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Display of chromosomes ordered by their length
- Having one copy of each chromosome
- N = 1
- Human gametes
- Having two copies of each chromosome
- Human somatic cell
Having one or more missing or extra chromosomes
Balanced chromosomal sbnormality
No net gain or loss of chromosomal material
Unbalanced chromosomal abnormality
Net gain or loss of genetic material
A chromosome pair is derived solely from one parent in the diploid offspring
p and q arms of chromosome
p = short arm
q = long arm
Both arms are of equal length
One arm is a bit shorter than the other arm
One arm is much shorter than the other arm
Any somatic chromosomes
Contrast with autosomes
In humans, X and Y are the sex chromosomes
decondensed, active form of a chromosomal region
Condensed, inactive form of a chromosomal region
Facultative heterochromatin can become decondensed but constitutive is always condensed
Staining of bands of chromosome segments
Allows for the precise identification of individual chromosomes or parts of chromosomes
The failure of the paired chromosomes to segregate properly during meiosis or mitosis
Results in daughter cells with an abnormal number of chromosomes
Segments of two different chromosomes have been exchanged
Joining of two acrocentric chromosomes at the centromeres with loss of their short arms to form a single abnormal chromosome
A segment of the chromosome is flipped around the and the genetic material is inverted
Usually occurs when a chromosome breaks in two places and the ends of the chromosome arms fuse together to form a circular structure
Origin of replication
Site on DNA molecule where replication starts
The strand of DNA double helix that is copied in a continuous fashion
The strand of the DNA helix that is copied in a discontinuous fashion
Class of enzymes that alter the supercoiling of double-stranded DNA
Enzyme that separates the strands of the DNA double helix
Short segment of RNA-primed DNA that is synthesized on the lagging strand during replication
A drug or substance that is an antagonist to or resembles a normal metabolite and thus interferes with its function, usually by competing for its receptors or enzymes.
Antimetabolites used as anticancer agents include 5-fluorouracil (5-FU)
Enzyme consisting of RNA and protein components that maintains the ends of chromosomes by adding specific repeat sequences.
DNA polymerase can lose its place in a repetitive sequence tract, and either leaves out or add an inappropriate number of repeat units.
Base Excision Repair (BER)
DNA repair process that involves the excision and replacement of a normal base
Nucleotide excision repair (NER)
DNA repair process involving the excision and resynthesis of a polynucleotide region
In the context of DNA repair, a process involving the recombination between homologous double-stranded DNA molecules.
Base + Sugar + Phosphate
One of the alternative versions of a gene or DNA sequence at a given locus.
- A pattern of inheritance in which an affected individual has one copy of a mutant gene and one normal gene on a pair of autosomal chromosomes
- (example: Huntington disease).
A pattern of inheritance in which an affected individual has two copies of the mutant gene (example: cystic fibrosis).
If both alleles of a pair are expressed in the heterozygous state, then the alleles (and/or traits determined by them) are codominant.
An individual or genotype with two different mutant alleles at the same locus.
Related by descent from a common ancestor.
The extent to which a genetic defect is expressed. If there is variable expressivity, the trait may vary in expression from mild to severe but is never completely unexpressed in individuals who have the corresponding genotype. Contrast this concept with that of penetrance.
A high frequency of a mutant allele in a population founded by a small ancestral group when one or more of the founders was a carrier of the mutant allele.
- The progressively earlier onset and increased severity of certain diseases in successive generations of a family. Anticipation is caused by expansion of the
- number of unstable repeats within the gene responsible for the disease.
- The genetic constitution f an individual, as distinguished from the phenotype.
- More specifically, the alleles present at one locus.
An individual or genotype with two different alleles at a given locus on a pair of homologous chromosomes.
An individual or genotype with identical alleles at a given locus on a pair of homologous chromosomes.
The position occupied by a gene on a chromosome. Different forms of the gene (alleles) may occupy the locus.
Any permanent heritable change in the sequence of genomic DNA.
The fraction of individuals with a genotype known to cause a disease who have any signs or symptoms of the disease. Contrast with expressivity.
- The observed biochemical, physiological, and morphological characteristics of an individual, as determined by his or her genotype and the environment in which it is expressed. Also, in a more limited sense, the abnormalities resulting from a particular
- mutant gene.
- Inheritance determined by many genes at different loci, with
- small additive effects; not to be confused with multifactorial inheritance, in which environmental as well as genetic factors may be involved.
The affected family member through whom the family is ascertained.
Random (disassortative) mating:
- Selection of a mate without regard to the genotype of
- the mate. In a randomly mating population, the frequencies of the various matings between individuals with particular genotypes are determined solely by the frequencies of
- the alleles concerned.
- Genetic inheritance by which a dominant gene is carried on the X chromosome. A gene responsible for a genetic disorder is located on the X chromosome,
- and only one copy of the allele is sufficient to cause the disorder when inherited from a parent who has the disorder.
- Genetic inheritance in which a mutation in a gene on the X chromosome causes the phenotype to be expressed (1) in males (necessarily hemizygous for the gene mutation because they have only one X chromosome) (2) in
- females (homozygous for the gene mutation: They have a copy of the gene mutation on each of their two X chromosomes).
DNA sequence is shredded into random segments and the small fragments are then individually sequenced
The sequences of these fragments are then used to determine the sequence of the original DNA sample
Hierarchical shotgun sequencing approach
Large, overlapping DNA fragments of a known location in the genome are shredded and sequenced.
The sequences of these large fragments are then used to determine the sequence of the human genome
Whole-genome shotgun sequencing
Genome is shredded into small fragments and then sequenced to determine the sequence of the entire genome
The complete exon conent of an individual
A class of specific repeat sequences in the human genome
Consit of LINE, SINE, and retro-virus like elements as well as DNA transposon fossils
Long interspersed nuclear elements
- a specific type of interspersed repeat element
- that encode the proteins necessary for their own replication
Short interspersed nuclear elements are
- a specific type of interspersed repeat element
- that do not encode the proteins necessary for their own replication.
Retrovirus like elements
Specific type of interspersed repeat element that may or may not encode the proteins necessary for their own replication
DNA transposon fossils
Specific type of interspersed repeat element that may or may not encode the proteins necessary for their own replication.
Sequences >1-kb in length that share 90-98% identity. A segmental duplication can contain interspersed repeat sequences.
de novo mutations
a sequence change that is present for the first time in one family member as a result of a mutation in a germ cell of one of the parents or in the fertilized egg
Copy number variants
sequence that is at least one kilobase in length and polymorphic. This definition may vary slightly depending on the source.
Single nucleotide polymorphism
A polymorphism in DNA sequence consisting of variation in a single base.
- A set of DNA variations, or polymorphisms that tend to be inherited together. A haplotype can refer to a combination of alleles or to a set of single nucleotide polymorphisms
- (SNPs) found on the same chromosome.
Genome-wide association study (GWAS)
- a case-control study in which genetic variation,
- often measured as SNP genotypes, is compared between people with a particular trait and unaffected individuals.
The type of non-Mendelian inheritance shown by traits that are determined by a combination of multiple factors, genetic, and environmental.
It is also termed complex inheritance. In principle, multifactorial inheritance can be polygenic (involving many genes at different loci), but it always has to be influence by the environment.
Genes on the same chromosome are linked if they are transmitted together in meiosis more frequently than by chance
The nonrandom association between two or more alleles such that certain combinations of alleles are more likely to occur together on a chromosome than other combinations of alleles
Inheritance determined by many genes at different loci, with small additive effects. It is distinct from multifactorial inheritance in that environmental factors are not involved.