Biology Lecture 5 - Genomic Variation
Independent Study Outcomes
1. The meaning of C-Value.
- refers to the amount of DNAcontained within a haploid nucleus (a gamete for ex)
- OR one half the amount in a diploid somatic cell of a eukaryotic organism
- expressed in picograms
- the terms C-value and genome size are sometimes used interchangeably (in some cases)
- in polyploids (cells and organisms that contain more than two paired, homolo-
gous, sets of chromosomes) the C-value may represent two or more genomes contained
within the same nucleus
- polyploidy is most common in plants
2. The “paradox” or “enigma” associated with C values.
- complex puzzle surrounding the extensive variation in nuclear (the evolution of the) genome
size among eukaryotic species
- at center of enigma is the observation that genome size does not correlate with organismal com-
3. The meaning of haploid (n) and diploid (2n).
- gametes are haploid - 23 chromosomes
- somatic cells are diploid - 46 chromosomes
4. The relationship between C and n as measures of genome size.
- C = n
5. The proportion of the human genome that codes for protein.
8.3a - Chromosomes are the Genetic Units Divided by Mitosis
- most eukaryotes have two copies of each type of chromosome in their nuclei
- chromosome is said to be diploid (2n)
- humans have 23 different pairs of chromosomes ~> diploid # of 46
- other eukaryotes only have one copy of each type of chromosome in their
nucleus, haploid (n)
- 2n=32 and n=16
- some plants species have 3, four, or even complete sets of chromosomes in
- number of chromosome sets is called ploidy
- equal distribution of daughter chromosomes is called chromosome segregation
- since sister chromatids remain attached to each other at their centromeres
following DNA synthesis, the pair of them is still referred to as just one chro-
- two daughter cells can each receive eight chromosomes even though there were only eight
chromosomes in the original cell
15.3b - Genome Sequence Determination and Annotation Involves Obtaining
and Analyzing the Sequence of Complete Genomes Biology Lecture 5 - Genomic Variation
- Genome Shotgun Sequencing
1. isolate genomic DNAand break it into random overlapping fragments
2. clone each DNAfragment (ex - plasmid cloning vector)
3. sequence the genomic DNAfragment in each clone
4. Enter DNAsequences into computer and use computer to assemble overlapping se-
quences into the continuous sequence of each chromosome of the organism.
- after genome has been sequenced the next step is annotation
- the identification of genes and other sequences of importance
- Bioinformatics - fuses biology with mathematics and computer science and is used to pre-
dict the structure and function of gene products and to postulate evolutionary relationships of se-
- eukaryotic genomes contain large numbers of noncoding sequences, most of them in the form
of repeated sequences of nucleotides of various lengths and numbers
- all the protein coding sequences occupy less than 2% of the human genome
- introns occupy 24%
- 50% of the total genome consists of repeated sequences that have no known function
1. The non-nuclear genomes in typical plant and animal cells.
- plants have three different genomes, a nuclear one, a mitochondria one, and a chloroplast one
- animals have ove