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Peacemaking reading notes

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Department
Psychology
Course Code
PSY230H1
Professor
Peterson

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Chapter 4 DNA, Chromosomes, and Genomes
(pg. 202-206, 208-218)
Chromosomal DNA and Its Packaging in the Chromatin Fibre
Eukaryotic DNA is Packaged into a Set of Chromosomes
-The complex of DNA and protein is called chromatin (Greek chroma colour”)
-The maternal and paternal chromosomes of a pair are called homologous
chromosomes
-Each human cell contains 46 chromosomes; 22 pairs common to both males and
females, plus two so-called sex chromosomes (XY male, XX female)
-DNA hybridization is a technique where a labelled nucleic acid strand serves as a
probe that localizes a complementary strand
oUsed to distinguish human chromosomes by painting each one a different
colour
Painting is typically done during mitosis, when chromosomes are
compacted and easy to visualize
-The display of the 46 chromosomes at mitosis is called the human karyotype
-Cytogeneticists detect chromosome abnormalities associated with inherited defects,
and characterize cancers associated with specific chromosome rearrangements in
somatic cells by detecting changes in banding patterns or changes in the pattern of
chromosome painting
Chromosomes Contain Long Strings of Genes
-*Gene segment of DNA containing instructions to make proteins (some make
RNA)
-Some correlation exists between the complexity of an organism and the number of
genes in its genome; Simple bacteria = 500 genes vs. human = 25,000
oHowever, chromosomes from many eukaryotes (including humans) carry
junk DNA that doesnt seem to carry critical information; some of it is
useful for the proper expression of certain genes
-Although the human genome is 200x that of the yeast S. Cerevisiae, it is 30x smaller
than some plants and amphibians, and 200x smaller than a species of amoeba
-There is no simple relationship between chromosome number, species
complexity, and total genome size
The Nucleotide Sequence of the Human Genome Shows How Our Genes Are
Arranged
-Very little of the human genome codes for proteins; the rest are short, mobile pieces
of DNA that have gradually inserted themselves in the chromosome over time
(transposable elements)
www.notesolution.com
-In humans, the average gene size is 27,000 nucleotide pairs; only 13,000 are
required to encode a protein of average size (430 amino acids for humans)
oThe coding sequences are called exons, noncoding sequences are called
introns
oeach gene is also associated with regulatory DNA sequences to ensure that
genes are turned on or off at the right time, expressed at the appropriate
level, and only in the proper kind of cell these sequences are spread over
thousands of nucleotide pairs
-pseudogene nucleotide sequence of DNA closely resembling a functional gene,
but contain multiple mutations that prevent its proper expression (accumulated
damaging mutations)
Chromosomes Exist in Different States Throughout the Life of a Cell
-the cell cycle provides for a temporal separation between the duplication of
chromosomes and their segregation into two daughter cells
oduring interphase, the cell actively expresses its genes and synthesizing
protein, DNA is also replicated
oin the M phase, mitosis occurs, and the nucleus is divided into two daughter
nuclei
chromosomes condense, nuclear envelops breaks, mitotic spindle forms
spindles pull chromosomes to each end of the cell
nuclear envelope re-forms around each chromosome set to produce 2
cells
most of a cells time is spent in interphase, with an average of 1 hour
in many mammalian cells
Each DNA Molecule Forming a Linear Chromosome Must Contain a Centromere,
Two Telomeres, and Replication Origins
-experiments in yeasts have identified the minimal DNA sequence elements
responsible for replication/segregation functions
one type of nucleotide sequence acts as a DNA replication origin, where DNA
duplication begins
-eukaryotic chromosomes contain many origins of replication to allow for rapid
replication
-after replication, daughter chromosomes remain attached to one another, and are
condensed further to produce mitotic chromosomes
a centromere allows one copy of each chromosome to be pulled into each
daughter cell
-a complex called a kinetochore forms at the centromere and attaches the duplicated
chromosomes to the mitotic spindle, allowing them to be pulled apart
www.notesolution.com

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Description
Chapter 4 DNA, Chromosomes, and Genomes (pg. 202-206, 208-218) Chromosomal DNA and Its Packaging in the Chromatin Fibre Eukaryotic DNA is Packaged into a Set of Chromosomes - The complex of DNA and protein is called chromatin (Greek chroma colour) - The maternal and paternal chromosomes of a pair are called homologous chromosomes - Each human cell contains 46 chromosomes; 22 pairs common to both males and females, plus two so-called sex chromosomes (XY male, XX female) - DNA hybridization is a technique where a labelled nucleic acid strand serves as a probe that localizes a complementary strand o Used to distinguish human chromosomes by painting each one a different colour Painting is typically done during mitosis, when chromosomes are compacted and easy to visualize - The display of the 46 chromosomes at mitosis is called the human karyotype - Cytogeneticists detect chromosome abnormalities associated with inherited defects, and characterize cancers associated with specific chromosome rearrangements in somatic cells by detecting changesin banding patterns or changesin the pattern of chromosomepainting Chromosomes Contain Long Strings of Genes - *Gene segment of DNA containing instructions to make proteins (some make RNA) - Some correlation exists between the complexity of an organism and the number of genes in its genome; Simple bacteria = 500 genesvs. human = 25,000 o However, chromosomes from many eukaryotes (including humans) carry junk DNA that doesnt seem to carry critical information; some of it is useful for the proper expression of certain genes - Although the human genome is 200x that of the yeast S. Cerevisiae, it is 30x smaller than some plants and amphibians, and 200x smaller than a species of amoeba - There is no simple relationship between chromosome number, species complexity, and total genome size The Nucleotide Sequence of the Human Genome Shows How Our Genes Are Arranged - Very little of the human genome codes for proteins; the rest are short, mobile pieces of DNA that have gradually inserted themselves in the chromosome over time (transposable elements) www.notesolution.com
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