genetics Flashcards
define phenotype
The characteristics of an individual ie. eye colour
define genotype
the types of genes and allies an individual contains.
define homozygous
a genotype consisting of 2 identical alleles eg BB, bb
denine heterozygous
a genotype consisting of 2 different alleles eg Bb
define dominant
the allele that shows up in the phenotype eg. B for brown eyes
define recessive
The allele that is hidden by a dominant allele eg. b for blue eyes.
define codominance
2 allele that shows up together in the phenotype eg, pink flowers from red flowers crossed with white flowers.
define allele
an alternative version of a gene
what are the 2 types of cell division
mitosis and meiosis
define mitosis
It is the division of a diploid cell into 2 diploid cells. The cells produced have identical sets of chromosomes.
When does mitosis occur
It occurs during the growth of a zygote into an embryo and then into an adult. It also occurs during growth and repaire tissues, cloning of cell and in asexual reproduction.
define meiosis
it is the division of a diploid cell into 4 haploid cells. The chromosome number is halved. The cells are the gametes and each of the 4 cells made are genetically different from each other. Meiosis forms the gametes used in sexual reproduction.
How the sex of an individual determined
The sex chromosomes are X and Y. Females are XX and Males are XY. When gametes are formed by meiosis, the sex chromosomes are separated so an egg contains one X and each sperm contains either an X or Y chromosome. Therefore, if an X-contaning sperm fertilises and egg, a girl is made and if a Y-containing sperm fertilises an egg a boy is made.
