Chapter 11 Study Guide - Mrs. Mabe's Science Page



STUDY GUIDE CHAPTER 11 AND 14 ANSWER KEY

Chapter 11

1. Who is Mendel and what did he do?

• Father of Genetics – Experimented with pea plants and discovered major laws of genetics that hold true today, such as Inheritance of Traits, Principle of Dominance, Law of Independent Assortment.

2. What is the Law of Dominance?

• One trait is sometimes stronger than another and always shows up if present.

3. What is the Law of Independent Assortment?

• Genes for different traits can segregate (or separate) independently during the formation of gametes.

4. What is a True-Breeding plant?

• A plant that only has one type of allele to give (they are homozygous) for instance TT = two alleles for tall or tt = two alleles for short.

5. What are Traits (or Alleles)? Different forms of a gene. For instance, the gene for hair color in humans has many different alleles or traits that could be expressed: blond, brown, black, red, etc.

6. How are Dominant traits represented in a Punnett square? What about Recessive traits?

• Dominant is expressed with a capital letter and recessive with a lowercase letter.

7. In a genetic cross what is the P generation? What about the F1 and F2 generation?

• The P generation is the parents (they go on the outside of the punnett square.

• The F1 generation are the first round of offspring created (they are found inside the square, in this case all four are Tt)

• If you were to do another cross with the offspring, crossing Tt with Tt, they would become your new parents (or the P2 generation) and their offspring would be the F2 generation.

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8. When you do a Punnett square what does the inside of the square represent?

• The offspring

9. What do the words Genotype and Phenotype mean?

• Geneotype refers to the actual genes (the letters) and uses the words heterozygous and homozygous to describe the letters. So the genotype for Tt would be heterozygous Tall (meaning there are two different letters and it codes for tall).

• Phenotype refers to how an organism looks (its physical appearance). So the phenotype for Tt would be Tall.

10. What is the difference in the terms Homozygous and Heterozygous and when do you use these words - when describing genotype or phenotype?

• Homozygous means you have two of the same letter TT or tt. Heterozygous means you have two different types of letters Tt (one is uppercase and one is lowercase). They are used to describe genotype.

Chapter 14

1. What is a karyotype used for?

• To look at the chromosomes to see if they are normal in number – there should be 46 (23 pairs). If there are too many or too few it reveals that there is a genetic disorder.

2. What is a pedigree chart, and what is it used for?

• A chart that shows how a genetic disorder has passed through generations of a family.

3. What causes cystic fibrosis?

• A recessive gene on chromosome 7 that makes the person unable to make a protein needed for normal breathing. It creates thick mucus in these individuals.

4. What is the difference between the red blood cells of a normal person and someone with sickle cell disease?

• A person with sickle cell disease has misshaped red blood cells that stick together and clog the blood vessels and do not carry oxygen as well. It causes pain and tissue damage.

5. Why are people who are heterozygous for the sickle cell disease usually healthy?

• They have enough healthy red blood cells to carry oxygen effectively in most cases, unless they engage in strenuous activity.

6. Why is colorblindness more prevalent in males than females?

• Colorblindness is a sex-linked disease carried on the X chromosome. Males only have one X chromosome (from their mother), and if it codes for colorblindness they are affected. A female must get a bad X from Mom and Dad to be affected.

7. What do Barr bodies do?

• They are thickened areas on an X chromosome that are turned off (in females). They allow for an X chromosomes (with a disorder present or other trait) to be inactiviated (or turned off) so that the disorder is not expressed. For instance, a female with one bad X chromosome for a sex-linked disorder can form a Barr Body where the bad gene is located and it turns off the bad gene. The information on the other good X chromosome is expressed instead.

8. Can a baby be born without an X chromosome? Why or why not?

• No scientists believe that the X chromosome has information necessary for life, since no one has ever been born without one.

9. What are genetic markers used for?

• To mark a gene that is being transferred from one organism to another through genetic engineering. For example in human insulin, a human gene with instructions for making insulin is marked with a marker that glows under UV light. If the gene is successfully placed in a bacterial cell during the process of transformation the bacterial cells should glow. Markers help us make sure that we achieved what we wanted.

10. What are autosomal chromosomes, and how many do you have?

• All of the choromsomes in your body are autosomes except for the sex chromosomes (which determine sex). You have 44 (22 pairs) in every cell.

11. What blood type can a person with type O receive in a blood transfusion? What about people with type A or B? Is one blood group dominant over another?

• A person with type O can only receive type O blood.

• A person with type A can receive type A and type O blood.

• A person with type B can receive type B and type O blood.

• Type A and B are codominant and O is recessive.

12. What is phenylketonuria? What are people with this disorder unable to do?

• A recessive genetic disorder (also known as PKU) in which a person in unable to break down a protein frequently found in milk and other products.

13. What is a sex-linked genetic disorder? Which chromosome (the one passed from the mother or the one from the father) usually carries the sex-linked genetic disorder?

• A genetic disorder liked to the sex chromosomes (usually to the X chromosome).

• If you are male and you have a sex-linked disorder found on the X chromosome, then it definitely came from the mother because a male has XY for the sex chromosomes and the Y had to have come from the Dad because Mom only has XX to give.

• If you are female you xould have to get a bad X chromosome from both parents to have this type of disorder.

14. Does the mother or the father usually pass on the genes for hemophilia to a male child? Why?

• Hemophilia is a sex-linked disorder on the X chromosome, so the mother usually passes it on to a male child. See above for further explanation

15. What is Turner’s syndrome?

• It is a chromosomal disorder (affecting the number of chromosomes) and it affects females. A female will have too few X chromosomes in this disorder. Their genotype will be XO. They are unable to reproduce and have other physical symptoms (thickened short neck, short stature, etc.)

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