455178
Description
Flashcards by Joanna Elliott, updated more than 1 year ago
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Created by Joanna Elliott
over 10 years ago
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| Question | Answer |
| Genotype | Genetic constitution of the individual |
| Locus | Generic term. A unique chromosomal region that corresponds to a gene or some other DNA sequence |
| Phenotype | Physical manifestation of the genotype (+ the environment) |
| Germ cells | AKA gametes. Sperm cells/Egg cells |
| Haploid | Contains one copy of each chromosome and one copy of each gene |
| Different forms of the same gene may encode different forms of the same protein: True of False | True |
| Malformation | A morphological abnormality that arises because of an abnormal developmental process: a primary error in morphogenesis |
| Dismorphology | The recognition and study of birth defects and related syndromes |
| Congential | Present at birth |
| In disease pedigrees which symbol represents a diseased person | A filled in shape |
| In disease pedigrees which symbol represents a female | Circle |
| In disease pedigrees which symbol represents a male | Square |
| In disease pedigrees which symbol represents a carrier | Dot in the middle of the shape |
| In disease pedigrees which symbol represents a deceased person | A line through the shape |
| In disease pedigrees which symbol represents closely related people | Double line between shapes |
| In disease pedigrees which symbol represents a miscarriage | Triangle |
| In disease pedigrees which symbol represents a termination | Triangle with a line through it |
| In disease pedigrees which symbol represents a stillbirth | Circle with a line through it and a number underneath describing the age in weeks |
| In disease pedigrees which symbol represents an adopted person | Shape in square brackets |
| What is Mendel's first law of inheritance | 1. Law of uniformity - If 2 parents are homozygous for different alleles at locus Z, all their children will have the same genotype at locus Z |
| What is Mendel's second law of inheritance | 2. Law of segregation - An individual receives with equal probability one of the 2 genes from the genotype of the mother and the same goes for the father |
| What is Mendel's third law of inheritance | 3. Law of independent assortment - The segregation of the genes for one trait is independent of the segregation of genes for the other traits. |
| Monogenic (single gene) disorders (Mendelian) | The genotype at one locus is necessary and sufficient for the phenotype to be expressed, given a normal genetic and environmental background |
| What are the 3 characteristic pedigree patterns for monogenic disorders | 1. Autosomal recessive. 2. Autosomal dominant. 3. Sex-linked inheritance |
| Autosomal recessive inheritance | 1. No sex bias. 2. Disorder manifests in homozygotes (both alleles have the same mutation) & compound heterozygotes (both alleles are mutated with different mutations). |
| What needs to be considered in autosomal recessive inheritance | 1. Carrier status of the parent. 2. Consanguinity (a relationship between individuals who are 2nd cousins or closer). 3. Incest. |
| Autosomal Dominant inheritance | 1. No sex bias. 2. Disorder manifests in heterozygotes (when only one copy of the mutant allele is present). |
| In autosomal disorders what is: Penetrance | The percentage of individuals expressing the disorder, to any degree. Eg age dependent penetrance (eg Huntington disease) and incomplete penetrance (carriers) |
| In autosomal disorders what is: Expressivity | The variation in severity between individuals with the same mutation |
| In autosomal disorders what is: Anticipiation | The worsening of disease severity in successive generations |
| Somatic mosaicism | A new mutation arising at an early state of embryogenesis can give rise to a partial phenotype |
| Germline mosaicism | A new mutation arising that may not affect the parent but can affect the offspring |
| Sex linked disorders | Genetic disorders that are carried on the X or Y chromosome |
| What are males described as being, in regard to sex chromosomes | Hemizygous for loci on the Y & X chromosome as they do not possess a second Y or X (therefore the concept of dominance doesn't apply) |
| Genes on the Y chromosome can be transmitted to both Y and X chromosomes: True or False. | False. Genes on the Y chromosome can only be transmitted to another Y chromosome so the transmission is from father to son only |
| All sons of a father with a Y linked disease Will get the disease. True or False. | True |
| The Y chromosome is rich in genes: True or False | False. Gene poor, carries mostly testis determining genes and genes involved in spermatogenesis. |
| What are most Y liked defects associated with | Male infertility/sub-fertility |
| Recessive X linked inheritance | 1. Affects mainly males. Affected males are usually born to unaffected parents (the mother will be a carrier who often has male affected relatives). 3. No male-male transmission. |
| The father with an X linked recessive disease will pass the disease on to both his sons and daughters: True or False | False. Will only pass on to all his daughters. |
| Dominant X linked inheritance | 1. Affects more females than males but can affect both sexes. 2. Females are often only mildly affected, whereas men are severely affected, and the disease can be fatal for them. |
| Rett syndrome | 1. Females mainly affected. 2. Causes neurological regression. X linked dominant inheritance. 3. Mutation of MECP2 gene as well as duplication & transcriptional repression |
| Genomic imprinting | Expression of the disease allele depends on the parent from which it is inherited |
| When do genetically imprinted genes cause disease | 1. When the maternal/paternal gene that is usually expressed is lost/mutated/silenced/deleted. 2. Uniparental disomy |
| Uniparental disomy | In euploid offsprings, one of the chromosome pairs has been inherited exclusively from one parent |
| Physical basis of mutations: Nucleotide substitution | Synonymous mutation (substitution doesn't result in an amino acid change). Missense mutation (Substitution results in an amino acid change). Nonsense mutation ( if the substitution generates a stop codon). |
| Physical basis of mutations: Nucleotide deletion/insertion | These cause shifts in the reading frame (frameshift mutation), almost always resulting in premature truncation of the protein |
| Copy Number Variation | Deviation from the diploid copy number. Can involve small genomic regions/whole genes/contiguous stretches of genes. |
| What are copy number variation disorders known as | Genomic disorders |
| Hereditary haemochromatosis | 1. A disorder of iron metabolism (excessive iron absorption). 2. Autosomal recessive inheritance of mutated HFE. 3. Penetrance is incomplete. 4. Treatment = venesection (removing blood from your body) |
| Hereditary haemochromatosis diagnosis | Based upon phenotype (clinical presentation & raised blood Fe levels) & genotype (mutation specific detection of the p.C282Y allele using PCR and DNA sequencing). |
| What would you used to detect a known mutation without DNA sequencing | Restriction fragment length polymorphism. Amplify and see if the mutation destroys or creates a restriction enzyme cleavage site, then use gel electrophoresis |
| What can cytogenic karyotype analysis be used to look for | Genomic disorders |
| FISH analysis | 1. Fluorescent in situ hybridisation. 2. Standard - Hybridisation of DNA probes targeted to specific genome regions. 3. Painting - Hybridisation of multiple chromosome-specific probes. |
| DiGeorge syndrome | 1. Disorder caused by hemizygous deletion of a small region on the long arm of chromosome 2 (haploinsufficiency) |
| Molecular diagnosis of DiGeorge syndrome | Interphase FISH (dual probe) |
| a-CGH | Array comparative genomic hybridisation. 2. Uses BAC or oligonucleotides as probes. |
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