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UNIT 6 HEREDITY STUDY GUIDE
Biology
CONTENT GUIDE
(This includes the major concepts for which students will be responsible in this unit. Additional
content as studied in the unit under these major concepts may be included. Examples would
include information from labs, activities, diagrams, tables and charts. The student must also be
able to use the basic content to make applications, analyze, synthesize and evaluate information.)
I.
Classic Mendelian Genetics (p. 263)
A) Gregor Mendel is known as the father of genetics
B) Working vocabulary
1) Different forms of a gene are called alleles
2) Dominant – gene that will always show if present
3) Recessive – gene that will be hidden or masked when the dominant gene is present
4) Genotype – genes/alleles that an organism has for a trait
(a) Dominant homozygous (DD) vs. heterozygous (Dd) vs. recessive homozygous (dd)
(b) Genotypic ratio - # homozygous dominant : # heterozygous : # homozygous recessive
5) Phenotype – physical appearance of the organism (what it looks like)
(a) expresses (shows) the dominant trait or shows the recessive in its appearance
(b) Phenotypic ratio - # show the dominant trait : # show the recessive trait
C) Probability is the likelihood that a particular event will occur
1) The results of the first trial of a chance event do not affect the results of later trials of the same
event.
2) The probability of two or more independent events occurring together is the product of their
separate probabilities.
D) Punnett squares
1) Punnett squares are used to determine the possible genetic combinations between two parents.
2) Be able to complete Punnett squares including analyzing the gametes formed, giving
phenotypic and genotypic ratios as well as other probability questions.
E) Advanced Genetics
1) Two Factor Crosses – dihybrid crosses
(a) gametes formed, offspring produced
(b) phenotypic and genotypic ratios as well as other probability questions
2) Multiple alleles occur when there are more than two alleles for a certain trait.
(a) Chinchilla rabbits – four alleles for coat color
(b) Human blood groups – three alleles for blood type
3) Sex-linked traits
(a) Hemophilia - recessive
(b) Colorblindness - recessive
(c) Duchenne Muscular Dystrophy - dominant
4) Codominance occurs when both alleles contribute to the phenotype of an organism.
(a) Human blood groups – Type AB blood has both types of antigens
(b) Sickle-Cell Anemia – Heterozygote has sickle and normal shaped red blood cells
II. Human Genetics (p. 341)
A) Karyotypes are pictures of chromosomes arranged in homologous pairs (by size and shape) and
assigned a number.
1) Types of chromosomes:
(a) Autosomes - body/somatic chromosomes; pairs 1-22 in humans (44 chromosomes)
(b) Sex chromosomes – chromosomes that determine the sex of the individual; pair #22 in
humans (2 chromosomes), two types: X and Y, XX female, XY male
2) Be able to identify the following disorders by analyzing a karyotype:
(a) Down Syndrome – Three copies of chromosome 21
(b) Turner’s Syndrome – Female with only 1 X chromosome
(c) Klinefelter’s Syndrome – Male with XXY
Heredity Study Guide - Biology TEACHER (Revised June 21, 2007)
(printed 6/26/2017) p. 1
B) Pedigrees visually show the genetic relationships between family members. Students should be
able to create and analyze pedigrees for autosomal recessive, autosomal dominant, as well as sexlinked traits.
III. Applications of genetics in the real world (p. 318, 341)
A) Genetic screening involves DNA analysis for the discovery of certain DNA sequences that signal
the presence of a harmful allele in an unborn or newborn child.
B) DNA fingerprinting is used to identify individuals for paternity or criminal purposes.
C) The Human Genome Project is an effort to discover and analyze the human DNA sequence.
D) Gene therapy requires changing a faulty or missing gene by replacing it with a working copy.
E) Genetic engineering: cloning and transgenic organisms
F) Ethics
BIOLOGY OBJECTIVE AND TEKS
Objective 9: GENETICS
Interpret the role of genetics in determining heredity and as it applies to biotechnology.
Subobjective:
a)
b)
c)
d)
Review classical Mendelian genetics as necessary.
Apply Punnett squares and probability to find possible genotypes and phenotypes.
Predict possible genotypes in crosses involving sex-linked traits and multiple alleles
Use a pedigree chart to identify persons at risk for passing genetic traits to offspring (including sex-linked
traits and multiple alleles).
e) Analyze and identify karyotypes as normal or abnormal and recognize such abnormalities as Down, Turner’s
and Klinefelter’s.
f) Identify clinical tests and techniques for identification of genetic disorders such as ultrasound, amniocentesis,
and karyotyping.
g) Apply genetic knowledge to medical, technological and ecological issues.
TEKS:
(6A) Describe components of deoxyribonucleic acid (DNA), and illustrate how information for specifying the traits of
an organism is carried in the DNA.
(6C) Identify and illustrate how changes in DNA cause mutations and evaluate the significance of these changes.
(6D) Compare genetic variations observed in plants and animals.
(6F) Identify and analyze karyotypes.
NOTES:
1) Although the TEKS do not seem to emphasize classical genetics, the TAKS Information Booklet clearly
indicates that students must be able to work genetics problems, including crosses, Punnett squares,
discerning probability and predicting outcomes. Included are concepts of genotypes, phenotypes,
sex-linked traits, multiple alleles and multi-hybrid crosses.
2) TAKS also includes application of genetics to medical, ecological and technological issues, as well as
genetic engineering, the Human Genome Project and other biotechnology issues.
SAMPLE TEST QUESTIONS
(These are samples of the type of questions which might be on the test. Questions may require students to
use the basic content to make applications, analyze, synthesize and evaluate information. Tests contain
unit content questions as well as general scientific processing questions.)
1. In certain breeds of dogs, deafness is due to a recessive allele (d) of a particular gene, and normal
hearing is due to its dominant allele (D). What percentage of the offspring of a normal heterozygous (Dd)
dog and a deaf dog (dd) would be expected to have normal hearing?
A.
B.
C.
D.
0%
25%
50%
100%
Heredity Study Guide - Biology TEACHER (Revised June 21, 2007)
(printed 6/26/2017) p. 2
2. In humans, the gene for polydactyly (having extra fingers or toes) is dominant over the gene for the
normal number of digits. If parents who are both homozygous dominant for polydactyly have four children,
how many of these children would most likely have extra fingers or toes?
A.
B.
C.
D.
0
2
3
4
3. A homozygous condition resulting in the formation of abnormal hemoglobin that distorts certain blood
cells is known as
A.
B.
C.
D.
hemophilia
phenylketonuria
Tay-Sachs
sickle-cell anemia
EAR LOBE PEDIGREE
Figure 26
4. Look at Figure 26. The genotype of individual 1 could be
A.
B.
C.
D.
EE, only
Ee, only
ee
EE or Ee
5. Look at Figure 26. The genotype of individual 2 could be
A.
B.
C.
D.
EE, only
Ee, only
ee
EE or Ee
6. Which of these is not an inherited trait?
A.
B.
C.
D.
Eye color
Tendency to grow hair on fingers
Type of blood
Style of handwriting
Heredity Study Guide - Biology TEACHER (Revised June 21, 2007)
(printed 6/26/2017) p. 3
7. When Mendel crossed purebred tall plants with purebred short plants, all the offspring were
A.
B.
C.
D.
homozygous short.
homozygous tall.
heterozygous tall.
purebred like their parents.
8. A rabbit with white fur was crossed with a rabbit with black fur. The cross produced offspring with black
and white fur. This type of inheritance is known as
A.
B.
C.
D.
dihybrid recessive.
dominance.
codominance.
multiple alleles.
9. Organisms that have two identical alleles for a particular trait are said to be
A.
B.
C.
D.
hybrid.
homozygous.
heterozygous.
dominant.
10. One plant has the genotype TT. The second plant has the genotype Tt. The two plants would
A.
B.
C.
D.
have the same phenotype.
have different phenotypes.
have the same genotype.
have all dominant alleles.
11. All of these characterize most laboratory accidents except
A.
B.
C.
D.
carelessness
lack of attention
inappropriate behavior
reduced risk-taking
Heredity Study Guide - Biology TEACHER (Revised June 21, 2007)
(printed 6/26/2017) p. 4
GENDER IN SEA TURTLES
Figure 6
12. According to this information, the sex of developing sea turtles is determined by
A.
B.
C.
D.
clutch size
incubation temperature
available seawater
sand composition
TRIBBLE TRAITS
Tribble Traits
Gene
S
s
L
l
Trait
Solid coat (dominant)
Plaid coat (recessive)
Long fur (dominant)
Short fur (recessive)
SSLI (male) x Ssll (female)
13. What trait will most likely be observed in all offspring of the above set of parents?
A.
B.
C.
D.
Solid coat color
Plaid coat color
Long fur
Short fur
14. A tribble with the genotype SsLL is crossed with a tribble with the genotype ssLl. How many different
genotypes can be expressed in the offspring?
A.
B.
C.
D.
1
2
3
4
Heredity Study Guide - Biology TEACHER (Revised June 21, 2007)
(printed 6/26/2017) p. 5
KARYOTYPES
15. A karyotype such as the one shown above shows which of the following?
A.
B.
C.
D.
autosomes
sex chromosomes
homologous chromosomes
all of the above
16. Genes in sex-linked traits are carried on the
A.
B.
C.
D.
X chromosome only
Y chromosome only
X and Y chromosome
autosomes
17. The probability that a human sperm cell will carry a Y chromosome is:
A.
B.
C.
D.
0%
25%
50%
100%
18. Which of the genotypes would have the same blood type?
A.
B.
C.
D.
IAIA and IAi
IBIB and IAIB
IBi and ii
IAIA and IAIB
Heredity Study Guide - Biology TEACHER (Revised June 21, 2007)
(printed 6/26/2017) p. 6
PEDIGREE INHERITANCE
19. The pedigree above shows that a certain disease was found equally in males and females and that all
children who had the disease had at least one parent who also had the disease. The gene coding for the
disease is probably
A.
B.
C.
D.
autosomal recessive
autosomal dominant
sex-linked recessive
sex-linked dominant
20. Hemophilia is more common in males than in females because
A.
B.
C.
D.
fathers can only pass the allele for hemophilia to their sons.
mothers cannot pass the allele for hemophilia to their daughters.
the allele for hemophilia is dominant and located on the Y chromosome.
the allele for hemophilia is recessive and located on the X chromosome.
Answer Section
1.
2.
3.
4.
5.
6.
7.
8.
9.
10.
11.
12.
13.
14.
15.
16.
17.
18.
19.
20.
ANS:
ANS:
ANS:
ANS:
ANS:
ANS:
ANS:
ANS:
ANS:
ANS:
ANS:
ANS:
ANS:
ANS:
ANS:
ANS:
ANS:
ANS:
ANS:
ANS:
C
D
D
D
C
D
C
C
B
A
D
B
A
D
D
A
C
A
B
D
OBJ:
OBJ:
OBJ:
OBJ:
OBJ:
OBJ:
OBJ:
OBJ:
OBJ:
OBJ:
OBJ:
OBJ:
OBJ:
OBJ:
OBJ:
OBJ:
OBJ:
OBJ:
OBJ:
OBJ:
9
9
9
9
9
9
9
9
9
9
1
1
9
9
9
9
9
9
9
9
STO:
STO:
STO:
STO:
STO:
STO:
STO:
STO:
STO:
STO:
STO:
STO:
STO:
STO:
STO:
STO:
STO:
STO:
STO:
STO:
6D
6D
6D
6D
6D
6D
6D
6D
6D
6D
1A
2C
6D
6D
6D
6D
6D
6D
6D
6D
Heredity Study Guide - Biology TEACHER (Revised June 21, 2007)
(printed 6/26/2017) p. 7