1.3: The Language of Genetics Flashcards
What is a genome?
- The entire set of heritable material (usually DNA, sometimes RNA) found in a cell or organism
What is a chromosome?
- An organized structure of DNA containing all or part of the genetic material of an organism
- Each have unique feature that are specific to that chromsome, including length and position of centromere.
- 1centromere per chromosome
What is chromatin?
- The substance of a chromosome
- Contains DNA, RNA and protein
DO NOT confuse with chromatic (one half of a replicated chromosome)
What is Euchromatin?
- Loosely packed forms of chromatin
What is heterochromatin?
- Tightly packed forms of chromatin
- Holds onto certain dyes/stains more tightly
What is a chromatid?
A replicated chromosome, prior to recombination and/or cell division
What are sister chromatids?
- Found within the same replicated chromosomes, held togehter by a single centromere.
- During the cell cycle, DNA is replicated prior to cell division. Following DNA replication, each chromosome produces an identical copy of itself called sister chromatids
- Nonsister chromatids refer to chromatids on homologous chromosomes
What is a homologous pair of chromosomes?
- Have same genes in same order but might be variation resulting in different alleles
- Pair of chromosomes where one is from father and one is from mother
- Only organisms that are greater than or equal to 2N have homologous chromosomes
- Generally same centromere location, same length, and same banding patterns (gene location)
What is dna? What are the different types?
- DNA= deoxyribonucleic acid, hereditary material
- ssDNA= single stranded DNA
- nDNA= nuclear DNA (DNA found in nucleus, nDMA typically contains multiple chromosomes)
- mtDNA= mitochondrial DNA (DNA found in the mitochondria)
- cpDNA= chloroplast DNA (DNA found in the chloroplast)
What things typically contain a single chromosome?
- bacteria, viruses, mtDNA, and cpDNA
- the complete unit of DNA in these organelles/organisms are often referred to as the bacterial, viral, mitochondrial, or chloroplast genome
What is someone referring to when they talk about a eukaryotic genome?
- Typically referring to nDNA only, even though the true genome of a eukaryote includes nDNA, mtDNA, and cpDNA
- Context is important
What is a gene?
- Heritable unit that contributes to a characteristic.
- Often encodes a protein, but can also encode RNAs
- The term gene can refer to the coding sequence only, or the coding sequence and regulatory sequences that are proximal to the coding sequence
What is coding DNA?
- regions of genome that represent protein-coding sequences
What is an allele?
- A version or variant of a particular locus on the genome
- Alleles frequently refer to gene variants, but can also refer to variation in DNA sequences at any position on a genome. Allele names can be anything as long as they are defined (A, a, cox1, wt, etc.)
What is a wild-type (wt) allele?
- one of many possible alleles of a gene that allow the gene to function “normally,” recognizing that normal can be context-specific
- Typically refers to the most common allele/phenotype in a population
- Is sometimes defined as the allelic variant that was observed in the first individual of a species whose genome was sequenced
What is a 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
What is a null (-) allele?
- Allele that results in the absence of function of the gene product at the phenotypic level
- Can be the result of an allele that prevents gene product from being produced at all or the result of an allele that produces a non functioning gene product
How are genotypes for a particular locus in a diploid organism abbreviated as?
- +/+ = 2 wt alleles
- +/- = 1 wt and 1 null allele
- -/- = 2 null alleles
What is a locus (plural: loci)?
a specific position on a genome
phenotype vs genotype?
- phenotype= observable characteristics
- genotype= combination of alleles for a particular individual
What is chromosome number (N)?
- refers to the number of unique (nuclear) chromosomes in a cell or organism
- exludes mtDNA and cpDNA
What is ploidy?
- the number of complete sets of chromosomes in a cell
- haploid= 1N
- diploid= 2N
- triploid= 3N, etc.
What is a karyotype?
- an individual’s collection of chromosomes
- or the image of a person’s organized chromsomes
What does homozygous and heterozygous mean?
- Refers to the state of an individual with identical/non-identical alleles at a particular locus
- ex. +/+ or -/- vs +/-
How many genomes do virus and bacteria have?
1
What are viruses and what are some things they cause?
- infectious particles comprised of a genome surrounded by a protein coat, come in many forms and structures
- require a host for survival, often invade the genomes of their host s we can see the signatures of viral DNA in our own genomes either due to our own recent infections or evolutionarily ancient infections
- cause the common flu, chicken pox, COVID-19, AIDS, and measels
What are viruses’ genome made of?
- single or double stranded RNA, or double-stranded DNA
- can be a single, circular chromosome; a single, linear chromosome, or a segmented genome containing short RNA or DNA pieces
What is a knockout allele?
- A genetic engineering technique that removes a particular gene or sequence from the genome
- Considered null bc it cannot produce gene product because they lack the sequence all together
What is a variant allele?
- Anything not wild-type (includes mtant and null)
- An alternative sequence that may or may not alter gene function
What is p/q on arms of chromosome?
p for short arm q for long arm
What is a centromere?
- protein DNA/RNA complex that’s used to anchor sister chromatids together and that aid in chromosomal segregation during cell division
- Appear as constricted/pinches on a karyotype
- Position can be used to help idenfity each chromosome
What are the different areas for centromere to be?
- metacentric: in middle
- submetacentric: closer to middle than to telomere
- acrocentric: closer to telomere than to middle
- telocentric: on telomere
What are eukaryotic genomes comprised of?
- double-stranded RNA found in nuclei, mitochondria, and chloroplast (plants only)
- nucleus contains majority of eukaryotic DNA, so the term genome typically is just applied to nuclear chromosomes
chromosomes in multiple copies. most animals are diploid
How are eukaryotic genomes divided?
into linear chromosomes (nuclear DNA, which is double stranded)
What does mtDNA and cpDNA look like an what is their function?
- circular
- contain genes related to cellular energy production
What are Prokayotic (bacterial) genomes comprised of?
- a single chromosome found in the bacteria cells’ nucleoid
- made of a double stranded DNA molecule. Only one copy (haploid)
What are plasmids?
- small circles of autonomously replicating DNA.
- Often contain genes involved in stress responses and provide antibiotic or heavy metal resistance, thus providing bacteria w/ genetic advantages
- Plasmids are sometimes found in eukaryotic cells like fungi and some higher order plants. Are not considered part of an organisms genome though, despite being DNA
