Chapter 15

Question 1

mutation

Answer 1

a change in the nucleotide sequence of DNA that can be passed on ot the next generation

Question 2

somatic mustations

Answer 2

occur in somatic (body) cells. Passed to daughter cells in mitosis but not to sexually

Question 3

germ line mutations

Answer 3

occur in germ line cells that give rise to gametes. A gamete passes these mutations on at fertilization

Question 4

loss of fun mutations

Answer 4

gene may not be expressed at all, or protein doesn’t functions (non-functional protein)
-tumor suppression gene

Question 5

gain of fun mutation

Answer 5

leads to a protein with altered function

• dominant
• common in cancer

Question 6

point mutation

Answer 6

change in a single nucleotide (alters mPNA sequence, and may not result in a change in the protein)

• transition
• transversion

Question 7

transition

Answer 7

substitution of one purine for the other, or one pyrimidine for the other

Question 8

transversion

Answer 8

substitution of a purine for a pyrimidine of vice versa

Question 9

silent mutation

Answer 9

usually don’t affect protein function

• might be in non-coding region/code for same amino acid as original
• common: a result in genetic diversity that isn’t expressed

Question 10

missense mutation

Answer 10

may have no effect on protein function (or the protein functional efficiency may be reduced, but not commonly inactivated, eg. Sickle Cell anemia)

Question 11

nonsense mutation

Answer 11

a base substitution causes a stop codon to form somewhere in the mRNA (if its near the 3’ end, usually no effect)- results in a shortened protein that in typically non-functional

Question 12

frameshift mutation

Answer 12

insertions or deletions of bases

-alter reading-frame for 3 base codons during translation (nonfunctional proteins produced)

Question 13

chromosomal mutations

Answer 13

result in extensive changes in DNA

• break and rejoin
• can be caused by damage to chromosomes by mutagens/errors in chromosome replication

Question 14

deletions

Answer 14

chromosomes may break in two places and rejoin, leaving out a large part of DNA

Question 15

duplications

Answer 15

can occur with deletions when homologous chromosomes break at different places

Question 16

inversions

Answer 16

chromosome breaks and rejoins, with one segment flipped

Question 17

translocations

Answer 17

segment of DNA breaks off and attaches to another chromosome; can cause duplication and deletion (uneven exchange of genetic material)

Question 18

spontaneous mutations

Answer 18

occur with no outside influence and are permanent (imperfect cellular processes)

• errors in replication by DNA polymerase
• most errors are repaired by proofreading fn, but some become permanent
• imperfect meiosis: nondisjunction and random breaking and rejoining of chromosomes

Question 19

induced mutations

Answer 19

are due to outside agents or mutagens such as chemicals or radiation or retroviruses

• chemicals can alter bases (some chemicals add other groups to bases)
• radiation damages DNA: ionizing radiation (x-rays/gamma rays/radiation from unstable isotopes) creates highly reactive free radicals

Question 20

genetic screening

Answer 20

tests to determine if a person has a genetic disease, is predisposed, or is a carrier

Question 21

prenatal screening

Answer 21

to detect changes in a fetus’s genes or chromosomes before birth (eg. down syndrome)

Question 22

screening of newborns

Answer 22

used just after birth to identify genetic disorders that can be treated early in life (eg. PKU)

Question 23

carrier testing

Answer 23

identify ppl who carry one copy of a gene mutation that when present in two copies can cause a genetic disorde

Question 24

DNA testing

Answer 24

direct analysis of DNA for mutations-the most accurate way of detecting abnormal alleles