DNA to Genes to Chromosomes (Part 2) Flashcards
Minisatellite extragenic DNA is further divided into what subcategories?
- Telomeric
- Hypervariable
What are the characteristics of Telomeric minisatellite extragenic DNA?
-short (~6 nt) repeats found at the end of chromosome (telomeres) - Added by telomerases after DNA replication and necessary to prevent shortening of chromosomes
What are the characteristics of hypervariable minisatellite extragenic DNA?
-Short sequences (15-100 nt) repeated a variable number of times - Found in and around genes and were previously used for genetic fingerprinting (VNTR)
What are the characteristics of microsatellite tandem repeat extragenic DNA?
- Very short sequences, usually 2 nucleotides long (e.g. CACACA) but can be 3 or 4, repeated 5-50x
- Highly variable in number of repeats so often used in genetic fingerprinting, linkage studies (STR: short tandem repeat )
- Trinucleotide repeat expansion associated with a number of disease 12 syndromes
Highly repeated Interspersed Repetitive Sequences, the other type of Extragenic DNA besides Tandem Repeat, are categories into what?
- Short interspersed nuclear elements (SINEs)
- Long Interspersed Nuclear Elements (LINEs ~6000 base pairs)
What are short interspersed nuclear elements (SINEs) and what are their characteristics?
- short sequences of <500 bp that are found up 1,500,000 times in the genome - make up about ~10% of the human genome
- appear to be “normal” RNAs that were converted to DNA by reverse transcriptase and were reinserted into the genome.
What are the most common SINEs in humans?
Alu elements
LINEs are able to make RNA (T/F)
True!!!
What codes for the enzyme Reverse Transcriptase?
Long Interspersed Nuclear Elements
How are LINEs capable of copying themselves and enlarging the genome?
Reverse transcriptase make a DNA copy of the LINE or SINE mRNA that can be integrated into the genome at a new site
LINEs and SINEs are suspected to be responsible for what?
Many of the mutations that have arisen due to unequal crossover during meiosis
What are pseudogenes?
Sequences that look like real genes but are not functional (no protein product).
What is important to know about Mitochondrial (non-nuclear) DNA?
- Maternally inherited in humans (all mitochondria come from the cytoplasm of the oocyte)
- Mitochondrial disorders are only passed through maternal line
- Mitochondrial genes are more prone for mutation
Centromere divides the chromosome into two arms… what are they?
p arm (short q arm (long)
What are the hierarchical levels of chromatin packaging in a human chromosome?
DNA double helix (2nM) < nucleosome fiber “beads on a string” (10nM) <Solenoid (30nM)
Condensation begins during what phase of Mitosis?
Prophase
During what phase of Mitosis is a chromatid maximally condensed and fully visible?
Metaphase
The microtubules attach to the _____ during cell division
centromere kinetochores
Genes are present in the telomeres and the centromere
FALSE!!!
Genes are usually absent in the telomeres and the centromere
Chromosome nomenclature denotes 3 types of chromosomes. What are they?
- Metacentric chromosome
- Submetacentric chromosome
- Acrocentric chromosome
Describe and give examples of metacentric chromosomes.
- p and q arms are of equal length.
- Centromere in the centre: Chromosome 1
Describe and give examples of submetacentric chromosomes.
p arm is shorter than q arm: Chromosome 4
Describe and give examples of Acrocentric chromosomes.
- p arm contains little genetic information.
- Chromosome 13, 14, 15, 21, 22: Involved in Robertsonian translocation
Describe a standard Karotype.
22 pairs of autosomes and one pair of sex chromosomes (Total: 23 pairs of chromosomes)
