Genetics Test 5

o A karyotype may be abnormal in two ways:

-Chromosome count - Chromosome abnormalities o Abnormal chromosomes account for at least 50% of spontaneous abortions

· The chromosomal composition of a normal female is

46, XX

· Males who have Jacobs syndrome have an extra Y chromosome in addition to the normal chromosome set. The chromosomal shorthand for Jacobs syndrome is 4

7, XYY

· Visualizing Chromosomes from fetal tissue

Amniocentesis Chorionic villi sampling Fetal cell sorting Chromosome microarray analysis

telocentric chromosome

Chromosome in which the centromere is at one end.

submetacentric chromosome

Chromosome in which the centromere is displaced toward one end, producing a short arm and a long arm

· Trisomy 18 is known as

Edwards syndrome

· In the __________ technique, DNA probes are labeled with fluorescent molecules and used to identify specific DNA sequences

FISH

p arm of a chromosome

The shorter arm of a chromosome

· 45, X is the chromosomal composition of a female with

Turner syndrome

Visualizing chromosomes in adult tissue

White blood cells Skin-like cells from cheek swab

· A cell with a single extra chromosome or missing chromosome is

aneuploid

an extra or missing chromosome

aneuploidy

metacentric chromosome

centromere is in the middle

acrocentric chromosome

centromere is near one end

· A cell with a normal chromosome number is

euploid

Turner Syndrome

female 45, X

· Cancer susceptibility is passed onto future generations when an _______________________ has occurred

germline mutation

q arm of a chromosome

long arm of chromosome

Klinefelter syndrome

male 47, XXY

Jacobs syndrome

male 47, XYY

The process of a tumor spreading is called

metastasis

one chromosome absent

monosomy

· Aneuploidy is usually the result of an error in meiosis called

nondisjunction

· Karyotype

o A chromosome chart o Displays chromosomes arranged by SIZE and CENTROMERE LOCATION o Humans have 2 chromosome types -Autosome 1-22 - Sex chromosomes XX or XY

· Is the chromosome balanced or unbalanced?

o A chromosome with a point mutation: balanced o A chromosome with a duplication: unbalanced o A chromosome with an inversion: balanced o A chromosome with a deletion: unbalanced o A chromosome with an extra piece of another chromosome due to translocation: unbalanced

· A chromosome normally has the structure ABCD-centromere-EFGHIJ.

o ABCD-centromere-EFGHFGHIJ: duplication o ABCD-centromere—EFIJ: deletion o ABCD-centromere-EIHGFJ: inversion

· Oncogenes

o Activation causes cancer o Cancer entails a gain-of-function o Activation is usually associated with a point mutation, translocation, or inversion

· Centromere Positions

o At tip: telocentric o Close to end: acrocentric o Off-center: submetacentric (produces long and short arm) o At midpoint: metacentric

· The drug bevacizumab is used to treat a number of different cancers including colorectal cancer, lung cancer, and breast cancer. This drug is a VEGF inhibitor. In what way do you predict bevacizumab affects cancer?

o Bevacizumab inhibits angiogenesis

· Karyotypes can

o Can confirm a clinical diagnosis o Reveal effects on environmental toxins o Clarify evolutionary relationships

· Breast cancer is classified into four different categories based on the genes that are expressed in the cancer cells. Two of the subtypes are luminal A and luminal B. Both of these cancers start in luminal cells that line the mammary ducts. However, gene expression patterns ultimately differ between the two cancer types. What best characterizes the type of pathway that was disrupted to lead to this difference?

o Cell fate pathways

· Example that shows the interplay between environmental and genetic factors in cancer:

o Certain mutations in the genes that encode the cytochrome P450 complex lead to poorer detoxification of cigarette smoke, and thus greater cancer risk

· Chromosomes

o Consists of primarily of DNA and protein o Distinguished by size and shape o Essential parts are: -Telomeres -Replication origins -Centromere

· Cytogenetics is a subdiscipline within genetics

o Deals with chromosome variations o Excess genetic material has a milder effect than a deficit o Most large chromosomal abnormalities disrupt or halt prenatal development resulting in miscarriage

· Events at the Cellular Level that can result in development of cancer

o Dedifferentiation o Activation of cancer stem cells o Increase in the proportion of stem cells within a tissue o Defect tissue repair

· FISH

o Fluorescence in situ hybridization o DNA probes labeled with fluorescing dye bind complementary DNA o In picture: Fluorescent dots correspond to three copies of chromosome 21

· Tumor suppressor genes

o Inactivation causes cancer o Cancer entails a loss-of-function o Often inactivated by a point mutation or deletion

· A normal version of a certain chromosome contains in the following structure: Genes X Y Z Centromere Genes A B C. In a cell you are studying, you find a chromosome containing the structure Genes C B A Centromere Genes A B C. What is the most likely explanation for this result?

o Isochromosome formation

· Characteristics of cancer cells

o Loss of cell cycle control o Dedifferentiated o Lack contact inhibition o Can induce blood vessel formation

· Which unequal division during spermatogenesis leads to the highest chance of producing a child with trisomy in all cells of their body?

o Nondisjunction at meiosis I

· Which of the four types of chromosomes (normal chromatid, dicentric chromatid, inversion chromatid, acentric fragment) that result from a paracentric inversion that are balanced

o Normal chromatid o Inversion chromatid

· Centromeres

o The largest constriction of the chromosome and where spindle fibers attach o Site where the spindle apparatus during mitosis and meiosis occurs during the splitting of the sister chromatids

visualizing chromosomes

o Tissue is obtained from person o Chromosomes are extracted o Then stained with a combination of dyes and DNA probes DNA probes are localized and targeted

· A cell with extra chromosome sets is

polyploid

extra chromosome sets

polyploidy

· Genes that normally stimulate cell division when it is appropriate are called

proto-oncogenes

· A mutation that occurs in cells that do not develop into gametes is called an

somatic mutation

· Sporadic cancer is due to

somatic mutations

· Cancer cells often have longer telomeres due to reactivation of the enzyme

telomerase

· Repeats of the sequence TTAGGG compromise the

telomere

· A acentric fragment does not have a centromere

true

· A chromosome without a centromere disappears from a cell as soon as cell division begins

true

· A dicentric chromosome has two centromeres

true

· A fusion protein can be produced due to the translocation of a proto-oncogene to a site next to another gene

true

· A male missing part of the short arm of chromosome 2 would have the chromosomal designation 46, XY, del(2p)

true

· A mutation present in all stages of a tumor acts early in the disease process

true

· A replication fork begins to form at an origin of replication site

true

· A ring chromosome forms when a chromosome loses its telomeres and the ends fuse

true

· A tumor suppressor gene mutation that causes cancer is usually a deletion

true

· Activation of a proto-oncogene into an oncogene could occur due to a mutation or a change in the expression of the wild-type gene

true

· An ideogram is a schematic chromosome map that indicates the chromosome arms and identifies the major banding patterns on the chromosome with numbers

true

· An isochromosome is a chromosome with two identical arms

true

· Cancer can result from a failure of a cell cycle checkpoint

true

· Chromosomes are mainly composed of DNA and proteins, with a small amount of RNA

true

· Chromosomes in cancer cells may bear translocations

true

· Chromothripsis shatters several chromosomes and may kill the cell—or trigger cancer

true

· Chronic villus cells are genetically identical to the fetus

true

· Down syndrome may be the result of a trisomy or an translocation

true

· In amniocentesis, fetal cells are obtained from the fluid surrounding the fetus

true

· In an Robertsonian translocation, the long arms of two acrocentric chromosomes fuse to form a single long chromosome

true

· In an deletion, part of a chromosome is missing

true

· In an duplication, part of a chromosome is present twice

true

· In an inversion, the order of a segment of a chromosome is reversed

true

· In an paracentric inversion, the inversion does not include the centromere

true

· In an pericentric inversion, the centromere is within the inverted region

true

· In an reciprocal translocation, two different chromosomes exchange parts

true

· In an translocation, parts of two chromosomes have been exchanged

true

· In monosomy, one chromosome is missing

true

· In trisomy, there is an extra copy of one chromosome

true

· Individuals with Down syndrome have an extra copy of chromosome 21. The chromosomes of a male with Down syndrome would be designated 47, XY, +21

true

· Jacobs syndrome (47,XYY) is the result of nondisjunction in the male parent only

true

· Klinefelter syndrome (47,XXY) is the result of nondisjunction in either the male or female parent

true

· Polyploidy occurs very commonly in plants

true

· RB1 and p53 are tumor suppressors

true

· Radiation is a method of treatment that causes adverse effects by harming healthy cells

true

· Somatic cells may develop mutations in cancer-causing genes

true

· Telocentric chromosomes are not found in human cells

true

· The most common chromosomal abnormality detected in fetuses is a trisomy

true

· The older a tumor is, the more genetic changes it will have

true

· The oldest approach to treating cancer is surgery

true

· Traditional treatments for cancer, such as radiation and chemotherapy, are effective because they kill rapidly dividing cells

true

· Translocations that join parts of nonhomologous chromosomes can turn proto-oncogenes into oncogenes

true

· Turner syndrome (45, X) is the result of nondisjunction in either the male or female parent

true

· Tyrosine kinase inhibitor is targeted based on genetic information

true

· When chromosomes are stained with dyes, heterochromatin stains darkly, whereas euchromatin stains lighter

true

centromere of a chromosome

where the sister chromatids are connected

lighter stained, contains more protein encoding genes

· Euchromatin:

darkly stained, consists of repetitive DNA

· Heterochromatin:

chromosome tips made of repetitive DNA

· Telomeres: