Genetics Flashcards
define genetics
genetic is the study of heredity/ transmission of body features (both similarities and differences) from parents to offspring and the laws relating to such transmission
define heredity
transmission of genetically based characteristics from parents to offspring
define variations
small differences among the individuals of the same species
define characters
any inheritable feature of an organism
define traits
alternative forms of characters
what is karyotype
a chart where photographs of chromosomes are used for artificially arranging the chromosomes according to their size and shape on a chart.
define homologous chromosomes
a pair of corresponding chromosomes of the same shape, size, one obtained from each parent
what do autosomes determine (autosomes)
general body features like complexion, height, seed colour
what do sex chromosomes (allosomes) determine
sex of organism
define genes
specific parts/ DNA segments of a chromosome, which determine the hereditary characteristics
define genomes
full complement of DNA (including all genes and intergenic regions) of an organism
define alleles
alternative forms of a gene, occupying the same position on homologous chromosome and affecting the same characteristic but in different ways.
define dominant allele
the kind of allele which expresses itself regardless of the presence of other alleles for a given gene
define recessive allele
the kind of allele whose expression is suppressed by the presence of another dominant allele for a given gene. a recessive allele can express itself only in the presence of another recessive allele
define genotype
the set of genes present in the cells of an organism
define phenotype
the observable characteristics which are genetically controlled
define sex-linked inheritance
appearance of a trait which is due to the presence of an allele exclusively either on the X or Y chromosome.
example of X linked inheritance
haemophilia and colour-blindness
define monohybrid ratio
the ratio obtained by crossing for two different traits of a single character (phenotypic and genotypic ratio)
5 generalised principle based on breeding experiments are
- each pair of contrasting character depends on genes
- each individual carries such genes in duplicate
- an individual produces gametes which have only one member of a pair of genes
- fertilization of gametes restores duplicate condition of the genes
- sex cells with respect to the genes they contain, get fertilised at random
define dihybrid ratio
gives us the breeding results with two pairs of contrasting characters
Mendel’s laws of inheritance
- law of dominance
- law of segregation
- law of independent assortment
law of dominance
out of a pair of contrasting characters present together, only one is able to express itself while the other remains suppressed
law of segregation/ purity of gametes
two members of a pair of factors separate at the time of formation of gametes
law of independent assortment
when there are two pairs of characters, the distribution of alleles of one character into a gamete is independent of the distribution of the alleles of the other character
seen in F1 hybrid in dihybrid cross
application of Mendel’s laws
- knowledge of the basic Mendelian principles gives us an idea of new progeny and enables us to predict their frequency
- useful info for plant and animal breeders who want to produce better breeds
- new types of plants with new combination of useful characters can be produced by hybridisation
define mutation
mutation is the sudden change in one or more genes, or in the number or in the structure of chromosomes
examples of mutation
- sickle cell anaemia(forms sickle-shaped RBCs)
- radioactive radiations
