2. A typical cell of any organism contains genetic instructions that specify its traits. Those traits may be modified by environmental influences. As a basis for understanding this concept:
b. Students know sexual reproduction produces offspring that inherit half their genes from each parent.
c. Students know an inherited trait can be determined by one or more genes.
d. Students know plant and animal cells contain many thousands of different genes and typically have two copies of every gene. The two copies (or alleles) of the gene may or may not be identical, and one may be dominant in determining the phenotype while the other is recessive.
e. Students know DNA (deoxyribonucleic acid) is the genetic material of living organisms and is located in the chromosomes of each cell.
2. Mutation and sexual reproduction lead to genetic variation in a population. As a basis for understanding this concept:
a. Students know meiosis is an early step in sexual reproduction in which the pairs of chromosomes separate and segregate randomly during cell division to produce gametes containing one chromosome of each type.
b. Students know only certain cells in a multicellular organism undergo meiosis.
c. Students know how random chromosome segregation explains the probability that a particular allele will be in a gamete.
d. Students know new combinations of alleles may be generated in a zygote through the fusion of male and female gametes (fertilization).
e. Students know why approximately half of an individual's DNA sequence comes from each parent.
f. Students know the role of chromosomes in determining an individual's sex.
g. Students know how to predict possible combinations of alleles in a zygote from the genetic makeup of the parents.
3. A multicellular organism develops from a single zygote, and its phenotype depends on its genotype, which is established at fertilization. As a basis for understanding this concept:
a. Students know how to predict the probable outcome of phenotypes in a genetic cross from the genotypes of the parents and mode of inheritance (autosomal or X-linked, dominant or recessive).
b. Students know the genetic basis for Mendel's laws of segregation and independent assortment.
c. * Students know how to predict the probable mode of inheritance from a pedigree diagram showing phenotypes.