Lecture 1.3 - The Language of Genetics

Chromosome

an organized structure of DNA containing all four part of the genetic material of an organism

Chromatid

a replicated chromosome, prior to recombination and/or cell division

Sister chromatids

Found within the same replicated chromosome

Non-sister chromatids refer to…

chromatids on homologous chromosomes

DNA

deoxyribonucleic acid, hereditary material

ssDNA

single stranded DNA

nDNA

• nuclear DNA (DNA found in the nucleus)

• Typically contains multiple chromosomes

mtDNA

mitochondrial DNA (DNA found in the mitochondria)

cpDNA

chloroplast DNA (DAN found in the chloroplast)

Gene

heritable unit that contributes to a characteristic (often encodes a protein, but can also encode RNAs)

Coding DNA

regions of genome that represent protein-coding sequences

The term gene can refer to…

the coding sequence only OR the coding sequence and regulatory sequence that are proximal to the coding sequence

Allele

• a version or variant of a particular locus on the genome

• Refer to gene variants OR variation in DNA sequences at any position on a genome

• Names can be anything as long as they’re defined (A, a, cox1, dpm⁵²-x etc.)

Wild type allele (Wt)

one of many possible alleles of a gene that allow the gene to function “normally”, recognizing that “normal” can be context specific

Mutant allele

• an allele that results in “abnormal” function of a gene

• can also refer to scenarios where researchers are monitoring changes (mutation) in DNA, whether they are involved in gene function or not

Null (-) allele

an allele that results in either no gene product being produced or the absence of function of the gene product at the phenotypic level

+/+ indicates

2 wt alleles

± indicates

1 wt and 1 null allele

-/- indicates

2 null alleles

Locus (loci)

specific position on a genome

Phenotype

observable characteristics

Genotype

combination of alleles for a particular individual

Genome information for a species can be described by an equation such as

2N = x

N = chromosome number

• the number of unique (nuclear) chromosomes in a cell or organism (excludes mtDNA and cpDNA)

• Ex: humans have 23 diff types of chromosomes so N of humans is 23

X =

total number of chromosomes in a cell

Genome information for humans

2N = 46

Homozygous/heterozygous

the state of an individual with identical/non-identical alleles at a particular locus (eg. +/+ or -/- vs ±)

Chromosome Microarray Test

Examines chromosomes to see if pieces atre missing or gained

Copy Number Variant

any chromosome missing/gained

When is a CNV considered harmless?

• small size

• no important gene

• inherited from a healthy parent

When is a CNV considered harmful?

• big size

• important gene

• not inherited