BIO 190- Ch #9 *The Info of Life: DNA,RNA structure, DNA replication, chromosome structure*

what is chromatin

the DNA and protein that makes up the chromosomes

(the DNA wraps around the proteins)

how are chromosomes packed

linearly

chromosomes

threadlike structures made of DNA molecules that contain the genes (discrete unit of genetic material)

histones

protein molecules around which DNA is tightly coiled in chromatin

Eukaryotic DNA is first compacted by wrapping around a group of proteins called _______which forms structures called ______

histones; nucleosomes

nucleosomes

DNA wrapped around histone proteins.

DNA + histone =

nucleosome

how are nucleosomes organized

into a more compact structure that is 30 nm in diameter

they have a pleat/zig zag shape that can stretch to allow DNA access or pack tightly to close off access

interactions between the 30 nm fibers and proteins form ...

radial loop domains

can be tightened or pulled out

what 4 criteria are needed for genetic material

1. information- to construct the organism

2. replication- must be accurately copied

3. transmission- must be passed from parents to off spring and from cell to cell during cell division

4. variation- be able to account for differences between individuals and species

Griffiths bacterial transformation experiments indicated the existence of ...

genetic material

describe Griffiths bacterial transformation experiment

rough bacteria (no capsule)=immune system cleared bacteria= mouse lived

smooth bacteria (capsule)= immune system could not attack = mouse died

heated smooth bacteria= bacteria died= mouse lived

mix smooth and rough bacteria = type S cells transformed the R cells into type s

conclusion "something had instructions in it"

Avery, MacLeod, McCarty asked...

their conclusion was...

" what substance is transferred from the dead type S to live in the type R"

conclusion: DNA is responsible for transforming type R cells into Type S cells

Avery, MacLeod, McCarty vs Griffiths conclusions

griffith = something had instructions in it

Avery, MacLeod, McCarty= that something was DNA

DNA and RNA are ________, polymers of _______

nucleic acids; nucleotides

DNA and RNA are reponsible for

storage, expression, and transmission of genetic info

nucelotides

the building blocks (monomer)

strand

a linear polymer

double helix

2 strands twisted

chromosomes

DNA associated with different proteins , whole length of double helix

genome

the complete complement of genetic material of an organsim (all of the DNA in the nuclei of the cell*

what reading nucleotides what is the "capital letter/start" of the "sentence"

its based in the sugars phosphate group

carbon 5'

what reading nucleotides what is the "period/end" of the "sentence"

free hydroxyl group

in a nucleic acid structure the phosphate group will always be ...

free

the first nucleotide will always have a ...

free phosphate group

whats the directionality of a nucleotide strand

5' to 3'

the 5' end is

the first nucleotide/ free phosphate

the free phosphate group is on the ...

5' end

the free hydroxyl group is on the ....

3' end

bond rules for DNA

A-T

C-G

strands of double helix are _________ and _________

complementary and antiparallel

complementary strands

two nucleotide chains of the DNA molecule

antiparallel strands

Strands parallel to each other going in opposite directions (3'-5' and 5'-3')

________ was a key tool that lead to the discovery of DNA double helix structure

x- ray diffraction

rosalind frankiln

___________ determined base pairing rules

Erwin Chargaff

__________&________ put together other ppls work to discover the structure of DNA

watson and crick

simple description of how DNA is replicated

1. G1 phase; signals occur here

2. S chase/ DNA replication: each chromosome replicates itself "staples two together"

3. G2 phase additional growth/preparation

what is the goal of the S phase

start with a template chromosomes, copy it, attach copies together "staple it"

DNA polymerase builds ________ daughter strand

anti parallel

half parent + half daughter =

semi conservative replication

DNA cant start it's job ________ starts it

primase

primase

is necessary for starting DNA polymerase it only needs it to get work started before it can go for millions of nucleotides

describe replication forks

A replication fork is the Y-shaped region that forms when DNA is being unzipped for replication.

Helicase unwinds the double helix by breaking hydrogen bonds between base pairs.

This creates two single strands of DNA.

The area where this separation occurs is called the replication fork.

Unzips the DNA strands

helicase

Adds new nucleotides to form the new strands

DNA polymerase

Primase

lays down RNA primers

Seals fragments together

ligase

what type of bonds does DNA polymerase make

Phosphodiester bonds

These are strong covalent bonds that link the phosphate group of one nucleotide to the sugar (deoxyribose) of the next nucleotide.

primase created what type of bonds

Primase creates phosphodiester bonds, just like DNA polymerase.

🧪 Here's what primase does:

It synthesizes a short RNA primer on the DNA template strand to provide a starting point for DNA polymerase.

DNA polymerase can only add nucleotides in the __________ direction.

5′ → 3′ direction.

leading vs lagging strand

Leading strand = 5′ → 3′ toward fork

Lagging strand = 5′ → 3′ away from fork

Leading strand

✅ Leading strand:

Synthesized continuously

Goes toward the replication fork

Follows the helicase as it unwinds the DNA

🔁 Lagging strand:

🔁 Lagging strand:

Synthesized in short segments (Okazaki fragments)

Goes away from the replication fork

Must keep restarting as more DNA is exposed

the "pieces" of the lagging strand are called

Okazaki fragments

lagging strands are

discontinuous

leading strands are

continuous

what 3 proteins are responsible for fork formation/movement

DNA helicase

DNA topoisomerase

single stranded binding proteins

DNA topisomerase

prevents super coiling

single stranded binding proteins

prevent the double helix from forming in the fork

DNA helicase

unzips the helicase

what 2 enzymes are needed to synthesize DNA strands during replication

DNA polymerase and DNA primase

DNA polymerase ________________ nucleotides together

covalently links

DNA polymerase has what 2 important functional constraints

it can not begin synthesis on a bare template it needs a existing strand

it synthesizes DNA in a 5 to 3 direction

DNA primase makes a complimentary _____ of RNA that can be extended by DNA polymerase

primer

DNA polymerase can not lay down the first strand because....

there is no hydroxyl group for it

Permanent mistakes in DNA replication are rare because...

DNA polymerase can proofread and remove mismatched pairs

list the complementary bases

A, T, C, G

outline the structural features of DNA at 5 levels of complexity

✅ Summary of 5 Levels:

Nucleotide – Base + sugar + phosphate

Strand – Linear chain of nucleotides

Double helix – Two antiparallel strands with base pairing

Nucleosome – DNA wrapped around histones

Chromosome – Fully compacted, organized DNA structure

in the work of griffith the mixture of heat killed S strain bacteria living R strain bacteria resulted in death of the mouse. the correct interpretation of these results is

genetic material was transformed from the head killed S strain to the R strain

transformation may result in horizontal gene transfer. this process occurs when an organism incorporates genetic material from another organism without being offspring of the organism. in griffths experiment what was the function of the genes that were transformed to type R bacteria and converted to Type S

the function of the genes was to enable the bacteria to synthesize a capsule

a nucleotide composed of deoxyribose, a phosphate, and adenine can only be found in...

DNA only

the 5' and 3' labels that identify the directionality of a DNA strand are based on ...

the orientation of sugar molecules in the backbone

carbon 5 is where phosphate group is attached

if sequence is 5'-GCTAGATG-3' what is sequence of the other strand

3′-C G A T C T A C-5′

which protein is needed to form a replication fork and keep it moving

DNA helicase

okazaki fragments are made during the synthesis of the _____ strand they are connected together by _____

lagging; DNA ligase

what is the primary purpose of a nucleosome

to cold and compact hundreds of millions of base pairs and DNA in the nucleus

describe the difference between chromosomes and chromatin

chromosomes are made of chromatin which is composed of DNA and proteins

what is the role of histones in chromatin structure

histones help condense DNA by acting as spools around which DNA is wrapped

where is the messenger/ coding strand versus the template strand

coding/messenger is on top

template is on bottom

what are the difference between a message strand and mRNA

when converting to a mRNA strand everything remains the same minus T becomes U

when writing an amino acid what do you start the chain with versus end

start with N = free amino group

end with C = free carboxyl group