3.2: chromosomes. prokaryotes one chromosome (single copy of each gene). dna is not associated with...
TRANSCRIPT
Prokaryotes
One chromosome (single copy of each
gene).
DNA is not associated with proteins (naked).
Plasmids are present in prokaryotes in MOST
cases.
Plasmids
Typically only found in prokaryotes
Contain some useful DNA e.g. genes for antibiotic resistance
Can easily transferred between cells – even between species.
Scientific research takes advantage of these traits.
Beads on a string
Each bead is a nucleosome
A nucleosome is DNA wrapped around 8
histones.
DNA has negative charge, histone is
positive.
DNA becomes condensed/supercoile
d. Forming chromosomes.
Task
1. What is the Human genome project? Dates? Aims? Findings?
2. What were the techniques used in the project?
3. Where did the material come from? Ethical considerations?
4. Who ‘controls’ this information? How should/could it be used?
5. Junk/satellite DNA, what? Why?6. Future applications of this research?
The Human Genome.
The complete sequence of Human DNA.
Genome of eukaryotes has lots of highly repetitive sequences. (5-45% of total genome). Between 5 – 300 base pairs per repetitive sequence.
Satellite DNA – repetitive DNA clustered in discrete areas. Also known as ‘junk DNA’
It is thought dispersed DNA has no specific coding function, but can move from one location to another (transposable elements). Importance not yet understood.
Who is Barbara McClintock?
Homologous chromosomes
Defined as: Two chromosomes
carrying the same sequence of genes.
Not identical because although the genes are the same, the
alleles are different.
A - ancestral EutherianB - ChickenC - Short-tailed opossumD - AardvarkE - MinkF - Red foxG - Ancestral SciuridaeH - MouseI - Human
Haploid V’s Diploid
Haploid nuclei Diploid nuclei• 23 chromosomes
(humans)• Gametes (sex
cells)• Single copy of
each gene
• 23 chromosome pairs
• Haploids fuse to form zygote
• Two copies of each gene
Reproduction by fusing haploid cells leads to much greater variation, reduced chance of inheriting recessive mutations & increased
hybrid vigour (stronger offspring – sometimes!).
Observing mitosis in garlic root tip
• http://www.nuffieldfoundation.org/practical-biology/investigating-mitosis-allium-root-tip-squash