a change in the nucleotide sequence of DNA creating alternative alleles of a gene
passing of genes to offspring in humans
the copies of each gene are separated from each other
not every child rec eives the same combination of alleles
it is the unique combination of maternal and paternal alleles that come together during fertilization that determines a person's genotype and contributes to his or her phenotype
describe the steps of sexual reproduction
each parent is a diploid (2 copies of each chromosome) organism which produce specialized sex cells called gametes
gametes are haploid (only one copy of each chromosome)
sperm fertilizes the egg resulting in a diploid zygote
zygote divides by mitotic cell division eventually generating enough cells to form a diploid baby
gametes
specialized reproductive cells that carry one copy of each chromosome
result of cell division called meiosis
sperm are male gametes
eggs are female gametes
the 2 divisions of meiosis
meiosis I
meiosis II
meiosis I
homologous chromosomes pair and line up next to one another in the middle of the cell
the chromosomes of each homologous pair separate from one another and are divided into separate cells
each daughter cell is haploid
each chromosome is still in its replicated state
meiosis II
sister chromatids separate, creating four haploid daughter cells
each daughter cell will develop into egg or sperm
why don't children look and behave exactly like one parent
they inherit alleles from both parents and are genetically a combination of the 2
why are no 2 gametes produced by the same parent identical
recombination
independent assortment
recombination
when maternal and paternal chromosomes pair and physically exchange DNA segments
as a result, maternal chromosomes actually contain segments (therefor alleles) from paternal chromosomes and vice versa
independent assortment
alleles of different genes are distributed independently of one another
unique combination of maternal and paternal chromosomes is distributed into each sperm and each egg because possible combinations of alleles is very numerous (>8 million)
maternal and paternal chromosomes separate according to how they have randomly lined up in the cell
heterozygous
having 2 different alleles
homozygous
having 2 identical alleles
homologous chromosomes
the 2 copies of each chromosome in a diploid cell
one chromosome from the mother and one from the father
phenotype
the visible or measurable features of an individual
genotype
the particular genetic makeup of an individual
zygote
cell that is capable of developing into and adult organism
embryo
early stage of development reached when a zygote undergoes cell division ro form a multicellular structure
carrier
individual who is heterozygous for a particular gene of interest, and therefore can pass on the recessive allele without showing any of its effects