ucsc genetics midterm

phenotype

observable characteristic

alleles

alternate forms of a gene

independent assortment

alleles of one gene separate into gametes randomly with respect to alleles of other genes

gametes

reproductive cells containing only one copy of each gene

gene

the heritable entity that determines characteristic

segregation

the separation of two alleles of a gene into different gametes

heterozygote

an individual with two different alleles of a gene

dominant

the allele expressed in the phenotype of a heterozygote

F1

offspring of the P generation

test cross

the cross of an individual of ambiguous genotype with a homozygous recessive individual

genotype

the alleles an individual has

recessive

the allele that does not contribute to the phenotype of the heterzygote

dihybrid cross

a cross between two individuals both heterozygous for two genes

homozygote

having two identical alleles of a given gene

epistasis

the alleles of one gene masks the effect of allele in another gene

modifier genes

genes whos alleles alter phenotypes produced by the actions of other genes

conditional lethal

a genotype that is lethal in some situations but viable in others

permissive condition

environmental conditions that allows conditional lethals to live

reduced penatrance

less than 100% of the individuals possessing a particular genotype express the it in their phenotype

multifactorial trait

traits determines by two or more factors

incomplete dominance

the heterozygote resembles neither homozygote

codominant

heterozygous individual that resembles both parents equally for a particular trait

mutation

a heritable change in a gene

pleitropy

a gene that may affect more than one phenotype

variable expressitivity

the degree to which an affected individual displays the phenotype associated with that individuals genotype

meiosis

one diploid cell gives rise to four haploid cells

karyotype

the array of chromosomes in a cell

mitosis

one diploid cell gives rise to two diploid cells

interphase

the part of the cell cycle which the chromosomes are not visible

syncytium

an animal cell containing more than one nucleus

synapsis

pairing of homologous chromosomes

sex chromosomes

X and Y

cytokenisis

division of the cytoplasm

anaphase

the time during mitosis where sister chromosomes separate

chromatid

one of the two identical halves of a replicated chromosome

autosomes

chromosomes that do not differ between the sexes

centromere

connection between sister chromatids

centrosome

microtubule organizing centers at the spindle poles

polar body

cell produced by meiosis that does not produce a gamete

spermatocytes

cells in the testes that undergo meiosis

recombination

process by which offspring derive a combination of alleles different from that of either parent

linkage

the proximity of two or more markers on a chromosome

chiasma

a point at which paired chromosomes remain in contact during the first metaphase of meiosis, and at which crossing over and exchange of genetic material occur between the strands

locus

a designated location on a chromosome

coefficient of coincidence

the ratio between the actual frequency of double crossovers and the expected (actual/expected)

interference

if there is a crossover at one spot on a chromosome, this decreases the likelihood of a crossover in a nearby spot