Exam 2 Genetics

How does an RNA nucleotide differ from a DNA nucleotide?

1. DNA nucleotides, or deoxyribonucleotides, have a deoxyribose sugar that lacks an oxygen molecule at the 2′ carbon of the sugar molecule.

2. Ribonucleotides, or RNA nucleotides, have a ribose sugar with an oxygen linked to the 2′ carbon of the sugar molecule

3. Ribonucleotides may contain the nitrogenous base uracil, but not thymine.

4. DNA nucleotides contain thymine, but not uracil.

Which bases are capable of forming hydrogen bonds with each another?

Adenine is capable of forming two hydrogen bonds with thymine. Guanine is capable of forming three hydrogen bonds with cytosine.

What different types of chemical bonds are found in DNA and where are they found?

• The deoxyribonucleotides in a single chain or strand of DNA are held by covalent bonds called phosphodiester linkages between the 3′ end of the deoxyribose sugar of a nucleotide and the 5′ end of the deoxyribose sugar of the next nucleotide in the chain.

• Two chains of deoxyribonucleotides are held together by hydrogen bonds between the complementary nitrogenous bases of the nucleotides in each chain.

nucleotides

a large number of linked repeating units

Tetranucleotide hypothesis

Imposed by Levene; incorrectly implied that the structure of DNA was not variable enough to make it the genetic material.

→ part of the reason people thought protein mightve been the genetic material

What did Chargaff etc discover?

They found that DNA from different organisms varies greatly in base composition.

Regularity in ratios of the nucleotide bases: amount of A=T (adenine and thymine)& amount of G=C(guanine and cytosine) = 1

• disproved Levene’s hypothesis

What are hairpins and how do they form?

Hairpins are a type of secondary structure found in single strands of nucleotides.

• The formation of hairpins occurs when sequences of nucleotides on the single strand are inverted complementary repeats of one another.

The four nitrogenous bases of DNA?

• adenine

• cytosine

• guanine

• thymine

Describe the structure of DNA:

• consists of a large number of repeating units (nucleotides)

• 2 strands of nucleotides that are anti-parallel & wind around each other to form a right-handed helix w/ sugars and phosphates on the outside & bases in the interior

• helical in structure

• polymer

What is the nucleotide structure?

a sugar, phosphate and a base

What does it mean to say DNA has antiparallel strands?

the 2 strands of nucleotides run in different directions; the 3’ end is paired with the 5’ end

Polymer

A chain made up of repeating units linked together

Phosphodiester linkages

a covalent; The bonds that connect nucleotides

Polynucleotide strand

a series of nucleotides linked

What is DNA methylation?

DNA methylation is when methyl groups (CH-3) are added to a certain postion on the nitrogenous base of nucleotide

What are the three major pathways of information that flow within the cell?

The major transfers of genetic information are replication, transcription, and translation.

→ These are the components of the central dogma of molecular biology.