Exam 1 Flashcards
1
Q
Chromosomes are seen when?
A
Only when a cell is dividing. So just during mitosis or meiosis.
2
Q
What are the parts to a chromosome?
A
2 chromatids that run from one tip to another and centromere is a piece of protein that holds 2 chormatids together and can be torn apart separating the 2 chromatids during cell division anaphase.
3
Q
80% of a chromosome is what?
A
Protein.
4
Q
Human chromosomes complements come in pairs called?
A
Diploidy.
5
Q
What is diploidy?
A
Organisms have 2 of a given kind of chromosome.
6
Q
How many chromosomes do humans have?
A
23 pairs or 46 chromosomes.
7
Q
The 23 pairs are what type of pairs?
A
Homologous pairs because they are very similar.
8
Q
How similar are the pairs of homologous chromosomes?
A
They have the essential information (genes), but the specific info may differ.
9
Q
What are the pairs of chromosomes each called?
A
Maternal homolog and a paternal homolog.
10
Q
What are the chromosomes that are not directly related to the sex of an individual called and how many are there?
A
Autosomes and there are 44 total or 22 pairs.
11
Q
What are the chromosomes that are directly related to the sex of an indivdual called and how many of them are there?
A
Sex chromosomes and there are 2 total or 1 pair.
12
Q
There are 3 different location for a centromere where are they and what are these positions called?
A
Middle- metacentric. Little off center- submetacentric. Near end/tip- acrocentric.
13
Q
What is a chromosome satellite?
A
Small masses on narrow stalks of the chromatids that conatin DNA found on chromoses 13, 14, 15, 21, 22.
14
Q
What is the first classification system of chromosomes called?
A
The Denver system.
15
Q
What is a Karyotype?
A
A graphical display of chromosomes.
16
Q
How did the Denver system organize chromosomes?
A
Into 7 categories based upon length and centromeric position.
17
Q
What is a Karyotype from the Denver system used for?
A
It is possible to identify changes in chromosome number and major changes in chromosme structure. Minor changes could be missed.
18
Q
What did the Paris conference system karyotypes show that the Denver did not?
A
Banding patterns.
19
Q
What can the Paris conference karyotypes show that the Denver could not?
A
It was now possible to see fairly small deletions, additions or re-arrangements of chromosomes.
20
Q
How did the International system of Human chromosome nomenclature label each end of a chromosome?
A
The short end is labeled P and the long end is termed q.
21
Q
How are specific locations on chromosomes labled with the international system of human chromosome nomenclature?
A
List the chromosome number, the arm (p or q), the region and the band. The region and the band numbers get larger the farther from center they get.
22
Q
What are the bands on a chromosome?
A
It is unknown, but they are a staining of protein more than anything.
23
Q
How are Karyotypes conventionally abreviated?
A
By listing the number of chromosomes, followed by the sex chromosomes, followed by derangements in the chromosomes. 46,XX for females, 46,XY for males.
24
Q
What part of chromosome would 8q32 be?
A
The 8th chromosome the larger arm, the 3rd sub-region, and band 2 (not 32)
25
What is a modern karyotype used for?
to reveal major and minor deletions, duplications, larger rearrangements, and translocations. Very small changes are difficult to detect.
26
What is Euploidy and aneuploidy?
Euploidy- having a complete set of chromosomes. Aneuploidy- Having an extra or missing a chromosome.
27
What are the types of Euploidy?
Haploidy- 1 complete set (typically gametes). Diploidy- 2 complete sets.
28
What are the types of aneuploidy?
Monosomy- missing a chromosome so has a total of 45. Trisomy which is adding a chromosome so there are 47 total.
29
Down's syndrome is aka?
Trisomy 21.
30
What would be the way to lable a karyotype of someone with trisomy 21?
47,xx, +21.
31
What are some traits that effect facies of people with trisomy 21?
Oblique palpebral fissures, epicanthic folds.
32
What are the neurological signs like for someone with trisomy 21?
Hypotonia, mental retardation.
33
What % of severe mental retardation in children comes from trisomy 21?
1/3 of them.
34
What is the most important risk factor for having a child born with trisomy 21?
Maternal age.
35
What is a non-invasive way to screen for trisomy 21 before birth?
Ultrasound of nuchal area translucency. (Look for a presence of a Cystic Hygroma)
36
If women under the age of 40 have already had a child born with trisomy 21 what are the odds she could have another one?
1%.
37
What are 2 other types of trisomy that have severe mental retardation?
Trisomy 18 and 13.
38
Aneuploidy arises from what?
Failures during meiotic chromosome separation. They are produced through non-disjunction.
39
What are 4 other chromosome problems that are not aneuploidic states?
1. Deletion. 2. Duplication. 3. inversion. 4. translocation.
40
What is chromosome deletion?
A piece of a chromosome is removed.
41
What disease is seen with a deletion on chromosome 15?
parder-willi and angelman syndrome.
42
What disease is seen with a deletion on chromosome 5?
Cri Du Chat. Cry of the cat.
43
What is chromosome duplication?
a piece of chromosome is duplicated.
44
What disease is seen with a duplication on chromosome 12?
Pallister Killian Syndrome.
45
Pallister Killian syndrome is caused by duplication on chromosome 12 that usually involves what?
Mixture of cells called MOSAICISM.
46
What is chromosome inversion?
Wherein a piece of chromosome is flipped around or inverted.
47
What is chromosome translocation?
Wherein 2 chromosomes break and exchange pieces.
48
What chromosome defect is identical to trisomy 21?
A translocation between 21 and 14.
49
What happens with a translocation between chromosomes 9 and 22?
Chronic myelogenous (or myeloid) leukemia.
50
How would you calssifiy a translocation that caused chronic myelogenous leukemia?
t(9;22).
51
What % of live births can be shown to have a chromosome abnormality?
1 in 200.
52
What is a spontaneous abortion?
A miscarriage.
53
What % of recognizable pregnancies abort?
15%.
54
Of the total miscarriages (15% of all pregnancies) what % of the conceptuses have a APPARENTLY normal karyotype?
50%.
55
Conceptuses that have abnormal chromosomes what will typically happen to them?
Most of them will abort.
56
The incidence of a chromosomal disease is a function of what?
Conceptus production rate and likelihood of in utero survival.
57
Significant chromosome disturbance are what?
Not compatible with continued life.
58
Repeated miscarriage is suggestive of what?
Chromosomal problems in one (perhaps both) of the parents.
59
What is Meiosis?
Gametic cell division. It is the creation of the gametes that carry genetic information to the next generation.
60
What is an important role of meiosis?
Random assortment of chromosomes, and jumbling of paternal and maternal chromosomes in a process called crossing over.
61
What are the 2 parts of meiosis?
Meiosis I- a separation of homologous pairs. Meiosis II- a separation of chromatids.
62
When are chromosome visible?
Only when a cell is dividing. So just during mitosis or meiosis.
63
What is visible in the pre-meiotic interphase?
Only Chromatin.
64
What happens in pre-meiotic interphase?
A cell goes from 2N to 4N so the chromosomes double.
65
What are the 4 parts to meiosis?
Prophase, metaphase, anaphase, telophase.
66
What happens in Prophase I?
Chromosomes first appear and continue condensing. Then they line up in homologous pairs and crossing-over happens.
67
What type of chromosome duplication happens in Prophase I?
None.
68
Crossing-over is complete when?
At the end of prophase I.
69
What is metaphase I?
Homologous pairs line up on an equatorial plane and are attached to spindle apparatus.
70
When will random assortment take place?
In metaphase I the chromosomes will randomly line up so maternal and paternal chromosomes can go either way randomly.
71
What is anaphase I?
Separation of homolgous pairs termed disjunction.
72
What is nondisjunction?
If a chromosome pair fails to separate.
73
What is telophase I?
reconstruction of the nuclei and the division of the cytoplasm of the 2 new cells.
74
What is the end of telophase I called?
End of meiosis I.
75
What is cytokinesis?
Meiosis I.
76
What is prophase II?
Recoiling of chromosomes to a manageable size.
77
What is metaphase II?
Single chromosomes line up on equatorial plane and attach to a new spindle apparatus.
78
What is Anaphase II?
Separation of chromatids.
79
What is telophase II?
A final reconstruction period of the 4 new cells.
80
Cells starting out meiosis I have how many chromosomes?
they are 4N at the start so they have 92.
81
How many chromosomes are present in the 2 new cells at the end of meiosis I?
Each cell has 2N or 46 chromosomes that have gone through crossing over and random assortment.
82
How many chromosomes are present in the 4 new cells at the end of meiosis II?
Each cell has 1N or 23 chromosomes.
83
What does 7q31 mean?
Chromosome 7, long arm, region 3, band 1.
84
What does 47, XY, +16 mean?
47 chromosome, male, trisomy 16.
85
What does 49, XXXXY mean?
49 chromosome, male, 3 extra X's.
86
What does 45,XX, -21 mean?
45 chromosome, female, monosomy 21.
87
A couple, one a translocation Down syndrome carrier (of the 14/21 type discussed) and the other with a normal karyoptype, reproduce. IF ALL POTENTIAL ZYGOTES WERE TO SURVIVE AND BE BORN, what % of births would be expected to be chromosomally normal? Of births to normal appearing offspring, what % would be expected to be chromosomally normal?
25%. 50%.
88
What has been the unifying concept in all life siences?
The gene.
89
What is a gene?
The smallest unit of biological instruction.
90
What is the human genome?
The entire genetic constitution of humans. A general instruction set to build a human.
91
How many genes are estimated to exist for humans?
25,000 of them.
92
How similar is all life genetically on earth?
Remarkably small differences exist.
93
What is proteomics and epigenetics?
The field of studing the expression of genes and the proteins they code for.
94
What is the name of the area a gene can be found on a chromosome?
A locus.
95
Gene naming is not standardized yet, but name 2 genes?
BRCA1- breast cancer. P53- Tumor suppressor gene, c-myc- oncogene.
96
What is the name of a nucleotide sequence of genes?
Allele.
97
What is a significant allelic variation called?
Polymorphisms.
98
What are conserved alleles?
genes that don’t vary too much because of severe biochemical consequences if changed.
99
What is it called when a gene is created by the process of nucleotide change?
Mutation.
100
What is a wild-type allele?
Common type of alleles the normal ones.
101
What is a mutant allele?
Those that vary from "normal" or wild-type alleles.
102
What is considered a mutant strand/gene?
When there is ANY change in the nucleotide base-pair sequence whether or not it changes anything.
103
What is a dominant and a recessive gene?
Dominant just means the gene that gets expressed. Recessive is the gene that will not be expressed.
104
Since humans are diploid there will be ___ copies of each gene and this is known as what?
2, genotype.
105
What is the outward expression of a genotype known as?
Phenotype.
106
What would the name be for 2 dominant alleles?
Homozygous dominant.
107
What would the name be for 1 dominant and 1 recessive allele?
Heterozygous
108
What would the name be for 2 recessive alleles?
Homozygous recessive.
109
Alleles besides being dominant or recessive what else is there?
Incomplete dominance where neither allelic form is fully expressed.
110
Phenotype = ?
Genotype + environment.
111
What does phenotype= genotype + environment mean?
The environment can change how genotype will be expressed.
112
Any change in genetic material is a what?
Mutation.
113
Name a single gene mutation that we know the specific mutation that leads to a change?
Sickle cell anemia.
114
What causes sickle cell anemia?
A single base pair substitution in the beta-globin gene on chromosome 11.
115
The single amino acid substitution in sickle cell anemia leads to what?
Abnormal hemoglobin.
116
Abnormal hemoglobin leads to what?
Sickling erythocytes.
117
Where will sickling erythrocytes collect at and cause what?
Collect in the spleen and casues splenomegaly.
118
Since sickling RBC collect in the spleen this causes anemia which leads to what?
Tower skull and long bones, poor physical development, impaired mental function, weakness, lassitude and heart dilation.
119
Sickle shaped RBC clump and interfere with blood circulation and this causes what?
Heart damage, paralysis, pneumonia, abdominal pain, rheumatism, renal failure.
120
What causes mutations?
Unknown and 2 broad catagories of Radiation and chemicals.
121
What type of radiation causes mutations?
Cosmic rays, Radiocative decay, X-rays.
122
What type of chemicals of the 100's known where listed in the notes to cause mutations?
Polycyclic aromatic hydrocarbons, oxidative agents.
123
What is one model that explanes how radiation can cause mutations?
Tautomeric shift. When Radiation is present some base pairs will shift to their enol state a lot more frequently and this can cause the wrong base pair to match during division.
124
What did Hermann Muller prove in 1927?
That X-rays are mutagenic in Drosophila.
125
What is the safe level of radiation exposure to a geneticist?
There is no safe level.
126
The best guess is that every human is born with 5-8 harmful recessive alleles and they accumulate 30 new mutations in a lifetime, and this mutational load is often referred to as what?
Genetic load.
127
What are the 2 broad groups of gene products?
structural genes, and metabolic genes.
128
What are structural genes?
They code for structural components inside and or outside cells.
129
What are metabolic genes?
They code for metabolic components that control reactions.
130
What happens when metabolic genes fail?
They are usually recessive mutations and they are often termed inborn errors in metabolism.
131
Metabolic genes are like what?
Generic biochemical pathways.
132
What usually happens in the later stage of a metabolic pahtway?
feedback inhibition.
133
What happens with a metabolic pathway when the primary path is blocked?
It will activate an alternative pathway.
134
What happens with a failure to synthesize a necessary enzyme and the metabolic pathway is disrupted?
Metabolic disease.
135
What 2 things happen with a metabolic disease?
Accumulation of an immediate precursor and deficiency of a product.
136
What is Hartnup disease?
A metabolic disease of defective tryptophan transport. Which leaves an accumulation of tryptophan.
137
Hartnup disease is a problem of many amino acids in a group called what?
Neutral aminoacidurias.
138
The metabolic diseases in the notes are what type of inherited disease?
Homozygous recessive.
139
What is Galactosemia?
Defective carbohydrate metabolism that leads to an accumulation of galactose. This leads to GI problems.
140
What is hypomelanism?
Albinism that happens from an amino acid metablosm disease that leads to deficiency of melanin.
141
What is Phenylketonuria?
PKU. Amino acid metabolism disease that results in the accumulation of phenylalanine.
142
PKU does what to the person?
Severe mental retardation, hypo-pigmentation and unsual odor.
143
What causes the hypo-pigmentation seen with PKU disease?
It is due to low levels of blood/body tyrosine.
144
What causes the unusual odor seen with PKU disease?
Activation of an alternative pathway.
145
What is Lesch-nyhan syndrome?
A purine metabloism disease. That leads to a deficiency of adenosine and and accumulation of Uric acid.
146
Lesch-nyhan syndrome has a loss of what?
feedback inhibition.
147
Lesch-nyhan syndrome is seen in what type of people?
Only males.
148
Lesch-nyhan syndrome causes what?
Extreme hyperuricemia.
149
What is first seen in a baby with a metabolic disease phenotype?
failure to thrive.
150
If infants survive that have metaboic disease what will the phenotypes show besides failure to thrive?
Gradual onset, unusual dietary responses, mental retardation, dysmorphology.
151
Many genetic disorders are classified based on what?
Mode of inheritance. Like autosomal dominant, autosomal recessive and such.
152
The first description of gene regulation was described in prokaryotes as what?
Lac operon.
153
After the Lac operon what comes next?
Genes that control the production of the enzymatic machinery to digest lactose.
154
Why is it clear that gene expression is regulated?
The fact that they can turn on and off.
155
What is DNA microarray?
a grid of DNA probes that simultaneously identifies the expression of potentially thousands of genes. This is used to identify unique exprssion patterns in cells.
156
What is Epigenetics?
The science of gene expression through external influences since even identical genotypes produce different phenotypes.
157
How are most variations of gene expression done?
Due to epi-genetic interactions.
158
What is the first step to take to figure out inheritance of something?
Establish the parental genotypes.
159
What is the second step to take to figure out inheritance of something?
Consider the possible gamets of the parental genotypes
160
What would the genotype of offspring be for parents that have Aa and Aa?
AA-25%, Aa-50%, aa-25%.
161
What is the genotypic ratio and phenotypic ratio of heterozygous mating?
Genotypic ratio- 1:2:1 (AA, Aa, aa). Phenotypic ratio- 3:1 (3-A, 1-a)
162
What is variable expressivity?
Variable presentation of phenotype. People can vary in the amount of pheotypic display they show even if they have identical genes.
163
What is penetrance?
Expression/ non-expression of a dominant gene despite dominance some traits are not expressed. You can have the dominant gene and not show the phenotype.
164
What is Pleiotropy?
Where one gene will effect multiple traits.
165
How is penetrance calculated?
Take an expected probability and multiply it by the % penetrance.
166
The laws of mendelian inheritance will be violated in this calls and the final mode of inheritance will be called what?
Multifactorial inheritance. And there will be a topic called Linkage.
167
What should a pedigree include?
ANY and ALL relevant info about genetic relationships.
168
What is the symbol for a male and a female?
Male- square. Female- circle.
169
How is an affected individual marked?
Colored in or shaded.
170
What would a squar with the number 6 inside mean?
6 males.
171
What is the symbol for sex unknown and when would this be used?
Diamond and could be used when combining people that are both male and female.
172
How are deceased people marked?
A line is drawn through them.
173
What is the Proband and what is the Consultand? How are they marked?
Proband- the first affected family member coming to medical attention. Proband is colored in and has a P and an arrow pointing to it. Consultand- Individual seeking genetic counseling and is marked by an arrow pointing to it.
174
What would the triangle mean?
Pregnancy that stopped either a spontaneous abortion or anything else that stopped a pregnancy.
175
What would a P inside a circle mean?
A pregnant female.
176
How would inbredding be marked?
A double line for the relationship line.
177
How are twins marked?
there would be a v connecting them to their parents and if they are monozygotic there would be a line acrossed the V. If
178
How are adoptions marked?
They adopted person would be in brackets and dotted lines connect them to their adopted parents and connecting lines to their genetic parents.
179
What is the last thing that needs to be done with a pedigree chart?
Label the generations from top to bottom with roman numberals and number each generation from left to right.
180
The most common mutant allelic form for phenylalanine hydrozylase gene is at 12q24.1 and affected persons (with PKU) are homozygous recessive. What does all this mean?
The most prevalent genetic variant for the enzyme that converts phenylalanine to tyrosine is on chromosome 12 the long arm region 2 band 4.1. Persons have 2 copies of this mutation express a disease called phenylketonuria.
181
Where do mutations come from?
Ionizing (high energy) radiation. Chemicals.
182
How could a single base pair substition in the beta-globin gene result in rheumatism?
Point mutation leads to single amino acid substition---> sickling of erythrocytes -----> clumping of RBC and interference with blood circulation ----> Muscle and joint damage----> Rheumatism.
183
How might a base pair substitution (mutation) in a critical gene not result in any change in the phenotype?
1. A genetic code is degenerative. 2. The mutation might be in an intron. 3. The change might be in a non-critical part of the protein.
184
What do galactosemia, phenylketonuria and albinism have in common?
They are all metabolic defects. All autosomal recessive. They are all enzyme defects.
185
Why are most of the metabolic disorders recessive?
They usually result in a lack of function and in presence of a normal allel the work of the cell still gets done.
186
What would be the predicted genotype ratio of offspring from a couple when one parent is homozygous dominant and one parent is heterozygous?
AA x Aa= AA and Aa 50:50 or 1:1.
187
Depending upon the amount of phenylalanine that a PKU patient is exposed to, their symptoms can range from severe mental impairment and irritability to just hypo-pigmentation. This would be an example of what genetic term?
Variable expressivity.
188
The gene for albinism causes "white" hair, pale skin and red eyes. - or- The gene for cystic fibrosis causes thck respiratory mucous, excessive sweating and pancreatic insufficiency. -or- the gene for huntington's disease causes involuntary twitching and dementia. ALl of these disorders demonstrate what genetic phenomenon?
Pleiotropy.
189
Not all persons with the dominant gene for polydactyly exhibit the trait (though as heterozygotes, they should). This demonstrates what genetic concept? Now imagine that the _____ (answer from first part) was determined to be 80% and that one parent is an affected heterozygote with a 50:50 chance of passing the mutation to an offspring (and assuming that the other parent is normal); what would be the approximate probability of this parent having a child with polydactyly?
Penetrance, Aax aa ---> 50% x 80%= 40%.
190
Draw a well organized pedigree (using all standard symbols and notations) from the following data: you are the consultand and are the first born child in a sibship with 2 younger sisters; your parents are alive; your father had a brother ( your paternal uncle) who died of alzheimer's disease; your mother has a sister ( your maternal aunt) and she has a husband who together have 2 sons ( your first cousins); and this first born cousin and his spouse have a new set of identical twin daughters. There is no other info.
Check page 62 of notes.
191
What is the 3rd(Final) step to take to figure out inheritance of something?
Consider how the genes in the offspring might be expressed.
192
What is IMPRINTING (genetic or genomic imprinting)?
A phenomenon whereby inherited chromosomes from one parent are modified such that the genes at that location are not properly expressed.
193
What two conditions show imprinting?
Prader Willi & Angleman
194
What is the root cause for cystic fibrosis & involves a defect in which chromosome?
Cystic Fibrosis Transmembrane Conductance Regulator (CFTR); this 250kb stretch of DNA on chromosome #7 codes for a single protein involved in chloride ion transport in many epithelial cells.
195
Where are "homeobox"/HOX gene subsets found & what do they do?
The HOX gene subsets are found on
chromosomes 2, 7, 12 and 17, and they appear to control patterning of the body axis and the
resultant development of body organs.
196
What is the highly conserved CREB gene responsible for?
Regular brain development and function. When active it regulates the production of “neuropeptide
Y” (NPY) which, as the most common brain neuropeptide. CREB is critical for learning and memory.
197
What disease has been recently associated with the CREB gene?
Alcoholism
