Chapter 9: Mendelian Genetics And Mutation Flashcards
theory of blending inheritance
proposed that traits present on the parents mixed together like paint to produce a new combination in the offspring
horticulture
the artificial selection of plants
hybridizing
the process of crossing two different types of plants
true breeding
strains of plants that contain only one form of a trait
reciprocal cross
an experimental cross in which 2 different forms of a trait are interchanged between male and female plants
monohybrid cross
an experiment that uses parent varieties (or strains) differing in a single trait
self-crossing/self-fertilization
a plant is pollinated with its own pollen as opposed to pollen from another plant
genes
heritable factors; discrete unit of hereditary information
alleles
alternate forms of a gene
homozygous
has two identical alleles for a given trait
heterozygous/hybrid
has two different alleles for a given trait
genotype
an allelic combination
phenotypes
the physical expression of genes
recombination
the occurrence of an offspring whose phenotype differs from that of the parent
test-cross
crossing an organism of an unknown genotype with a homozygous recessive individual to determine the unknown genotype; the ratio of phenotypes in the offspring determines the unknown genotype
inheritance
the way traits are passed on from generation to generation
back cross
a test cross with the homozygous recessive parent (a reverse test cross)
Punnett square
invented by Reginald Punnett in 1905. It is a grid that shows all the possible gametes formed by each of the parents and all of the possible genotypes and phenotypes in the offspring.
dihybrid
a breeding experiment that uses parental varieties differing in two traits
independent assortment
the alleles for the two different traits must assort independently with respect to one another
meiosis
a type of cell division in sexually reproducing organisms which results in gametes with half of the chromosome number of the original cell
recombination
a process in meiosis that results from homologous chromosomes segregating into different gametes, resulting in multiple possible allele combinations
the multiplicative law of probability
the probability of two independent events co-occurring is the product of their individual probabilities
trihybrid
a breeding experiment that uses parental varieties differing in three traits
sickle cell anemia
caused by a defective hemoglobin protein in red blood cells which causes the cells to deform to a sickle shape and triggers blood clotting and other symptoms
the additive rule
the probability of one or another of two mutually exclusive (or separate) events occurring equals the sum of their individual probabilities
intermediate inheritance
the heterozygote genotype has a unique phenotype which is intermediate to the two parental phenotypes; neither allele dominates
codominance
both alleles of a heterozygote are distinctly expressed
antigen
a foreign substance that does not belong to a particular host organism and elicits an immune response
antibody
an immunoglobulin produced by B cells which binds to antigens, and in doing so function in immune response
pedigree
information categorized into a family tree which traces the inheritance of various traits (including disorders) throughout generations
Mendel’s 3:1 ratio
describes that in the F2 generation, dominant and recessive traits will occur 3-to-1
Mendel’s 9:3:3:1 ratio
the result of a dihybrid cross, where out of 16 individuals, 9 represent both dominant traits, 3 represent one dominant trait, 3 represent another dominant trait, and 1 represents the recessive traits.
epistasis
one gene’s expression modifies or suppresses another gene
albino
characterized by a complete lack of pigment
quantitative characters
traits that vary in population along a continuum, because there is more than one existing phenotype
polygenic inheritance
two or more genes have an additive affect on one phenotypic character
locus
the location of a gene
pleiotropy
one gene can affect many traits
lethal recessive
a condition that is lethal in the homozygous condition
dominant allele
in the heterozygote, the allele that is fully expressed
recessive allel
in the heterozygote, the allele that is completely masked
mutation
a recessive allele results in a defective enzyme
structural disorder
one defective, dominant allele results in a phenotypic effect
over-dominance
a population level phenomenon where the heterozygote has a selective advantage over either homozygote (ex: those will sickle-cell anemia are resistant to malaria)
linked genes
genes that stay on the same chromosomes
parental phenotypes
the offspring have an appearance which is identical to one of the parents
recombinant phenotypes
the offspring have an appearance which differs from either of the parents
map unit
a way of calculating the relative distance between genes, calculated by dividing the number of recombinants by the total number of offspring times 100
sex chromosomes
the pair of chromosomes that determine the sex of an organism
sex-linked gene
a gene located on a sex chromosome
chromosome theory
the theory that Mendel’s heritable factors are located on chromosomes
hemizygous
having a total of one allele for a given trait; a condition that is associated with genes located on sex chromosomes
Barr bodies
the inactive X chromosome present in each cell of the female which has been condensed into a compact object
mosaic
in art, the term is used to describe a pattern; in biology, it is used to describe patchiness in a characteristic
autosome
a chromosome that is not directly involved in sex determination; in humans there are 22 of these chromosomes
sex chromosomes
the chromosomes that are responsible for sex determination; in humans there is only one pair of these chromosomes
aneuploidy
a deviation in the chromosome number such that certain chromosomes are present in extra copies or are absent
polyploidy
a deviation in the chromosome number such that the organism has more than two complete sets of chromosomes
nondisjunction
a pair of homologous chromosomes or sister chromatids fail to separate properly during meiosis or mitosis
karyotype
a technique in which an individual’s metaphase I chromosomes are examined in order to determine their number and characteristics
deletion
the loss of a piece of chromosome during cell division, resulting in a fragment which lacks a centromere
syndrome
having a number of phenotypic effects
point mutation
a mutation that affects a single nucleotide of the DNA strand
silent mutation
the base pair substitution has no phenotypic effect
missense
the base pair substitution causes one amino acid to be substituted for another amino acid
nonsense
the base pair substitution causes an amino acid-specifying codon to be changed to a stop codon; the prematurely shortened protein is usually not functional
frameshift
if the number of nucleotides, inserted or deleted, is not a multiple of three, this can occur. The result is an improper grouping of codons leading to a changed protein product.
