Chapter 21 - Mendelian Genetics

Chapter 21 - Mendelian Genetics


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It's recommended you read "How to Approach Genetics Problems" prior to completing this study guide.

Terms to Know in This Chapter:

self-fertilization [fur teh leh ZAY shun]

cross fertilization
receptacle (sing.) pre SEP tah kul] pistil (sing.) [PISS tul]
stigma (sing.) [STIG mah]
stigmata (pl.) [stig MAH tah] 		style (sing.)
ovary (sing.) [OH vah ree]
ovaries (pl.) [OH vah reez]

sepal (sing.) [SEE pul]

calyx (sing.) [KAY licks]
calices (pl.) [KAY leh seez]

petal (sing.) [PET ul]
corolla (sing.) [co ROLL ah]
corollae (pl.) [co ROLL ee]		 stamen (sing.) [STAY men]
anther (sing.) [AN thur]

filament (sing.) [FILL ah ment]
chromosome (sing.) [CROW moe zome]

locus (sing.) [LOW kuss]
loci (pl.) [LOW kie] [LOW sigh]
allele (sing.) [ah LEEL] homozygous [hoe moe ZIE gus]
heterozygous [het er oh ZIE gus] dominant
recessive phenotype (sing.) [FIEN oh type]

genotype (sing.) [GIN oh type]

 parent generation (F1)
first filia generation (F1) [FILL ee ul]

gamete (sing.) [gah MEET]
sperm (sing. and pl.) Punnet square [PUN it]
monohybrid cross [moe no HIGH brid] dihybrid [die HIGH brid]
trihybrid [try HIGH brid] test or back cross
incomplete dominance multiple alleles
antigen (sing.) [AN teh gin] antibody (sing.) [AN teh body]
antibodies (pl.) [AN teh bod eez]
agglutination [ah GLUE teh NAY shun] blood type A
blood type B blood type AB
blood type O universal donor
universal recipient Rh factor
Rh plosive Rh negative
erythroblastosis fetalis [eh RYTH row blass TOE siss] [fee TAL iss]

placenta (sing.) [plah SIN tah]
placentae (pl.) [plah SIN tee]

umbilical cord [um BILL ah kul] penetrance [PEN eh trunz]
expressivity [ex press IVE eh tee]  

People You Need to Know:

Gregor Mendel


What You Need to Know:

You should be able to:

  1. outline the major contribution of Gregor Mendel to the field of genetics and explain how he was at a disadvantage in his endeavors,
  2. outline the breeding pattern of two pure strains (homozygous) for a single trait in pea plants, i.e. flower color, and show what occurs on the chromosomes,
  3. outline the breeding pattern of a heterozygous trait for a pea plant, i.e. flower color, and show what occurs on the chromosomes,
  4. identify the parts of a flower and explain what is meant by self-fertilization and cross fertilization,
  5. give the collective terms for sepals and petals,
  6. predict the outcome (phenotypic and genotypic ratios) of a monohybrid cross, heterozygous for a single, dominant-recessive trait,
  7. predict the outcome (phenotypic and genotypic ratios) of a dihybrid cross, heterozygous for a two, dominant-recessive traits,
  8. predict the number of different gametes in a monohybrid cross, heterozygous for the trait as well as a dihybrid cross, and trihybrid cross, heterozygous for all the traits,
  9. explain the purpose of a test or back cross,
  10. explain how an incompletely dominant cross differs from a dominant-recessive trait,
  11. work problems dealing with incompletely dominant crosses,
  12. explain the terms penetrance and expressivity,
  13. distinguish between an allele and a gene,
  14. distinguish between a locus and a gene,
  15. explain what is meant by multiple alleles,
  16. distinguish between chromosomes and homologs,
  17. explain blood types in terms of antigens and antibodies, and be able to predict which donor can give blood to which recipient,
  18. name the blood types considered to be the universal donor and universal recipient,
  19. explain what is meant by Rh factor and describe how it is inherited, and
  20. explain what conditions lead to erythroblastosis fetalis.

Exercises: Fill in the Blank.

  1. The is the name of the female reproductive structure of a flower composed of a stigma, style, and ovary.
  2. What is the collective term for the sepals of a flower?
  3. Pollen is located in the of the stamen of a flower.
  4. If a gene on a chromosome says "A" and the allele of that gene on the homolog says "A", then we say the chromosome and homolog are . (homozygous, heterozygous)
  5. The genotype "Aa" would be said to be an example of a(n) trait (dominant-recessive, incompletely dominant)
  6. A point on a chromosome is called a while the unit of heredity on a chromosome is called a .
  7. The collective term for sperm cells or egg cells is: .
  8. The genotype "AaBbCC" represents a cross. (mono-, di-, or tri-)
  9. Blood types are an example of alleles.
  10. Fill in the chart from left to right, top to bottom with either "+" signs or "-" signs to indicate clumping or not clumping of cells, respectively.
    DONOR DONOR DONOR RECIP RECIP RECIP RECIP
    Blood Type Antigen Antibody A B AB O
    A A anti B
    B B anti A
    AB A&B none
    O none anti A and
    anti B
  11. The only way one can have the potential for erythroblastosis fetalis is for the mother to be , the father to be and the fetus to be . (positive, negative)
  12. The percent of the population that expresses a trait is referred to as while the degree to which someone has a trait, i.e. how "blue" someone's eyes are, is called .
  13. What is the phenotypic ratio of a monohybrid cross between two, heterozygous parents expressing the trait "tall" as dominant?
  14. What is the genotypic ratio of a cross between two pink morning glories? (incomplete dominance)
  15. How many different gamete combinations are possible for the genotype AABbCc?
  16. Can a person with "O" blood donate blood to a person with "B" blood? (Yes or No)
  17. The ability to roll your tongue is a simple, dominant trait. What would be the expected phenotypic ratio if you crossed a person heterozygous for the trait with a person homozygous recessive for the trait?

      Exercises. Multiple Choice. Select the best answer.

      1. Which of the following indicates an incompletely inherited trait?
         (1) AA
         (2) Aa
         (3) ab
         (4) aa
         (5) AaBb

      2. Which of the following is an example of a dihybrid, homozygous individual?

        (1) AA
         (2) AaBb
         (3) abyz
         (4) BBCC
         (5) BbCc

      3. How many different gametes can be obtained from the genotype AABbCC?
         (1) one
         (2) two
         (3) four
         (4) eight

        (5) sixteen

      4. If a mother whose blood type is AB, has a child with a blood type of AO, accuses a man of blood type OO as the father of her child, is she telling the truth?

         (1) yes, no doubt
         (2) no, cannot be the father of the child
         (3) perhaps, he could be the father of the child
         (4) there is no way the child can be AO blood type

        (5) there is no way the man can be OO blood type

      5. If someone were to tell you that there are three heights in a corn plant, tall, medium, and short, what can you determine from this?
         (1) Plant height in corn is determined by a simple, dominant recessive trait.
         (2) This is an example of a dihybrid cross.
         (3) This is an example of a trihybrid cross.
         (4) This is an example of a back cross.
         (5) Plant height in corn is an incompletely inherited trait.