L12-L14 Definitions/terms/things to rememeber

One nucleotide changes, causing a different amino acid. Resulting in the WRONG amino acid

Missense

ONE gene effects MULTIPLE traits

Pleiotropy

MULTIPLE genes affect ONE trait

Polygenic

Mutations in different genes can cause the same disease.

Locus heterogeneity

Different mutations in the same gene can cause the same disease.

Allelic heterogeneity

One nucleotide changes, creating a premature STOP codon. Causes is shortened protein

Nonsense

Nucleotide(s) are inserted or deleted (not in multiples of 3). Causing a change in the reading frame and downstream amino acids

Frameshift

Insertion or deletion of nucleotides in multiples of 3, so the reading frame does NOT shift.

In-frame mutation

One gene affects multiple traits

Pleiotropy

Whether someone with a disease-causing genotype shows the phenotype

Penetrance

How severe or variable the symptoms are

Expressivity

Multiple genes contribute to one trait

Polygenic

Other genes influence the severity or presentation of a disease

Modifier genes

Mutations in different genes cause the same disease or phenotype

Locus heterogeneity

Different mutations within the same gene cause the same disease or phenotype

Allelic heterogeneity

Short DNA sequences repeated multiple times in a row.

Short Tandem Repeats (STRs)

Variation in a single DNA nucleotide (A, T, C, or G).

Single Nucleotide Polymorphisms (SNPs)

DNA nucleotides that are added (insertion) or removed (deletion).

Insertion/Deletion (Indels)

A group of genetic variants inherited together from one parent

Haplotypes

_______ = WHETHER a person with a disease-causing mutation shows symptoms (Yes or No)

Penetrance

• ______ = HOW SEVERE the symptoms are in someone who expresses the mutation.

• Expressivity

______ variation involves the loss or gain of whole chromosomes, such as monosomy or trisomy.

Genomic

_____ variants directly change the protein product.

Coding

______ variation is the most common cause of genetic disorders and involves a change at one point in the DNA sequence or a small insertion/deletion.

Gene-level

Two chromosomes that carry the same genes at the same locations, with one chromosome inherited from each parent.(One from mom + one from dad)

Homologous pair

A common variation in DNA sequence found in at least 1% of the population.

Polymorphism

_______ genetic testing examines single genes or short DNA sequences to identify specific genetic variants.

Molecular

________ genetic testing examines whole chromosomes or long DNA sequences to identify large genetic changes, such as extra chromosomes.

Chromosomal

_______ genetic testing measures protein amounts or activity to identify possible underlying DNA changes.

Biochemical

______ screening includes newborn screening and heterozygote (carrier) screening.

Population

_____ genetic screening is performed alongside genetic counseling.

Family

_________, also called cell-free DNA (cfDNA) screening (not diagnostic), examines fetal (placental) DNA circulating in the mother's blood and is used to screen form chromosomal abnormalities

Non-invasive prenatal testing (NIPT)

Friedreich ataxia is caused by a GAA trinucleotide repeat expansion in an _____.

intron

Huntington disease is caused by a CAG trinucleotide repeat expansion in an ______

exon (coding region).

Myoclonus epilepsy is associated with a 12-mer repeat expansion in the _______

promoter region.

Fragile X syndrome is caused by a CGG trinucleotide repeat expansion in the _______

untranslated region (UTR).

Myotonic dystrophy is caused by a CTG trinucleotide repeat expansion in the _______

untranslated region (UTR).

______ defects can cause cystic fibrosis (CF), resulting in abnormal fluid balance.

Transporter

_______ protein defects can cause Marfan syndrome, which involves fibrillin-1.

Structural

Noninvasive prenatal testing (NIPT) = ____ test

Amniocentesis = ____ test

Chorionic virus sampling (CVS) = ______ test

Screening

Diagnostic

Diagnostic

what are the three stop codons in DNA

TAA, TAG, and TGA

A purine is replaced by another purine, or a pyrimidine by another pyrimidine.

Transition

• Transition = stays within the same group

• Transversion = switches groups

A purine is replaced by a pyrimidine, or vice versa.

tranversion

• Transition = stays within the same group

• Transversion = switches groups

○Variants in different genes creates the same phenotype

●Locus Heterogeneity

○Different variants in the same gene creates the same phenotype

●Allelic Heterogeneity

○Several genes shape one trait (epistasis, modifier genes)

●Polygenic / modifiers

○One gene creates many phenotypes, across pathways or tissues

Pleiotropy

○Same genotype but differences in whether, and how strongly, it shows

●Penetrance / expressivity 

○The proportion of people with a genotype who show the phenotype at all. Think of it as a yes/no count across a population.

Penetrance

○The severity of the phenotype among the people who do show it. Same genotype, dial turned up or down.

Expressivity

What three traits does cystic fibrosis show?

Plietropy

Allelic heterogeniety

modifier genes/epistais

in cystic fibrosis, one gene (CFTR) affects multiple organs. What is this trait?

Plietropy

in cystic fibrosis, many CFTR alleles cause the same disease, what is this trait?

●Allelic Heterogeneity

in cystic fibrosis, varients in other genes change the severity

modifier genes/epistais

a permanent change in the genome's nucleotide sequence, which may change phenotype

Mutation

not disease-causing, >1% of the population, usually silent or conservative (Val for Ile).

Polymorphism

Individuals with the same genetic mutation show different degrees of severity or symptoms.

Variable expressivity

Differences in DNA or genes between individuals

Genetic variability

A DNA mutation that causes one amino acid to be replaced by another in a protein.

Missense

What are the three scales of variation?

genomic, chrosomal, and gene

Thee scales of variation:

______ = Loss or gain of whole chromosomes

genomic

Thee scales of variation:

_______ = Translocations and rearrangements

chromosomal

Thee scales of variation:

_______ = A change at one point, or a small insertion/deletion

gene

what are the three types of point variants?

missense, nonsense and silet

Point variants