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Chapter 7 Study Guide
Inheritable Genetic Traits
REGULAR BIOLOGY
1. A ________________ is a graphic representation of genetic inheritance
It is a diagram made up of a set of symbols that identify males and females, individuals
affected by the trait being studied, and family relationships
2. In a pedigree:
a. Carrier: __________
b. females are represented by _________
c. males are represented by _________
d. affected traits are represented by _________
f. death is represented by __________
g. Mating is represented by __________
h. Siblings: ____________
3. Generations are marked by using a ______________
Individuals are in order based on ________________
Simple Recessive Heredity
4. Most genetic disorders are caused by ________________
5. __________________ (CF) is a fairly common genetic disorder among white Americans
About 1 in 28 white Americans carries the recessive allele & 1 in 2500 children born to
white Americans inherits the disorder.
Due to a defective protein in the plasma membrane, cystic fibrosis results in the
formation and accumulation of thick mucus in the lungs and digestive tract
6. _______________ disease is a recessive disorder of the central nervous system among
the Jewish people in the U.S. & eastern European descent
A recessive allele results in the absence of an enzyme that normally breaks down a lipid
produced and stored in tissues of the central nervous system
Because this lipid fails to break down properly, it accumulates in the cells
Symptoms are not visual until around ______________ of age. The child gradually
becomes blind and helpless, develops seizures, and eventually paralyzed. The child dies
by the age of ___________. No treatment or cure but can be detected by amniocenteses
7. __________________ aka phenylketonuria is a recessive disorder that results from the
absence of an enzyme that converts one amino acid, phenylalanine, to a different amino
acid, thyrosine. The by-products of phenylalanine accumulates in the body and results in
severe damage to the central nervous system.
8. List some examples of simple dominant heredity
9. ___________________ is a lethal genetic disorder caused by a rare dominant allele. It
results in a breakdown of certain areas of the brain. Usually, dominant allele with such
severe effects would result in death before the affected individual could have children
and pass the allele on to the next generation. But because the onset of Huntington’s
disease usually occurs between the ages of 30 and 50, an individual may already have had
children before knowing whether he or she is affected. Leads to progressive degeneration
of brain cells, which causes muscle spasms, personality disorders & death in ________
years from onset
10. When traits are inherited in an incomplete dominance pattern, the presence of a
__________ appears.
Work the following problems for understanding
11. If a homozygous red-flowered snapdragon plant (RR) is crossed with a homozygous
white-flowered snapdragon plant (WW), Show the results that the F1 offspring will have
pink flowers
12. Codominant alleles cause the phenotypes of both homozygotes to be produced in
heterozygous individuals. In codominance, both alleles are expressed ____________
Work the following problems for understanding
13. Complete the Punnett square for a cross between a black chicken (BB) and a white
chicken (WW). Give the phenotype of the offspring in the F1 generation.
Key
BB - black
WW- white
BW- checkered
14. In an individual who is homozygous for the sickle-cell allele, the oxygen-carrying protein
hemoglobin differs by one amino acid from normal hemoglobin
This defective hemoglobin forms crystal-like structures that change the shape of the red
blood cells. Normal red blood cells are disc-shaped, but abnormal red blood cells are
shaped like a ______________
15. The __________ blood group is a classic example of a single gene that has multiple
alleles in humans.
16. What is the term that describes the following:
a. 22nd pair of chromosomes:
b. 23rd pair of chromosomes:
17. If you are _________, your 23rd pair of chromosomes are homologous, _____
18. If you are _________, your 23rd pair of chromosomes ______, look different
19. Traits controlled by genes located on sex chromosomes are called ____________
The alleles for sex-linked traits are written as superscripts of the X or Y chromosomes
Because the X and Y chromosomes are not homologous, the Y chromosome has no
corresponding allele to one on the X chromosome and no superscript is used
Work the following problems for understanding
20. If a female fruit fly heterozygous for red eyes (XRXr) crossed with a white-eyed male
(XrY), what are the genotypes of the offspring? What is the % of the offspring that will
have white eyes?
21. The pattern of sex-linked inheritance is explained by the fact that males, who are XY,
pass an X chromosome to each __________ and a Y chromosome to each _________
22. Traits that are governed by X-linked recessive inheritance in humans are
1.
2.
3.
23. People who have _______________________ can’t differentiate between these two
colors. It is caused by the inheritance of a recessive allele at either of two gene sites on
the X chromosome
24. _________________ is an X-linked disorder that causes a problem with blood clotting.
About one male in every 10 000 has hemophilia, but only about one in 100 million
females inherits the same disorder. Males inherit the allele on the X chromosome from
their carrier mothers. One recessive allele for hemophilia will cause the disorder in males
Females would need two recessive alleles to inherit hemophilia
25. In the early 1900s, the idea that _____________ inheritance occurs in humans was first
tested using data collected on skin color. Scientists found that when light-skinned people
mate with dark-skinned people, their offspring have intermediate skin colors
26. This chart of chromosome pairs is called a ____________, and it is valuable in
identifying unusual chromosome numbers in cells
27. List some inheritable disorders that can be detected with a karyotype
1.
2.
3.
4.
5.