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particular set of genes
What is a genotype?
Each gene
What specifies a particular trait with a different sequence of alleles?
two alleles for each trait
How many alleles do most eukaryotic organisms have for each trait?
at a locus
Where can alleles be located in order to be either dominant or recessive?
their corresponding phenotypes
When paired with any other allele for the same trait, what do dominant alleles give rise to?
when paired with another copy of the same allele
When do recessive alleles give rise to their corresponding phenotype?
in the production of gametes
When do alleles assort independently?
germ cells
What are gametes?
cell division
What does the growth, development, and reproduction of organisms rely on?
identical daughter cells
In cell division, what two cells are created?
DNA polymerases
What specialized enzyme is responsible DNA replication?
Because the DNA double helix is held together by base pairing
Why does the sequence of one strand completely specify the sequence of its complement?
semiconservative
What one word characterizes the process of DNA replication?
physically separate the two copies of the genome
What is one thing the cell must do once DNA replication is compete?
divide into two distinct membrane-bound cells
What is another thing the cell must do once DNA replication is complete?
circular
In binary fission, what shape is each genome?
as the membrane invaginates to split the cytoplasm
In binary fission. when does each genome separate into daughter cells?
extremely fast
Compared to the rates of cell division in eukaryotes, with what speed does binary fission occur?
molecular inheritance
The duplication and transmission of genetic material from one generation of cells to the next is the basis for what?
cells of the offspring contain copies of the genes in their parents' cells
Why do organisms inherit the characteristics of their parents?
In asexually reproducing organisms
In what type of organism will the offspring be a genetic copy or clone of the parent organism?
In sexually reproducing organisms
In what type of organism will a specialized form of cell division called meiosis produce cells called gametes?
eggs or ova
What are the gametes produced by females called?
During the process of meiotic cell division
When can an event called genetic recombination or crossing-over sometimes occur?
no effect
If the alleles on the chromatids are the same, what effect arises from genetic recombination?
reassortment of otherwise linked alleles
If the alleles on the chromatids are different, what effect arises from genetic recombination?
independent assortment
Each of a parent's two genes for each trait will sort independently into gametes according to what Mendelian principle?
a crossover point
In genetic linkage, what sort of point is extremely unlikely to occur?
mutations
What is it called when errors occur in DNA replication?
10−8 per nucleotide per replication
What is the lowest error rate that occurs in eukaryotic cells?
10−3
What is the highest error rate that can occur for some RNA viruses?
DNA replication
What can small mutations be caused by?
errors in recombination
What can larger mutations be caused by?
polymorphic
What is it called when multiple different alleles for a gene are present in a species's population?
different phenotypic traits
What can some alleles give rise to?
the wild type
What is a gene's most common allele known as?
mutants
What are rare alleles called?
genetic drift
What is one cause of the genetic variation in relative frequencies of different alleles in a population?
silent mutations
What are mutations that have no effect on an organism's phenotype called?
synonymous mutations
What are mutations that do not change the amino acid sequence called?
conservative mutations
What are mutations that lead to amino acid sequence changes but leave the protein functioning similarly called?
Genetic disorders
What is a result of deleterious mutations?
adaptive evolution
What does the directional selection of beneficial mutations lead to?
homologs
What are genes with a most recent common ancestor called?
gene duplication within an organism's genome
What is one reason for homologs to appear?
paralogous genes
What are genes that occur from duplication within an organism's genome called?
orthologous genes
What are genes that result from divergence of the genes after a speciation event called?
The relationship between genes
What does comparing the sequence alignment of genes' DNA measure?
conserved sequence
What is the degree of sequence similarity between homologous genes called?
by neutral molecular evolution
How do genes typically accumulate mutations over time?
stabilizing
Under what type of selection are genes constrained so they change more slowly?
phylogenetic
What type of analyses can the sequence differences between genes be used for?
gene duplication
What is the most common source of new genes in eukaryotic lineages?
gene duplication
What creates copy number variation of an existing gene in the genome?
paralogs
What are the genes that result from eukaryotic gene duplication called?
nonfunctional
What type of copy can gene duplication sometimes result in?
pseudogenes
What are functional copies of a gene which have a loss of function due to mutation called?
De novo or "orphan" genes
What is a gene whose sequence shows no similarity to existing genes called?
18 to 60
What is the estimate of the number of orphan genes in the human genome?
typically shorter
How do the lengths of orphan genes compare to most eukaryotic genes?
simpler in structure
How does the structure of orphan genes compare to most eukaryotic genes?
gene duplication followed by extremely rapid sequence change
What is one primary source of orphan protein-coding genes?
Horizontal gene transfer
What is the transfer of genetic material through a mechanism other than reproduction known as?
prokaryotes
In what type of organism is horizontal gene transfer a common source of new genes?
antibiotic resistance
What is one trait that horizontal gene transfer is a common means of spreading?
eukaryotes
In what type of organism is horizontal gene transfer rare?
alga genomes containing genes of bacterial origin
What is one example of horizontal gene transfer in eukaryotes?
genome size
What is one characteristic that varies widely between organisms?
viruses
In which type of organism do the smallest genomes occur?
2
What is the smallest number of protein coding genes that a virus can have?
viroids
Which organism acts as a single non coding RNA gene?
5 million
What is the estimate for the total number of protein coding genes on Earth?
the 1960s
Since when has the number of base pairs of DNA in the human genome been known?
2,000,000
What was the highest initial theoretical prediction of the number of human genes?
alternative variants
What sort of variants did the Human Genome Project indicate that many of the measured transcripts were?
13
After the Human Genome Project, how many genes were encoded on the mitochondrial genome?
1–2%
What percentage of the human genome consists of protein coding genes?
Essential genes
What are the set of genes which are thought to be crucial for the survival of an organism?
environmental stress
What does the definition of essential genes assume an absence of?
250–400
How many genes are essential for Escherichia coli?
Half
What fraction of Escherichia coli's essential genes are orthologs?
1000 genes
How many essential genes does Saccharomyces cerevisiae have?
Housekeeping genes
What type of genes are necessary for performing basic cell functions?
constant
At what relative level are housekeeping genes expressed at?
housekeeping genes
When investigating gene expression, what type of genes are used as a control for experiments?
developmentally
How are some essential genes regulated?
at certain times during the organism's life cycle
When are some essential genes expressed?
HUGO Gene Nomenclature Committee (HGNC)
What committee has established gene nomenclature for every known human gene?
through a database maintained by HGNC
How can the gene nomenclature be accessed?
only one
How many symbols does each gene have?
homologs in other species
With what is it preferred that symbols are kept consistent with?
common model
What type of model does the mouse play a role for?
Genetic engineering
What is known as the modification of an organism's genome through biotechnology?
the 1970s
When did techniques begin to be developed to add, remove and edit genes?
engineered nuclease enzymes
What sort of enzymes do recently developed genome engineering techniques use?
targeted
What sort of DNA repair is created by modern genetic engineering techniques?
synthetic biology
What term refers to extensive genetic engineering of an organism?
Genetic engineering
What has become a common research tool with model organisms?
that gene's function
What do scientists explore by adding genes to mice with a certain gene's function disrupted?
agriculture
What is an application for which organisms have been modified for?