chapter 2 terminonlgy Flashcards
(35 cards)
chromatin
the substance of chromosomes; now known to include DNA and chromosomal protiens
histone
a type of basic protein that forms the unit around which DNA is coiled in the nulceosomes 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 recessive allele; thus; if A is dominant over a, then A/A and A/a have the same phenotype
recessive phenotype
the a parental phenotype effect is not expressed in a 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 generatione
heterozygous
a cell/organism having different alleles at a given genes (A/a)
homozygous
a cell/organism having identical alleles at a given gene (A/a, a/a)
monohybrid
an indiviual heterozygous at one gene ( A/a )
monohybrid cross
a cross between two individuals identically heterozygous at one gene pair (A/a x A/a)
product rule
the probability of two independent events occurring simulataneously 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 chromosomes 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 have the same genetic loci
-may have different alleles
meiocyte
a cell in which meiosis takes place
