Exam 3 Genetics

what are the three levels of chromosome compaction ?

1. DNA binding to histones 2. Histone-bound DNA coils through non-histone proteins 3. Other proteins ( condensins, topoisomerases, etc) fold the coiled DNA into scaffolds

What are the two functions have Centromeres ?

1. Hold sister chromatids together( through action of cohesin) 2. Attachment sites for chromosome segregation machinery ( through formation of kinetochore)

Four core histones tails be modified with chemical groups by ?

1. Tails extend outward from nucleosome 2. Enzymes can add chemical groups (methyl group, phosphate group, ubiquitin, etc) 3. Modified tails can alter nucleosomes and bind chromatin modifier proteins.

What are probes in fish ?

A DNA sequence is labeled with a fluorescent tag to make a probe.

What is a telomere?

Are caps that protect the ends of Eukaryotic chromosomes.

What chromosomes is ?

Are the separate pieces of chromatin that behave as a unit during the cell division.

Know what contribution of condensins in a radial loop?

Condensins may further condense chromosomes into a compact bundle for mitosis.

Replication unit (replicon)

DNA being replicated in both directions one origin

Telomeres shorten slightly at each _____ ______ ?

Each cell division

Arrangement along chromatin is not highly defined and varies in different cell types and under same conditions. True or false

False, It is highly defined in varies. Also, it will be under different conditions.

Segregation of condensed chromosome don't depends on centromeres: True or False

False, it does depend on centromeres.

Replication in Eukaryotes must not be fast: True or false

False, it should be fast. So there cannot be any mistakes

What is FISH?

Fish- Depends on hybridization between metaphase chromosomes and labeled DNA sequence.

What cells have high expression of telomerase ?

Germ cells, Stem cells, and tumor cells At each generation, telomere length is maintained.

Metaphase chromosomes stained with ____ have alternating bands of light and dark staining.

Giemsa

What are the five types of Histone ?

H1,H2A, H2B, H3, and H4

Core histones make up what ?

H2A, H2B, H3 and H4

The karyotype of a human is examined by _______

High-resolution G-banding

What are the affects methylation of histone tails ?

Histone Methyltransferases add methyl group to histone tails. Affect depends on specific amino acid modified Adding methyl group H3 lysine 9 favors heterochromatin formation

what chromatin is ?

Is the generic term for any complex of DNA and protein found in a nucleus of a cell.

Histone H1 associates with __________ DNA as it enters and leaves the nucleosome core

It is associated with Linker.

Nucleosomes compact DNA, but ___ enough to to be able to fit within the cell.

It will not be enough to fit into the cell.

What are the roles of non-histone proteins?

LARGE variety of function: 1.Structural role- Chromosome scaffold. 2. Chromosome replication- e.g. DNA polymerases 3. Chromosomes segregation- kinetochore proteins 4. Active in transcription- largest group

Fun fact of ORI

Most mammalian cells have - 10,000 origins of replication Many ORI are active at the same time Ori are in accessible regions of DNA that are devoid of nucleosomes

What are nucleosomes?

Nucleosomes resemble beads on a string.

Spacing and structure of ____ affect genetic function ?

Of Nucleosomes

Histones are small ____ charged, and highly conserved!

Positively

Why is Telomeres essential to the maintenance of chromosomes?

Prevent chromosomes fusions and maintain integrity of chromosomal ends.

The ___ hybridizes to chromosomes at complementary regions

Probes

What is euchromation ?

Relaxed, usually active transcriptionally 1. Lightly stained regions of chromosomes

What effects do acetylation histones on gene expression?

Results in more open conformation of chromatin. Prevent close packing of nucleosome Favorite expression is Euchromatin Histone acetyltransferases add acetyl group to histone tails. Residues on a Histone H4 negates a positive charge. Thus, decreasing the attraction to the negatively-charged DNA.

Model 2:what is radial-loop scaffold model ?

Several non-histone protiens ( NHPS) bind to chromatin every 60-100kb and tether the 300 A fiber into structural loops.

Telomeres species- ______ sequences

Specific

telomeres consist of ?

Specific repetitive sequences and don't contain genes.

Model 1: _______ of DNA around histones and nonhistone proteins

Supercoiling

Ribonucleoprotein is ?

Telomeres is Ribonucleoprotein that extends the end of a chromatin.

What is Shugoshin?

The protein shugoshin protects the cohesin (at the centromeres only) from degradation by separase. This holds the sister chromatids together at their centromeres during anaphase I of meiosis, so they don't separate until anaphase II. What does this do? Protects the cohesin at the centromere through stage I of meiosis. This is why the spindle fibers pull, they pull apart the homologs and not the sister chromatids. Then in anaphase II, shugoshin gets degraded, separates and the cohesion breaks down, thus allowing the sister chromatids to separate. This is what allows for the unique separation of meiosis.

Histone to what ?

They bind to the negatively charged DNA

Cell autonomous processes and aging telomere shortening: True or False

True

DNA interaction with histones and _nonhistones proteins produces a sufficient level of compaction to fit into a cell nucleus True or False

True

G-bands correspond to regions of densely packed chromatin: True or False

True

Without a special mechanism, DNA would be lost from every new DNA strand at each cell cycle: False or True

True

Core histones make up nucleosome: true or false

True, it does make it up.

Nucleosomes are disassembled during replication then quickly added to new DNA: True or False

True, it is done fast

What is heterochromatin?

highly condensed, usually inactive transcriptionally 1. Darkly stained regions of chromosomes 2. Constitutive- condensed in all cells. 3. Facultative- condensed in only some cells and relaxed in other cells.

What is short arm is ?

p-arm - Within each arm, light and a dark bands are numbered consecutively

Spectral Karyotyping (sky)

probes specific for each chromosome are labeled with a different fluorescent dye

what is long arm ?

q-arm- Within each arm, light and dark bands are numbered consecutively