Bio Exam 3

What are the 4 criteria that genetic material must fulfill? (Explain)

1. Information. Carrier of information

2. Replication. Ability to replicate

3. Transmission. Transmit info between parent and offspring or cell to cell

4. Variation. Ability to slowly mutate

What makes up a DNA nucleotides structure?

Phosphate group + Deoxyribose sugar + nitrogenous base

What makes up the structure of a RNA nucelotide?

Phosphate group + Ribose Sugar + Nitrogenous Base

What’s a Purine?

Double ringed nucleotide. Includes Adenine and Guanine.

What’s a Pyrimidine?

Has a single ring. Includes: Cytosine, Uracil, and Thymine

Hint: CUT the PY (pie)

Pyrimidines pair with Pyrimidines and Purines pair with Purines

False. Pyrimidines pair with Purines.

What does Chargaff’s (AT/GC) Rule state?

The percent of Adenine will equal the percent of Thymine

The percent of Guanine will equal the percent of Cytosine

If you know the percent of one nucleotide you can figure out the percent of the other nucleotides

In which groove can proteins bind to DNA to influence gene expression?

Major Groove

Genome

An organisms complete set of genetic material

What were the three proposed ways of DNA replication?

1. Semiconservative Replication

2. Conservative Replication

3. Dispersive Replication

Semiconservative Replication

The accepted way that DNA replicates.

Each new DNA strand consists of one parental strand and one daughter strand

Conservative Replication

The replication of a helix results in one copy of the parental helix and one completely new daughter helix

Dispersive Replication

Old DNA and New DNA is dispersed through the new helixs

Explain Griffiths experiment and why its important

Importance: The concept of bacterial transformation

How? Using two strains of strep and mice. One strain was deadly the other was not. Mixing together the killed deadly strain and he live undeadly strain still killed the mice. Meaning that the bacteria uptook the deadly strain.

Explain the Avery, Macleod, and McCarty Experiment and why it is important

Importance: established DNA as genetic material

How: Built off of Griffith experiments. This time used enzymes to kill either proteins, RNA, or DNA. This time when injected into the mice only the strain that still had DNA in it, killed the mice. This means that the DNA had to be the carrier of genetic information for the deadly strain to be taken up by the bacteria

Explain the Waston and Crick Experiment and why its important

Importance: built a structural model of DNA’s structure

How: built off several experiements; Chargaff’s base pairing, Franklin Rosalind’s X-rays of the double helix, etc. They just complied research and deduced.

Explain the Meselson- Stahl Experiment and why its important

Importance: DNA Replication is semi conservative.

How: Using E.coli, heavy and light nitrogen, and a centrifuge. The e.coli was grown in heavy nitrogen but then put in light nitrogen environment to reproduce further generations. After their DNA was extracted and put into a centrifuge, you could see that after the first replication the DNA had one strand heavy (parental) and one strand light (daughter).

Chromatin

The material that makes up chromosomes

Histones

A protein that acts as a spool for DNA to wrap around

(Only found in eukaryotes)

Nucleosome

Consists of DNA wrapped around a core of 8 histones twice

What are the steps of chromatin packing?

1. Making Nucleosomes

2. Formation of 30 nm fiber

3. Radial Loop Domains

What happens in the first step of chromatin packing? (How much does this condense the DNA?)

Nucleosomes are made

This condenses the DNA 7-fold

What happens in the second step of chromatin packing ? (How much does this condense the DNA)

The Nucleosomes come together to form a fiber, zig-zag like formation.

This condenses the DNA another 7 fold

What happens in the third step of chromatin packing? (How much does this condense the DNA)

The 30 nm fibers are folded in to loops by proteins

Euchchromatin

Loosely packed chromatin

Heterochromatin

Tightly packed chromatin

What are the two main differences of DNA replication in prokaryotes and eukaryotes?

Eukaryotes: multiple origins of replication and slower replication rate

Prokaryotes: One origin of replication and faster replication rate

Origin of Replication

Where DNA replication begins

Topoismerase

Used in the first step of DNA replication. It’s an enzyme that relaxes the twist of DNA and unwinds it

Helicase

Used in the first step of DNA replication. It’s an enzymes that unzips DNA, breaks hydrogen bonds.

Replication Fork

The location where helicase breaks hydrogen bonds, creating a fork

Single Stranded Binding Protiens (SSB)

Proteins that keep the DNA single stranded and from being cut or damaged

Primase

Used in the second step of DNA replication. It’s an enzyme that places RNA primers on the DNA for DNA polymerase to bind with

What is the purpose of RNA primers

They show where DNA polymerase should bind

DNA Polymerase III

Used in the second step of DNA replication. It’s an enzyme that pairs free-floating nucleotides to their complementary base

Leading Strand

DNA strand that is synthesized continuously in the 5’ to 3’ direction

Lagging strand

DNA strand that is synthesized in fragments in the 3’ to 5’ direction.

Okazaki fragments

Fragments of the lagging strand

DNA polymerase I

Used in step 3 of DNA replication. It’s an enzyme that removes the RNA primers and adds in DNA nucelotides

Ligase

Used in step 3 of DNA replication. It’s an enzyme that bonds fragments of the lagging strand

What is the molecular definition of a gene?

It’s a unit of heredity. Duh

Gene Expression

The process by which DNA directs protein synthesis

Transcription

Process of duplicating a segment of DNA into RNA

Translation

Process of using mRNA to synthesize a protein

Central Dogma

Theory that genetic information flows from DNA to RNA to Protien

What is the first step of Transcription?

Initiation. RNA polymerase attaches to the promoter on DNA and the helix unwinds

What is the second step of Transcription?

Elongation. RNA polymerase moves along one of the DNA strands, adding complementary RNA nucleotides to create a mRNA molecule.

What is the third step of Transcription?

Termination. RNA polymerase reaches a terminator sequence and the mRNA molecule is released

What determines the direction of transcription?

The promoter region

Where does eukaryotic transcription occur?

Nucleus

Where does prokaryotic transcription occur?

Cytoplasm

Does transcription occur simultaneously in prokaryotes or eukaryotes?

Prokaryotes

Does transcription occur before or after translation in eukaryotes?

Transcription occurs before Translation

Where can pre-mRNA be found? (Prokaryotes or Eukaryotes)

Eukaryotes

5’ cap

The 5’ end of the pre-mRNA gets a modified guanine nucleotide added to it

Poly-A tail

The 3’ end of the pre-mRNA gets many adenine nucleotides added to it

What is the purpose of adding a 5’ cap and Poly-A tail to pre-mRNA?

These help protect the mRNA from damage as they are transferred from the nucleus to cytoplasm for translation

Exons

Regions in the pre-mRNA that are translated into amino acid sequences

Introns

Regions that are spliced out of pre-mRNA and not translated.

RNA splicing

Introns are removed and exons join together to prepare for translation

Spliceosomes

Consists of proteins and nuclear RNAs and carries out RNA splicing

Codon

A three nucleotide unit that specifics an amino acid

Degenerate Codons

Multiple codons that code for the same amino acid

Ambiguous Codon

Only one codon can code for a specific amino acid

tRNA

Transfers amino acids to the growing polypeptide in a ribosome

Anticodons

On the ends of tRNA molecules; contain complementary codons to mRNA

Explain the different sites in a ribosome

A site. tRNA enters

P site. tRNA adds an amino acid to the chain

E site. tRNA exits the ribosome

Reading Frame

Defined by the start codon and read one codon at a time. No overlapping.

What’s the first stage of Translation?

Initiation. Small and large subunit assemble around the mRNA and the corresponding tRNA for the start codon will bind

What is the second stage of translation?

Elongation. The amino acid chain grows as tRNAs add them by translating mRNA

What is the third stage of translation