Five-carbon sugar

Phosphate molecule

Nitrogen-containing bases (adenin, guanine, cytosine,thymine)

Locus

Alternative forms of a gene or marker due to changes at the level of DNA.

Different forms of a gene.  Homans have 2 copies, or alleles, of all autosomal genes.

ie ABO blood groups have 3 allels A, B, and O

DNA

The first 22 pairs of chromosomes.

23rd pair determines sex.

XX= female

XY= male

p= short arm

q= long arm

an alteration in a single base pair

missense mutaion: a single base pair substitution resulting in a change in the amino acid coded for  by the codon. 

nonsense mtuation: results in a premature stop codon causing either an abnormally shaped protein with altered function or a protien that is very unstable.

occur when the number of deleted or inserted base pairs IS a multiple of three resulting in a change of only a few amino acids. 

The protein may still function even with a slightly diff. sequence.

only one copy of a disease allele is necessary for an individual to be susceptible to expressing the phenotype.

50% chance of offspring inherting the allele

Often called vertical inheritance

ie myotonic muscular dystrophy and huntington's disease

Two copies of a disease allele are required for an individual to be susceptible to expressing the phenotype.

affected males=affected females

25% chance offspring will inherit 2 allele and therefore have phenotype

25% chance offspring will not inherit copies of disease allele and will not express [henotype or be a carrier.

50% chance the offspring will inherit one cpy of the disease allele and willbe a carrier

i.e sickle cell anemia and Cysitc fibrosis

Only one copy of a disease allel on the X chromosome is required for individual to be susceptible.  Both males and females can be affected. 

Males more severe than females

I.E. oral-facial-digital syndrome type 1 and Fragile X syndrome

two copies of a disease allel on the x chromosome are required for an individual to be affected.

• Males with one copy are still affected because they are hemizygous.
• Females are usually carriers( - 50% chance her sons will inherit & 50% chance her daughters will be carrier)unless they have two copies of disease allele( - all daughters will be carriers, all sons will be affected). 

Complex disorders

(multifactorial disorders)

caused by the intereactions of variations in multiple genes and environmental factors.  The genes involved may make the person susceptible to the disorder. and the environmental factors trigger this susceptibility. 

i.e. diabetes, asthma, heart disease

The probability that an individual who carries one copy of a dominant allele OR two copies of a recessive allele shows the condition. 

May be age dependant i.e. male pattern baldness

Whena  condition is expressed in a varity of different ways.  A disorder may have a constellation of symptoms, but an individual may only express certain ones.

Creates Gametes.  genetic info is exchanged b/w maternally and paternally inherited copies of a pair of chromosomes in order to create new combinations of genes. Genetic recombination: increase in genetic variability within a species. 

Process sprem and egg cells go thru for reproduction; shuffles gnetic information and cuts number of chromosomes in half 

Homologous chromosomes are a pair of chromosomes, noe member from the mother and one from the father.

During meiosis they pair together

an expansion of a segment of DNA that contains a repeat of 3 nucleotides, such as... CAGCAGCAG...CAG

Individuals have a variable number of triplet repeats witha threshold where a higher number of repeats cause disease.  The threshold varies in diff. disorders.

The number of triplet repeats increases from generation to generation and may become more severe or have earlier onset.   

a normal, but unstable number of repeats. 

when number of repeats falls int his range then they may or may not transmit to the next generation.  Normal individuals may carry the premutation and are unaffected, but their child may inherit the full mutation and be affected. 

methylation of a gene preventing it from expression (inactivation) 

expression of genes are varible depending on which parent the gene came from. 

Imprinting only occurs on 9 chromosomes

Imprinting is reversible when passing on to new generation.

the occurrence of cells that differ in their genetic component from other cells of the body.  the individual will have a mixture of cells, some mutated some not. 

How early in developement mutation occurrs determines what tissue(s) and what % of cels have mutation. 

affecting only egg and sperm cells and is passed onto offspring.

a person only with germline will not be affected with disorder b/c the mutation is not in the other cells of the body. 

Typically unaffected parent will have affected childern( b/c mutation will occur in other cells of body).

Usually autosomal dominant or X-linked disorders. 

Mitochondrial DNA, a small double stranded circular molecule containing 37 genes. 

Mutaitn rate is 10Xs higher in mtDNA than DNA b/c mtDNA is subject to damage from reactive oxygen molecules released as biproduct of phosphorylation during ATP production. Also mtDNA has no repair mechanisms like DNA has.   

When a cell has some mitochondria that have a mutation in the mtDNA and some that do not.

The proportion of mutant mtDNA molecules determines both the penetrance and severity of expression of some diseases. 

(maternal inheritance)

Genereally, only egg cells contribute mitochondria to offspring.

If mom is homplasmic for mutation then all her childern will be homoplasmic for the mutation.

If mom is heteroplasmic for mutation then risk of passing on to children is reduced due to random assortment of both mtDNA and mitochondria during replication and division.

↑porportion of mutant mtDNA=↑chance of passing on mutation to offspring