Biology Chapter 8

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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


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