Biology 1001A Lecture Notes - Lecture 5: Homo Sapiens, Nucleosome, Small-C
Course CodeBIOL 1001A
ProfessorBeth Mac Dougall- Shackleton
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Biology Lecture 5 - Genomic Variation
Independent Study Outcomes
1. The meaning of C-Value.
- refers to the amount of DNA contained 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
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