Biology Chapter 8
Chromosomes that are NOT involved in determining gender are known as
autosomes
Most inherited human genetic disorders are inherited as what alleles
recessive
Which of the following statements about homologous chromosomes is true?
they contain the same genes in the same location
In a karyotype of a male, which of the following would indicate an abnormality?
three copies of chromosome 22
In which of the following situations would looking at a pedigree be most useful?
three young boys who are first cousins show symptoms of a neurological disorder
On chromosomes within an individual, there are how many alleles for a given gene found on what chromosome?
two; homologous
What information is NOT visible in a karyotype
whether the individual carries genetic mutations
Humans have how many pairs of homologous chromosomes
23
Sickle-cell disease is an inherited chronic blood disease caused by an autosomal recessive allele. Suppose a man who is homozygous recessive for the sickle-cell gene fathers a child by a woman who is a carrier for sickle-cell. What are the chances their children will exhibit the disease?
50 percent
Amoung children with parents who are both carriers of Tay-Sachs, an autosomal recessive disorder, chances are that
50 percent will be carriers
A person is genetically XX and develops as a male. How can this be explained?
A piece of a Y chromosome has become attached to one of the X chromosome
If a genetic disorder is caused by a dominant allele, individuals with which of the following genotypes would be affected by the disorder
AA and Aa
Which of the following must be true for a woman who is heterozygous for a given gene?
All of her eggs will contain one allele or the other, but not both alleles
Both members of a couple are carriers for a recessive disease allele. If the couple has four children., which of the following statements must be true?
Fifty percent of the children could be carriers of the disease
During cell division a piece of a chromosome breaks off and reattaches to the same chromosome, but the piece is now in reverse order. How would this abnormality affect the chromosome?
Genes in the section that was inverted could lose normal function
Because an individual with an XX genotype is a female, is an individual with an XO ( no sex chromosome) a male?
No, because the Y chromosome contains the gene that makes an embryo male
What information in a pedigree would indicate a condition is likely dominant?
Non of the affected individuals have unaffected parents
In humans, the "master sex switch" that determines whether an embryo will become a male is the
SRY gene
The gene for a certain sex-linked trait is found only on the Y chromosome. If the make parent carries this gene, which of the following statements about the inheritance of that trait is true?
The trait will be expressed in 100 percent of the male offspring
Autosomal dominant disease are exhibited by anyone who carries at least one dominant allele for that gene. How is it that dominant lethal genes, such as the one that causes Huntington disease, can persist in a population?
These diseases usually take effect later in life after people have had children
A female who is a carrier of the sex-linked gene A has the genotype
XAXa
Which of the following genotypes represents a human male?
XY
Which of the following would explain two chromosomes in an individual cell that contain some, but not all, of the same genes at the same loci?
a chromosomal alteration has occurred
Which of the following genetic changes would NOT be passed from parent to child?
a mutation in a skin cell
A karyotype from an adult make indicates a chromosomal abnormality, which does not affect his health. Which of the following abnormalities is most likely seen?
a translocation between chromosome 14 and chromosome 15
Two copies of the same gene on a single chromosome would indicate what had occurred?
duplication
Why are X-linked recessive genetic disorder more commonly seen in males?
females must receive two copies of the recessive allele to exhibit the disorder, but males need only one copy
The X chromosome in humans is
found as a pair in females
A karyotype of an individual with mild mental retardation shows three copies of the X chromosome. If this individual decides to have children, how is her chromosomal abnormality likely to affect her offspring?
half of her eggs will contain an extra copy of the X chromosome
If a father is affected by an X-linked condition and the mother is carrier, what is the probability of their children being affected?
half of the sons will be affected
A carrier is an individual with a what genotype who does not express the recessive trait but can pass it along to offspring
heterozygous
A karyotype shows a chromosomal abnormality that does not change the length of any of the chromosomes. Which abnormality is indicated?
inversion
Which of the following statements would indicate a pedigree that shows the inheritance pattern of a recessive X-linked disease?
most affected individuals are males
What is a chart that shows genetic relationships within a family over several generations
pedigree
Which of the following information is available in a Punnett square showing the inheritance pattern for an autosomal recessive disorder
percentage of all children likely to be affected by the disorder
Most inherited human disorders are the result of
recessive mutations of genes located on autosomes
An allele that appears more frequently in males is most likely
sex-linked
The gender of a human child is determined by the
sperm
In humans, X-linked genetic diseases
tend to be expressed more in males than in females
One chromosomal abnormality that is usually fatal is
the addition of an extra autosomal chromosome
If a recessive allele causes a fatal disease that kills the affected individual before he or she can reproduce, why doesn't that allele quickly became extinct in the population
the recessive allele is carried in the genome of heterozygotes, who do not suffer from the disease
If two parents are heterozygous for an autosomal recessive disease
they are both considered genetic carriers for the disease
