How many chromosomes are shown in a normal human karyotype? • 2 • 23 • 44 • 46
Which of the following are shown in a karyotype? • homologous chromosomes • sex chromosomes • autosomes • all of the above
Which of the following can be observed in a karyotype? • a change in a DNA base • an extra chromosome • genes • alleles
In humans, a male has • one X chromosome only. • two X chromosomes. • one X chromosome and one Y chromosome. • two Y chromosomes.
Human females produce egg cells that have • one X chromosome. • two X chromosomes. • one X or one Y chromosome. • one X and one Y chromosome.
What is the approximate probability that a human offspring will be female? • 10% • 25% • 50% • 75%
What percentage of human sperm cells carry an X chromosome? • 0% • 25% • 50% • 100%
A human female inherits • one copy of every gene located on each of the X chromosomes. • twice as many sex chromosomes as a human male inherits. • one copy of every gene located on the Y chromosome. • all of the same genes that a human male inherits.
In a pedigree, a circle represents a(an) • male. • female. • child. • adult.
A pedigree can be used to • determine whether a trait is inherited. • show how a trait is passed from one generation to the next. • determine whether an allele is dominant or recessive. • all of the above
Which of the following would you be least likely to see in a pedigree? • All of the symbols are unshaded. • All of the symbols are shaded. • All of the symbols are squares. • About half of the symbols are circles.
Which of the following is caused by a dominant allele? • Huntington’s disease • PKU • Tay-Sachs disease • none of the above
Which of the following is determined by multiple alleles? • Rh blood group • ABO blood group • PKU • Huntington’s disease
A person who has PKU • inherited the recessive allele for the trait from one parent. • inherited the recessive allele for the trait from both parents. • is heterozygous for the trait. • will not pass the allele for the trait to his or her offspring.
Which of the following genotypes result in the same phenotype? • IAIA and IAIB • IBIB and IBi • IBIB and IAIB • IBi and ii
If a man with blood type A and a woman with blood type B produce an offspring, what might be the offspring’s blood type? • AB or O • A, B, or O • A, B, AB, or O • AB only
Which of the following statements is NOT true? • A person with Huntington’s disease might not pass the allele for the disease to his or her offspring. • A person with Huntington’s disease might be homozygous for the disease. • Huntington’s disease is caused by a recessive allele. • A person who inherits one allele for Huntington’s disease will develop the disease.
Sickle cell disease is caused by a • change in one DNA base. • change in the size of a chromosome. • change in two genes. • change in the number of chromosomes in a cell.
In cystic fibrosis, a change in a single gene causes the protein called CFTR to • become less soluble. • fold improperly. • destroy the cell membrane. • transport sodium ions instead of chloride ions.
Compared with normal hemoglobin, the hemoglobin of a person with sickle cell disease • is longer. • is shorter. • has a different sequence of amino acids. • is wider.
Which of the following does NOT lead to cystic fibrosis? • missing codon in mRNA • shorter CFTR polypeptide chain • point mutation • absence of CFTR in cell membrane
People who are heterozygous for sickle cell disease are generally healthy because • they are resistant to malaria. • they usually have some normal hemoglobin in their red blood cells. • their abnormal hemoglobin usually doesn’t cause their red blood cells to become sickle shaped. • they do not produce abnormal hemoglobin.
The sequencing of human chromosomes 21 and 22 showed that • some regions of chromosomes do not code for proteins. • all of the DNA of chromosomes codes for proteins. • different chromosomes have the same number of genes. • different chromosomes contain the same number of DNA bases.
Alleles found on the same chromosomes • are dominant. • are never separated by recombination. • are linked. • contain repetitive DNA.
The long stretches of repetitive DNA in chromosomes 21 and 22 are unstable sites • that contain genes. • where rearrangements occur. • that cause genetic disorders. • that do not allow crossing-over to occur.
Most sex-linked genes are located on • the autosomes. • the X chromosome only. • the Y chromosome only. • both the X chromosome and the Y chromosome.
Colorblindness is more common in males than in females because • fathers pass the allele for colorblindness to their sons only. • the allele for colorblindness is located on the Y chromosome. • the allele for colorblindness is recessive and located on the X chromosome. • males who are colorblind have two copies of the allele for colorblindness.
Which of the following statements is true? • Females cannot have hemophilia. • The father of a colorblind boy may be colorblind. • A sex-linked allele cannot be dominant. • The mother of a colorblind boy must be colorblind.
Which of the following form(s) a Barr body? • the Y chromosome in a male cell • the X chromosome in a male cell • one of the X chromosomes in a female cell • both of the X chromosomes in a female cell
The formation of a Barr body • causes the genes on one of the X chromosomes in a female cell to be switched off. • always causes the same X chromosome in a female’s cells to be switched off. • switches on the Y chromosome in a male cell. • none of the above
A cat that has spots of only one color • has no Barr bodies. • must be a male. • must be a female. • may be a male or a female.
The failure of chromosomes to separate during meiosis is called • nondisjunction. • X-chromosome inactivation. • Turner’s syndrome. • Down syndrome.
Because the X chromosome contains genes that are vital for normal development, no baby has been born • with one X chromosome. • with three X chromosomes. • without an X chromosome. • with four X chromosomes.
Which of the following combinations of sex chromosomes represents a female? • XY • XXY • XXXY • XX
If nondisjunction occurs during meiosis, • only two gametes may form instead of four. • some gametes may have an extra copy of some genes. • the chromatids do not separate. • it occurs during prophase.
Nondisjunction can involve • autosomes. • sex chromosomes. • homologous chromosomes. • all of the above
Scientists test for alleles that cause human genetic disorders by • making karyotypes. • making DNA fingerprints. • detecting the DNA sequences found in those alleles. • making pedigrees.
The process of DNA fingerprinting is based on the fact that • the most important genes are different among most people. • no two people, except identical twins, have exactly the same DNA. • most genes are dominant. • most people have DNA that contains repeats.
What conclusion CANNOT be made from two DNA fingerprints that show identical patterns of bands? • The DNA from the two DNA fingerprints almost certainly came from the same person. • The DNA from the two DNA fingerprints definitely came from two different people. • The DNA from the two DNA fingerprints was separated by size. • The DNA repeats that formed the bands in each DNA fingerprint are the same length.
The Human Genome Project is an attempt to • make a DNA fingerprint of every person’s DNA. • sequence all human DNA. • cure human diseases. • identify alleles in human DNA that are recessive.
The human genome was sequenced • by sequencing each gene on each chromosome, one at a time. • using DNA fingerprinting. • by looking for overlapping regions between sequenced DNA fragments. • using open reading frames.
Which of the following information CANNOT be obtained from the Human Genome Project? • causes of genetic disorders • amino acid sequences of human proteins • locations of genes on chromosomes • whether an allele is dominant or recessive
The purpose of gene therapy is to • cure genetic disorders. • determine the sequences of genes. • remove mutations from genes. • change dominant alleles to recessive alleles.
Which of the following is the first step in gene therapy? • splicing the normal gene to viral DNA • allowing recombinant viruses to infect human cells • using restriction enzymes to cut out the normal gene from DNA • identifying the faulty gene that causes the disease
Gene therapy is successful if the • viruses carrying the replacement gene infect the person’s cells. • replacement gene is replicated in the person’s cells. • replacement gene is transcribed in the person’s cells. • replacement gene is successfully spliced to viral DNA.
In a human karyotype, 44 of the chromosomes are autosomes. _________________________ • True • False
In a human karyotype, 23 chromosome pairs are similar in size and shape. _________________________ • True • False
In humans, the mother determines the sex of the offspring. _________________________ • True • False
In a pedigree, if a mother is represented by a shaded circle and a father is represented by a shaded square, their children can be represented by either shaded or unshaded circles or squares. _________________________ • True • False
A pedigree showing the inheritance of Huntington’s disease within a family would show shaded symbols for people with the disease. _________________________ • True • False