Unit 3 Review Guide
Key Concepts
 Sickle cell disease is caused by an abnormal type of hemoglobin which causes red blood cells to become shaped
like crescents or sickles.
 Sickle cell disease and anemia cause many health problems and affect daily life for someone with the disease.
 Proteins are produced through the processes of transcription and translation.
 Changes in the genetic material may cause changes in the structure and function of a protein and consequently
the traits of an organism.
 Chromosomes transfer genetic material from cell to cell as well as from generation to generation, in processes
called mitosis and meiosis.
 There are often several forms of each gene, some being dominant over the others.
 The expression of a trait through the generations of a family can be visualized using a pedigree.
 A Punnett square is a simple graphical way of discovering all of the potential combinations of genotypes of an
offspring and can be used to determine the percent chance of each genotype occurring.
Essential Questions
1. What is sickle cell disease?
2. Why does the sickling of red blood cells cause health problems?
3. What is sickle cell anemia?
4. How is anemia diagnosed?
5. How does sickle cell disease affect daily life?
6. What is the DNA code?
7. What is the connection between genes and proteins?
8. How are proteins produced in a cell?
9. How does the sequence of nucleotides in DNA determine the sequence of amino acids in a protein?
10. What is a mutation?
11. What determines the shape of a protein?
12. Is the shape of a protein affected by its surrounding environment?
13. How does a change in the DNA code affect the shape of a protein?
14. Can changing just one nucleotide in a gene change the shape of a protein?
15. How is DNA passed to new cells during cell division?
16. What is a chromosome?
17. How are traits passed through the generations?
18. Why does sickle cell disease run in families, yet is not present in every generation?
19. How can doctors and genetic counselors calculate the probability of a child inheriting a disease?
20. How does the presence of malaria in a region affect the frequencies of normal versus sickle cell alleles?
Key Terms
 Anemia- A condition in which the blood is deficient in red blood cells, in hemoglobin, or in total volume.
 Blood Plasma- The pale yellow fluid portion of whole blood that consists of water and its dissolved constituents
including, sugars, lipids, metabolic waste products, amino acids, hormones, and vitamins.
 Erythrocytes (Red Blood Cells)- Any of the hemoglobin-containing cells that carry oxygen to the tissues and are
responsible for the red color of vertebrate blood.
 Hematocrit- The percent of the volume of whole blood that is composed of red blood cells as determined by
separation of red blood cells from the plasma usually by centrifugation.
 Leukocytes (White Blood Cells)- Any of the blood cells that are colorless, lack hemoglobin, contain a nucleus, and
include the lymphocytes, monocytes, neutrophils, eosinophils, and basophils.
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Sickle Cell Disease- Individuals who are homozygous for the gene controlling hemoglobin S. The disease is
characterized by the destruction of red blood cells and by episodic blocking of blood vessels by the adherence of
sickle cells to the vascular endothelium.
Thrombocytes (Platelets)- A minute colorless anucleate disklike body of mammalian blood that assists in blood
clotting by adhering to other platelets and to damaged epithelium.
Amino Acid- An organic monomer which serves as a building block of proteins.
Anticodon- A triplet of nucleotide bases in transfer RNA that identifies the amino acid carried and binds to a
complementary codon in messenger RNA during protein synthesis at a ribosome.
Codon- A three-nucleotide sequence of DNA or mRNA that specifies a particular amino acid or termination
signal; the basic unit of the genetic code.
Hydrophilic- Having an affinity for water.
Hydrophobic- Having an aversion to water; tending to coalesce and form droplets in water.
Messenger RNA (mRNA)- A type of RNA, synthesized from DNA and attached to ribosomes in the cytoplasm; it
specifies the primary structure of a protein.
Mutation- A rare change in the DNA of a gene, ultimately creating genetic diversity.
Nucleotide- The building block of a nucleic acid, consisting of a five-carbon sugar covalently bonded to a
nitrogenous base and a phosphate group.
Protein A three dimensional polymer made of monomers of amino acids.
Protein Synthesis- The creation of a protein from a DNA template.
Ribonucleic Acid (RNA)- A type of nucleic acid consisting of nucleotide monomers with a ribose sugar and the
nitrogenous bases adenine (A), cytosine (C), guanine (G), and uracil (U); usually single-stranded; functions in
protein synthesis and as the genome of some viruses.
Ribosome- A cell organelle that functions as the site of protein synthesis in the cytoplasm; consists of ribosomal
RNA and protein molecules and is formed by combining two subunits.
Transcription- The synthesis of RNA on a DNA template.
Transfer RNA (tRNA)- An RNA molecule that functions as an interpreter between nucleic acid and protein
language by picking up specific amino acids and recognizing the appropriate codons in the mRNA.
Translation- The synthesis of a polypeptide using the genetic information encoded in an mRNA molecule. There
is a change of language from nucleotides to amino acids.
Autosome- A chromosome that is not directly involved in determining sex, as opposed to a sex chromosome.
Chromosome- Any of the usually linear bodies in the cell nucleus that contain the genetic material.
Dominant trait- A genetic trait is considered dominant if it is expressed in a person who has only one copy of the
gene associated with the trait.
Gene- A discrete unit of hereditary information.
Genetic Material- Molecules responsible for heredity and variation of organisms.
Genotype- All or part of the genetic constitution of an individual or group.
Heredity- The transmission of traits from ancestor to descendant.
Homologous Chromosomes- Chromosomes having the same or allelic genes with genetic loci usually arranged in
the same order.
Karyotype- A display of the chromosome pairs of a cell arranged by size and shape.
Meiosis- The cellular process that results in the number of chromosomes in gamete-producing cells being
reduced to one half and that involves a reduction division in which one of each pair of homologous
chromosomes passes to each daughter cell.
Mitosis- A process that takes place in the nucleus of a dividing cell, involves a series of steps, and results in the
formation of two new nuclei each having the same number of chromosomes as the parent nucleus.
Mutation- A rare change in the genetic material, ultimately creating genetic diversity.
Pedigree- A diagram of a family tree showing the occurrence of heritable characteristics in parents and offspring
over multiple generations.
Phenotype- The observable properties of an organism that are produced by the interaction of the genotype and
the environment.
Recessive Trait- A condition that appears only in individuals who have received two copies of a mutant gene,
one copy from each parent.
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Sex Chromosome- One of the pair of chromosomes responsible for determining the sex of an individual.
Allele- Any of the alternative forms of a gene that may occur at a given locus.
Chromosome- Any of the usually linear bodies in the cell nucleus that contain the genetic material.
Dominant Trait- A genetic trait is considered dominant if it is expressed in a person who has only one copy of the
gene associated with the trait.
Gene- A discrete unit of hereditary information.
Genotype- All or part of the genetic constitution of an individual or group.
Heredity- The transmission of traits from ancestor to descendant.
Pedigree- A diagram of a family tree showing the occurrence of heritable characters in parents and offspring
over multiple generations.
Phenotype- The observable properties of an organism that are produced by the interaction of the genotype and
the environment.
Punnett Square- A simple graphical way of discovering all of the potential combinations of genotypes of an
offspring, given the parents’ genotypes.
Recessive Trait- A condition that appears only in individuals who have received two copies of a mutant gene,
one copy from each parent.
Other study tools:
 Lab Notes
 Conclusions Questions
 Activity Introductions
 Career Journals
 Online Tools from Website
 URLs on Website
You should be able to:
 Describe the link between malaria and SCD
 Describe the symptoms, complications, treatments and prognosis for SCD
 Complete a Punnett square
 Answer probability questions about a Punnett square with phenotypic and genotypic ratios
 Understand and answer questions about a pedigree
 Describe the wok of a genetic counselor
 Discuss the relationship between DNA, genes and chromosomes
 Describe the steps protein synthesis, from DNA to a protein (DNA, DNA polymerase, mRNA, A,C,T,G,U,
transcription, translation, ribosome, tRNA, codons, anti-codons, amino acids, polypeptide, protein)
 Code for transcription and translation and assign amino acids using the matrix
 Discuss protein structure
 Discuss at least two important geneticists
 List Mendel’s Laws
 Descibe his experiments
 Describe how proteins get their shape and why shape is important
 Describe a karyotype
 Describe mitosis and meiosis and be able to compare and contrast the two
 Describe the mutation that causes SCD
 Discuss evolution and natural selection
 Describe Darwin’s main ideas
 Answer questions about Survival of the Sickest
 Discuss the link between SCD and malaria (and other examples from Survival of the Sickest)
 List the four requirements for evolution via natural selection