genetics level 1 Flashcards
different forms of the same gene. they can be dominant or recessive
allele
reproduction involving only one parent (usually a female). the offspring are genetically identical to the parent and to each other
asexual reproduction
parts of dna that are involved in pairing. the bases on dna are cytosine. guanine, adenine and thymine.
base
a threadlike structure of nucleic acids and protein found in the nucleus of most living cells. they carry genetic information in the form of genes.
chromosome
a self-replicating molecule present in nearly all living organisms. it’s the main constituent of chromosomes
deoxyribonucleic acid
an allele which is always expressed, even if only one is present. usually given an upper case letter
dominant
male or female reproductive cells (sperm and ova) that contain half the number of chromosomes compared to the parent cell
gamete
a short length of DNA that carries the genetic code for a particular characteristic or cell activity
gene
the pairs of alleles an organism has for particular traits
genotype
an individual with two alleles that are different for a particular trait
heterozygous
having the same structural features and pattern of genes
homologous
an individual with two alleles that are the same for a particular trait
homozygous
a type of cell division that results in four daughter cells, each with half the number of chromosomes of the parent cell (e.g. the production of gametes and plant spores)
meiosis
a type of cell division that results in two daughter cells each having the same number and kind of chromosomes as the parent nucleus (e.g. tissue growth and repair
mitosis
a change in the base sequence of dna
mutation
nucleotides form the basic structural unit of dna. composed of a sugar, a phosphate and a base
nucleotide
a diagram that shows the phenotypes of related individuals
pedigree chart
the observable characteristics of an individual resulting from its genotype
phenotype
a group of identical individuals that always produce offspring of the same phenotype when interbred
pure bleeding
an allele which is only expressed when two of them are present. usually given a lower case letter
recessive
reproduction involving only two parents. the offspring are different to the parent and to each other.
sexual reproduction
the organism in question is crossed with an organism that is homozygous for the recessive trait, and the offspring of the test cross are examined
test cross
a genetically determined characteristic
trait
the differences between organisms within a population. can be continuous or discontinuous
variation
a fertilised ova (egg) that contains the full set of chromosomes
zygote
