Week 11

Question 1

spontaneous mutation

Answer 1

arise in cells without exposure to agents capable of inducing mutation, arise primarily through errors in DNA replication or spontaneous changes in chemical structure of a nucleotide base

Question 2

induced mutation

Answer 2

produced by mutagens in an experimental setting to study types of damage caused the mutation process itself, or repair responses to damage

Question 3

mutagen

Answer 3

a chemical, physical, or biological agent capable of damaging DNA and creating a mutation

Question 4

Base-pair substitution mutation

Answer 4

the replacement of one nucleotide base pair by another

Question 5

frameshift mutation

Answer 5

insertion or deletion of one or more base pairs leads to addition or deletion of mRNA nucleotides, which may alter the reading frame of the message

Question 6

thymine dimer

Answer 6

the specific type of lesion formed on DNA due to exposure to ultraviolet irradiation

Question 7

strand slippage

Answer 7

involves alterations in number of DNA repeats, DNA poly of replisome temporarily dissociates from the template and a portion of newly replicated DNA forms a temporary hairpin. Resumption of replication leads to re-replication of some of the repeats and overall increase in the number of repeats on the daughter strand

Question 8

Depurination

Answer 8

the loss of a purine from a nucleotide by breaking the covalent bond linking the nucleotide base to the sugar&raquo_space;» base substitution (adenine and guanine)

Question 9

Deamination

Answer 9

the loss of an amino group (NH2) from a nucleotide base

Question 10

nucleotide base analogs

Answer 10

a compound with a size and shape that mimics a natural nucleotide base.&raquo_space; point mutation

Question 11

deaminating agents

Answer 11

an agent that removes an amino group from a nucleotide base with a mutagenic effect&raquo_space; point mutation

Question 12

alkylating agents

Answer 12

add bulky side groups such as methyl and ethyl groups to nucleotide bases.&raquo_space;> base substitution

Question 13

oxidizing agents

Answer 13

ROS damage DNA by modifying bases, disrupting the sugar-phosphate backbone, and forming DNA-protein cross-links.&raquo_space;> base substitution & frameshift

Question 14

hydroxylating agents

Answer 14

hydroxylation is the addition of a hydroxyl (OH) group to a recipient compound by a donor called a hydroxylating agent.&raquo_space;> point/base substitution

Question 15

intercalating agents

Answer 15

molecules that are able to fit between DNA base pairs, distort DNA duplex.&raquo_space;> frameshift

Question 16

UV radiation

Answer 16

photoproducts involve additional bonds with nucleotides (thymine dimer), disruption of replication, lead to mutation and cancer.&raquo_space;> thymine dimer

Question 17

proofreading

Answer 17

by DNA polymerase, which identifies DNA base-pair mismatches during DNA replication, removes a segment of DNA containing the erroneous nucleotide, and resynthesizes the excised sequence

Question 18

mismatch repair

Answer 18

mismatched nucleotides that escape DNA polymerase. Repair enzymes distinguish between the original, correct nucleotide and the new, mismatched nucleotide using the presence of methylation on the original strand.

Question 19

photo-reactive repair

Answer 19

UV-induced damage, takes place in bacteria, eukaryotes (single celled), and some animals. Photolyase uses energy from visible light to break the bonds producing the photoproduct.

Question 20

base excision repair

Answer 20

multiple step process to repair damage to a base or replace an incorrect base. DNA glycosylases recognize and remove modified bases, creating an AP

Question 21

nucleotide excision repair

Answer 21

often used to repair UV-induced damage to DNA, known as UV repair. Enzymes recognize and bind damaged region, segment of nucleotides are removed from the damaged strand, DNA poly fills in the gap and DNA ligase seals the sugar-phosphate backbone.

Question 22

pre symptomatic genetic testing

Answer 22

When: anytime after birth; however some states require individuals to be at least 18 years old for certain tests.
Why: determine if an individual carries a mutation that will cause disease or increase their chances of disease in the future
How: DNA sequencing or Polymerase Chain Reaction to determine if an individual has wild-type or mutated alleles

Question 23

carrier genetic testing

Answer 23

When: In adults either before conception or during the first trimester
Why: to determine if they are heterozygous for mutations that cause serious or fatal recessive diseases in children
How: by detecting wild-type and mutant proteins in a blood sample, DNA analysis (sequencing or PCR)

Question 24

newborn genetic screening

Answer 24

When: in the first few days after birth
Why: to test for genetic diseases that can be treated if they are identified at birth
How: blood sample obtained from pricking the baby’s heel, usually includes a hearing test

Question 25

prenatal genetic testing

Answer 25

When: during pregnancy Why: examines fetuses for chromosomal abnormalities, developmental or growth conditions, & hereditary disease How: Fetal cells are used for biochemical analysis, DNA analysis or chromosome analysis. Cells are obtained from: amniocentesis using a needle to penetrate the uterus and placenta to withdraw 2-3 tbsp of amniotic fluid, chorionic villus sampling using a tube to suction off cells from outside of the placenta, or examining fetal cells circulating in the mother’s blood

Question 26

preimplantation genetic screening

Answer 26

When: after in vitro fertilization when the embryos have reached the 8-cell or 16-cell stage Why: embryos with a genetic condition will not be used for implantation How: one cell is removed to perform chromosome and DNA analyses

Question 27

direct-to-consumer genetic testing

Answer 27

When: anytime as an adult Why: determine ancestry, susceptibility to certain diseases, hereditary diseases or traits How: profit companies that you can pay to have your DNA analyzed from a cheek swab

Question 28

explain pros and cons of having genetic testing performed

Answer 28

Pros: early detection/prevention, diagnoses, identifying risk factors, Cons: can cause stress/anxiety, false or misleading results, high costs, privacy concerns

Question 29

Describe the role of BRCA1 and BRCA2 and how mutations in these genes r increase the risk of certain types of cancer but do not guarantee that someone will develop cancer

Answer 29

BRCA 1 & BRCA 2 are tumor-suppressor genes: encode proteins involved in DNA damage repair to prevent abnormal cell growth that would lead to cancer. With mutation, they don’t function correctly increasing the risk of developing some cancers. Although this doesn’t guarantee that someone will develop cancer just at a higher risk, it's also dependent on their lifestyle, genetics, etc.

Question 30

base-pair mismatch during DNA replication

Answer 30

occurs when an incorrect nucleotide is incorporated into the newly synthesized DNA strand instead of the complementary base on the template strand. These mismatches are typically caused by errors during DNA polymerase activity or by base modifications that alter the base pairing