M2C Weeks 1-3

Genotype

genetic constitution of an organism- includes gene sequence, spatial arrangement, expression, and regulation

Phenotype

observable characteristics of an organism determined by interaction between genotype and environment. Includes observable attributes, disease states, and abnormal lab results.

What counts as genetic info?

• Clinical dx of Huntington’s: assume variant in HTT gene

• Abnormal hemoglobin screen for Sickle Cell disease: we can assume a specific genetic change in HBB gene

• Gower sign: Duchenne Muscular dystrophy

Allele

one of two or more alternative forms of a gene that arise by mutation and are found at the same place on a chromosome

Compound heterozygous in trans

2 mutations on opposite alleles

compound heterozygous in cis

2 different variants on same allele in same gene

homozygous

both alleles have same variant

Pleiotropy

1 genetic variant can cause multiple different traits

epistasis

interaction of genes that are not alleles, suppression of the effect of one such gene by another

heterogeneity LOCUS AND ALLELIC

same disorder/phenotype caused by different genetic changes (different genes altogether or different variants in the same gene)

Polygenic/Multifactorial

traits that are influenced by a combination of multiple genes/alleles as well as environmental factors (ex: skin color- many genes + how much sun exposure)

Expressivity

condition may present differently in different people. can affect symptoms, severity, and age of onset.

Penetrance

yes or no- get condition or don’t. some individuals have sx, others don’t.

Two sources of DNA

• nuclear (chromosomes, 2 copies ea gene except X + Y material, inherit from both parents)

• mitochondrial (small, circular, only genes for mito inheritance, 100s or 1000s copies per cell, inherited from egg)

non-protein-coding segments

LINES + SINES, pseudogenes, retrotransposons, regulatory sequences, non-coding RNA sequences, introns

pseudogenes

resemble functional genes but are nonfunctional and never translated

acrocentric chromosomes

13, 14, 15, 21, 22

chromosomes are made of ____, but not all _____ is made of ______.

DNA, DNA, genes

chromatin composition

DNA, RNA, and Protein. Euchromatin (gene-rich) areas are light, heterochromatin (gene-poor) areas are dark.

genes do NOT usually cluster based on ______.

function (may cluster if controlled by the same regulatory elements)

Chromosomes with the fewest number of genes

13, 18, and 21 (only viable trisomies of the autosomes that survive pregnancy)

X-inactivation

in females, 1 X ch in ea cell is randomly turned off. inactivated X remains the same in all daughter cells.

all genes contain:

transcriptional unit (exons, introns, RNA pol binding site, 3’ non-coding sequence), promotor region (TATA box, CCAT box, GC box), and enhancer regions

gene

individual instruction

genome

all genes + everything in between

transcriptional unit

5’ UTR, start codon (met), exons + introns, stop codon, 3’ UTR