same 5' to 3' base sequence in both of its antiparallel DNA strands. Most _______ ________ recognize palindromic sequences.
restriction enzymes
92
what do restriction enzymes do?
cut DNA at specific sequences
93
Scientists use data from restriction experiments, including the number of restriction sites and the number of base pairs between the sites, to create maps of specific DNA sequences. these are called...
restriction maps
94
_________ ____ provide a foundation for further manipulation of the DNA fragments—for example, by suggesting where to further subdivide cloned fragments in order to clone still smaller fragments in a process known as subcloning.
restriction maps
95
After a genome under study has been reduced to smaller pieces by restriction enzymes, the individual pieces must be reproduced in large amounts—generally, either by molecular cloning or by the polymerase chain reaction (PCR)—so that each of them can be analyzed in greater detail. This is called...
molecular cloning
96
In ____________ ________, isolated DNA fragments are inserted into a vector. Then the recombinant DNA molecule is introduced into a biological system (a living organism) that amplifies the DNA, making many identical copies called DNA clones. ____________ ________ produces a large quantity of identical DNA molecules that can be analyzed by a variety of techniques, including restriction enzyme analysis and DNA sequencing.
Molecular cloning (both)
97
molecular cloning has 3 steps...
1. The joining together of the cloning vector and a donor DNA fragment to produce a recombinant DNA molecule
2. Screening to select recombinant vectors containing copies of the DNA segment of interest
3. Amplification (cloning) of the recombinant DNA molecule in a biological system
98
These vectors have a small copy number, origin of replication, a selectable marker and an MCS. They are used to carry big fragments of DNA, usually in a genome sequencing project. What are these?
Artificial chromosomes
99
_________ are circular DNA molecules that replicate autonomously in bacteria and usually carry nonessential genes.
plasmids
100
_____ _______________ libraries are made from
mRNAs that are actively transcribed in a population of cells
cDNA (complementary DNA)
101
The introduction of a gene from one organism into the genome of another organism creates a transgenic organism. The introduced gene is known as a ____________
transgene
102
The use of genes as therapeutic agents to cure or alleviate disease symptoms is termed...
gene therapy
103
Sporadic retinoblastoma is a retinoblastoma resulting when both copies of an autosomal gene known as ___, located on chromosome 13, are mutated in the same somatic cell.
RB1
104
RB1 plays an essential role in...
cell division
105
what is the difference between a tumor suppressor and an oncogene?
Tumor suppressors indicate the loss of function resulting in cancer. Typically, the gene which has lost its function is one responsible for regulating cell division.
Oncogenes are usually stuck “on” and wont stop driving cell expression, leading to overexpression.
106
What is the two-hit model for tumor development, and how does it specifically relate to inherited versus sporadic forms of retinoblastoma?
Both copies of the same gene must be mutated for retinoblastoma to develop. By inheriting a defective copy of RB1 in familial retinoblastoma, individuals need only one more mutation to develop retinoblastoma. For sporadic retinoblastoma two mutations are needed: one in each copy of RB1
107
Describe one example of a chromosomal mutation causing cancer.
A translocation of chromosomes 8 and either 2, 14 or 22, results in Burkitt’s lymphoma. This is due to an overproduction of c-Myc.
108
A scientist performs two types of reporter fusions with the same gene:
- The transcriptional fusion shows uniform expression.
- The translational fusion shows expression only in nuclei of a certain cell type.
explain the observed difference in expression?
1. The gene product is regulated after mRNA has been made.
2. Protein localization or modification occurs after translation.
3. Translation efficiency is selectively controlled in certain cells.
109
Used when a gene sequence is already known and its function is being explored
Reverse genetics
110
Focuses on discovering unknown genes that affect a known biological trait
Forward genetics
111
what are metagenomics?
metagenomics involves sequencing a group of organisms from the same environment to gain an understanding of environmental affect on organisms, gene diversity, etc.
112
what are comparative genomics?
studies how genes evolve by comparing genes to one another. They compare their function, content, and organization among other things.
113
what are functional genomics?
involves utilizing known genome sequences to understand gene function in an organism.
114
What is a multigene family
Multigene families are groups of related genes within an organism that share a common ancestor.
115
Repeated duplication events produce families of genes, and through this mechanism genes can become more ___________. This leads to phenotypic variation, and _________ ___________.
specialized
genetic diversity
116
what do cas genes do in CRISPR?
The cas genes encode a DNA endonuclease, either as a single protein or as a protein complex depending on the species.
117
____________ ____ ______________ is the set of techniques developed for amplifying, maintaining, and manipulating specific DNA sequences in vitro and also in vivo.
recombinant DNA technology
118
what is the ultimate goal of recombinant DNA technology?
studying specific genes and their functions
119
Describe the ingredients involved in Polymerase Chain Reaction (PCR).
i) Double stranded DNA containing target sequence
ii) the four DNA nucleotides (dNTPs)
iii) a heat stable polymerase
iv) two distinct single-stranded DNA primers that flank the area complementary to the target sequence
120
What are the three main temperature-based steps in a PCR cycle?
1. DNA is denatured using heat (95℃) to separate the strands
2. Primers are then annealed to the single strands of DNA by lowering the temperature to approximately 50℃
3. Temperature is raised to 72℃ causing the heat stable polymerase to polymerize the nucleotides as new complementary strands.
121
Describe one real-world application of expressing a heterologous gene in a bacterial or fungal host.
Human growth hormones are produced by bacterial systems
122
Why do we model complex traits as if the genes contributing to them are additive?
Because many traits are quantitative, meaning that each allele represents a “dose” of a trait, thus the more dominant alleles present the more intense the “dose” is and the more obvious the phenotypical expression becomes.
123
What are the assumptions we use for modeling complex traits as additive?
These genes do not have much environmental influence. They do not display linkage, and they have a limited number of loci.
124
in a certain plant, height varies from 6 to 36 cm. When 6-cm and 36-cm plants were crossed, all F1 plants were 21 cm. In the F2 generation, a continuous range of heights was observed. Most were around 21 cm, and 3 of 200 were as short as the 6-cm P1 parent.
What mode of inheritance does this illustrate, and how many gene pairs are involved?
There are six pairs of genes involved. This is quantitative inheritance.
125
Does somatic gene therapy affect future generations?
Somatic gene therapy does not affect the future generations genomes
126
_________ annotation identifies the location of genes and other functional sequences within the genome sequence.
genome
127
what is annotation?
Annotation is the process of attaching biological functions to DNA sequences, and gene annotation describes the biochemical, cellular, and biological function of the gene products the genome encodes. Until annotated, a genome sequence is nothing but a very long string of As, Ts, Cs, and Gs.
128
what is interspecific comparison?
Any comparison between different species
129
what are intraspecific comparisons?
Any comparison between individuals of the same species.
130
Genes encoding transcription factors or signaling molecules direct the formation of what?
specialized cell types
131
The majority of traits result from ________ gene interactions, are due to the influence of multiple genes (polygenic), and environmental influence.
epistatic
132
describe quantitative traits
Quantitative traits are influenced by multiple genes and may also be influenced by the environment. They are continuously distributed along a phenotypic scale. Some quantitative traits are separated into distinct phenotypes by a threshold.
133
_________ ________ result from the influence of multiple genes.
polygenic traits
134
The inheritance of polygenic traits is identified as ___________ ______________
polygenic inheritance
135
what is a multifactorial trait?
Traits whose phenotypic variation is the result of polygenic inheritance and environmental influences
136
what is a quantitative trait?
A trait exhibiting polygenic inheritance and displaying continuous phenotypic variation.
137
what is discontinuous variation?
A phenotype distribution containing discrete or separable categories.
138
phenotypes of single-gene traits often display...
discontinuous variation
139
polygenic and multifactorial traits usually display ____________ ____________.
continuous variation
140
what is continuous variation?
In polygenic and multifactorial traits, the observation of phenotypic distribution over a continuous range.
141
eye color is a polygenic trait that is influenced by up to ___ genes.
15
142
what is a major gene?
A gene that has a substantial effect on phenotypic variation.
143
what is a modifier gene?
A gene that modifies the effect of a major gene.
144
Two genes having strong effects on human eye color are OCA2 and HERC2.
TRUE OR FALSE
TRUE
145
Polygenic traits for which no individual gene or genes exert major gene effects have a continuous phenotypic distribution that results from incremental contributions by multiple genes. Genes contributing to phenotypic variation in this way are known as....
additive genes
146
what are threshold traits?
In polygenic and multifactorial inheritance, a trait with different phenotypes (e.g., affected and unaffected) that are determined by whether individual organisms are above or below a particular critical value on the phenotypic scale. Also known as threshold trait.
147
what contributions did Fisher make to genetic analysis?
Fisher used statistical analysis to show that quantitative traits result from the segregation of alleles of multiple genes displaying an additive effect. Fisher also showed that interactions between genes (i.e., epistasis) can be detected by these methods. In addition, he explored the role of gene–environment interaction and concluded that environmental factors contribute to continuous variation by blurring the lines between phenotypic classes.
148
The genes that contribute to the variation in a quantitative trait are collectively called quantitative trait loci or _____.
QTLs
149
Individually, a gene that contributes to a quantitative trait is referred to as a ...
quantitative trait locus.
150
explain QTL mapping
A chromosome region likely to contain a QTL is identified by the frequent co-occurrence of a specific genetic marker such as SNP. The inherited DNA sequence variation of a SNP is usually not the molecular basis of the QTL. Instead, the SNP is usually genetically linked to the QTL. The connection between the genetic marker and the phenotype implies that a QTL exists near the genome location encoding the genetic marker.
151
Contemporary QTL mapping uses DNA markers that have known chromosome locations to assist with the mapping and identification of genes. _____ are typically used for this.
SNPs
152
QTL mapping is a statistical process that seeks to identify...
regions of genomes containing genetic markers that are linked to QTL
153
Genetic diversity is essential for what?
evolution
154
mutation ____________ gene pools
diversifies
155
what is one reason that mutation alone is a slow evolutionary process?
The forward mutation rate pertains to mutations that create a new 𝐴2 allele by mutation of A1, whereas the reverse mutation rate, also known as the reversion rate, pertains to mutation of alleles in the opposite direction, 𝐴2 to 𝐴1
156
In evolutionary terms, _____ _____, also known as migration, refers to the movement of alleles into and out of populations.
gene flow
157
Gene flow brought about by the addition of new organisms to an existing population generates a new population, identified as an _______ population, consisting of members from the two formerly distinct populations
admixed
158
The term ________ ______ refers to chance fluctuations of allele frequencies that result from “sampling error,” a statistical term signifying that a small sample taken from a larger population is not likely to contain all alleles in exactly the same frequencies as in the larger population.
genetic drift
159
The first special case of genetic drift is called the founder effect. Describe this
This occurs when a new small population branches off from a larger population. Since the numbers of funder are small, their allele frequencies may be higher or lower than that of the larger population they came from (they also may have missing alleles). This is due to a sampling error, the founder effect can create new populations having allele frequencies that differ substantially from those found in the original population.
160
what are the genetic effects of inbreeding?
The likelihood of homozygosity is increased because related organisms share alleles and are thus more likely to produce homozygotes, especially when the alleles involved are rare in the general population
161
The increased frequency of homozygosity can lead to a phenomenon known as ___________ _________, the reduction in fitness of inbred organisms, often as a result of the reduced level of genetic heterozygosity.
inbreeding depression
162
evolution can be examined at the level of the gene, gene families or entire genomes.
TRUE OR FALSE
TRUE
