inheritance Flashcards
what is the mezel’s model of heredity?
-heredity factors are responsible for transmission of characteristics from one generation to the next. these factors are called genes.
-each characteristic is controlled by a pair of alleles (different forms of the same gene) in an organism. for eg. flower colour in pea plants is controlled by an allele for purple flowers and an allele for white flowers. in other words, the gene for the flower colour has two alleles: purple and white
-each organism inherits one allele from the mother and one allele from the father during sexual reproduction. each body cell of an organism contains two alleles for each trait.
-if an organism has two different alleles, then the dominant allele will show its effect while the recessive allele will have no effect on the organism’s appearance.
-the two alleles will segregate during gamete formation. each gamete will only contain one allele out of the two that are present in the body cells of an organism.
what is a chromosome?
a chromosome is an organised structure of deoxyribonucleic acid(DNA) and protein that is found in the nuclei of cells. DNA contains genetic information used in the development and functioning of all organisms
what is a gene?
a gene is a dna segment located in the chromosome, which codes for a single unit of inheritance. the place on the chromosome where the gene is located is called the gene locus.
what is an allele?
alleles are different versions of the same gene. they are located on the same gene locus in homologous chromsomes.
what is a phenotype?
an observable characteristic of an organism. it can be physical (appearance), behavioural or physiological. it depends on the genotype of the organism.
what is a genotype?
the genetic make-up of an organism. the genotype of an organism cannot be easily predicted from the phenotype (appearance) because of the existence of dominant and recessive alleles.
what is homozygous?
each organism inherits two alleles for a given characteristic, one from the mother, one from the father. an organism is said to be homozygous for a given trait when it contains two identical alleles for that trait.
what is heterozygous?
an organism is said to be heterozygous for a given trait when it contains two different alleles for the characteristic.
what is a dominant allele?
a dominant allele is the allele that is fully expressed in the phenotype under both homozygous and heterozygous conditions.
what is a recessive allele?
a recessive allele is the allele that is only expressed in the phenotype under the homozygous condition. it is masked in the phenotype under the heterozygous conditions.
