MT1 Flashcards
chromatin
the substance of chromosomes; now known to include DNA and chromosomal proteins
histone
a type of basic protein that forms the unit around which DNA is coiled in the nucleosomes of
eukaryotic chromosomes
nucleosome
the basic unit of eukaryotic chromosome structure; a ball of eight histone molecules that
is wrapped by two coils of DNA
dominant phenotype
the parental phenotype that is expressed in a heterozygote
dominant allele
an allele that expresses its phenotypic effect even when heterozygous with a
recessive allele; thus, if A is dominant over a, then A/A and A/a have the same phenotype
recessive phenotype
– the parental phenotype that is not expressed in the heterozygote
recessive allele
an allele whose phenotypic effect is not expressed in a heterozygote
first filial generation (F1)
the first generation resulting from a controlled cross between two known
parents (P)
second filial generation (F2)
the second generation resulting from a controlled cross between two
known parents (P), generated by selfing/intercrossing the F1 generation
heterozygous
a cell/organism having different alleles at a given gene(s) (e.g. A/a)
homozygous
(= true-breeding) – a cell/organism having identical alleles at a given gene(s) (e.g. A/A or
a/a)
monohybrid
an individual heterozygous at one gene (e.g. A/a)
monohybrid cross
a cross between two individuals identically heterozygous at one gene pair, e.g. A/
a x A/a
product rule
the probability of two independent events occurring simultaneously is the product of
their individual probabilities
sum rule
the probability that one or the other of two mutually exclusive events will occur is the sum
of their individual probabilities
test cross
– a cross of an individual organism of unknown genotype or a heterozygote with a tester
tester
an individual organism homozygous for one or more recessive alleles; used in a test cross
gamete
a specialized haploid cell that fuses with a gamete of the opposite sex or mating type to form
a diploid zygote; in mammals, an egg or a sperm
diploid
a cell having two chromosome sets or an individual organism having two chromosome sets in
each of its cells
haploid
a cell having one chromosome set or an organism composed of such cells
chromatid
one of the two side by side replicas produced by chromosome replication
sister chromatids
the juxtaposed pair of chromatids arising from the replication of a chromosome
homologous chromosomes
chromosomes that pair with each other during meiosis and (usually) have
the same genetic loci (may have different alleles)
meiocyte
a cell in which meiosis takes place
dyad
a pair of sister chromatids joined at the centromere
tetrad
(1) four homologous chromatids in a bundle in the first meiotic prophase and metaphase
chiasma
– a cross-shaped structure commonly observed between nonsister chromatids in meiosis; the
site of crossing over
molecular marker
a site of DNA heterozgosity (difference), not necessarily associated with
phenotypic variation, used as a tag for a particular chromosomal locus
sex chromosome
a chromosome whose presence is correlated with the sex of an individual
autosome – any chromosome that is not a sex chromosome
homogametic sex
the sex with (homologous) homomorphic sex chromosomes (e.g., XX)
heterogametic sex
the sex that has heteromorphic sex chromosomes (e.g., XY)
hemizygous gene
a gene that is present in only one copy in a diploid organism
reciprocal cross
a pair of crosses of the type genotype A (female) x genotype B (male) and B
(female) x A (male)
sex linkage
the location of a gene on a sex chromosome
genetics
experimental study of genes/hereditary
gene
fundamental unit of hereditary
genome
complement of all genes in an organism; the genetic material of a chromosome set
mutation
a change in DNA sequence (as compared to wild type)
allele
an alternate form of a gene (resulting from a mutation)
genotype
the specific allele composition of a genep
phenotype
outward manifestation of a specific genotype
independent assortment
(Mendel’s 2nd Law) – unlinked or distantly linked segregating gene pairs
assort independently at meiosis
dihybrid
an individual heterozygous at two genes (e.g. A/a.B/b)
dihybrid cross
a cross between two individuals identically heterozygous at two gene pairs, e.g.
A/a.B/b x A/a.B/b
chi-squared test
a statistical test used to determine the probability of obtaining observed proportions
by chance, under a specific hypothesis
null hypothesis
a hypothesis that proposes no difference between two or more data sets
recombination
the process that generates a haploid product of meiosis whose genotype is different
from either of the two haploid genotypes that constituted the meiotic diploid
recombinant gamete
any gamete with a genotype that differs from the genotypes of the two haploid
parents that fused to form the diploid meiocyte
parental gamete
any gamete with a genotype identical to one of the haploid parents that fused to
form the diploid meiocyte
maternal inheritance
a type of uniparental inheritance in which all the progeny have the genotype
and phenotype of the parent acting as the female
