genetic crosses Flashcards
Genetics
the study pf heredity and variation in plants and animals
Gametes
haploid cells that are capable of fusion
Fertilisation
The union of 2 gametes to form a single cell called a zygote
Alleles
Different forms of the same gene
(We have 2 versions of most genes 1 from each parent. One acts as a backup incase there is a mistake. If both genes have a problem the person will have a genetic disorder.)
Locus
the position of a gene on a chromosome
Dominant
the allele prevents the recessive allele from working.
Recessive- the recessive allele is prevented from working y a dominant allele
Genotype
The genetic makeup of an organism or the genes that are present eg Bb
Phenotype
The physical makeup of an organism eg blue eyes.
Genotype + environment= phenotype
Chromosomes
- Thread like structures
- found in the nucleus of every cell
- Composed of a dna strand wrapped around a protein
- Divided along its length into genes
- Controls the activity of a cell
Homologous chromosomes
Chromosomes which are the same size and shape containing the same genes.
two of each type of chromosomes in the nucleus. 46 chromosomes and each chromosome has a corresponding pair so 23 pairs.
Heterozygous
The alleles are different Bb
Homozygous
The alleles are the same BB or bb
Incomplete dominance
Neither allele is recessive or dominant with respect to the other. Both alleles work in the heterozygous genotype to produce and intermediate phenotype
EG red flower x white flower =pink flower
1st law- Law of segregation
Inherited characteristics are controlled by pairs of factors. The factors separate from eachother at gamete formation with only one member of the pair being found in each gamete.
We call factors alleles. Deal with monohybrid crosses.
2nd law- Law of independent assortement
Each member of one pair of alleles can combine randomly with either member of another pair at gamete formation. Deals with dihybrid crosses.
AaBb - AB Ab aB ab
