Cell Division. Mitosis & Meiosis . Mitosis. The form of cell division by which a eukaryotic somatic cell (body cell) duplicates. Mitosis is asexual reproduction. Cell division is the continuation of life based on the reproduction of cells . Liver Cell. Liver Cell. 46
DNA double helix
23 pairs (46) of chromosomes in human
Genes & Heredity
Why Do I Look Like My Parents???
Why Don’t You Look Like a rhinoceros?
Heredity is the passing of traits from parents to offspring.
Traits and characteristics pass from parents to offspring through genes.
Alleles: the different forms of a gene.
Dominant allele: an allele whose trait always shows up when it is present.
Recessive allele: an allele that is masked when a dominant allele is present.
If both the alleles inherited by the zygote(fertilized egg) for a particular characteristic are the same they are called homozygous.
If they are different from each other they are called heterozygous.
Each set of chromosome is a homologous pair
Homologouschromosomes – chromosomes which contain the same genes, one from each parent
Homologous chromosomes look alike with similar information stored on them
One member of each homologous pair is inherited from each parent through egg or sperm.
A set of alleles inherited by an individual is called a genotype.
The way the genes express themselves in the individual's appearance is their phenotype.
Some traits show more often than other traits.
The traits that show often are called dominant traits.
Those traits that don’t show often are recessive traits.
Both mother and father are heterozygous for tongue rolling.
Genotype: heterozygous alleles (one dominant & one recessive)
Ability to roll tongue
Albino snake, a recessive trait of not having colors
Attached earlobe vs. free
(or detached) earlobe
Attached is a recessive trait
Some Dominant Traits
Punnett Squares are diagrams used to help us to figure out how inherited traits (characteristics) will be distributed
Dominant trait is written by capital letter (A)
Recessive trait is written by lower case letter (a)
Both parents birds are homozygous, with the red bird having 2 dominant alleles, and the blue bird having 2 recessive alleles.
There is only one possible genotype for all the offspring, and that is heterozygous.
What is the phenotype of the offspring? ______
In rabbits, black fur is dominant to white fur. A male rabbit with BB genotype and a female with a Bb genotype are crossed.
What is their phenotype?
What are the possible genotypes and phenotypes of the offspring? (Show using a Punnett square)
What is the percent chance for each type?
Inside the nucleus of a cell long strings of DNA are coiled up and spooled onto chromosomes, and on each chromosome there are several thousand genes - shorter sections of DNA which act as a code for a particular characteristic. Since we inherit particular chromosomes through the egg and sperm, we also inherit the particular characteristics coded for by the genes on those chromosomes.