Exam 2: Key Terms Flashcards
allele
different versions of a gene
codominance
the effect of both alleles is equally visible in the phenotype of the hetero zygote
dihybrid
individuals that are heterozygous for two traits
dominant allele
the allele that exerts a controlling influence on the phenotype in a gene heterozygote is said to be dominant
epistasis
when the phenotype effect of the alleles of one gene depends on the presence of certain alleles for another, independently inherited gene
gene
a piece of DNA that codes for genetic traits and are located on chromosomes
genetic cross
controlled mating experiment performed to examine how a particular trait is inherited
genetic trait
inherited characteristic of an organism that can be observed or detected in some manner
genotype
the allelic makeup of that individual with respect to the specified genetic trait
heterozygote
an individual whose genotype consists of two different alleles for a given phenotype
homozygote
an individual whose genotype consists of two copies of the same allele
hybrid
the offspring resulting from a cross between to purebreds (ex. mule & donkey)
incomplete dominance
produces an intermediate phenotype in the heterozygote (white & red make pink)
- no single allele completely dominates over the other and the heterozygote displays an “inbetween” phenotype
law of independent assortment
when gametes form, the alleles of a particular gene segregate during meiosis independetly of the alleles of other genes - located on separate chromosomes
law of segregation
the two copies of a gene are separated during meiosis and end up in different gametes
phenotype
the display of a particular version of a genetic trait in a specific individual
pleiotropy
a single gene influences two or more distinctly different traits (albinism)
recessive allele
an allele that has no effect on the phenotype when paired with a dominant allele in a heterozygote is said to be recessive
autosome
all chromosomes that don’t determine sex
chromosome theory of inheritance
all genes are located on chromosomes
crossing over
- happens during meiosis
- reciprocal exchange of segments of non sister chromatids
- only thing that can unlink gene
deletion in relation to chromosomes
occurs when a piece of a chromosome breaks off and is lost (chromosomes with deleted will be shorter. only have 1 copy of gene)
duplication
a chromosome becomes longer because it ends up with two copies of a particular chromosome fragment (piece copied more than once)
genetic carrier
individuals that are heterozygous for a recessive disorder Ww
genetic linkage
genes that are positioned close to each other on the same chromosome tend to be inherited together
-located on the same chromosome
inversion
occurs when a fragment of a chromosome breaks off and returns to the correct place on the original chromosome, but with the genetic loci in reverse order (expresses the gene backward)
locus
the physical location of a gene on a chromosome
random fertilization
any sperm can fertilize any egg, so that the gentic combinations possible for a single fertilization is huge
sex chromosome
chromosomes that determine the sex (XY –> male XX –> female)
sex linked
genes found only on the X or Y chromosome
somatic mutation
occur in any cell of the body except the germ line cells (sperm & egg) and cannot be passed onto children
SRY gene
- carried by the Y chromosome
- a master gene that causes other genes located on autosomes to produce male sexual characteristics , without it develops as a female
test cross
a cross in which one parent is known to be a recessive homozygote and allows geneticists to evaluate whether an individual with a dominant phenotype is homo or heterzygote
translocation
occurs when a broken piece from one chromosome becomes attached to a different, nonhomologous chromosome (cross over event of different chromosomes)
trisomy
when a person inherits three copies of a chromosome (down syndrome –> chromosome 21)
independent assortment of chromosomes
creates new combinations of alleles through the random distribution of maternal and paternal chromosomes into gametes during meiosis
base pair
G-C
A-T(U)
-two nitrogenous bases held together by hdrogen bonds in a DNA molecule
DNA polymerase
is the enzyme that connects nucleotides to make the new strand, using the old strand as the template
(proofreads and mismatches are detected and removed
-enzyme involved in DNA replication
DNA repair
- recognition
- removal
- replacement
genome
all the DNA based information in its chromosomes
housekeeping gene
play an essential role in the maintenance of cellular activities in all kinds of cells
non coding DNA
DNA that does not code for any kind of functional RNA
ribosome
where proteins are made directed by mRNA molecules
semiconservative replication
one old strand (template strand) is retained, in each new double helix and used as a template for a new complementary strand
anticodon
mRNA binding site
frameshift
insertion or deletion of one or two nucleotides
deletion in relation to DNA
when a base is inserted into or deleted from a DNA sequence
exon
segments of genes that actually code for amino acids
insertion
when a base is inserted into a DNA sequence
messenger RNA
delivers the genetic information, or instructions, from DNA to the ribosomes, where proteins are made
gene promoter
sections of a gene/dna that function as an off/on switch for transcription.
genetic code
the nucleotide triplets of DNA and RNA molecules that carry genetic information in living cells.
intron
stretches of DNA that do not code for amino acid sequences of proteins and must be spliced out
translation
process by which ribosomes covert the genetic information in mRNA into proteins
regulatory DNA
can activate or inactive gene expression
regulatory protein
interact with the environment and with regulatory DNA to promote or repress gene transcription
Ribosomal RNA
assists in making the covalent bonds that liknk amino acids together to make a protein
RNA Polymerase
synthesizes RNA using one strand of the DNA as a template
-binds to a segment of DNA near the beginning of a gene
DNA fingerprinting
is the process of identifying DNA unique to a species or individual
substitution
one base is substituted for another in the DNA sequence of the gene
template strand
one of the two DNA strands is used as a template
transfer RNA
transports the correct amino acid to ribosome, using the information encoded in the mRNA
adult stem cell
undifferentiated cells in the adult body that produce only a limited number of different cell types
RNA interference
selectively blocks the expression of a given gene
directional selection
when individuals at one extreme of an inherited phenotypic trait have an advantage over other individuals in the population (one side)
DNA hybridzation
target DNA is cut into fragments by restriction enzymes and converted to a single stranded form by treatments that break the hydrogen bonds holding the two strands together
DNA miccroarray
consists of a solid support, the size of a microscope slide, on which known DNA sequences from a genome have been arranged in an orderly fashion
gene flow
the movement of genes from one population to another
gene therapy
seeks to correct genetic disorders through genetic engineering and other methods that can alter gene function
genetic drift
a random process that can cause the gene pool of a population to change randomly from one generation to the next over time
natural selection
is a nonrandom, directional process that shifts the genetic characteristics of a population in one direction that leads to adaptation over successive generations
sexual dimorphism
males and females are distinctly different in appearance
sexual selection
when individuals differ in inherited characteristics that affect their ability to get mates
stem cell
undifferentiated cells with the extraordinary attribute of self renewal
zygote
union of an egg and sperm
adaptation
evolutionary process by which a population as a whole becomes better suited to its habitat
artificial selection
the breeding of animals and plants with specific, desirable characteristics
founder effect
occurs when a small group of individuals establishes a new population far from existing population
disruptive selection
changes in population genetics in which extreme values for a trait are favored over intermediate values
stabilizing selection
favor of the intermediate phenotypic traits
