Science Assessment ~ Ideas ~ There are similarities and differences between organisms living today, and between organisms living today and those that lived in the past, both within the same species and between species.

Key Idea: Genetic variation results from mutations and allele shuffling during reproduction, which leads to variation in proteins and, finally, to variation in traits.

Sub-Ideas
Items & Student Performance
Misconceptions
NGSS

Students are expected to know that:

During reproduction, genetic information (DNA) passes from parent to offspring.
Heritable traits pass by way of genes (made of DNA) from parent to offspring.
Variation in DNA sequences leads to variation in proteins, which leads to variation in traits.
Heritability can be determined by comparing traits in parents and offspring. If a trait is heritable, offspring tend to resemble parents.
During sexual reproduction, individuals inherit two copies of each gene, one from each parent. Each copy is called an allele.
Alleles of the same gene have some nucleotide sequences in common and some that are different.
Alleles are shuffled during sexual reproduction (recombination, independent assortment, and fertilization), which produces new allele combinations.
Allele shuffling during reproduction contributes to genetic variation in a population.
Mutation is a natural process that generates variation in DNA sequences, i.e., new alleles.
DNA variations that arise through mutation can be beneficial, harmful, or neutral (to the organism). DNA variations that decrease viability or reproduction are not propagated, so they are eliminated from the population. Most DNA variations have no effect on viability or reproduction, and through random chance many are maintained in the population.
Only when it happens in sex cells can mutation generate new alleles that can be passed to offspring. Mutations that occur in body cells cannot be passed on to offspring.
Mutations can occur in sex cells at any time.

Percent of students answering correctly (click on the item ID number to view the item and additional data)
Item ID Number	Knowledge Being Assessed	Grades 6–8	Grades 9–12	Select This Item for My Item Bank
RH007002	If a mutation occurs to a DNA molecule in an organism's skin cell before the organism reproduces, none of the organism's offspring will have the mutation.	12%	16%

Frequency of selecting a misconception
Misconception ID Number	Student Misconception	Grades 6–8	Grades 9–12
RHM015	The timing of the occurrence of an environmentally induced characteristic will affect whether the characteristic is transmitted to offspring (Kargbo et al., 1980).	29%	24%
ENM037	Changes in a population occur through a gradual change in all members of a population, not from the survival of a few individuals that preferentially reproduce (Brumby, 1979; Bishop & Anderson, 1990; Anderson et al., 2002; Stern & Roseman, 2004).	N/A	N/A
ENM031	Individual organisms can deliberately develop new heritable traits because they need them for survival (Bishop & Anderson 1990; Passmore et al., 2002; Stern & Roseman, 2004).	N/A	N/A

Frequency of selecting a misconception was calculated by dividing the total number of times a misconception was chosen by the number of times it could have been chosen, averaged over the number of students answering the questions within this particular idea.

NGSS Statements
Code	Statement
LS3.A MS	Genes are located in the chromosomes of cells, with each chromosome pair containing two variants of each of many distinct genes. Each distinct gene chiefly controls the production of specific proteins, which in turn affects the traits of the individual. Changes (mutations) to genes can result in changes to proteins, which can affect the structures and functions of the organism and thereby change traits.