Genetics Review Sheet Answers

• • • • • • • • • • 1.Define the following genetics terms on a separate sheet of paper.

Genetics Heredity Chromosome Gene Allele Trait Dominant Recessive Genotype Phenotype • • • • • • • • Homozygous Heterozygous Purebred Hybrid Punnett Square Codominance Incomplete dominance Mutation

Vocabulary

• genetics – the science of how traits are inherited through alleles passes from one generation to another • heredity – passing of traits from parent to offspring • chromosome – threadlike strands of DNA and protein in a cell nucleus that carry the code for the cell characteristics of an organism

Vocabulary

• gene – the segment of DNA on a chromosome that directs the making of a specific protein, thus controlling traits that are passed to offspring • allele – a different form a gene may have for a trait • trait –another name for a characteristic

Vocabulary

• dominant – the form of a trait that appears to dominate or mask another form of the same trait • recessive – the form of a trait that seems to disappear in a population but can reappear depending on the way the alleles combine • genotype – the genetic makeup of an organism • phenotype – a physical trait that shows as a result of an organism’s particular genotype

Vocabulary

• homozygous – an organism that has two identical alleles for a trait • heterozygous – an organism that has two different alleles for a trait • purebred – an organism that always produces the same traits in it’s offspring • hybrid – an organism that produces different traits in it’s offspring

Vocabulary

• Punnett square – a tool that shows how genes can combine; used to predict the probability of types of offspring • codominance – the production of a phenotype in an offspring that has both dominant and recessive traits shown in a heterozygous offspring • Incomplete dominance– the production of a phenotype in an offspring that is a combination or mix of the dominant and recessive traits shown in a heterozygous offspring • mutation – any permanent change in an organism’s genetic material

2. What are the 3 parts of the DNA molecule?

• • • Sugar Phosphate Nitrogen base

3. Nucleotides are the building blocks of DNA, what makes up a nucleotide? • 1 sugar + 1 phosphate + 1 nitrogen base

4. What are the 4 types of nitrogenous bases in DNA? • • • • A (Adenine) C (Cytosine) G (Guanine) T (Thymine)

5. What is the base-pairing rule?

• • A pairs with T C pairs with G

6. List 3 examples of genetic traits (traits that can be passed from parent to offspring).

• • • • • Natural hair color Eye color Hitchhikers thumb Height Cleft chin

• • • • • 7. List 3 examples of traits that are NOT genetic.

Dyed hair color Personality Having a broken arm Hair length Intelligence

8. Blue eyes are recessive and brown eyes are dominant; write all possible genotypes for: • • A blue eyed individual? bb A brown eyed individual? BB or Bb

• 9. Why are genotypes written with two letters? (Why is one letter not enough?) A genotype has two letters because one letter is the allele from the mom and the other letter is the allele from the dad

Genotypes

• 10. What is the genotype for a homozygous dominant individual?

• HH 11. What is the genotype for heterozygous dominant individual? • Hh 12. What is the genotype for a homozygous recessive individual? hh

13. Can an organism be heterozygous recessive for a trait? Explain why or why not?

• No, the only way an organism can be recessive for a trait is if both alleles (letters) are lowercase. If there is at least one dominant allele (capital letter) then the trait is dominant NOT recessive.

• • 14. The example of eye color is a “normal” dominant/recessive situation. How is incomplete dominance or codominance different from a normal dominant/recessive situation? Use an example from the alien lab in your answer.

In “normal” dominance there is 2 possible phenotypes for the trait – HH and Hh = dominant, hh = recessive In incomplete or codominance there is 3 possible phenotypes for the trait – – HH = dominant, hh = recessive, Hh = codominant or incomplete dominance

15. A blue eyed father and a heterozygous brown eyed mother wanted to know what color eyes their children might have. • • Genotype for father = ee Genotype for mother = Ee Complete the punnett square

e e E Ee Ee

Punnett Square

e ee ee Possible offspring genotypes:

Ee-2 ee-2

Possible offspring phenotypes:

Brown eyes-2 Blue eyes-2

16. Is the trait for curly tail dominant or recessive? How do you know?

Male with curly tail Male without curly tail Female with curly tail Female without curly tail Dominant-In the F3 generation all of the children had curly tails even though the dad has no curly tail…the mom’s curly tail “covered up” or was dominant to not having a curly tail

17. What are the genotypes of the parents in the P 1 generation?

Male with curly tail Male without curly tail Female with curly tail Female without curly tail • • Male = hh because he does not have a curly tail (he is recessive) Female= Hh because there is a female offspring without a curly tail, the female in P1 had to be able to give the female offspring in F1 “h”

• 18. Know and be able to answer the following questions about a genetic disorder. How would you describe the disorder? What is its cause? What are 2 symptoms of the disorder? What are 2 other facts about the disorder? (ex: treatments, cures)