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
