Molecular Genetics exam 1

What is Centromere?

A centromere is a constricted region of a chromosome that separates it into a short arm (p) and a long arm (q)

Serve as the site where the kinetochore assembles

Kinetochore Formation

A protein complex that forms at the centromere during cell division. The kinetochore acts as an attachment site for spindle fibers during cell division. This ensures accurate segregation of chromosomes to daughter cells.

Spindle fibers start during prophase

Cohesion Protiens

Cohesion proteins hold sister chromatids together, more concentrated towards the middle giving them the pinched appearance. .

Whys it help?

Ensures that chromosomes are evenly divided.

Telomere

Nucleoprotien caps composed of repetitive DNA sequences (TTAGGG) titi aniya GGGS, Prevents chromosome ends as being recognized as DNA damage.

ROLE: Prevents the loss of essential genetic information during DNA replication PTL

Protects against: 1.Fusion, Degredation, inappropriate repair mechanisms. DIF

degredation, inappropriate repair mechanisms, fusion.

Fun fact my fav: Telomeres cant replicate all the way to the end of the chromosome. This excessive shortening leads to loss of genes, aging, genetic disorder, and cancer

LOG, AC, GD

Loss of genes, aging cancer, genetic disorder

In cancer: an enzyme called TELOMERASE extends the telomeres is reactivated and allows uncontrolled cell proliferation

Gene

A segment of DNA that contains information for making proteins that ultimately decide traits.

Structural gene

A gene that encodes any RNA or polypeptide product other than a regulator

Regulatory gene

A gene that encodes a protein involved in the expression of STRUCTURAL or NON-STRUCTURAL genes

alleles bruh

Variants of a gene that determine traits

Karyotyping

The process of visualizing and analyzing the number size shape and structure of a chromosome.

How many chromosomes do ollie have

78 total 39 pairs

hb cats bro

38 total 19 pairs

Karyotyping prep

Chromosomes prepared from dividing cells. They are stained with Giemsa stain, and analyzed under a brightfield microscope at high magnification

Dark area on G-banded chromosome

AT Rich

Light area on G- banded chromosome

GC Rich

Name the 4 types of chromosomes

1. Autosomes: chromosomes that dont decide gender

2. Sex-chromosome Chromosomes that decide gender

TASM together Aidan Sofia marchuk

1. Telocentric: Centromere is located at the tip of the chromosome, appearing as a single arm.

2. Arcocentric: Centromere is positioned very near to one end

3. Submetacentric: Centromere is slightly off center

4. Metacentric: Centromere is located in the middle of the chromosome

Ploidy

number of complete sets of chromosomes in a cell or an organism

Aneuploid (2n ± 1)

A condition where the number of chromosomes is not an exact multiple of a complete set due to the gain or loss of chromosomes

(2n ± 1)

Trisomy (2n+1)

Gain of one chromosome (2n+1)

Monosomy (2n-1)

Complete or partially missing one chromosome EX. Turner syndrome monosomy X0

(2n-1)

Monoploid (n)

ngl idk research more

Chromosomal territory

Each chromosome occupies a distinct space in the nucleus with minimal overlap in non-dividing cells.

Weight of one base pair

650 Daltons

Euqation for moles

moles = mass / molecular weight

One Base pair weights

650 Da

One nucleosome has about how many BP

200

One nucleosome weights approx

130 kD

Linker DNA is approx how many base pairs (H1)

7-115 BP

Histone modification 6

1. Methylation: Inactivates/ turns off genes, low expression, condesned chromatin.

2. Acetylation: Leads to high expression making the chromatin more loos and relaxed.

3. phosphorylation: Addition of a phosphate group, this can change how tightly DNA is packed around histones, can affect which proteins bind to the chromatin.

4. Ubiquitin: A protein tag (protein signaling/ regulation)

5. sumoylation: A regulatory tag that says “slow down” (Transcriptional repression)

6. ADP- ribosylation: DNA damage/repair

Package of DNA

1. Nucleosome

2. solenoid fiber

3. scaffold loop

4. chromatid

5. chromosome
   NSSCC

Composition of DNA

• Horizontally between the two strands: 20 A (2nm)

• Major Groove: 22A

• Minor Groove: 12A

• One complete turn 34A (10-10.5 bp)

• Distance between each base pair is 3.4

CHemical composition of DNA

1. Phosphate group

2. Pentose sugar

3. Nucleotides (Nitrogenous bases)
   - Adenine: Purine (2 rings)
   - Guanine Purine (2 rings)
   -Thymine: Pyrimidine (1 ring)
   -Cytosine: Pyrimidine (1 ring)

AT: 2 bonds

GC: 3 bonds

Nucleotide vs Nucleoside

Tide: Sugar + Base + Phosphate

Side: Sugar + base

NUCLEOSIDE DOESNT HAVE A PHOSPHATE GROUP

Oligonucleotide

Once you connect lots of nucleotides together you get a DNA strand.

oligonucleotide is a relatively short chain of nucleotides, usually 2-50 bases long.

Polynucleotide

A longer chain of nucleotides usually greater than 50 bases

Phosphodiester bond

Nucleotides are linked y the phosphodiester bond, this link occurs between the C-5 position of the incoming nucleotide and the OG group on the C3 position of the previous nucleotide

• during this process one molecule of H2O is removed.

Nucleotide synthesis pathways

1. De Novo Pathway: From scratch, take more energy has to make everythin from scratch.

2. Salvage pathway: recycles existing bases/ nucleotides. Its always available for the cell. energetically less expensive.

The forms of DNA

B form: normal DNA form

Z form: is the opposite of B form( left handed, negatively supercoilded.)

A for: like B form but dehyrdrated or certain protein binding.

Who Discovered DNA

Friedrich Miescher.

to discover DNA he mustve been so fried. (1869)

First evidence of DNA being double helical

Rosalind franklin (1951) she used x-ray diffraction images, however watson and crick (1953) got the final proof. for the stucture of DNA

Chargaffs rule

Total amount of purines AG equal same amount of Pyrimidines TC