Adapted from L. Miriello by S. Sharp
AP Biology
Chapter 14 Guided Reading Assignment
Name _________________________
1. Who were the two strong influences on Mendel’s education?
Christian Doppler and Franz Unger.
2. Define the following terms:
a. Character—Heritable feature
b. Trait—Variant for a character
c. True-breeding—Organisms that when they self-pollinate produce identical offspring.
d. Hybridization—Crossing of two true-breeding varieties.
e. P generation—Parental generation
f. F1 generation—First filial generation
g. F2 generation—Second filial generation
h. Alleles—alternative versions of a gene (purple vs white)
i.
Punnett Square—a handy diagrammatic device for predicting the allele composition
of offspring from a cross between individuals of known genetic makeup.
j.
Homozygous—identical alleles for the same gene
k. Heterozygous—to different alleles for the same gene.
l.
Phenotype—organisms traits (physical expression, although not always visible)
m. Genotype—genetic makeup
3. In your own words, what is Mendel’s Law of Segregation?
When alleles separate independently of each other (looked at a single trait, needed
heterozygous individuals)
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Adapted from L. Miriello by S. Sharp
4. Give an example of a monohybrid cross and a dihybrid cross.
Monohybrid Cross
Dihybrid Cross
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Adapted from L. Miriello by S. Sharp
5. What is the Law of Independent Assortment and how does this “law” relate to meiosis?
When allele pairs segregate independently from each other. (Chromosomes sort
independently from each other). For humans 8,388,608 combinations.
6. Write your own example for the Law of Independent Assortment.
Pea color allele segregates separately from seed shape alleles.
7. Define and then explain in your own words both the Rules of Multiplication and the Rules of
Addition.
Rule of multiplication—Method in which one determines the probability that two or more
independent events will occur together in some specific combination.
Rule of addition—Method in which one determines the probability that one of two
outcomes will happen (but not both at the same time) you simply add the probability of
each together.
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Adapted from L. Miriello by S. Sharp
8. Contrast codominance and incomplete dominance.
Co-dominance—The situation in which the phenotypes of both alleles are exhibited in
the heterozygote. No ‘blending’ of the trait. Example: speckled chicken.
Incomplete dominance—The blending of traits. Example, a red flower is crossed with a
white flower to produce a pink flower.
9. Does having a dominant allele mean that it will be found in greater frequency in the
population?
A dominant allele is the expressed phenotype (i.e. masks the recessive allele.) This
does not affect the frequency of the gene within the population. It is still an inherited
trait and will be passed to offspring according to the laws of genetics. It would only
increase in the population if it offered some type of evolutionary advantage.
10. What are multiple alleles?
When there are more than two alleles for a given trait. The ABO blood types have three
possible alleles. Each person will have TWO of those alleles
11. What does the term Pleiotropy mean?
When a single gene influences several distinct and unrelated phenotypic traits
Example: PKU (phenylketonuria). Can cause mental retardation and reduced hair and
skin pigmentation, and can be caused by any of a large number of mutations in a single
gene that codes for an enzyme (phenylalanine hydroxylase) that converts the amino
acid phenylalanine to tyrosine, another amino acid.
12. In your own words, explain epistasis.
phenomenon in which the expression of one gene depends on the presence of one or
more "modifier genes." A gene whose phenotype is expressed is called epistatic, while
one whose phenotype is altered or suppressed is called hypostatic
13. What would be your “clue” that a character would have polygenic inheritance pattern?
Continuous range of the trait is seen. For instance, in humans, hair color does not
exhibit a co-dominance pattern (Black, white, or black and white). In addition, hair color
does not exhibit a blending pattern (Black, white, or grey).
14. What is a pedigree and how does it help in our understanding of genetics?
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Diagram of a family tree showing the occurrence of heritable characters in parents and
offspring over multiple generations. The use of such a diagram can help determine if a
trait is autosomal or sex linked.
15. Describe and discuss the genetics of the following inherited disorders:
a. Cystic Fibrosis-- autosomal recessive genetic disorder that affects most critically the
lungs, and also the pancreas, liver, and intestine. It is characterized by abnormal
transport of chloride and sodium across an epithelium, leading to thick, viscous
secretions
b. Sickle cell disease-- autosomal recessive genetic blood disorder with overdominance,
characterized by red blood cells that assume an abnormal, rigid, sickle shape.
Sickling decreases the cells' flexibility and results in a risk of various complications.
The sickling occurs because of a mutation in the hemoglobin gene.
Sickle-cell anaemia is the name of a specific form of sickle-cell disease in which
there is homozygosity for the mutation that causes HbS. Sickle-cell anaemia is also
referred to as "HbSS", "SS disease", "haemoglobin S" or permutations thereof. In
heterozygous people, who have only one sickle gene and one normal adult
haemoglobin gene, it is referred to as "HbAS" or "sickle cell trait"
c. Achondroplasia-- common cause of dwarfism. It occurs as a sporadic mutation in
approximately 75% of cases (associated with advanced paternal age) or may be
inherited as an autosomal dominant genetic disorder.
d. Huntington’s disease-- neurodegenerative genetic disorder (caused by a lethal
dominant allele) that affects muscle coordination and leads to cognitive decline and
psychiatric problems. It typically becomes noticeable in mid-adult life. HD is the
most common genetic cause of abnormal involuntary writhing movement
16. Contrast amniocentesis and chorionic villus sampling
Chorionic villus sampling-- form of prenatal diagnosis to determine chromosomal or
genetic disorders in the fetus. It entails sampling of the chorionic villus (placental
tissue) and testing it for chromosomal abnormalities, usually with FISH or PCR. CVS
usually takes place at 10–12 weeks' gestation, earlier than amniocentesis or
percutaneous umbilical cord blood sampling. It is the preferred technique before 15
weeks
Amniocentesis-- prenatal diagnosis of chromosomal abnormalities and fetal infections,[2]
in which a small amount of amniotic fluid, which contains fetal tissues, is sampled from
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Adapted from L. Miriello by S. Sharp
the amnion or amniotic sac surrounding a developing fetus, and the fetal DNA is
examined for genetic abnormalities. This process can be used for prenatal sex
discernment and hence this procedure has legal restrictions in some countries
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