Heredity and Genetics (C652)(WGU)

gene

a string of nucleotides within a DNA molecule that is the basic structural and functional unit of genetics

allele

this is the term for one of a number of different forms of a gene

phenotype

physical characteristics of an organism

genotype

genetic makeup of an organism

heterozygous

this term describes an organism that has two different alleles for a trait

homozygous

this term describes an organism that has two identical alleles for a trait

dominant

describes a trait that covers over, or dominates, another form of that trait

recessive

an allele that is masked when a dominant allele is present

meiosis

cell division that produces reproductive cells in sexually reproducing organisms; one diploid cell containing forty six chromosomes undergoes one round of chromosome replication and two rounds of division to produce four haploid cells each of which contains one copy of each chromosome

Interphase

this is the phase during which the chromosomes replicate

Prophase I

during this phase chromosomes condense and become visible under a microscope, the nuclear envelope disappears, and the spindle becomes organized

Metaphase I

during this phase paired homologous chromosomes line up at the equator of the cell with each chromosome attached to spindle fibers from opposite poles of the cell

Anaphase I

during this phase the paired chromatids are separated from each other and move towards opposite sides of the cell

Telophase I

during this phase the cytoplasm begins to divide resulting in two haploid cells

Prophase II

during this phase the unpaired chromosomes consist of two sister chromatids joined by a centromere

Metaphase II

during this phase the twenty three unpaired chromosomes are at the equator of the cell with spindle fibers from opposite poles of the cell attached to their centromeres

Anaphase II

during this phase spindle fibers pull the chromatids apart in both cells

Telophase II

during this phase the chromosomes uncoil and the nuclear envelope reforms and the cytoplasm begins to split resulting in four haploid cells

crossing over

this is the process in which homologous chromosomes exchange portions of their chromatids during the first prophase and metaphase in meiosis and this allows for genetic codes to be swapped between homologous pairs of chromosomes

Principle of Segregation (Mendel's First Law)

this principle states that members of a gene pair must separate or segregate from each other during gamete formation and each gamete receives only one of the two genes that control a particular trait

Principle of Independent Assortment

this principle states that genes for different traits can segregate independently during the formation of gametes

incomplete dominance

this describes a situation in which one allele is not completely dominant over another allele such as a red flower crossing with a white flower and producing a pink flower

codominance

this describes a situation in which both alleles of a gene are fully expressed such as with blood types

autosomal recessive

this inheritance pattern is characterized by affected individuals having unaffected parents, all the children of two affected individuals being affected, and male and female children being affected in roughly equal numbers

autosomal dominant

this inheritance pattern is characterized by every affected individual having at least one affected parent and males and females being affected in roughly equal amounts

x-linked dominant

this pattern of inheritance is characterized by affected males having affected daughters and more females are affected than males

x-linked recessive

this pattern of inheritance is characterized by mostly males being affected

y-linked

this pattern of inheritance is characterized by all affected males having all affected male offspring

polygenic traits

these are traits controlled by two or more genes and result in a variation of certain traits

discontinuous variation

a variation in a characteristic in which individuals show two, or a few, traits with large differences between them

continuous variation

this variation is characterized by the appearance of many different phenotypes

polyploidy

this is the term for an increase in the number of chromosome sets in a cell

triploidy

this is a type of polyploidy in which there are three sets of chromosomes

tetraploidy

this is a type of polyploidy in which there are four sets of chromosomes

aneuploidy

this term is the gain or loss of a single chromosome

monosomy

the term for the loss of a single chromosome

trisomy

term for the gain of a single chromosome

nondisjunction in meiosis I

this occurs when one pair of chromosomes fails to separate properly at anaphase I of meiosis and results in two gametes carrying both members of a chromosome pair and two missing one chromosome

nondisjunction in meiosis II

this occurs in one cell and produces two cells with the normal haploid number of chromosomes and one cell with an extra chromosome and one cell with a missing chromosome

missense

this type of mutation occurs due to a change in the nucleotide sequence and results in a changed amino acid

nonsense

this type of mutation occurs due to a change in the nucleotide sequence and results in an amino acid being changed to a stop codon

sense

this type of mutation occurs due to a change in the nucleotide sequence and changes a stop codon to code for a different amino acid

silent

this type of mutation occurs due to a change in the nucleotide sequence and changes a single nucleotide but it does not change the amino acid that is coded for

frameshift mutation

this type of mutation involves the insertion or deletion of a nucleotide and changes the reading frame resulting in different amino acids

deletion

this is a frameshift mutation in which one or more nucleotides are removed from the sequence

insertion

this is a frameshift mutation in which one or more nucleotides is inserted into a DNA sequence

point (single nucleotide replacement)

this is a mutation in which a single base pair in DNA has been changed

tautomeric shift

this is a mutation caused by small atomic changes to the purine and pyrimidine bases in nucleotides that change the hydrogen bonding properties of bases and allow bonding with noncomplementary bases

radiation

this is an environmental factor that can cause mutations if it interacts with DNA by splitting hydrogen ions into hydroxyl radicals

chemical modification of nucleotides

this is used to describe the mutations that occur in DNA due to different chemicals in the environment and all chemicals can cause different mutations and changes

base analogs

this term describes a purine or pyrimidine that differs in chemical structure from those normally found in DNA or RNA and these differently structure bases can result in mutations

senescence

this is a cell's response to damaged DNA in which the cell becomes dormant

apoptosis

this is a cell's response to damaged DNA in which the cell induces suicide and destroys itself

cancer

this can occur when the DNA in a cell becomes so damaged that it escapes the normal control of the cell cycle

DNA polymerase proofreading

this process occurs during replication and allows DNA polymerase to reverse and remove an incorrectly placed nucleotide and place the correct one

DNA repair enzymes

these enzymes monitor DNA for distortions and if they detect one they can cut the distorted portion of the strand and allow DNA polymerase to repair it

PCR (polymerase chain reaction)

this is a laboratory technique for amplifying specific sequences of DNA

DNA microarray

this is a laboratory technique in which there is immobilized single-stranded DNA fragments of a known nucleotide sequence that is used especially in the identification and sequencing of DNA samples and in the analysis of gene expression

DNA sequencing

this laboratory technique is the process of determining the precise order of nucleotides within a DNA molecule

southern blot

this laboratory technique is used to locate a specific sequence of DNA within a complex mixture

recombinant DNA

this laboratory technique involves the creation of DNA that has been formed artificially by combining DNA from different organisms

DNA profiling

a procedure that analyzes DNA fragments to determine whether they come from a specific individual

biopharming

this is the use of genetically engineered animals to act as biofactories for producing drugs, vaccines, antibodies, hormones, industrial chemicals such as plastics and detergents, and human body organs

genetically modified organisms

this is an organism whose genetic material has been altered through some genetic engineering technology or technique

stem cells

these are unspecialized cells that are able to renew themselves for long periods of time by cell division

cloning

this is the creation of a genetically identical copy of DNA or of an organism

Hardy-Weinberg Equilibrium

this term describes the five criteria that must be met including that the population is very large, all genotypes have equal ability to survive and reproduce, mating in the population is random, no mutations affect the gene pool, and factors that change allele frequency like mutation and migration are absent or are rare events and can be ignored

founder effect

this term states that alleles carried by the founders, or a small number of individuals in a population, will become established in the new population

genetic drift

this term describes the random fluctuations of allele frequencies from generation to generation that take place in small populations

natural selection

a process in which individuals that have certain inherited traits tend to survive and reproduce at higher rates than other individuals because of those traits

nonrandom mating

this term describes mating among individuals on the basis of their phenotypic similarities or differences rather than mating on a random basis

speciation

the formation of new and distinct species in the course of evolution

mutation

this term describes the creation of new alleles in a population