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Flashcards in Genetics Deck (146)
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1

Nonsense mutation

Introduce stop codon within gene sequence resulting in formation of shorter nonfunctional protein.

2

Silent mutation

Ex. UAA--> UAG (both stop codons)
Ex. UUU-->UUA (both code for phenylalanine)
Mutation does not alter protein structure, and is thus silent.

3

Frameshift mutation

Occur with deletion, or less commonly, insertion of base pairs which are not a multiple of three therefore altering the reading frame of genetic code. Usually results in formation of shorter, nonfunctional proteins.

4

Missense mutation

Base substitution resulting in an amino acid change, creating a dysfunctional but usually same sized protein. Eg, UUU to UCU changes translated AA from phenylalanine to serine.

5

Splice site mutation

Formation of larger proteins that are usually nonfunctional, but often retain immunoreactivity of normal protein (binding to antibodies). Eg, nonfunctional protein contains 156 AA residues rather than the 130 AA residues seen in the functional protein. Nonfunctional protein still detected by specific Abs against the functional protein.

6

Homeobox

A highly conserved DNA sequence, usually ~180 nucleotides in length. A gene containing a homeobox sequence is called a homeobox gene. Homeobox genes typically code for DNA-binding transcription factors which alter expression of genes involved in morphogenesis (the proper formation and placement of tissues, organs, and structural elements of the body).

7

Anticipation

Earlier age of onset associated with larger number of trinucleotide repeats. During spermatogenesis, CAG repeats in the abnormal HD gene rapidly increase. Thus, patients who receive an abnormal gene from their fathers tend to develop the disease earlier in life. Number of trinucleotide repeats on HD gene remains the same during maternal transmission. Anticipation is common in d/o associated with trinucleotide repeats aka Fragile X, myotonic dystrophy, Friedreich ataxia.

8

Deletion

The loss of genetic material. Examples of deletion are DiGeorge syndrome (22q11 microdeletion) and cri-du-chat syndrome (5p deletion).

9

Kozak sequence

1. Kozak consensus sequence occurs on eukaryotic mRNA [(gcc)gccRccAUGG, where R is either A or G] and plays a role in initiation of translation (mRNA binding to ribosomes).
2. When AUG (methionine codon) positioned near the beginning of an mRNA molecule and is surrounded by the Kozak sequence, it serves as the initiator for translation.
3. The purine (A or G) in the R position, 3 bases upstream from AUG, appears to be a key factor in initiation.
4. A mutation in which G is replaced by C three bases upstream from start codon (AUG) in the Kozak sequence of the β-globin gene is associated with β-thalassemia intermedia.
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10

Stop codons

1. UGA "U're Going Away"
2. UAA "U Are Away"
3. UAG "U Are Gone"
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11

Genetic disorders with mutations on chromosome 1

1. Chediak-Higashi syndrome (CHS1/LYST gene)
2. Factor V Leiden (factor V gene)
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12

Genetic disorders with mutations on chromosome 2

1. Gilbert syndrome/Crigler-Najjar Syndrome (UGT1A1 gene) 2. HNPCC (microsatellite instability)
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13

Genetic disorders with mutations on chromosome 3

1. von Hippel-Lindau disease (VHL gene on 3p)
2. Renal cell carcinoma (VHL gene)
3. HNPCC (microsatellite instability)
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14

Genetic disorders with mutations on chromosome 4

1. Achondroplasia (FGFR3 gene)
2. Huntington disease (CAG repeats in HD gene)
3. ADPKD (PKD2 gene)
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15

Genetic disorders with mutations on chromosome 5

1. Cri-du-chat (5p microdeletion)
2. Familial Adenomatous Polyposis (APC gene on 5q)
3. Gardner syndrome (APC gene)
4. Turcot syndrome (APC gene)
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16

Genetic disorders with mutations on chromosome 6

1. Hemochromatosis (HFE gene, C282Y > H63D)
2. Congenital Adrenal Hyperplasia (21-β-hydroxylase gene)
3. ARPKD (polyductin gene)
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17

Genetic disorders with mutations on chromosome 7

1. Williams syndrome (7q microdeletion)
2. Cystic Fibrosis (CFTR gene, ΔF508)
3. Osteogenesis imperfecta (COLIA2)
4. HNPCC (microsatellite instability)
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18

Genetic disorders with mutations on chromosome 9

1. Friedreich ataxia (GAA repeat in frataxin gene)
2. Tuberous sclerosis (TSC1 gene)
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19

Genetic disorders with mutations on chromosome 10

MEN 2a/2b (RET proto-oncogene)

20

Genetic disorders with mutations on chromosome 11

1. MEN 1 (MEN1 gene)
2. Sickle cell anemia (β-globin gene, HBB)
3. Hb C disease (β-globin gene, HBB)
4. β-thalassemia (β-globin gene, HBB)
5. Oculocutaneous albinism (TYR gene)
6. Ataxia-Telangiectasia (ATM gene)
7. Wilms tumor
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21

Genetic disorders with mutations on chromosome 13

1. Patau syndrome (trisomy 13)
2. Wilson disease (ATP7B gene)
3. Retinoblastoma (RB1 gene)
4. BRCA2 gene
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22

Genetic disorders with mutations on chromosome 14

α-1-antitrypsin disease (A1AT gene, PiZZ genotype)

23

Genetic disorders with mutations on chromosome 15

1. Marfan syndrome (FBN1 gene)
2. Prader-Willi syndrome (15q11-13 paternal chromosome deletion)
3. Angelman syndrome (15q11-13 maternal chromsome deletion)
4. Bloom syndrome (BLM gene)
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24

Genetic disorders with mutations on chromosome 16

1. ADPKD (PKD1 gene)
2. α-thalassemia, (HBA1, HBA2 genes)
3. Tuberous sclerosis (TSC2 gene)
4. Mediterranean Familial Fever (MEFV gene)
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25

Genetic disorders with mutations on chromosome 17

1. Neurofibromatosis type 1 (NF1)
2. LiFraumeni (TP53)
3. BRCA1 gene
4. Osteogenesis imperfecta (COLIA1)
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26

Genetic disorders with mutations on chromosome 18

Edwards syndrome (trisomy 18)

27

Genetic disorders with mutations on chromosome 19

1. Myotonic dystrophy type I (CTG repeats in DMPK gene)
2. Peutz-Jeghers syndrome (LKB1 gene)
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28

Genetic disorders with mutations on chromosome 20

1. Pseudohypoparathyroidism (PTH receptor gene)
2. Hyper IgM syndrome (CD40 receptor gene)
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29

Genetic disorders with mutations on chromosome 21

Down syndrome (trisomy 21)

30

Genetic disorders with mutations on chromosome 22

1. Neurofibromatosis type 2 (NF2)
2. DiGeorge syndrome (22q11 microdeletion)
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