1 Mendelian Genetics and Beyond Chapter 4 Study Prompts 1. What is a mode of inheritance? 2. Can you define the following? a. Autosomal dominant b. Autosomal recessive 3. Who was Gregor Mendel? 4. What did Mendel call the units that were inherited from generation to generation? What do we call these today? 5. What do the following mean? a. P 1 b. F 1 c. F 2 6. Can you explain what a monohybrid cross is? 7. Can you describe Mendel s Law of Segregation? 8. What are variations of a trait called? 9. Define the following: a. Homozygous dominant b. Homozygous recessive c. Heterozygous d. Wild type e. Carrier 10. How are alleles symbolized? 11. What is the difference between genotype and phenotype? 12. In humans, albinism is a homozygous recessive form of the trait for pigment in the skin. Use the letter a and give the possible genotypes for a normally-pigmented skin individual and an individual with albinism. 13. What is meant by a mutant allele? 14. What is the probability of a child having an albino condition from parents that are both carriers of the trait? 15. What is one way that a mutant allele may become more predominant in a population? 16. In people, having dimples is an autosomal dominantly inherited trait. If a woman that is heterozygous for dimples has children with a man that is homozygous recessive for this trait, what is the probability that their offspring will have dimples? Use the letter d in your Punnett square. 17. What is consanguinity? 18. If a woman has dimples and her mother did not, what is the woman s genotype for dimples? What could her father s genotype be? 19. Describe the Law of Independent Assortment in genetics. 20. What is a dihybrid cross? 21. What are the possibilities of all of the outcomes of a woman that is heterozygous for dimples and homozygous recessive for curly hair (she has strait hair) having children with a man that is
2 homozygous recessive for dimples (he does not have dimples) and homozygous dominant for curly hair (he has curly hair)? Study Prompt Answers 1. A mode of inheritance is a pattern in which traits are inherited from one generation to the next. 2. Definitions: a. Autosomal dominant is a trait that is on one of the 22 autosomal chromosomes and will mask another trait. These traits are evident in every generation. b. Autosomal recessive is a trait that is on one of the 22 autosomal chromosomes and will only be expressed if two copies are inherited. This type of trait skips generations. 3. Gregor Mendel was known as the father of genetics. He was the son of a farmer that became a priest and studied natural history. Through his studies of pea plants he described the fundamentals of inheritance of traits that, until this day, have not been disproven and, in fact, are applicable to all diploid species of organisms. 4. Elementen. Genes. 5. Definitions: a. P 1 - the original parent cross between two organisms b. F 1 - the first generation of offspring (first filial) c. F 2 - the second generation of offspring (second filial) 6. A monohybrid cross is when two version of the same trait are crossed by breeding individuals. For example a green-pea plant is crossed with a yellow-pea plant. The trait is pea color, the two versions are green and yellow. 7. Mendel s Law of Segregation states that an individual s alleles for a trait (one from their mother and one from their father, located on homologous chromosomes) separated into individual gametes when the chromosomal number is halved in meiosis. 8. Alleles. 9. Definitions: a. Homozygous dominant- When two dominant alleles (same version of the trait that would mask a recessive) are inherited b. Homozygous recessive- When two recessive alleles (same version of the trait that would be masked by a dominant allele) are inherited c. Heterozygous- When one dominant and one recessive allele are inherited d. Wild type- the most frequently occurring (abundant) allele in a population of organisms e. Carrier- A heterozygous individual. These individuals do not display the recessive allele, but can pass it on to their offspring. 10. Dominant alleles are given an upper case letter. Recessive alleles are given a lower case letter. 11. Genotype is the actual alleles that are inherited by an individual from their parents. Phenotype is the expression ( what it looks like ). 12. Normally pigmented could be AA or Aa (remember, dominant alleles mask recessive alleles, so even with one dominant allele inherited the individual is normally pigmented). The only genotype for albino individuals is aa.
3 13. A mutant allele arises when a gene undergoes mutation. It may results in a phenotype different than the wild type allele. 14. In the Punnett square, 1 of 4 children have albino. So each child from this set of parents would have a 25% chance of inheriting the condition. A a A AA Aa Aa aa a 15. Sexual selection. If a mutant allele causes a version of a trait that is desirable, the individual may be selected for as a mate, thereby passing on the allele to the next generation, which produces more individuals in the population with that allele. 16. The answer: The woman is: Dd The Man is: dd D d d Dd dd d Dd dd 50% of the offspring will have dimples. 17. Marriage between relatives which increases the potential of inheritance of a particular trait because there are fewer sets of ancestors. 18. The woman s genotype must be Dd. Her mother could only pass on a recessive allele since she did not have dimples. Since the woman has dimples, her other allele must be a D. The woman s father could either be Dd or DD. In either case he could pass on the D allele for dimples to the woman (his daughter). 19. The Law of Independent Assortment describes that homologous chromosomes randomly align on either side of the equatorial in meiosis (for example all of dad s chromosomes are not on one side and all of mom s chromosomes are not on the other. There is a mixture of mom and dad chromosomes on either side of the equatorial plate). 20. A dihybrid cross is when alleles of TWO traits are followed in a cross. 21. Answer: