Grade 8 Science Quiz Cells Genetics | Challenging 20 Questions US Middle School

Grade 8 Science Quiz Cells Genetics | 20 Questions with Answers

Challenging Grade 8 Science Quiz! 20 NGSS cells/genetics: interphase DNA replication, 46 chromosomes, mitochondria ATP, 25% recessive Punnett, frameshift mutations, Down syndrome trisomy 21. US middle school!

Science Quiz Cells Genetics Questions with Answers for Grade 8 Students

Grade 8 cells genetics quiz: interphase DNA replication (S-phase), 46 human chromosomes, mitochondria ATP powerhouse, Punnett 25% recessive, frameshift mutations, Down syndrome trisomy 21. 20 CHALLENGING NGSS questions!

Join Our Learning Community

Get daily quizzes, practice tests, and free learning updates.

Join WhatsApp Channel Follow on Facebook

20 challenging Grade 8 cells & genetics questions for US middle school. NGSS MS-LS1/MS-LS3 aligned. 70% (14/20) to PASS! Advanced concepts.

Results

Outstanding Grade 8 cells & genetics mastery!
You’ve conquered challenging NGSS MS-LS1/MS-LS3 concepts: mitosis phases, Punnett squares, frameshift mutations, and chromosomal disorders.
Perfect preparation for middle/high school biology transition and state science assessments!

More Quizzes – Click Here.

Strong cellular biology foundation building!
Grade 8 genetics requires mastering DNA replication, meiosis phases, and probability ratios through diagrams and practice.
Review detailed explanations — you’ll ace advanced cells/genetics next time!

More Quizzes – Click Here.

#1. Which cell type lacks nucleus (prokaryotic)?

Bacterial

Animal

Fungal

Plant

Explanation: Prokaryotes: circular DNA in nucleoid, no membrane organelles. Eukaryotes: true nucleus + organelles.

#2. In which meiosis phase do homologous chromosomes separate?

Anaphase I

Telophase II

Prophase I

Metaphase I

Explanation: Meiosis I: homologous pairs (tetrads) align/separate → haploid. Meiosis II: sister chromatids separate.

#3. What bonds nitrogenous bases in DNA?

Covalent

Hydrogen

Ionic

Peptide

Explanation: A-T (2 H-bonds), G-C (3 H-bonds). Complementary base pairing. Weak bonds allow unzipping replication.

#4. What mutation adds/deletes nucleotide (shifts reading frame)?

Frameshift

Silent mutation

Point mutation

Missense

Explanation: Insertion/deletion changes all downstream codons. Often severe (cystic fibrosis example).

#5. What inheritance pattern shows both alleles expressed?

Complete dominance

Codominance

Sex-linked

Multiple alleles

Explanation: Example: AB blood type (IAIB). Both A + B antigens expressed on RBC surface.

#6. What is the probability of two heterozygous parents having recessive child?

25%

75%

50%

Explanation: Punnett square: Tt × Tt → TT (25%), Tt (50%), tt (25%). Recessive phenotype 25%.

#7. Which phase shows chromosomes at cell equator?

Prophase

Anaphase

Metaphase

Cytokinesis

Explanation: Spindle fibers attach centromeres. Chromosomes align metaphase plate (genetic variation max).

#8. What phase of mitosis does DNA replicate?

Metaphase

Telophase

Interphase

Prophase

Explanation: Interphase (G1, S, G2) prepares cell division. S-phase: DNA replicates from 2n→4n chromosomes. Longest phase (~90% cell cycle).

#9. Which organelle packages proteins into vesicles?

Golgi apparatus

Peroxisome

Lysosome

Endoplasmic reticulum

Explanation: Modifies, sorts, packages proteins/lipids into secretory vesicles. “Post office” of cell.

#10. Which genetic principle states “one allele masks another”?

Incomplete dominance

Codominance

Complete dominance

Polygenic inheritance

Explanation: Dominant allele (capital letter) expressed over recessive. Example: TT/Tt = tall pea plants (Mendel); tt = short.

#11. How many daughter cells from one mitosis division?

2 identical diploid

Explanation: Mitosis: growth/repair. Identical 2n cells. Meiosis: 4 unique haploid gametes.

#12. Which process converts mRNA into protein chain?

Mutation

Replication

Transcription

Translation

Explanation: Ribosomes read mRNA codons. tRNA brings amino acids. rRNA catalyzes peptide bonds.

#13. What crosses cell membrane via facilitated diffusion?

H₂O

Glucose

O₂, CO₂

Na⁺, K⁺

Explanation: Channel/carrier proteins transport polar/large molecules down concentration gradient (no energy). Active transport requires ATP.

#14. What DNA sequence codes for specific amino acid?

Gene

Codon

Anticodon

Exon

Explanation: 3-base codon (AUG = methionine/start). 64 codons → 20 amino acids + stop codons. Universal genetic code.

#15. Which scientist discovered cell theory (cells basic unit of life)?

Leeuwenhoek

Virchow

Hooke

Schleiden/Schwann

Explanation: Schleiden (plants 1838), Schwann (animals 1839). Virchow added: cells from pre-existing cells (1855).

#16. What genetic disorder from extra chromosome 21?

Klinefelter

Cystic fibrosis

Down syndrome

Turner syndrome

Explanation: Trisomy 21 (nondisjunction meiosis). 1/700 births. Intellectual disability, characteristic features.

#17. What structure controls cell activities as “powerhouse”?

Golgi apparatus

Nucleus

Mitochondria

Ribosomes

Explanation: Mitochondria produce ATP via cellular respiration (glucose + O₂ → ATP + CO₂ + H₂O). Own DNA; maternal inheritance.

#18. How many chromosomes in human somatic cells?

Explanation: 23 pairs (46 total): 22 autosomes + 1 sex pair (XX/XY). Gametes have 23 (haploid). Mitosis maintains diploid number.

#19. Which scientist discovered penicillin (destroyed bacterial cell walls)?

Koch

Pasteur

Fleming

Salk

Explanation: Alexander Fleming (1928). Beta-lactam antibiotics inhibit peptidoglycan cross-linking.

#20. What provides cell rigidity in plant cells?

Cell wall

Cytoplasm

Chloroplast

Plasma membrane

Explanation: Cellulose (plants), chitin (fungi), peptidoglycan (bacteria). Protects/prevents lysis.

Finish

More Quizzes –

Grade 9 Science Quiz Test	Click Here
Grade 6 Science Quiz	Click Here
Grade 8 History Quiz	Click Here