HS-LS3-1: Asking Questions About DNA, Chromosomes and Inherited Traits
In plain English: HS-LS3-1 is the NGSS high school performance expectation that asks students to ask questions that clarify how DNA and chromosomes carry the instructions for traits passed from parents to offspring. Students connect genes, alleles, chromosome pairs and proteins, and turn inheritance data into testable questions. It is usually taught in Biology.
Ask questions to clarify relationships about the role of DNA and chromosomes in coding the instructions for characteristic traits passed from parents to offspring.
Assessment Boundary: Assessment does not include the phases of meiosis or the biochemical mechanism of specific steps in the process.
Next Generation Science Standards · Disciplinary Core Idea: Heredity: Inheritance and Variation of Traits · Official standard
Students ask and refine questions about how the instructions for traits are stored and passed on. They connect four ideas: a gene is a stretch of DNA whose base order codes for a protein, different alleles of a gene differ in that base order, genes sit at fixed places on chromosomes, and chromosomes come in pairs with one member from each parent. Students practice the science practice of asking questions: they sort questions into testable and not testable, rewrite vague questions so they name a relationship, and decide what data (chromosome counts, gene maps, crosses, karyotypes) would answer each one.
HS-LS3-1 has no Clarification Statement. The official Assessment Boundary reads: "Assessment does not include the phases of meiosis or the biochemical mechanism of specific steps in the process." So the lesson says only that each sperm or egg receives one chromosome from every pair; it does not name or sequence the phases of meiosis, and it does not describe the enzymes or chemical steps that copy DNA or build proteins (beyond this standard). Chromosome sizes and gene counts are approximate values rounded from public human genome databases; fly and mouse data sets are invented for teaching and labeled as invented.
Learning Objectives
By the end of this lesson, students will be able to:
Explain that a gene is a stretch of DNA whose base sequence codes for a protein, and that alleles of a gene differ in their base sequence
Describe chromosomes as long DNA molecules that carry many genes, arranged in pairs with one member from each parent
Use chromosome counts to predict the number of chromosomes in body cells and in sperm or eggs
Ask questions that clarify a relationship among DNA, chromosomes and a trait, and sort questions into testable and not testable
Name the data or investigation that could answer a question about how a trait is passed from parents to offspring
Prior Knowledge Required
Students should already be comfortable with:
Sexual reproduction gives offspring genetic information from two parents MS-LS3-2
Changes to genes on chromosomes can change proteins and traits MS-LS3-1
Cells, the nucleus, and proteins as molecules that do the work of cells
Probability of a single chance event as a fraction 7.SP.C.7
Show a photo of a family (a stock image or a well-known family portrait) and read the scenario aloud.
Warm-Up Prompt
"Maya has her father's curly hair and her mother's freckles, yet neither parent has her red hair. Write three questions you would need answered to explain how Maya's cells got the instructions for these traits. Put a star next to the question you think someone could actually test."
Collect a few questions on sticky notes and post them on the board in two columns without labels: questions that could be answered with data and questions that could not. Students guess the rule for the columns. Keep the notes up: students will rewrite them in the Closure.
Direct Instruction15-20 minutes
From DNA to chromosomes to traits. DNA is a long molecule made of four kinds of bases (A, T, G, C) in two paired strands. A gene is a stretch of DNA whose base order codes for a protein, and proteins such as pigments, enzymes and channels shape traits. Different versions of a gene are alleles: they differ in base order and can code for proteins that work differently. A chromosome is one very long DNA molecule packed with proteins; it carries hundreds to thousands of genes in a fixed order. Human body cells have 46 chromosomes in 23 pairs. The two members of a pair (homologous chromosomes) carry the same genes in the same order, one member from the mother and one from the father, and they may carry different alleles. Sperm and eggs carry one chromosome from each pair. Use Diagram 1 to show a pair.
Asking questions that clarify relationships. A strong question names two things and asks how they are related ("How does the allele on chromosome 15 relate to eye color?"), and it points to evidence that could answer it. A question that asks for a value judgment or has no possible data ("Is it fair that I got my dad's nose?") is not a science question.
Chromosome counts across generations
Dog body cells have 78 chromosomes. Question: how many chromosomes are in a dog sperm, and how many does a puppy have?
Result: 78 ÷ 2 = 39 pairs, so each sperm or egg has 39. The puppy has 39 + 39 = 78. If each parent passed on all 78, the count would double every generation (156, then 312), which is never observed: evidence that offspring get one chromosome from each pair.
Chromosome size and gene number
Human chromosome 13 is about 114 million base pairs long with about 320 protein-coding genes. Chromosome 19 is about 59 million base pairs with about 1,470 genes.
Result: Chromosome 13: 320 ÷ 114 ≈ 2.8 genes per million base pairs. Chromosome 19: 1,470 ÷ 59 ≈ 24.9. The smaller chromosome carries more genes, which raises the question "What does the rest of the DNA on chromosome 13 do?"
A trait that follows a chromosome
Red-green color blindness is caused by alleles of genes on the X chromosome. A mother carries one such allele (XBXb) and the father has typical color vision (XBY).
Result: Each son gets his X from his mother: P(color-blind son) = 1/2. Each daughter gets her father's XB: P(color-blind daughter) = 0, P(carrier daughter) = 1/2. The pattern only makes sense if the gene is on the X chromosome.
DNA to protein to trait
Albinism in many mammals results from two copies of an allele that cannot code for a working enzyme needed to make the pigment melanin. Two carriers (Aa × Aa) have offspring.
Result: P(aa) = 1/2 × 1/2 = 1/4. The chain is: base order in the gene, then the enzyme (protein), then the pigment, then the trait. A clarifying question: "Does the a allele differ from A in its base sequence, and does the protein it codes for still work?"
Refining a question
A student asks: "Why do kids look like their parents?"
Result: Refined: "How does the allele a child inherits from each parent at a gene on chromosome 15 relate to the child's eye color?" It names a gene location, an inherited allele and a trait, and it can be answered with family data and DNA tests.
After each example, ask: "Which words in the question name DNA, a gene, a chromosome or a trait, and what data would answer it?" Point out that a question can be about DNA (the instructions), about chromosomes (how the instructions are packaged and passed on), or about the link between the two.
Guided Practice15 minutes
Pairs study the table (approximate values rounded from public human genome databases), compute genes per million base pairs for each chromosome, and compare with Diagram 2. Then they write questions the data raise.
Four human chromosomes (approximate)
Chromosome
Length (million base pairs)
Protein-coding genes (about)
Genes per million base pairs
1
248
2,050
8.3
13
114
320
2.8
19
59
1,470
24.9
21
47
230
4.9
Rank the chromosomes by length, then by number of genes. Are the two rankings the same?
Write one question the table raises about DNA (for example, about the DNA between genes) and one about chromosomes (for example, about why gene density differs).
For each question, name the data you would need. Could a karyotype answer it, or would you need the base sequence?
Trade questions with another pair and mark each one testable or not testable, with a reason.
Independent Practice10-15 minutes
Each student analyzes an invented data set from a fruit fly cross like the ones that first linked a gene to a chromosome. A white-eyed male was crossed with a red-eyed female. All 120 offspring (61 females, 59 males) had red eyes. These offspring were then crossed with each other.
Invented second-generation fly counts
Offspring
Red eyes
White eyes
Females
205
0
Males
109
98
Students compute the fraction of white-eyed flies (98 of 412, about 0.24, close to 1/4), note that every white-eyed fly is male, and write two questions that connect the pattern to chromosomes. Then they explain which question the data already help answer and which would need a new cross.
Closure5 minutes
Exit ticket: "Pick one warm-up question from the board. Rewrite it so it names a gene, an allele or a chromosome and a trait, and say what data would answer it." Collect the rewrites and compare two of them with the originals.
Differentiation Strategies
For Struggling Students
Give a word bank with DNA, gene, allele, chromosome, protein and trait, and a sentence frame: "How does the ___ on ___ relate to ___?"
Use a paper model of one chromosome pair with three colored gene bands before moving to chromosome counts
Start the question sort with 6 cards instead of 12 and add the rest once students can explain the testable rule
For Advanced Students
Ask students to find why chromosome 19 is so gene dense by writing three questions and ranking them by how easily data could answer them
Have students predict the eye colors in a reciprocal fruit fly cross (white-eyed female × red-eyed male) and write the question the prediction tests
Ask students to design a table of data that would test whether two genes sit on the same chromosome (beyond this standard: linkage mapping)
Assessment Guidance
What to Look For
Check that students use gene, allele and chromosome correctly: a chromosome carries many genes, and alleles are versions of one gene. Look for questions that name a relationship and a source of evidence rather than yes-or-no questions with no data. Listen for students who think each parent passes on all of its chromosomes, and for students who describe a chromosome as a single gene.
02
Classroom Activities
3 Activities
1
Question Card Sort
20 minGroups of 3-4
Each group receives 12 question cards. They sort the cards twice: first into testable and not testable, then by what each question is about (DNA, chromosomes, or the link to a trait). Finally they rewrite two weak questions.
The 12 Cards
Why do I look like my grandmother?
How does the base sequence of the allele for a flower-color gene differ between purple and white pea plants?
Is it better to have a dominant allele?
How many chromosomes does a chicken egg cell carry?
Do genes on the X chromosome show different patterns in sons and daughters?
Should people be allowed to choose their children's traits?
Does a larger chromosome always carry more genes?
What would happen to the chromosome number if sperm and eggs had full sets?
How does the protein made from each allele of a pigment gene affect coat color in mice?
Why is DNA so beautiful?
Do both chromosomes of a pair carry the same genes in the same order?
How does DNA feel about being copied?
Sorting Key
Not testable: cards 3, 6, 10 and 12 (value judgments or questions with no possible data). Card 1 is testable only after it is refined. Testable about DNA: 2 and 9. Testable about chromosomes: 4, 7, 8 and 11. Card 5 links a chromosome to a trait pattern.
Discussion Questions
Which card could you turn from not testable into testable by changing a few words?
Card 7 asks about size and gene number. What data from the Guided Practice table answer it?
Which cards connect DNA and chromosomes in one question?
Modification for Distance Learning
Put the cards on a shared slide with two columns. Groups drag cards in breakout rooms, then post their two rewritten questions to the class board.
2
Paper Chromosome Pairs
20 minPairs
Pairs build three chromosome pairs for an imaginary animal from paper strips: one color for chromosomes from the mother, another for the father. Each strip has gene bands with allele letters. Students flip a coin to choose which member of each pair goes into a sperm or egg, combine the two sets into an offspring, and then list questions the model cannot answer.
Procedure
Cut 12 strips: 6 blue (from the mother) and 6 tan (from the father), two long, two medium and two short in each color. Tape them into three pairs for each parent, so each parent has 3 pairs (6 chromosomes).
Mark the same gene bands at the same places on both members of a pair: gene F (fur color) on the long pair, gene T (tail length) on the medium pair, gene E (ear shape) on the short pair. Write allele letters: mother Ff, Tt, EE; father ff, Tt, Ee.
For each parent, flip a coin once per pair to pick one strip. Heads keeps the left strip, tails the right strip. The chosen three strips are that parent's sperm or egg.
Put the two sets of three together to make the offspring (6 chromosomes, 3 pairs) and record its alleles.
Discussion Questions
How many chromosomes does each sperm or egg in the model carry, and how many does the offspring carry? Why must the numbers be 3 and 6?
With 3 pairs, how many different sets of strips can one parent pass on? (2 × 2 × 2 = 8.)
Write one question about real chromosomes that this paper model cannot answer, and say what data would.
Challenge Variation
Pairs add a second gene band to the long pair and ask whether two genes on the same chromosome can be passed on separately. They write the question and the cross that would test it (beyond this standard: crossing over is treated in HS-LS3-2).
3
Data Detective Stations
25 minGroups of 3-4
Three stations each hold a short data set. Groups write two clarifying questions per station, mark which one the data can already answer, and name the extra data needed for the other. Groups rotate every 8 minutes.
Station Data
Station 1, chromosome counts (real values): horse 64 and donkey 62 in body cells. A mule, the offspring of a horse and a donkey, has 63.
Station 2, a mouse pigment gene (invented data): the gene sits on mouse chromosome 7. Mice with two copies of allele c have white fur, and an enzyme test finds no working pigment enzyme in their skin cells. Mice with at least one C allele have colored fur and a working enzyme.
Station 3, sex chromosomes (approximate values): the X chromosome is about 156 million base pairs with about 840 protein-coding genes; the Y chromosome is about 57 million base pairs with about 63 genes.
Discussion Questions
At Station 1, 32 chromosomes come from the horse parent and 31 from the donkey parent. What question does the odd total of 63 raise about the mule's own sperm or eggs?
At Station 2, which step of the chain from DNA to trait do the enzyme data show?
At Station 3, the X carries more than 10 times as many genes as the Y. What question does this raise about traits in males, who have one X?
Modification for Distance Learning
Post each station as a slide. Groups work in breakout rooms and submit their questions on a shared form, one row per station.
03
Diagrams & Visual Aids
2 diagrams
Diagram 1: A Chromosome Pair, Its Genes and a Zoom Into DNA
One homologous pair: the chromosome from the mother (left) and from the father (right) carry the same genes (A, B, C) at the same places, but can carry different alleles, here A and a. The zoom shows that an allele is a stretch of paired DNA bases whose order codes for a protein, which in turn shapes a trait.
Diagram 2: Gene Density on Four Human Chromosomes
Protein-coding genes per million base pairs, computed from the approximate Guided Practice values and drawn to scale. Chromosome 19 is the second shortest of the four but has the highest gene density, so chromosome length alone does not tell how many genes a chromosome carries.
04
Homework Assignment
~30 min
HS-LS3-1 Homework: Questions About DNA, Chromosomes and Traits
Directions: Chromosome counts are real values; chromosome sizes are approximate; all cross and lab data are invented for practice. Show each calculation, and when a problem asks for a question, make it name a relationship and the data that could answer it.
Part 1: DNA, Genes and Chromosomes (Problems 1-3)
Pea plant body cells have 14 chromosomes. (a) How many pairs is that? (b) How many chromosomes are in a pea pollen grain's sperm cell? (c) A student says, "A pea seedling gets 14 chromosomes from each parent." Use your answers to correct the student, and write one question that the correction raises.
A karyotype of a boy shows 46 chromosomes: 22 matching pairs plus one X and one Y. (a) How many chromosomes did he receive from each parent? (b) Which parent gave him the Y, and which gave him the X? (c) Write a testable question about a trait whose gene is on his X chromosome.
In cats, a gene for orange versus black fur is on the X chromosome. An orange female (XOXO) is mated with a black male (XoY). (a) What fraction of the sons will be orange? (b) What fraction of the daughters will carry both alleles? (c) Use chromosomes to explain why a male cat with typical sex chromosomes cannot carry both alleles.
Part 2: Asking and Refining Questions (Problems 4-6)
Four students asked these questions about a family where several members have a white patch of hair: (i) "Is the white patch pretty?" (ii) "Does the white patch appear in about half the children of a parent who has it?" (iii) "Why do families have traits?" (iv) "Does the allele linked to the white patch differ in base sequence from the usual allele?" (a) Mark each testable or not testable. (b) Say whether each testable question is about DNA or about how chromosomes are passed on. (c) Rewrite question (iii) so it is testable.
Invented data: two brown lab mice, each carrying one c allele of the pigment gene on chromosome 7, had 40 pups over several litters: 29 brown and 11 white. (a) What fraction of the pups are white? (b) Compare it with the 1/4 expected if each pup gets one chromosome 7 from each parent at random. (c) Write one question these data raise that a DNA test of the white pups could answer.
A human body cell holds about 6.2 billion base pairs of DNA, and each base pair adds about 0.34 nanometers of length. (a) Compute the total length of DNA in one cell, in meters. (b) A cell nucleus is about 6 micrometers across. How many times longer is the DNA than the nucleus is wide? (c) Write two questions that connect how DNA is packed into chromosomes with how it is passed on to new cells.
Rubric
Criterion
Full Credit (2 pts)
Partial Credit (1 pt)
Chromosome Counts
Correct pairs, gamete and offspring counts with a reason based on pairs
Correct numbers with no reason, or one counting error
DNA, Gene and Allele Ideas
Uses gene, allele, chromosome and protein correctly to connect DNA to a trait
Terms mostly correct, but the chain from DNA to trait has a gap
Quality of Questions
Questions name a relationship and a source of evidence, and testable questions are identified correctly
Questions are relevant but vague, or one testable question is misclassified
05
Quiz: 20 Questions
Interactive, with answers
Instructions
Chromosome counts are real values, chromosome sizes are approximate, and cross data are invented. Your score updates as you answer, and Reset quiz clears everything so you or your students can try again.
Multiple choice: pick an option to check it. Short answer: write your answer, then reveal the model answer.
0 of 20 answered · 0 correct
Question 1 of 20 · Multiple Choice
A karyotype shows a band on chromosome 11 where the gene for a hemoglobin chain sits. Which statement best describes that gene?
Answer: B
The gene is one segment of the long DNA molecule that forms chromosome 11, and its base sequence carries the instructions for the protein. Choice A confuses a gene with a chromosome, which carries many genes. Choice D describes the product of a gene, not the gene itself.
Question 2 of 20 · Multiple Choice
A fruit fly body cell has 8 chromosomes. How many chromosomes are in a fruit fly egg?
Answer: D
Body cells hold 4 pairs, and an egg carries one chromosome from each pair, so it has 4. Choice B forgets that the number is halved. Choice A doubles the count, as if both parents' full sets went into one egg.
Question 3 of 20 · Multiple Choice
Which question is testable and clarifies a relationship between a chromosome and a trait?
Answer: C
Choice C names a chromosome, an allele and a trait pattern that family and medical data can answer. Choices A and D are value judgments with no data that could settle them, and choice B does not mention DNA, chromosomes or traits.
Question 4 of 20 · Multiple Choice
A cat's body cells have 38 chromosomes. How many of them came from the cat's mother?
Answer: A
The 38 chromosomes form 19 pairs, and one member of each pair came from the mother, so 19 did. Choice B assumes the mother gave a full set. Choice C doubles the count instead of halving it. Choice D halves the count twice (38 ÷ 2 ÷ 2 = 9.5) and rounds down, but only one halving is needed to find the mother's share.
Question 5 of 20 · Multiple Choice
What is true of the two chromosomes in a homologous pair?
Answer: D
Homologous chromosomes, one from each parent, have the same genes at the same places, and each gene can be present as a different allele. Choice A ignores that alleles can differ. Choices B and C would mean the two chromosomes hold different sets of genes.
Question 6 of 20 · Multiple Choice
Which order shows how DNA leads to a trait?
Answer: B
The base sequence of a gene codes for a protein, and the protein helps produce the trait. Choice A reverses the direction. Choice D starts from chromosome number, which does not code for any single trait.
Question 7 of 20 · Multiple Choice
Hemophilia A is caused by an allele of a gene on the X chromosome. A father with hemophilia (XhY) and a mother with two typical alleles (XHXH) have children. What is the chance that a daughter carries the allele?
Answer: C
Every daughter gets her father's only X, which carries h, so every daughter is a carrier: probability 1. Choice A treats the father as if he had two different X chromosomes to choose from. Choice B confuses daughters with sons, who get the father's Y and cannot receive the allele from him.
Question 8 of 20 · Multiple Choice
Which observation is the strongest evidence that genes are carried on chromosomes?
Answer: B
A trait that follows the path of one chromosome from parent to offspring links the gene to that chromosome. Choice A shows inheritance but not where the instructions are. Choices C and D are true but say nothing about chromosomes and traits.
Question 9 of 20 · Multiple Choice
A student asks, "Why do some families have many redheads?" Which revision is the best clarifying question?
Answer: C
Choice C names the gene location, the alleles the parents carry and a measurable pattern in the children. Choices A and D are opinions. Choice B is too broad to point to any data.
Question 10 of 20 · Multiple Choice
Approximate values: human chromosome 17 is about 83 million base pairs with about 1,190 protein-coding genes, and chromosome 18 is about 80 million base pairs with about 270 genes. Which conclusion do the data support?
Answer: A
Chromosome 17 has about 1,190 ÷ 83 ≈ 14.3 genes per million base pairs, while chromosome 18 has about 270 ÷ 80 ≈ 3.4, even though their lengths are close. Choice B is contradicted because chromosome 17 is only slightly longer yet has over four times as many genes. Choice C reverses the densities. Choice D applies chromosome 17's density to both.
Question 11 of 20 · Multiple Choice
A karyotype shows 47 chromosomes, with three copies of chromosome 21 instead of two. Which question does this observation best help answer?
Answer: A
An extra chromosome 21 means extra copies of the genes it carries, which links chromosome number to traits. Choice B is ruled out by the karyotype, which shows only chromosome 21 in three copies. Choice D asks about the phases of cell division, which this standard does not assess, and a karyotype alone cannot answer it.
Question 12 of 20 · Multiple Choice
Two alleles of the same gene differ in which way?
Answer: C
Alleles are versions of one gene at the same place on homologous chromosomes, and they differ in base sequence. Choice A describes two different genes. Choice D is a misconception: a dominant allele is not necessarily the more frequent one.
Question 13 of 20 · Multiple Choice
A change in the DNA of a skin cell and a change in the DNA of an egg cell occur in the same person. Which change can be passed to that person's children?
Answer: D
Offspring receive chromosomes only through sperm and eggs, so only DNA in the egg cell can be inherited. Choice A has it backward: skin cells do not form offspring. Choice B assumes every cell passes its DNA to children.
Question 14 of 20 · Multiple Choice
Which question could be answered with a karyotype (a picture of all the chromosomes in a cell) alone?
Answer: A
A karyotype shows the number and shape of chromosomes, so it shows the sex chromosomes. Choices B and C need the DNA sequence, not just chromosome pictures, and choice D needs a protein measurement.
Question 15 of 20 · Short Answer
Rice body cells have 24 chromosomes. (a) How many pairs is that? (b) How many chromosomes are in a rice egg cell? (c) Write one question about rice chromosomes that a karyotype could answer.
(a) 12 pairs. (b) An egg carries one chromosome from each pair: 12. (c) Example: "Do all 12 pairs in a rice plant have two members of matching length?" A karyotype shows the size and number of chromosomes, so it can answer this.
Question 16 of 20 · Short Answer
Invented data: in a lab strain of rabbits, animals with two copies of allele h have hairless patches, and a skin test shows they make a shorter form of a hair protein. Write a testable question that links the allele, the protein and the trait, and name the data that would answer it.
Example: "Does the h allele differ in base sequence from the usual allele in a way that shortens the hair protein, and do rabbits with two h alleles always show hairless patches?" Data: DNA sequences of both alleles from several rabbits, protein length from skin samples, and the trait recorded for rabbits with hh, Hh and HH. A full answer names the gene (DNA), the protein and the trait.
Question 17 of 20 · Short Answer
Human chromosome 1 is about 248 million base pairs long, and each base pair adds about 0.34 nanometers. How long is the DNA molecule of chromosome 1, in centimeters? Write one question the answer raises.
248 × 106 × 0.34 × 10-9 m = 0.0843 m, about 8.4 cm. Example question: "How is an 8 cm DNA molecule packed so that it can be passed on whole to a new cell?" Any question that connects the length to packing or to passing chromosomes on earns credit.
Question 18 of 20 · Short Answer
In fruit flies, a gene for eye color is on the X chromosome, and the red allele (XR) is dominant over white (Xr). Predict the eye colors of the sons and daughters of a white-eyed female (XrXr) and a red-eyed male (XRY), and explain the prediction with chromosomes.
Every son gets an Xr from his mother and the Y from his father: all sons white-eyed. Every daughter gets Xr from her mother and XR from her father: all daughters red-eyed (carriers). The pattern follows the path of the X chromosome, which is evidence that the gene is on it.
Question 19 of 20 · Short Answer
A student writes the question "How do genes work?" Say which parts of the chain (DNA, gene, protein, chromosome, trait) it leaves vague, and rewrite it so it clarifies one relationship and could be tested.
It names genes but not which gene, which trait or which relationship, and it points to no data. Example rewrite: "Do people with two copies of a certain allele of the lactase gene on chromosome 2 make less lactase protein as adults than people with one copy?" It names a gene and its chromosome, an allele, a protein and a trait-related measurement.
Question 20 of 20 · Short Answer
Real values: chromosome counts in body cells are about 100 in goldfish, 78 in chickens, 46 in humans and 24 in rice. A student claims, "The more chromosomes a species has, the more complex it is." Use the data to evaluate the claim, and write a better question about chromosomes and traits.
The data do not support the claim: goldfish have about twice as many chromosomes as humans, and chickens have more than humans. Chromosome number reflects how the DNA is divided into pieces, not how many genes or how complex the organism is. Better question: "Do species with more chromosomes carry more protein-coding genes, and how would we compare their gene counts?"
0 of 20 answered · 0 correct
06
Frequently Asked Questions
10 Questions
What does HS-LS3-1 mean?
HS-LS3-1 asks students to ask questions that clarify how DNA and chromosomes carry the instructions for traits passed from parents to offspring. The emphasis is on the practice of asking questions: students connect genes, alleles and chromosomes to traits and propose what data would answer their questions. The code means High School, Life Science, core idea 3 (Heredity), performance expectation 1.
Is HS-LS3-1 taught in biology?
Yes, it is usually taught in a high school Biology course, in the genetics or heredity unit. It often comes right after lessons on DNA and proteins (HS-LS1-1) and before lessons on variation (HS-LS3-2) and probability of traits (HS-LS3-3).
What is the assessment boundary for HS-LS3-1?
Assessment does not include the phases of meiosis or the biochemical mechanism of specific steps in the process. Students need to know that sperm and eggs carry one chromosome from each pair, but not the names or order of the stages that produce them, and not the enzymes that copy DNA.
What is the difference between DNA, a gene and a chromosome?
DNA is the molecule, a gene is one stretch of it that codes for a protein, and a chromosome is one very long DNA molecule, packed with proteins, that carries many genes. A useful comparison is a book: the letters are bases, a sentence is a gene, and a whole volume is a chromosome.
What does asking questions look like in a genetics lesson?
Students write questions that name a relationship, such as "How does the allele on the X chromosome relate to the trait in sons?", and then decide what evidence could answer them. They sort questions into testable and not testable, refine vague questions and match questions to data such as karyotypes, crosses or DNA sequences.
What is an allele?
An allele is one version of a gene. Alleles of the same gene sit at the same place on the two chromosomes of a pair and differ in their base sequence, so they can code for proteins that work differently. A person can carry two identical alleles or two different ones.
Does every part of DNA code for a protein?
No. In humans, only a small share of the DNA, under 2 percent, codes for proteins. The rest includes regions that control when genes are used and regions whose role is still being studied. Gene density also varies a lot between chromosomes, which is a good source of student questions.
What misconceptions do students have about chromosomes and traits?
Frequent ones are that each chromosome codes for one trait, that a parent passes on all of its chromosomes, that dominant alleles are always the more frequent ones, and that genes and chromosomes are the same thing. Chromosome count data and cross data help students test these ideas directly.
How does HS-LS3-1 connect to HS-LS3-2 and HS-LS3-3?
HS-LS3-1 builds the picture of genes on paired chromosomes. HS-LS3-2 uses that picture to argue where new genetic variation comes from, and HS-LS3-3 uses probability and statistics to explain how traits are distributed in a population. Questions students raise in HS-LS3-1 often become the claims they defend in HS-LS3-2.
How can I grade student questions?
Use a short rubric: does the question name a relationship, does it use gene, allele or chromosome correctly, and does it point to evidence that could answer it? The homework rubric on this page gives two points for questions that do all three and one point for relevant but vague questions.
07
Related Standards
6 standards
These standards connect to HS-LS3-1: prerequisites to review first, parallel standards at the same level, and next steps that build on it.
Before this lesson
MS-LS3-2Prerequisite
Model why sexual reproduction gives offspring varied genetic information
NGSS is a registered trademark of WestEd. Neither WestEd nor the lead states and partners that developed the Next Generation Science Standards were involved in the production of this product, and do not endorse it.
