Download BIOLOGY I Study Guide # 5: Topic – Genetics 1 Name: Define:

BIOLOGY I Study Guide # 5: Topic – Genetics 1
Name: ____________________
Biology Textbook pg. 262 – 285, 340 - 365
I. Mendelian Genetics (pg. 263 – 272)
Define:
a. genetics: ____________________________________________________________________________________
b. fertilization: _________________________________________________________________________________
c. true-breeding: ________________________________________________________________________________
d. trait: ________________________________________________________________________________________
e. hybrid: ______________________________________________________________________________________
f. gene: ________________________________________________________________________________________
g. allele: ________________________________________________________________________________________
h. segregation: ___________________________________________________________________________________
i. phenotype: ____________________________________________________________________________________
j. genotype: ______________________________________________________________________________________
k. heterozygous: __________________________________________________________________________________
l. homozygous: ___________________________________________________________________________________
Matching: On the lines provided, write the letter of the definition of each term.
_____ 1. genetics
a. likelihood that something will happen
_____ 2. trait
b. process by which the number of chromosomes per cell is cut in half
_____ 3. hybrid
c. specific characteristic
_____ 4. gene
d. offspring of crosses between parents with different traits
_____ 5. allele
e. containing a single set of chromosomes
_____ 6. gamete
f. sex cell
_____ 7. probability
g. factor that determines traits
_____ 8. Punnett square
h. diagram showing possible gene combinations
_____ 9. haploid
i. the scientific study of heredity
_____ 10. meiosis
j. form of a gene
Explain the following principles of inheritance according to Gregor Mendel:
1. Principle of dominance: __________________________________________________________________________
________________________________________________________________________________________________
2. Principle of segregation: __________________________________________________________________________
________________________________________________________________________________________________
3. Principle of independent assortment: _______________________________________________________________
________________________________________________________________________________________________
Complete the following:
1. Circle the letter of each sentence that is true about Mendel’s principles.
a. The inheritance of biological characteristics is determined by genes that are passed from parents to their offspring.
b. Two or more forms of the gene for a single trait can never exist.
c. The copies of genes are segregated from each other when gametes are formed.
d. The alleles for different genes usually segregate independently of one another.
2. When two or more forms of the gene for a single trait exist, some forms of the gene may be _______________
and others may be _________________.
3. Although organisms with the same physical characteristics have the same ________________, they might have
different ________________, or genetic makeup.
4. When Mendel allowed the tall F1 pea plants (Tt) to self-pollinate,
a. some of the offspring were short. b. the offspring were of medium height.
c. all of the offspring were tall.
5. Two plants with the genotypes TT and Tt
a. would have the same phenotype.
b. would have different phenotypes.
c. have all dominant alleles.
6. In humans, being a tongue roller (R) is dominant over non-roller (r). A man who is a non-roller marries a woman who
is heterozygous for tongue rolling.
Father’s phenotype ________
Father’s genotype ________
Mother’s phenotype _________
Mother’s genotype _________
What is the probability of this couple having a child who is a tongue roller? ________
Show the cross using the Punnett square provided.
7. In guinea pigs, the allele for a rough coat (R) is dominant over the allele for a smooth coat (r). A heterozygous guinea
pig and a homozygous recessive guinea pig have a total of nine offspring. Explain how all nine offspring can have smooth
coats. ___________________________________________________________________________________________
__________________________________________________________________________________________________
__________________________________________________________________________________________________
8a. In a two-factor cross, Mendel followed _______ different genes as they passed from one generation to the next.
8b. Write the genotypes of the true-breeding plants that Mendel used in his two-factor cross.
Phenotype
Genotype
a. round yellow peas
___________
b. wrinkled green peas
___________
8c. Circle the letter that best describes the F1 offspring of Mendel’s two-factor cross.
a. Homozygous dominant with round yellow peas
c. Heterozygous dominant with round yellow peas
b. Homozygous recessive with wrinkled green peas
d. Heterozygous recessive with wrinkled green peas
8d. How did Mendel produce the F2 offspring? ________________________________________________________
8e. Complete the Punnett square below to show the predicted results of
Mendel’s two-factor cross.
8f. What were the phenotypes of the F2 generation that Mendel
observed? ________________________________________________
________________________________________________________
________________________________________________________
8g. What did Mendel observe in the F2 offspring that showed him that
the alleles for seed shape segregate independently of those for seed
color? ___________________________________________________
________________________________________________________
________________________________________________________
________________________________________________________
________________________________________________________
V. Patterns of Inheritance (pg. 272 – 274)
1. What is the difference between a heterozygous phenotype produced by incomplete dominance and a heterozygous
phenotype produced by codominance? _________________________________________________________________
__________________________________________________________________________________________________
__________________________________________________________________________________________________
2. Complete the table of the different patterns of inheritance.
Type
Description
Examples
One allele is not completely dominant over another.
The heterozygous phenotype is somewhere in
between the two homozygous phenotypes.
Both alleles contribute to the phenotype of the
organism.
Genes have more than two alleles.
Two or more genes control a trait.
3. List three criteria Thomas Hunt Morgan was looking for in a model organism for genetic studies.
a. _______________________________________________________________________
b._______________________________________________________________________
c._______________________________________________________________________
4. Characteristics are determined by interaction between genes and the _____________________________.
VI. Linkage and Gene maps (pg. 279-280)
1. Linked genes
a. are never separated.
b. assort independently.
c. are on the same chromosome.
d. are always recessive.
2. Explain why it is chromosomes, not individual genes, that assort independently: _____________________________
________________________________________________________________________________________________
3. Which of the following shows the relative locations of each known gene in an organism?
a. polygenic trait
b. gamete
c. Punnett square
d. gene map
4. Gene maps are based on
a. the frequencies of crossing-over between genes.
b. independent assortment.
c. genetic diversity.
5. If two genes are on the same chromosome and rarely assort independently,
a. crossing-over never occurs between the genes.
c. the genes are probably located far apart from each other.
b. crossing-over always occurs between the genes.
d. the genes are probably located close to each other.
6. Explain how linkage is used to make gene maps. ___________________________________________________
_____________________________________________________________________________________________
_____________________________________________________________________________________________
_____________________________________________________________________________________________
7. Three genes, stumpy (S), mottled (M), and pale (P) are found on the same chromosome in a newly discovered
species of fly. A preliminary gene map places gene S in the middle, with M and P on opposite sides. The frequency
of genetic recombination between genes M and S is 5%, which means that a cross-over occurs between these two
genes in meiosis 5% of the time (one gamete in 20 has a cross-over). The frequency between genes S and P is 8%.
Which gene is closer to S – gene P or gene M? _________________
VII. The Human Genome (pg 341 – 360)
1. Define:
a. karyotype: __________________________________________________________________________________
b. sex chromosome: ____________________________________________________________________________
c. autosome: __________________________________________________________________________________
d. pedigree chart: _______________________________________________________________________________
e. sex-linked genes: _____________________________________________________________________________
f. nondisjunction: _______________________________________________________________________________
2. How many chromosomes are shown in a normal human karyotype?
a. 46
b. 23
c. 44
3. In humans, a male has
a. two X chromosomes.
b. one X chromosome and one Y chromosome.
c. two Y chromosomes.
4. Human females produce egg cells that have
a. one X chromosome.
b. two X chromosomes.
c. one X or one Y chromosome.
5. A pedigree can be used to
a. determine whether an allele is dominant or recessive.
b. show how a trait is passed from one generation to the next.
c. determine whether a trait is inherited.
d. all of the above
6. The pedigree below (Figure 1) shows the inheritance of free earlobes and attached earlobes in five generations of a
family. Attached earlobes is caused by a recessive allele (f).
a. Is individual 2 in Figure 1 homozygous or
heterozygous for free earlobes? Explain.
_________________________________________
_________________________________________
_________________________________________
_________________________________________
b. In Figure 1, how many children of
individuals 4 and 5 have attached earlobes?
_________________
c. Can you be certain of the genotype of individual 5 in Figure 1? Explain.
_______________________________________________________________________________________
_______________________________________________________________________________________
d. Predict the genotype and phenotype of individual 14 in Figure 1. ___________________________________
e. In Figure 1, are any of the descendents of individuals 1 and 2 homozygous for free earlobes? Explain your
answer. ________________________________________________________________________________
_______________________________________________________________________________________
_______________________________________________________________________________________
7. What does it mean when a trait is said to be sex-linked?
__________________________________________________________________________________________________
__________________________________________________________________________________________________
8. Why are sex-linked diseases more common in males than in females?
__________________________________________________________________________________________________
__________________________________________________________________________________________________
9. Explain why the father of a girl who is colorblind must also be colorblind.
__________________________________________________________________________________________________
__________________________________________________________________________________________________
10. What occurs during nondisjunction? _____________________________________________________________
_____________________________________________________________________________________________
11. A man who does not have hemophilia and a woman who is a carrier of the disorder have a son. What is the
probability that their son has hemophilia? Explain or show.
_____________________________________________________________________________________________
_______________________________________________________________________________________
12. Scientists test for alleles that cause human genetic disorders by
a. making karyotypes.
b. making DNA fingerprints.
c. using DNA probes.
13. The Human Genome Project is an attempt to
a. make a DNA fingerprint of every person’s DNA.
b. analyze the human DNA sequence.
c. cure human diseases.
14. The purpose of gene therapy is to
a. cure genetic disorders.
b. determine the sequences of genes.
c. search for genes on chromosomes.
15. The sequencing of human chromosomes 21 and 22 showed that
a. some regions of chromosomes do not code for proteins.
b. all of the DNA of chromosomes codes for proteins.
c. different chromosomes have the same number of genes.
16. Which of the following form(s) a Barr body?
a. the Y chromosome in a male cell
b. the X chromosome in a male cell
c. one of the X chromosomes in a female cell
17. Because the X chromosome contains genes that are vital for normal development, no baby has been born
a. with one X chromosome.
c. without an X chromosome.
b. with three X chromosomes.
d. with four X chromosomes.
18a. There are ___________________ alleles for the ABO blood group. They are ______, ______, ______
18b. Is it possible for a person with blood type alleles IA and IB to have blood type A? Explain.
_____________________________________________________________________________________________
19. What type of picture would a biologist look at to determine whether a fetus has Down syndrome? What abnormality
would he find out?
_____________________________________________________________________________________________
_____________________________________________________________________________________________
20. One example of a sex-linked disorder is
a. sickle cell disease.
b. hemophilia
c. Down syndrome.
d. Tay-Sachs disease.