Biology Genetics Flashcards
Mendel’s First Law: Law of Segregation posits that genes exist in alternative forms (now referred as alleles). A gene controls a specific trait in an organism.
An organism has two alleles for each inherited trait, one inherited from each parent.
The two alleles segregate during meiosis, resulting in gametes that carry only one allele for any given inherited trait.
If two alleles in an individual organism are different, only one will be fully expressed, and the other will be silent. A dominant allele only requires one copy present to be expressed whereas a recessive allele must have two copies present to be expressed. In genetics problems, dominant alleles are typically capital letters, and recessive alleles are assigned lowercase letters. organisms that contain two copies of the same allele are ___ for that trait; organisms that carry two different alleles are heterozygous. The dominant allele is expressed in the phenotype. This is known as Mendel’s Law of Dominance.
homozygous
Because only one trait is being studied in this particular mating, it is referred to as a ___ cross
monohybrid
The individuals being crossed are the parental or P generation; the progeny generations are the ___ or F generations, with each generation numbered sequentially
fillial
A ___ square indicates all the potential progeny genotypes, and the relative frequencies of the different genotypes and phenotypes can be easily calculated
punnet
Mendel also developed the testcross, a diagnostic tool used to determine the ___ of an organism
genotype
Homozygous ___ organisms always breed true
recessive
Generally, the closer the genes are on the chromosome, the more likely they are to be ___ together
inherited
Dihybrid cross involves the analysis of two ___ of inheritance
traits
An allele is incompletely dominant if the phenotype of the heterozygote is an ___ of the phenotypes of the homozygotes
intermediate
Codominance occurs when ___ alleles exist for a given gene and more than one of them is dominant
multiple
Only two alleles are present in any single individual (ABO blood groups) but the population contains ___ three alleles
all
In codominance, however, both alleles in the genotype are expressed at the same time without a ___ of phenotype
blending
In sexually differentiated species, most chromosomes exist as pairs of ___ called autosomes, but sex is determined by a pair of sex hormones
homologues
All humans have 22 ___ of autosomes; additionally, women have a pair of homologous X chromosomes, and men have a pair of heterologous chromosomes, an X and a Y chromosome
pairs
Genes located on the X or Y ___ are called sex-linked
chromosome
Examples of sex-linked recessives in humans are the genes for ___ and color-blindness
hemophilia
Sex-linked ___ generally affect only men; they cannot be passed from father to son, but they can be passed from grandfather to grandson via a daughter who is a carrier, thereby skipping a generation
recessives
Mutations are changes in the genetic information ___ in the DNA of a cell
coded
Mutagenic ___ induce mutations
agents
Mutagenic agents are ___ also carcinogenic (cancer-causing)
sometimes
In a point mutation, a nucleic acid is replaced by another ___ acid
nucleic
As a result of a point mutation, the new codon may code for the same amino acid (___ mutation), the new codon may code for a different amino acid (missense mutation), the new codon may be a stop codon (nonsense mutation)
silent
While point mutations may lead to proteins of a different length than the native protein, they do not affect the length of the genome itself as seen with ___ mutations
frameshift
In a frameshift mutation, ___ acids are deleted or inserted into the genome sequence
nucleic
In a frameshift mutation, the length of the ___ changes
genome
Many bacteria also contain smaller circular rings of DNA called plasmids, which contain ___ genes
accessory
Episomes are ___ that are capable of integration into the bacterial genome
plasmids
Bacterial cells reproduce by ___ fission and proliferate
binary
Although binary fission is an ___ process, bacteria have three mechanisms for increasing the genetic variance of a population: transformation, conjugation , and transduction
asexual
Transformation is the process by which a foreign ___ fragment (plasmid0 is incorporated into the bacterial chromosome via recombination, creating new inheritable genetic combinations
chromosome
Only bacteria containing ___ called sex factors are capable of conjugating
plasmids
A bacteriophage is a virus that infects its host bacterium by ___ to the bacterium, boring a hole through the bacterial cell wall, and injecting its viral DNA while its protein coat remains attached to the cell well
attaching
Transduction occurs when fragments of the ___ chromosome become packaged into the viral progeny produced during such a viral infection
bacterial
The closer two genes are to one another on a chromosome, the more likely they will be to ___ together; this fact allows geneticists to map genes to a high degree of precision
transduce
Recombination occurs when linked ___ are separated
genes
Recombination occurs by breakage and rearrangement of adjacent regions of DNA when organisms carrying different genes or ___ for the same traits are crossed
allelles
The ___ is the noncoding sequence of DNA that serves as the initial binding site for RNA polymerase
promoter
There is also a ___ gene, which codes for the synthesis of a repressor molecule that binds to the operator and blocks RNA polymerase from transcribing the structural genes
regulator
Regulation may be via inducible systems or ___ systems
repressible
In an inducible system, the repressor binds to the operator, forming a barrier that prevents RNA polymerase from transcribing the __ genes
structural
For transcription to occur, an inducer must bind to the repressor forming an ___-repressor complex
inducer
The ___ complex cannot bind to the operator, thus removing it as a barrier and permitting transcription
inducer-repressor
The proteins synthesized from an inducible system are said to be ___
inducible
In a ___ system, the repressor is inactive until it combines with the corepressor
repressible
The repressor can bind to the operator and prevent transcription only when it has formed a ___ complex
repressor-corepressor
Corepressors are often the ___ products of the biosynthetic pathways they control
biosynthetic
The proteins (usually enzymes) are said to be repressible because they are normally being synthesized; transcription and translation occur until the ___ is synthesized
corepressor
Operons containing mutations, such as deletions, or whose regulator genes code for defective repressors are incapable of being turned off; their enzymes, which are always being ___, are referred to as constitutive
synthesized
In pedigrees, affected individuals (those who express a particular phenotype) are shaded in and ___ are not
unaffected
If a trait is autosomal recessive, a person will only be affected if he or she possesses two copies of the recessive allele (homozygous ___)
recessive
Only individuals who are homozygous recessive will be unaffected by an autosomal ___ trait
dominant
If significantly more males are affected than females and two unaffected individuals produce an affected offspring, then a ___ is likely X-linked recessive
trait
The change in the genetic ___ of a population with time is termed evolution
makeup
A discredited theory proposed by Jean-Baptiste Lamarck posited that new organs or changes in existing ones arose because of the ___ of the organism
needs
In Charles Darwin’s theory, pressures in the ___ select for the organism most fit to survive and reproduce
environment
In the evolutionary sense, ___ is the ability to survive and reproduce
fitness
___ is when there are more offspring produced than can survive
overpopulation
Offspring naturally show differences in their ___ compared to those of their parents (variations)
characteristics
The developing ___ must compete for the necessities of life (competition)
population
Some organisms in a species have variations that give them an advantage over other ___ of the species
members
The individuals that survive (those with the favorable variations) live to adulthood to reproduce and thus ___ these favorable variations or adaptations to their offspring
transmit
Over many generations of natural selection, the favorable changes (adaptations) are ___ in the species (evolution of new species)
perpetuated
speciation is the evolution of new species, which are groups of individuals that can interbreed freely with each other but not with members of ___ species
other
gene ___ is impossible between different species
flow
Different selective pressures act upon the gene pools of each group, causing them to ___ independently
evolve
Before speciation, small, local populations called ___ often form within a species
demes
Members of the same deme are subject to similar ___ factors and thus are subject to the same selection processes
environmental
If these demes become ___, speciation may occur
isolated
over time, isolated demes may become so different that ___ may be impossible
mating
evolutionary history of ___ alive today is termed phylogeny
species
All of the descendants from the common ancestor form what is known as a ___ in phylogenies
clade
When two species from different ancestors develop similar traits, this is known as ___ evolution
convergent
___ evolution is similar to convergent evolution but ocurs when a more recent ancestor can be identified
parallel
In contrast, divergent evolution occurs when ___ with a shared ancestor develop differing traits due to dissimilarities between their environments
species
___ radiation is the emergence of a number of lineages from a single ancestral species
adaptive
A single species may diverge into a number of distinct species; the differences between them are those adaptive to a ___ lifestyle or niche
distinct
A ___ includes all members of a particular species inhabiting a given location
population
The ___ pool of a population is the sum total of all the alleles for any given trait in the population
gene
Gene ___ is the decimal fraction representing the presence of an allele for all members of a population that have this particular gene
frequency
p plus q is ___ to one
equal
Hardy Weinberg principle states an ideal situation as:
The population is very large
No mutations affect the gene pool
Mating between individuals in the population is random
There is no net migration of individuals into or out of the population
The genes in the ___ are all equally successful at reproducing
population
Hardy Weinberg equation where p is the frequency of allele T and q is the frequency of __ t
allele
p squared plus 2 times p times q plus q squared is ___ to one
equal
Hardy Weinberg equation holds that p squared is the frequency of TT (dominant ___), 2 times p times q is the frequency of Tt (heterozygotes), q squared is tt (recessive homozygotes)
homozygotes
Genotypes with low ___ values tend to disappear
adaptive
Gene mutations can either be ___ or detrimental for the offspring
favorable
If mates are not randomly chosen but rather selected according to criteria such as phenotype and proximity (sexual selection), the relative ___ ratios will be affected and will depart from the predictions of the Hardy-Weinberg equilibrium
genotype
Large die off events can also cause genetic drift and are called a ___ bottleneck
genetic
Migration of individuals between populations will result in a loss or gain of ___, thus changing the composition of a population’s gene pool
genes
Homologous structures have the same basic ___ features an evolutionary origins
anatomical
Analogous structures have similar functions but may have different evolutionary origins and entirely different ___ of development
patterns
Similarity of developmental stages suggests a common ___ and development history
ancestry
Vestigial structures have ___ known current function but apparently had some ancestral function
no
Species multiplication is generally accompanied by migration to lessen ___ competition
intraspecific
Among the first forms of life were ___ which depended on outside sources for food
heterotrophs
Colloidal protein molecules tend to clump together to form coacervate droplets (a cluster of ___ molecules surrounded by a shell of water
colloidal
The primitive heterotrophs slowly evolved complex ___ pathways, enabling them to use a wider variety of nutrients
biochemical
Autotrophs are able to produce ___ compounds, including energy-containing molecules, from substances in their surroundings
organic
Once molecular oxygen became a major component of the Earth’s atmosphere, both heterotrophs and ___ evolved the biochemical pathways of aerobic respiration
autotrophs
Autotrophic anaerobes include chemosynthetic bacteria. Autotrophic aerobes include the green plants and photoplankton. The heterotrophic anaerobes include yeasts. The heterotrophic aerobes include ___, earthworms, and humans
amoebas
___ is the system by which organisms are classified
Taxonomy
Every organism fits into eight categories, or ___, each one increasingly specific based on traits or common ancestors
taxa
Cladograms do not represent the ___ of change between ancestor and descendant
amount
