Chomosome Structure

Describe the condensation from DNA to chromosome

1. Short region of DNA wraps around histone (beads on a string) form of chromatin

2. Chromatin fiber is formed with associated nucleosomes

3. Chromatin fiber folds into loops

4. Mitotic chromosome

How much DNA does each cell have

About 6 feet

What does the p arm mean

Petite arm (shorter arm on top of chromosome)

What is in the center of a chromosome

Centromere

What is the q arm

The longer arms on the bottom of the chromosome

Metacentric

Centromere is right in the middle of= equal p and q arms

Submetacentric

Centromere is off-centered but just slightly

Acrocentric

Centromere near one end (small p arm and large q arm)

Which chromosomes are acrocentric

13,14,15,21,22

When can chromosomes be called chromatin

When associated with other proteins

How many copies of each chromosome in humans

2 (one from mom and one from dad)

What cells do not have DNA

RBC

Karyotype

Display of 46 chromosomes at mitosis

Who studies chromosomes

Cytogeneticists for chromosomal abnormalities

What is spectral karyotyping

Combined with M-FISH produces unique patterns of staining for each chromosome so different ones absorb different fluorophores

What is staining of each chromosome a different color also called

DNA hybridization

What is another type of staining in chromosome

Chromosome banding patterns

What does a darker stained region of a chromosome mean

Higher concentration of protein

What can a higher protein concentration give us information about

Folding strength, structure, and density of DNA

Is there a correlation between complexity of organism and number of genes in genome

Yes

What cannot be concluded about genome and number of genes

They are not correlated, a larger genome doesn’t mean more genes

What are transposons

Mobile genetic elements that were inserted there over long periods of time

What happens with DNA in transposons

Much is unused but after replicating they might insert themselves into different places causing mutations

What are transposons considered

Parasitic sequences, disrupting function or altering gene regulation

What is the replication origin

Where DNA duplication begins, many in eukaryotes

Centromeres

Allows one copy of each duplicate to be pulled into each daughter cell

How does the centromere work

A kinetic horse protein is formed at the centromere and attaches both chromosomes to the mitotic spindle

Compaction ratio for chromosomes

7,000 fold

Nucleosomes

Basic unit of chromatin structure

How much DNA does each nucleosomes have wrapped around

200bp

What are the different little sections of the histone called

Histone or tamer

What does linker DNA do

Separate the nucleosomes

What kind of bonds hold DNA to histones

Hydrogens + others

What chemistry is there going on between histones and DNA

Histones contain lots of arginine and lysine (positive) that interact/bind to the negative sequence of DNA’s sugar-phosphate backbone

Zigzag model

Histones arrange themselves in a ZIGZAGGG

What is a fractal globule

The ability of a chromosome to fold and unfold into densely or loosely packed chromatin, physical structure that allows it to change shape

Condensin

Protein that DNA can wrap around and when needed, it decondenses

What do poly teen chromosomes do

Help in understanding chromatin organization

How is the packaging throughout the genome

Different kinds of chromatin exist in different parts of the of the cell’s genome

Epigenetic inheritance

Inherited not within DNA but in addition to it

What is included in epigenetic inheritance

Histone variants and how they package chromatin in different ways

Heterochromatin

Highly condensed, contains very few genes OR silenced genes

Euchromatin

Less condensed, can be packaged into Heterochromatin

What is the nuclear pore’s function

Separate euchromatin from Heterochromatin

Where is chromatin in the nucleus

It moved but gene-rich regions move centrally

What happens during transcription to DNA

A gene loops out into the center where transcription proteins are

Why are genome comparisons made

To determine what sequences of DNA are functional and which ones vary without consequence

Conserved regions

Similar regions in human genomes and other eukaryotic genomes

What can conserved regions include

Exons and regulatory DNA sequences

Conserved synteny

Large blocks of human genome contain exact same genes in exact same order as other mammals

Dark matter

DNA outside of genes themselves that we don’t know what the functional gene of them were, new research found 3 million repeats of these across mammals leading to a belief they might have a significance