Chapter 4: Genes And Genetic Diseases

Question 0

Purines

Answer 0

Adenine and guanine

Question 1

Pyrimidines

Answer 1

Cytosine and thymine

Question 2

Silent Mutation

Answer 2

Base pair substitution that does not result into any amino acid change

Question 3

Missense Mutation

Answer 3

Base pair substitution that results in a single amino acid change

Question 4

Nonsense Mutation

Answer 4

Type of mutation in which an mRNA stop codon is: produced; resulting in premature termination of the protein sequence OR removed; resulting in an elongated protein sequence

Question 5

Frame Shift Mutation

Answer 5

Involved insertion or deletion of one or more base pairs to the DNA molecule. It can greatly alter then resulting amino acid sequence

Question 6

Euploid cells

Answer 6

Cells that have a multiple of the normal number of chromosomes, haploid and diploid cells are diploid forms

Question 7

Disjunction

Answer 7

Normal separation of chromosomes during cell division

Question 8

Nondisjunction

Answer 8

Usually the cause of aneuploidy, failure of homologous chromosomes or sister chromatids to separate normally during meiosis or mitosis

Question 9

Aneuploidy

Answer 9

Somatic cell that does not contain a multiple of 23 chromosomes, cell containing three copies of one chromosome is trisomic(trisomy), monosomy is presence of only one copy of any chromosome is often fatal but infants can survive with trisomy of certain chromosomes

Question 10

Autosomal Aneuploidy

Answer 10

Down syndrome, trisomy of 21st chromosome, 1:800 live births, mentally regarded, Low nasal bridge, epicanthal folds, protruding tongue, poor muscle tone, risk increases with maternal age, increased risk of congenital heart disease, gastrointestinal disease, and leukemia

Question 11

Turner Syndrome (sex chromosome aneuploidy)

Answer 11

females with only one X chromosome, characteristics: absence of ovaries(sterile), short stature(4’7”), webbing of the neck, edema, underdeveloped breasts; wide nipples, high number of aborted fetuses, X is usually inherited from mother

Question 12

Klinefelter Syndrome (sex chromosome aneuploidy)

Answer 12

Individuals with at least 2 X’s and one Y chromosome. Characteristics: male appearance, develop female-like breasts, small testes, sparse body hair, long limbs, some individuals can be XXXY and XXXXY the abnormalities will increase with each X

Question 13

Duplication

Answer 13

Repeated gene or gene sequence, rare occurrence, less serious consequences because better to have more genetic material than less (deletion)

Question 14

Inversions

Answer 14

Two breaks on a chromosome, reversal of the gene order, usually occurs from a breakage that gets reversed during reattachment: ABCDEFG may become ABEDCFG

Question 15

Deletion

Answer 15

Removal of a part of a chromosome, loss of particular genes

Question 16

Translocation

Answer 16

The interchanging of material between nonhomologous chromosomes, translocation occurs when two chromosomes break and the segments are rejoined in an abnormal arrangement

Question 17

Fragile X Syndrome

Answer 17

Site on the long arm of the X chromosome, associated with mental retardation, second in occurrence to Down syndrome, higher incidence in males because they have only one X chromosome

Question 18

Locus

Answer 18

Location occupied by a gene on a chromosome

Question 19

Allele

Answer 19

Alternate version of a gene at a locus; each individual possesses two alleles for each gene, homozygous: possessing identical alleles of a given gene, heterozygous: possessing two different alleles of a given gene

Question 20

Autosomal Dominant Disorder

Answer 20

Abnormal allele is dominant, normal allele is recessive and the genes exist on a pair of autosomes. Characteristics: condition is expressed equally in males and females, approximately half of children of an affected heterozygous individual will express the condition, no generational skipping

Question 21

Autosomal Recessive Disorder

Answer 21

Abnormal allele is recessive and a person must be homozygous for the abnormal trait to express the disease, the trait usually appears in the children, not the parents and it affects the genders equally because it is present on a pair of autosomes, generational skipping may be present, consanguinity may be present

Question 22

Consanguinity

Answer 22

Mating of two related individuals, dramatically increases the recurrence risk of recessive disorders

Question 23

X-Linked Recessive Disorders

Answer 23

• Males most commonly affected; cannot transmit the genes to sons, but they can to all daughters
• unaffected carrier females: son of female carriers have a 50% risk of being affected
• pedigree analysis: generational skipping often present, no father-to-son transmission