Molecular Biology 1 Ch 8
Sex chromosomes
-Carry sex determining genes
44 Chromosome Man
-Chromosome 14 and 15 fused -Family history of miscarriages -Could lead to new species
Examples of polyploidy
-Megakaryocytes for platelet production -Cancer cells -Human heart
What makes complex organisms have less dense genomes?
-intergenic sequences (unique, repetitive, junk) -Regulatory sequences -introns
What does the chromosome form of DNA do?
-stability/protection from degradation -means of transmission to daughter cells -contributes to regulation of expression/recombination
What are non-histone proteins in chromatin for?
-transcription -replication -repair -recombination -topolgoy
How many grams of DNA are in the human body?
0.5 g
How long are prokaryotic DNA?
1 mm
Overlapping gene
A gene in which part of the sequence is found within part of the sequence of another gene.
Example of overlapping genes in eukaryotes
A lot of *mitochondria*'s genes have jumped over to the human genome but it still makes up its own genes; *ATP synthase 8 and 6 are on the same strand but overlapping* (frameshift)
Monotreme
A mammal that lays eggs
How many base pairs do eukaryotic genomes have?
Billions of base pairs
Order of chromosome structure in decreasing order
Cell Nucleus Chromosome Nucleosome Histones DNA (double helix)
Which is accessible for transcription, chromatin or chromosomes?
Chromatin
What builds up the chromatin?
Chromatin fiber
Which is inaccessible for transcription, chromatin or chromosomes?
Chromosomes
Is mitochondrial DNA linear or circular?
Circular
Chromatin
Clusters of DNA and proteins in the nucleus of a cell; active, accessible
Is a chromsome condensed or uncondensed chromatin?
Condensed
Chromsome
Condensed *chromatin*, comprised of two identical pairs of DNA and associated proteins; mostly inaccessible for transcription
What are chromosomes made of?
DNA and proteins
What is chromatin?
DNA molecules that are tightly coiled around proteins call histones.
More complex organisms and their gene density
Decreased gene density -intergenic sequences (unique- mutated/pseudogenes, repetitive, junk DNA) -Regulatory sequences -introns -overlapping genes
Are eukaryotes diploid or haploid?
Diploid
Example of eukaryote with one chromosome
Male Jack jumper ants
Megakaryocytes and their ploidy
Megakaryocytes are predivided - so they have lots of nuclei that are ready to divide - they carry more than two copies of the genome polyploid
How many base pairs are in prokaryotic genomes?
Millions of DNA base pairs
How many base pairs do prokaryotes have in their genome?
Millions of DNA base pairs
Genome density and complexity
More complex organisms have decreased gene density
Gene density and complexity
More gene dense = less complex
What is junk DNA?
Much of this DNA codes for the expression of DNA
Do prokaryotes have histones?
No (but they have proteins similar to histones)
Where are prokaryotic chromosomes held?
Nucleoid region
Where are overlapping genes in prokaryotes?
On the same strand
Chromosome # and complexity
The more chromosomes you have, the more complex the organisms (NOT guaranteed)
T/F The mitochondrial genome has genes with overlapping exons
True
What is junk DNA correlated with?
Variability
Viruses and genome density
Very gene dense; some use both strands and have overlapping genes
E coli and genome density
Very gene density; composed almost entirely of genes
How do they know chromosome 2 is a fusion of two chromosomes?
Vestigial centromere and telomeres in the middle of it
What indicates chromosome 2 fusion point?
a telomere right in the middle of the sequence
Overlapping genes in eukaryotes
antiparallel
What is the accessible form of DNA?
chromatin
What is the inaccesible form of DNA?
chromosome
What is the inactive form of DNA?
chromsome
Chromatin fiber
consists of coiled nucleosomes which form a larger diameter fiber.
Diploid
containing two complete sets of chromosomes, one from each parent.
Denisovans
distant cousins to Neandertals, from Asia 400,000-50,000 years ago.
When are we talking about chromosome?
during mitosis when it is condensed once it is replicated
Plasmid
extra-chromosomal DNA in a prokaryote that they can share with other bacteria
Chromosome 2
fusion of 2 other chromosomes
Junk DNA
genomic DNA that does not encode proteins, and whose function, if it has one, is not well understood.
Haploid
having a single set of unpaired chromosomes
Where are genomes maintained?
in chromosomes
Where is there largest divergence between human and chimp DNA?
in the Y chromosome
How are chromosomes numbered?
largest to smallest
Example of overlapping gene in humans
mitochondria- carries its own DNA; ATP synthase 6 and 8 are overlapping
Genome size and complexity
more chromosomes = more complex NOT guaranteed (# of genes more closely linked to complexity)
Polyploid
more than two copies of the genome/chromosome
Intergenic DNA
noncoding DNA found between genes
Overlapping genes in prokaryotes
on the *same strand* and *parallel*
How many chromosomes do bacteria have?
one
Histone
protein molecule around which DNA is tightly coiled in chromatin
Nucleosome
repeating subunit of chromatin fibers, consisting of DNA coiled around histones
Organisms with a different number of chromosomes have a hard time _____ with their counterpart
reproducing
Plasmids
small circular DNA molecules that replicate separately from the bacterial chromosome extrachromosomal DNA
How many base pairs do eukaryotes have in their genome?
3 Billion of base pairs
How many cells in the human body?
37 trillion
How many chromosomes do humans have?
46 (23 pairs)
How much % are we genetically similar at the sequence level to all mammals?
92%
How genetically identical are humans and chimps?
98-99%
Where are overlapping genes in eukaryotes?
Antiparallel
Autosomes
Any chromosome that is not a sex chromosome Chromosomes 1-22; 1 copy from each parent In the nucleus
What is the core of a nucleosome?
Histone
How many pairs of chromosomes do humans and primates have? What causes this difference
Humans- 23 Primates- 24 Humans have one less chromosome because our chromosome 2 is split into two chromosomes in primates
Why don't you typically see trisomy 1?
It's so large that would mean you had to duplicate more genes
Which chromosomes carry more genes?
Larger ones (like 1)
Where do you typically find trisomies in the genome?
Later on, like chromosome 20 because they get smaller
What length is our DNA?
2 meters
How many chromosomes do eukaryote have?
2-100
What % neanderthal are humans?
2-6%
When did sex chromosomes arrive?
200-300 mil years ago after split from monotremes
When did sex chromosomes evolve?
200-300 million years ago after split from monotremes
How many chromosomes do chimps, bonobos, gorillas, and orangutans have?
24
How many chromosomes do primates have?
24 pairs (48 total)
How long would DNA of the human genome stretch?
10 billion miles (100 AU)
How long are prokaryotic chromosomes? What size are they packed into?
1mm chromosome into 1 micrometer
What is a nucleosome?
A region of DNA wound around histone proteins
Human heart and ploidy
Age 2: mostly diploid, the rest tetraploid Age 12: 50/50 for diploid and tetraploid Adult: tetraploid>diploid>octaploid
T/F The 46 chromosomes allow 1 mm of DNA to fit inside of the cell's nucleus
False 46 chromosomes is 2 meters of DNA
T/F As genome size increases, gene density increases and organism complexity tends to decrease
False As genome size increases --> gene density decreases
T/F The Drosophila genome has more repetitive DNA than the human genome
False Humans have the most repetitive DNA
T/F The male jack jumper ant is diploid
False Male jack jumper ant is *haploid*
What does geographic isolation lead to?
Genetic isolation --> reproductive isolation
Are prokaryotes haploid or diploid?
Haploid
When do we have haploid?
Sperm production
What is a chromosome comprised of?
two identical pairs of DNA and associated proteins
Gene density of viruses
very gene dense they use BOTH strands of DNA, even overlapping w/ each other (we use both but not typically overlapping)
Which are more gene dense: virus, E coli, humans
virus *** e coli also, but not humans
Which has more genes: fly or worm
worm; flies have less genes than a worm yet can do so much more with them
