Quiz Review: Chapter 11: Eukaryotic Genome Organization
Chapter 12: Introduction to Transcription
Chap. 11:
Why are eukaryotic genomes more complex than the genome of prokaryotes?
Eukaryotic genomes must code for organelles and complex proteins that are not present in
prokaryotic cells.
The eukaryotic genome contains two types of DNA sequences, what are they?
Coding sequences called EXONS and non-coding sequences called INTRONS. Introns are spliced
out of mRNA as a “final draft” is made for translation and protein folding.
What is a REPETITIVE SEQUENCE? What are the characteristics of a highly vs middle repetitive
sequences?
Repetitive sequences are REGIONS of DNA that have the same nucleotides or sequences of
nucleotides repeated multiple times. The majority of repetitive sequences DO NOT code for
proteins but we now know serve other functions within cells.
Highly repetitive sequences appear multiple times in the eukaryotic genome. Examples of highly
repetitive sequences include HETEROCHROMATIN and CENTROMERIC DNA.
Middle repetitive sequences appear in the genome at regular intervals and are useful tools in
genomic testing. Examples include Variable Number Tandem Repeats (VNTR’s), SINE’s and
LINE’s.
What is critically important about CENTROMERIC DNA?
Centromeric DNA is responsible for binding of the centromere to the spindle fibers during mitosis
and meiosis for proper separation of sister chromatids during cell division for diploid or haploid
amounts of DNA. Mistakes in centromeric DNA can result in misalignment of DNA with
deleterious results in the cells produced.
Describe TELOMERES, their location, and their importance.
Telomeres are the “caps” at the end of chromosomes, composed of highly repetitive sequences of
DNA. Each time a cell replicates its DNA prior to cell division, nucleotide(s) are result, leaving the
new cell with less DNA than the parent cell. As a cell continues to divide, especially labile cells, the
loss of telomeres can eventually lead to loss of function/coding nucleotides. This results in aging
and/or disease.
Describe the 3 types of Middle Repetitive Sequences
VNTR’s – found in and between genes; used in gel electrophoresis to find similarities among
samples for parentage and forensics.
SINE’s – about 500 bp long
LINE’s – about 6000 bp long; used by HIV for infection purposes
Eukaryotic Genome and Functional Genes. What is significant about the amount of DNA and the
functional genes present?
Pseudogenes are present and considered evolutionary “leftovers” of once functional genes that have
acquired too many insertions or deletions.
In humans, the estimated 20,000 function genes occupy only 2% of the total DNA sequence making
up the genome.
Chap. 12:
What is the Central Dogma of Biology?
DNA to RNA to functional Protein
Describe the 3 main types of RNA, their function, and their location of activity in the cell.
mRNA copies DNA in the nucleus and travels to cytoplasm
rRNA is the functional units of the ribosome in the cytoplasm.
tRNA is the molecule that correctly matched amino acids to the mRNa at the ribosome in the
cytoplasm.
Differences between DNA and RNA.
Location
DNA is confined to the nucleus
RNA can move from nucleus to cytoplasm
Function
Carries instruction
Copies instructions and builds proteins
Chemistry
Deoxyribose sugar and thymine
Ribose sugar and uracil
Size
Double helix
Single strand
Describe the codon dictionary. How many amino acids comprise the codon dictionary? How many start
codons? Stop codons?
64 possible CODON (3 base) sequences
20 biologically needed amino acids
61 codons code for amino acids
3 codons signals stop
What is transcription?
The ability of mRNA to make a PERFECT copy of DNA.