Describe how a karyotype is prepared and analyzed.
Biologists photograph cells in mitosis, cut out the chromosomes from the photographs, and group them together in pairs. They then check whether any chromosomes are missing or have extra copies.
What is the difference between
autosomes and sex chromosomes?
The sex chromosomes, X and Y, determine an individual's sex; the remaining chromosomes are autosomal.
How can a family pedigree be helpful in determining the probability of having a child with a genetic disorder?
A pedigree shows how a genetic trait has been passed from one generation to the next. This information can be used to infer the genotypes
of family members and predict the likelihood that a child will have the disorder.
In the pedigree below, the shaded
symbols indicate people who have
hemophilia. Which mothers certainly are carriers? Why did the sons of person 3 not inherit the trait?
Mothers 1 and 6 are carriers. Person 3 can pass his affected X chromosome only to his
daughters; his sons inherit his Y chromosome
and an X chromosome from their mother.
Is it possible for a person with blood type alleles IA and IB to have blood type A? Explain your answer.
No, the I A and I B alleles are codominant. When both alleles are present in an individual, that person has blood type AB.
Explain the significance of the Rh factor in blood groups.
Giving a person a transfusion of blood with the wrong Rh factor could be fatal.
What is Tay-Sachs disease?
Tay-Sachs disease is an autosomal recessive genetic disease that causes nervous system breakdown and death.
What determines whether an allele is dominant, recessive, or codominant?
The nature of the gene's protein product and its role in the cell; for example, if one copy of the normal allele can supply cells with enough
protein to function, then the normal allele is dominant. If both alleles contribute to the phenotype, they are codominant.
What is a chromosomal disorder? Name one chromosomal disorder that can re- sult from nondisjunction.
A chromosomal disorder occurs when abnormal numbers of chromosomes find their way into the gametes. Chromosomal disorders resulting from nondisjunction include Down syndrome, Turner's syndrome, and Klinefelter's syndrome.
Describe the process of DNA fingerpr-inting.
A small sample of DNA is cut with restriction enzymes. The fragments are separated by size using electrophoresis. Fragments containing
highly variable regions of DNA are detected with a DNA probe.
Describe what is meant by the term ra-pid sequencing.
It is a sequencing technique in which widely separated regions of DNA on each chromosome are first sequenced. Then, the sequence of
bases on randomly generated fragments of DNA are determined. Computers then find
overlapping regions between the fragments and
put the fragments together by linking
overlapping areas. Computers then align the fragments relative to the known markers to assemble the final sequence.
How does an open reading frame help molecular biologists search for genes?
An open reading frame helps biologists find a gene's promoter as well as its introns.