Genetics Test Practice Questions
ANSWER QUESTIONS ON A SEPARATE SHEET OF PAPER
LT16 (DNA Structure) – Describe structure and function and replication of DNA
LT18 – (Chromosomes) Describe the structure and function of chromosomes
1. Draw a short section of DNA with 10 base pairs in any order. Label the nitrogen bases, hydrogen bonding, and the
sugar-phosphate backbone.
2. Explain how information in DNA is stored, making specific reference to your diagram above.
Information in DNA is stored in the sequence of nitrogen bases. In the diagram above, you would read the “code” of
DNA by reading the letters of the nitrogen bases across on one side of the DNA strand.
3. Explain the relationship between DNA, genes and chromosomes. Consider drawing a diagram.
Chromosomes are made of tightly coiled strands of DNA. A segment of DNA that codes for a protein is called a gene.
There are many genes that can be found on chromosomes, and they are found in specific locations on the chromosomes.
4. What are homologous chromosomes? Where do they come from? What is the same about homologous
chromosomes? What can be different?
Homologous chromosomes are chromosomes that are approximately the same size and shape, and have the same genes
on them. You get one homologous chromosome from mom (maternal) and one from dad (paternal). Homologous
chromosomes have the same genes, but could have different alleles of those genes.
LT17 – (Protein Synthesis) Explain the process of protein synthesis.
5. What information is stored in a gene? How is this information stored?
Genes store information that codes for proteins. The information is stored in the sequence of DNA nucleotides that
make up the gene.
6. Using the sequence of bases in a gene in DNA, determine the sequence of bases in mRNA. Using the sequence of
bases in mRNA, determine the sequence of amino acids
Gene/DNA: T A C G T A A T A A T C A G C T A A
mRNA:
AUG CAU UAU UAG UCG AUU
amino acids: MET – HIS – TYR – TER – CYS – ILE
7. Describe the steps of protein synthesis beginning with an order of bases in a gene and ending with an order of amino
acids in a protein. (the gene, mRNA and amino acids above as an example) Include in your answer the following
vocabulary and how mRNA and tRNA function in this process: (You can also draw and label a diagram instead)
transcription
 translation
 amino acid
 mRNA
 codon
 tRNA
 anticodon
 nucleus
 cytoplasm
 ribosome
To make a protein, the cell first transcribes the DNA sequence (like in question 6) from DNA onto a strand of mRNA. The
DNA unzips, and free mRNA nucleotides in the nucleus come in and match up with the exposed DNA nucleotides
according to the base-pair rules A  U, T A, GC, CG. When the mRNA strand gets long enough, it leaves the
nucleus and the DNA zips back up. The mRNA goes to the cytoplasm, where translation occurs.
During translation, the mRNA gets fed through a ribosome like a ribbon. The ribosome reads the mRNA strand 3 letters
at a time. These 3 letters, or codons, match up with specific anti-codons on tRNA molecules. The tRNA comes into the
ribosome, carrying an amino acid, and matches with the codon. It leaves the amino acid behind, and another tRNA
comes in to match with the next codon, leaving another amino acid behind. The amino acids left behind from tRNA
make a longer and longer amino acid chain, which then coils up to make a protein.
LT15 (Protein and Traits) - Proteins express inherited traits and carry out most cell functions.
8. What is a trait? Provide several examples.
A trait is a physical or behavioral characteristic of an organism that can be passed down from parent to offspring. This
could be things like eye color, tongue rolling, skin color.
9. Explain how traits are controlled by proteins. Provide an example.
We have specific traits because of the proteins that are produced in cells. For example, a person can have sickle cell
anemia if their hemoglobin protein made in the red blood cells is a type of protein that sticks together. Because the
protein is a certain shape, the hemoglobin sticks together and causes the blood cells to form sickle shapes, which results
in the trait of sickle cell anemia.
10. Explain how genes on homologous chromosomes control our traits.
Every trait is determined by two (or more) genes on homologous chromosomes. It is the interaction of these two genes
that results in the traits that we see. For example, if someone is heterozygous for a particular trait, and the genes are
completely dominant, then the dominant trait would be the one that is expressed.
11. Diagram and explain the difference between the proteins and traits of someone with sickle cell anemia, and
someone with normal blood.
LT19 – (Meiosis) Explain the possible allele combinations in an egg or sperm through meiosis
LT21 – (Variation) Explain that mutation and recombination increases variation
12. Describe the overall process of meiosis. In your description, address:
a. Why meiosis occurs
b. Where meiosis occurs (in what types of cells)
c. What happens in meiosis I and meiosis II
d. The relationship between chromosome numbers for parent and daughter cells.
Meiosis is the process by which sex cells divide and reduce the number of chromosomes they have by half, creating
gametes. This needs to happen so that when fertilization occurs, it restores the correct number of chromosomes into a
normal cell in the offspring. Meiosis occurs in sex cells. In meiosis I, homologous chromosomes line up on the center
line and split into two difference cells. In meiosis II, the chromosomes line up again on the center line and sister
chromatids split up. There are 4 resulting gametes, and each gamete has half the number of chromosomes as the parent
cell.
13. Using words or a diagram, demonstrate that you understand how crossing-over can also increase genetic variability.
Crossing-over increases genetic variability by shuffling the combination of alleles that can be found on a single
chromosome.
14. Pretend that a fruit fly has two pairs of chromosomes: one long, and one short - each with the following genes and
genotype:

On the long chromosome is the gene for eye color (R/r) and this organism is heterozygous for eye color.

On the short is the gene for hairiness (H/h) and the fly is also heterozygous for hair.
a. Diagram two different options for how the homologous chromosomes could line up in metaphase I. For
each different option, determine the genotypes of the four gametes.
If both dominant alleles line up on the left and both recessive alleles line up on the right, the four gametes would have
genotypes of RH, RH, rh, and rh. If one of the homologous pairs switches locations, the resulting gametes would have
genotypes of Rh, Rh, rH, and rH.
15. Identify different types of mutation that can occur on a DNA strand, and describe how those mutations could affect
traits.
Substitution can result in new alleles for a gene. Deletion or insertion could result in completely different proteins,
because they will frame-shift how the codons are being read in the ribosome.
Punnett Squares
LT20 – (Punnett Squares) Explain the outcomes of monohybrid (one trait) and dihybrid (two trait) crosses.
15. Woodrats are medium sized rodents with lots of interesting behaviors. You may know of them as packrats. Let's
assume that the trait of bringing home shiny objects (H) is controlled by a single gene and is dominant to the trait of
carrying home only dull objects (h). Suppose two heterozygous individuals are crossed. What are the chances that
their offspring will bring home shiny objects? dull objects?
16. Travis is heterozygous for Polycystic kidney disease (a dominant allele disease) and homozygous recessive for Sickle
Cell Anemia. He and his partner Pei-Yee, are considering having children. Pei-Yee is homozygous recessive for
Polycystic kidney disease and heterozygous for Sickle Cell Anemia. Using the following allele key, create the di-hybrid
cross for this couple.
H – Polycystic kidney
h – normal kidney
A – normal hemoglobin
a – hemoglobin that sickles
What are the chances their offspring will have their father’s phenotype (traits)?
What are the chances their offspring will have their mother’s phenotype?
17. There are three possible genotypes and phenotypes for wing color in a species of moth:
RR = red wings; RY = orange wings; YY = yellow wings.
a. What is the pattern of inheritance in this example: complete dominance, incomplete dominance, or codominance?
b. An orange-winged moth mates with a red-winged moth. What are the genotypes of the parents?
c. What fraction of the offspring will have red wings? Yellow wings? Orange wings?
d. If this trait in moths exhibited co-dominance, what color of wings might the RY moths have?