Term
| What are mutations and polymorphisms? Distinguish between the two. |
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Definition
-Permanent changes in the nucleotide sequence or arrangement of DNA
M= the DNA change is rare; it occurs in less that 1% of the general population
P= if there are at least two relatively common alleles of a gene in the population (>1% of the general pop.), the gene is said to exhibit polymorphisms |
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Term
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Definition
| a hereditary unit. A sequence of chromosomal DNA that is required for the production of a functional unit |
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Term
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Definition
| alternative variants of a gene |
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Term
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Definition
| the physical location of a gene (or other segment of DNA) on a chromosome |
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Term
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Definition
| For many genes, the single, common, prevailing allele present in most people |
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Term
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Definition
| An allele of a gene that differs from the wild-type allele because of the presence of a mutation |
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Term
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Definition
| A permanent change in the nucleotide sequence or arrangement of DNA |
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Term
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Definition
| If there are at least two relatively common alleles at a locus or gene in the population (>1%), the locus is said to exhibit polymorphisms (rather than mutations) |
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Term
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Definition
| the set of alleles in a single gene in a person, or the set of alleles in every gene collectively in a person |
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Term
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Definition
| a given set of alleles at a locus, or cluster of loci on a chromosome |
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Term
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Definition
| the observed biochemical, physiological, and morphological characteristics of an individual, as determined by their genotype and the environment in which it is expressed. Also refers to the abnormalities resulting from a particular mutant gene |
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Term
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Definition
| Multiple phenotypic effects of a single allele or pair of alleles. The term is used especially when the effects are not obviously related |
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Term
| Define compound heterozygote. |
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Definition
An individual that contains two different mutant alleles of the same gene
Ex: often cystic fibrosis (there tons of different mutant alleles) |
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Term
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Definition
| A male with a mutant allele for a gene on the X chromosome |
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Term
| Humans are _______% identical at the DNA level. The ______% difference in our DNA sequences accounts for the genetically determined variability among humans |
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Definition
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Term
| What does a genome mutation affect? |
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Definition
| the number of intact chromosomes in the cell |
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Term
| What does a chromosome mutation effect? |
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Definition
| it alters the structure of the individual chromosome |
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Term
| What do gene mutations effect? |
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Definition
| they alter the individual genes |
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Term
| What causes genome mutations? Gene mutations that produce chromosomal _________ are the most common mutations seen in humans |
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Definition
-Missegregation of a chromosome pair during meiosis (trisomy 21)
-Aneuploidy (one too many or one too few of the chromosome--> down syndrome) |
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Term
| What type of mutations are common in cancer cells? |
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Definition
| genome mutations, chromosomal mutations |
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Term
| What is the rate of missegregation events in meiotic cells divisions? |
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Definition
| 1 missegregation event per 25-50 meiotic cell divisions |
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Term
| Chromosome rearrangements cause chromosome mutations at a rate of ___ rearrangement per ________ cell divisions |
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Definition
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Term
| Gene mutations can occur in ___________ cells or __________ cells. Only __________ mutations are heritable. |
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Definition
germline or somatic
germline |
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Term
| Gene mutations arise by either of two basic mechanisms, what are they? |
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Definition
-errors introduced during the normal process of DNA replication
-mutations arising from a failure to correctly repair DNA after damage |
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Term
| In contrast to DNA replication errors, _________ changes introduced by DNA damage and repair often result in ___________/______________ |
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Definition
nucleotide
permanent mutations |
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Term
| Mutations at the molecular level can involve ___________, _____________, or _____________ of one or more nucleotides in DNA |
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Definition
substitutions
deletions
insertions |
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Term
| What are nucleotide substitutions? |
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Definition
| mutations that involve substitutions of one or more nucleotides in a DNA molecule with other nucleotides (changes the sequence of the DNA but not the number of nucleotides) |
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Term
| What are the three type of nucleotide substitutions? |
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Definition
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Term
| What is a missense mutation? |
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Definition
mutations that cause the substitutions of one amino acid for another in a protein
(ex: as a result of different DNA mutations in the beta globin gene, a GAG codon in the mRNA can be changed to GUG, AAG, or GCG) |
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Term
| What is a sense mutation? |
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Definition
| mutations in a single nucleotide can change a stop codon into one that codes for an amino acid, producing longer-than-normal proteins |
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Term
| What is a nonsense mutations? |
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Definition
| mutations that change a codon specifying an amino acid to one of three termination codons, producing a shorter than normal protein |
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Term
| What is a frameshift mutation? |
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Definition
| mutational events in which a number of bases (other than multiples of three) are inserted into or deleted from DNA, causing a shit in the codon reading frame |
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Term
| What is a trinucleotide repeat? |
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Definition
| a mutation associated with the expansion in copy number of a nucleotide triplet in or near a gene |
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Term
| What is allelic expansion? |
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Definition
Increase in gene size caused by an increase in the number of trinucelotide sequences. Potential for expansion is characteristic of a specific allele
-Cuases several different genetic disorders.
*trinucleotide repeats--> allelic expansion |
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Term
| What type of nucleotide substitution (point mutation) causes the highest percentage of disease-causing mutations |
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Definition
| -missense mutations (amino acid substitutions) |
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Term
| What is the mutation rate? |
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Definition
| the number of new mutations per locus per generation |
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Term
| In terms of mutations in oogenesis and spermatogenesis females have more chance of __________/___________ as they age and males have more chance of ______________/_________ as they age. |
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Definition
chromosomal nondisjunction
point mutations |
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Term
| What is a molecular disease? |
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Definition
| one in which the primary disease-causing event is a mutation, either inherited or acquired. |
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Term
| What is a molecular disease? |
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Definition
| one in which the primary disease-causing event is a mutation, either inherited or acquired. |
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Term
| Mutations in DNA cause disease through one of four different effects on protein function, what are they? |
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Definition
-Loss of function mutations
-Gain of function mutations
-Novel property mutations
-Mutations associated with heterochronic or ectopic gene expression |
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Term
| What are some common causes of loss of function mutations? |
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Definition
| -alteration in a gene's coding, regulatory, or other critical sequences due to the introduction of nucleotide substitutions, deletions, or rearrangements |
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Term
| What are some causes of gain of function mutations? |
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Definition
| may result from either an increase in the abundance of the protein due to increased gene expression, or an increase in the ability of the protein to perform one or more normal functions |
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Term
| What are some causes of novel property mutations? |
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Definition
| may result from a change in the amino acid sequence that causes disease by conferring a novel property on the protein, without necessarily altering its normal function |
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Term
| What are some causes of mutations associated with heterochronic or ectopic gene expression? |
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Definition
| may result from alterations of gene's regulatory regions to cause its inappropriate expression at an abnormal time or place |
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Term
| Name and explain the three different types of dominant inheritance. |
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Definition
-Pure dominant: the phenotype is the same in heterozygotes and homozygotes (very rare)
-Incompletely dominant (semidominant): the phenotype is more severe in homozygotes than in heterozygotes (most common)
-Codominant: the phenotype is caused by the expression of two different alleles for the same gene in a heterozygote. The phenotypic effects of both alleles are equal, neither allele is dominant over the other |
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Term
| In most disorders, individuals with abnormal phenotypes can be easily distinguished from individuals who have not inherited the disorder. However, in some disorders, the phenotype may be different in individuals who have the same abnormal genotype. The factors that account for these differences and affect interpretation of pedigree patterns are what 4 things? |
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Definition
penetrance
expressivity
age at onset
other factors |
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Term
| What is penetrance? It can be described as an ______/__/_____ phenomenon |
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Definition
| The probability that a gene will have any phenotypic expression at all. Penetrance is an all or none phenomenon; either the gene is expressed or not. |
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Term
| When is a phenotype said to have reduced penetrance? |
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Definition
| When less than 100% of the people with the abnormal genotype exhibit the disease |
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Term
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Definition
| the severity of the expression of the disease phenotype among individuals with the same disease causing genotype. When the severity of the disease differs among people with the same abnormal gene, the phenotype has variable expressivity. |
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Term
| What is genetic heterogeneity? |
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Definition
| phenotypes of individuals appear similar but their genotypes are different |
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Term
| What is allelic heterogeneity? |
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Definition
| different mutations in the same gene (the most important cause of clinical variation in disease phenotypes) |
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Term
| What is locus heterogeneity? |
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Definition
mutations in different genes
(different genes that operate in the same pathway-->same phenotype) |
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Term
| What is phenotypic heterogeneity? |
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Definition
| different mutations in the same gene can give rise to strinkingly different phenotypes |
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Term
| Autosomal recessive inheritance occurs only in _________ or ___________/___________. |
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Definition
homozygotes
compound heterozygotes |
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Term
| Any child of a parent with an autosomal dominant disorder has a ______% risk of inheriting the trait |
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Definition
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Term
| In a male with a x-linked dominant disorder, will his sons or daughters be affected with the disorder? |
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Definition
| no sons will be affected but all daughters will be |
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Term
| The incidence of X-linked recessive disorders is much higher in which sex? |
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Definition
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Term
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Definition
the presence of at least two cell lines that differ genetically, but are derived from the same zygote.
-mutations arise in a single cell (either in prenatal or postnatal life) and give rise to daughter cells that also contain the mutation |
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Term
| What is the phenomenon of genetic imprinting? |
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Definition
For most genes, the allele inherited from the mother and the allele inherited from the father are expressed equally. However, for a small number of genes, the expression of the gene and the nature of the disease phenotype depends on whether the mutant allele was inherited from the mother or the father.
-maternally imprinted= mother's gene is not expressed.
-paternally imprinted= father's gene is not expressed |
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Term
| Usually inherited mutations are stable from generation to generation, however a small group of genetic diseases are caused by unstable repeat expansions. What does this mean? |
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Definition
| These diseases are characterized by an expansion within the affected gene of a DNA segment consisting of three or more nucleotides in tandem that are repeated multiple times |
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