Genetics Flashcards
The basic unit of heredity is the ___. They are composed of __ and are located on the ___
gene, DNA, chromosome
Mendel postulated four principles of inheritance: first that genes exist in ___ forms referred to as ___. A gene controls a specific ___ in an organism. The organism has ___ alleles for each inherited trait, one inherited from each ___. The two alleles ___ during ___ resulting in gametes that carry only one allele for any given trait. If two alleles in an individual organism are different, only one will be __ ___, and the other will be ____
alternative, alleles, trait, 2, parent, segregate, meiosis, fully expressed, silent
When only one trait is being studied in the mating
monohybrid cross
The individuals being crossed are the __ or ___ generation and the progeny generations are the ___ or __ generations
parental, P, filial, F
The hallmarks of mendelian inheritance are the ___ of the silent phenotype in the __ generation and its subsequent ___ in ___% of individuals in the __ generation
disappearance, F1, reappearance, 25, F2
The idea that the inheritance of one trait is completely independent of any other
mendel’s law of independent assortment
In modern, non mendelian genetics, genes on the same chromosome will __ __ unless __ __ occurs. This breaks the linkage of certain ___. Generally, the ___ the genes are on the chromosome, the more likely they are to be inherited together.
stay together, crossing over, patterns, closer
Fruit flies are advantageous for genetic research because they ___ often with a short __ __, they reproduce in __ __, its chromosomes are __ and easily recognizable in size and shape, and they are only ___ pairs. Also ___ occur relatively frequently
reproduce, lief span, large numbers, large, 4, mutations
When an a person heterozygous for an allele produces a phenotype that is an intermediate of the phenotypes of the homozygotes
incomplete dominance
When multiple alleles exist for a given gene and more than one of them is dominant, leading to full dominance only with the recessive allele. When more than one dominant allele is present, both will be expressed at the same time without a blending of the phenotype
codominance
The sex chromosomes pair during ___ and segregate during the first ___ ___. Since females can produce only gametes containing the __ chromosome, the gender of a zygote is determined by the __ ___ of the male gamete. If the sperm carries a ___ chromosome, the zygote will be male, if it carries an ___ chromosome, it will be female. For every mating, there is a ___% change that the zygote will be male or female
meiosis, meiotic division, X, genetic contribution, Y, X, 50
Genes located on the X or Y chromosome are called ___. In humans, most sex-linked genes are located on the __ chromosome.
sex-linked, X
In humans, women have two X chromosomes and men only have __. As a result, recessive genes carried on the X chromosome will produce the ___ ___ in men because no -_ __ is present to mask them. The recessive phenotype is therefore much ___ ___ found in men. Examples of sex-linked recessives in humans are the genes for ___ and _____.
1, recessive phenotypes, dominant allele, more frequently, hemophilia, colour-blindness
Men with an ____ recessive trait ___ pass the trait to their male offspring. However, they will pass the gene to all of their ___. Unless the daughter also receives the gene from the ___ she will be a phenotypically normal carrier of the trait. Because all of the daughter’s male children will receive their only X chromosome from her, ___ of her sons will receive the recessive linked allele
X-linked, cannot, daughters, mother, half
Sex-linked recessives generally affect only __, they cannot be passed from ___ to ____, and they can be passed from ___ to ___ via a daughter who is a carrier
men, father, son, grandfather, son
Interactions between the genotype and the ___ such as ____ can result in different ____
environment, temperature, phenotypes
Hereditary systems can exist outside of the ___. For example, DNA is found in ___ and other ___ ___. These cytoplasmic genes may interact with __ __ and are important in determining the characteristics of their ___. ___ ____ in many microorganisms is regulated by cytoplasmic DNA known as ___ that contain one or more genes. These can be passed from one ___ cell to another via ___
nucleus, mitochondria, cytoplasmic bodies, nuclear genes, organelles, drug resistance, plasmids, bacterial, transformation
The failure of homologous chromosomes to separate properly during meiosis I, or the failure of sister chromatids to separate properly during meiosis II
nondisjunction
Nondisjunction can result in ____ or _____. __ ___ is caused by Trisomy of chromosome ___. Most nondisjunctions are ___ causing the embryo to spontaneously ___ early in the pregnancy. Nondisjunction of __ __ may also occur, resulting in individuals with extra or ___ copies of the X or Y chromosomes
monosomy, trisomy, down syndrome, 21, lethal, abort, sex chromosomes, missing
Mutations in somatic cells can lead to ___. Mutations that occur in the gametes will be ___ __ to the offspring. Most mutations occur in regions of _____ ___, and are silent. Mutations that do change the sequence of amino acids in proteins are most often ___ and ____.
tumors, passed down, noncoding DNA, deleterious, recessive
____ agents induce mutations. These include ___ rays, ___, ___ rays, and ___. It can also be chemical compounds such as ___ which inhibits __ ___, or ___ gas, which ____ guanine in DNA. These agents are sometimes also ___.
mutagenic, cosmic, x-rays, UV, radioactivity, colchicine, spindle formation, mustard, alkylates, carcinogenic
In a gene mutation, ___ _ are added, deleted or ___ thus altering the amino acid sequence. This creates a -__ ___.
nitrogenous bases, substituted, mutated protein
when a nucleic acid is replaced by another nucleic acid; generally involves 1-3 nucleotides
point mutation
When a mutation results in the same amino acid and there is no change in the resulting protein
silent mutation
When a mutation results in a different amino acid and there is a change in the resulting protein
missense mutation
When a mutation results in a stop codon
nonsense mutation
___ mutations are often lethal or severely inhibit the organism function. While the length of the ___ does not change with any of the mutations, the ___ __ of the proteins formed from an RNA sequence with this type of mutation could be much ___ due to the ___ stop
nonsense, genome, primary structure, shorter, premature
When nucleic acids are deleted or inserted into the genome sequence; length of genome changes, is often lethal
frameshift mutation
____ is a molecular disease caused by the inability to produce the enzyme for the metabolism of ____. A degradation product called __ __ accumulates as a result. These individuals are unable to consume products containing ____. ____ may result from impaired conversion of phenylalanine to tyrosine. It also results in _____, and __ ___. This disease is caused by a deficiency of ____ _____.
phenylketonuria, phenylalanine, pheylpyruvic acid, aspartame, hyperpneylanemia, phenylketonuria, mental retardation, phenylalanine hydrolase
____ ___ is a disease in which red blood cells become __ shaped because they contain defective ___. The sickle-cell hemoglobin carry ____ ___. This disease is caused by a substitution of _____ for __ ____, because of a single base-pair substitution in the gene coding for hemoglobin. However patients do have less severe symptoms of ___ should they become infected
sickle-cell anemia, crescent, hemoglobin, less oxygen, valine, glutamic acid, malaria
The bacterial genome consists of a single __ ___ located in the __ region of the cell. Many bacteria also contain smaller circular rings of DNA called ___, which contain __ ___. ___ are plasmids that are capable of integration in to the bacterial ___.
circular chromosome, nucleoid, plasmids, accessory genes, episomes, genome
Replication of the bacterial chromosome begins at a unique ___, and proceeds in both directions ____. DNA is synthesized in the ___ direction
origin, simultaneously, 5’–>3’
Bacterial cells reproduce by __ __ and proliferate very ___ under favorable conditions. Although binary fission is an ___ process, bacteria have ___ mechanisms for increases the genetic variance of a population
binary fission, rapdily, asexual, 3
The process by which a foreign chromosome fragment is incorporated into the bacterial chromosome via recombination, creating new inheritable genetic combinations
transformation
sexual mating in bacteria; the transfer of genetic material between two bacteria that are temporarily joined
conjugation
During conjugation, a -_ __ __ is formed between two bacterial cells, and genetic material is transferred from the donor __ ___ type to the recipient __. __ type. Only bacteria containing plasmids called __ __ are capable of this.
cytoplasmic conjugation bridge, male plus, female minus, sex factors
The __ ___ is a sex factor in e coli. Bacteria possessing this plasmid are termed _____ cells, and those without it are called ___ cells. During conjugation, the ___ cell replicates its F factor and donates the copy to the ___, converting it to an F+ cell. Genes that code for other characteristics such as __ __, may be found on the plasmids and transferred into __ ___ along with these factors
F factor, F+, F-, F+ recipient, antibody resistance, recipient cells
Sometimes the sex factor becomes ___ into the bacterial ___. During conjugation, the entire bacterial ____ replicates and begins to move from the donor cell into the recipient cell. The __ __ usually breaks before the entire chromosome is transferred, but the bacterial genes that enter the recipient cell can easily ___ with the genes already present to form novel __ ___. These bacteria are called ___ or __ ____ __ ____ cells.
integrated, genome, chromosome, conjugation bridge, recombine, genetic combinations, Hfr, high frequency of recombination
a ____ is a virus that infects its host bacterium by attaching to the bacterium, boring a hole through the bacterial ___ ___ and injecting its __ ___ while its __ __ remains attached to the cell wall. Transduction occurs when fragments of the bacterial ___ become ___ into a -_ ___ produced during such a viral infection. These virons may infect other bacteria and introduce new __ __ through ____ with the new host cell’s DNA. The closer two genes are to one another on a ___, the more likely they will be transduce together. This fact allows ___ to map genes to a high degree of precision.
bacteriophage, cell wall, viral DNA, protein coat, DNA, packaged, viral progeny, genetic arrangements, recombination, chromosome, geneticists
Recombination occurs when __ ___ are separated. It occurs by ___ and rearrangement of __ ___ of DNA when organisms carrying different genes or ____ for the same traits are ___.
linked genes, breakage, adjacent regions, alleles, crossed
Regulation of transcription is based on the accessibility of __ ___ to the genes being transcribed, and is directed by an ____, which consists of ___ genes, an ____ region, and a ____ region on the DNA before the protein coding genes.
RNA polymerase, operon, structural, operator, promoter
The sequence of nontranscribable DNA that is the repressor binding site
operator
Noncoding sequence of DNA that serves as the inital binding site for RNA polymerase
promoter
Gene that codes for the synthesis of a repressor molecule that binds to the operator and blocks RNA polymerase from transcribing the structural genes
regulator gene
RNA polymerase must also move past the ___ to transcribe the structural genes. ___ __ function by preventing or permitting the RNA polymerase to pass on to the structural genes.
operator, regulatory systems
In an inducible system, the ___ binds to the operator, forming.a barrier that prevents RNA polymerase from ___ the structural genes. For transcription to occur, an ___ must bind to the repressor, forming an _____ ___. This cannot bind to the operator, thus removing it as a barrier permitting transcription. The proteins synthesized are thus said to be ____.
repressor, transcribing, inducer, inducer-repressor complex, inducible
in inducible systems, the structural genes typically code for an ____, and the inducer is usually the ____, or a ____ of the substrate, upon which the enzyme normally acts. When the ___ is present, the enzymes are ____, when it is absent, enzyme synthesis is ___. In this manner, enzymes are transcribed only when they are actually ____.
enzyme, substrate, derivative, inducer, synthesized, negligible, needed
In repressible systems, the repressor is ___ until is combines with the _____. These are often __ __ of the biosynthetic pathways they control. The proteins produced are usually ___ and are said to be ____, because they are normally being synthesized. Operons containing mutations such as ___ or whose __ ___ code for defective repressors are incapable of being _ ___. The resulting continuously synthesized enzymes are called ____
inactive, corepressor, end products, enzymes, repressible, deletions, regulator genes, turned off, constitutive
