Exam 5 Flashcards

Question

Trisomy

Answer 1

Most autosomal aneuploids cease developing as embryos or fetuses Most frequently seen trisomies in newborns are those of chromosome 21, 18, and 13

Answer 2

Result of Nondisjunction in maternal meiosis 1, not inheritance Doesn’t allow for transmission to future generations Most common trisomy among newborns Short stature, heart problems, slanted eye fissures, protruding tongues, single palm crease 80% of people with Down syndrome were born from a mother younger than 35

Answer 3

Edwards Syndrome Nondisjunction in maternal meiosis 2 Most common Small at birth, heart problems, intellectual disability, rocker bottom foot

Answer 4

Patau Syndrome Rare Small at birth, seizures, intellectual disability, cleft lip and pallets, hearing abnormalities

Answer 5

Called the XO Syndrome Lacks a copy of the second sex chromosome (Nondisjunction of paternal) Has to be a women 99% of affected fetuses result in abortion Short height, delayed puberty, don’t complete sexual development and often infertile, hearing problems, thyroid problems

Answer 6

Called the XXY syndrome Male Don’t fully reach sexual maturation and usually infertile, bigger than peers, often taller, described as quirky personality

Answer 7

ex. Cri du Chat (cries like cat) 46, XX, -5p Cat-like-cry, intellectual disability, often don’t develop the ability to speak, smaller than peers Deletions are not inherited, they are spontaneous and can occur in either the sperm or egg Larger deletions are more likely to have a phenotype than smaller deletions

Answer 8

Refers to the presence of an extra genetic segment on a chromosome Also spontaneous, and also more likely to have a phenotype if it is a larger duplication Duplications in Chromosome 15 Can be type 1 (least duplicated material), type 2, or type 3(most duplicated material) Type 1 and type 2 yield no symptoms while type 3 has symptoms Symptoms include seizures, mental retardation, poor muscle tone, epicanthic folds, small size, developmental delay, scoliosis, learning disabilities, and autistic features like poor speech, hand flapping, lack of eye contact, and need for routine

Answer 9

In a translocation, two nonhomologous chromosomes exchange segments There are two major types: 1. Robertsonian - involves acrocentric chromosomes (13, 14, 15, 21), two short arms are lost and two long arms fuse to make one chromosome resulting in 45 total chromosomes, produces unbalanced chromosome Is a cause of Down syndrome 1. Reciprocal - pieces of two chromosomes break and rearrange (not acrocentric), can result in balanced or unbalanced Can be balanced (all material there) or unbalanced (piece is lost resulting in not balanced) Unbalanced more likely to result in phenotype People with balanced translocation are at risk for their offspring to inherit unbalanced translocations

Answer 10

An inversion is a chromosome segment that is flipped in orientation Paracentric inversion - two cuts happen at a place on the chromosome that is not the centromere Pericentric inversion - inversion occurs at the centromere, which moves the position of centromere

Answer 11

Happens with metacentric chromosomes Can result in turner’s syndrome Can cut metacentric chromosomes at the wrong spot resulting in the deletion or duplication of chromosomes

Answer 12

May arise when telomeres are lost and sticky chromosome ends fuse Genes can be lost or disrupted causing symptoms, not likely for life

Answer 13

Cancer arises due to alterations in genes It takes years to develop as it accumulates mutations 10% due to single gene inheritance Inherited from parent Affects every cell in body Most are due to changes in the gene at the cellular level that increase susceptibility but still require environmental input

Answer 14

Oncogenes: Cancer causing gene, cause cancer when inappropriately activated, typically have a function in embryo but turned off afterwards in normal functioning, more than 100 oncogenes Similar to autosomal dominant traits Tumor suppressor genes: Normal function is to prevent cancer, fix DNA, send cells to apoptosis, deletion or inactivation causes cancer, controls cell cycle checkpoints, more than 30 genes Usually if one copy is inactive or deleted we can still function normally In addition, changes in gene expression accompany cancer (epigenetics)

Answer 15

Cancer is due to a cell cycle disruption, where cancerous cells divide more often and quickly than the cell it originated from Timing, rate, and number of cell divisions depend on: Protein growth factors, signaling molecules from outside the cell, transcription factors Cancerous cells arise often - but most of the time the immune system or cell cycle checkpoints will destroy them Checkpoints control the cell cycle Ensure that mitotic events occur in the correct sequence DNA Damage Checkpoint in S phase, the Apoptosis Checkpoint between G2 and prophase, and Spindle assembly checkpoint during anaphase all play a role in cancer Cancer Cells take on a stem cell style look

Answer 16

Loss of control of telomere length may also contribute to cancer Telomerase: enzyme that adds telomere sequence to the end of the chromosomes Normal, specialized cells have telomerase turned off to limit cell division Cancer cells have to express telomerase to divide infinitely Activation of telomerase is not enough to cause cancer

Answer 17

Somatic Mutations: Occur sporadically in nonsense cells result from a single dominant mutation or two recessive mutations in the same gene Cancer susceptibility not passed on to offspring Germline Mutations: Cancer susceptibility is passed on to offspring Requires second somatic mutation Rare but results in early onset of cancer

Answer 18

Divide continually and quicker and than normal cells Contain heritable mutations - cancer cell divides to produce cancer cells Transplantable Dedifferentiated: lose their specialized identity Have a different appearance Express different cell surface proteins/antigens Lack contact inhibition (continue to proliferate after taking up space) Induce angiogenesis: formation of local blood vessels Invasive: squeeze into any space available Metastasize: move to new location in body

Answer 19

Cancer can begin at the cellular level in at least four ways: 1. Activation of stem cells that produce cancer cells 2. Dedifferentiation 3. Increase in proportion of a tissue that consists of stem cells or progenitor cells 4. Faulty tissue repair

Answer 20

Early stem cells can become cancerous while a totipotent stem cell or a progenitor cell

Answer 21

A specialized cell become a progenitor cell, then to a cancer like cell

Answer 22

In a normal tissue we have a small amount of stem cells naturally spaced far away (6% of tissue) A mutation can occur and cause some of the cells to dedifferentiate back into stem cells, this can then become an abnormal growth or a tumor

Answer 23

Acute injuries cause a resting stem cell to become activated, so it can heal the minor injury In chronic injuries there becomes a build up of activated stem cells causing cancer

Answer 24

Proto-oncogenes are normal versions of genes that promote cell division Expression at the wrong time or in the wrong cell type leads to cell division and cancer Overexpression of a normal function: Viruses integrated next to a proto-oncogene can cause transcription when the virus is transcribed Moving a proto-oncogene next to a highly transcribed gene can lead to overexpression of the proto-oncogene

Answer 25

Oncogenes are activated when a proto-oncogene moves next to another gene The gene pair is transcribed together The double gene product is a fusion protein It activates or lifts control of cell division

Answer 26

A gene on chromosome 9 called abl and a gene on chromosome 22 called bcr are involved 9 and 22 swap genetic information and fuses the abl-cbr gene on chromosome 22 (tip of 9 on 22 called Philedelphia) BCR-ABL oncoprotein is a tyrosine kinase that excessively stimulates cell division Understanding cellular changes allowed development of a new drug called Gleevac Before the development of medication, chemotherapy was used the BCR-ABL oncoprotein usually binds to a substrate, atp fits into the BCR-ABL which has phosphorous bonded to it, then the phosphorous binds to tyrosine The Gleevac prevents ATP from fitting into the BCR-ABL protein, which keeps the tyrosine normal

Answer 27

Transfusion between 15 and 17 Combination of retinoic acid cell surface receptor and an oncogene Instead of chemotherapy, vitamin A has to be suggested

Answer 28

Product of an oncogene Excessive levels in approximately 25% of breast cancer patients Too many receptors on cell Too many signals to divide Monoclonal antibody drug, herceptin binds to the HER2 receptors which blocks division

Answer 29

Cancer can be caused by loss of genes that inhibit cell division Tumor suppressor genes normally stop a cell from dividing Mutations of both copies of a tumor suppressor gene is usually required to allow cell division Genes can also be lost by deletion or silenced by promoter hypermethylation

Answer 30

Tumor in retina A rare childhood cancer The RB gene is on chromosome 13 The RB protein binds transcription factors so taht they cannot activate genes that carry out mitosis Normally halts the cell cycle at G1 Study of RB was the origin of the “two-hit” hypothesis of cancer causation

Answer 31

Two mutations or deletions are required One in each copy of the RB gene Sporadic Cases (non-inherited) Retinoblastoma is a result of two somatic mutations Familial Cases (inherited) Individuals harbor one germline mutant allele for the RB gene in each of their cells This is followed by a somatic mutation in the normal allele

Answer 32

The p53 gene is the “guardian of the genome” Li Fraumeni Syndrome Every cell in the body has a mutation in the p53 gene

Answer 33

Most often, discovery of cancer follows a screening test Oldest treatment is surgery which removes the tumor Radiation and chemotherapy non-selectively destroy rapidly dividing cells Other drugs help patients tolerate the side effects New Types of Cancer Drugs: Herceptin, gleevac, all are developed to hit specialized cancer, others are being made to prevent angiogenesis, micro RNAs are also being used

Exam 5 Flashcards

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