Genetics DNA Structure

DNA

deoxyribonucleic acid

• carries genetic information

• made of alternating sugar & phosphate groups (ATCG)

RNA

ribonucleic acid

• present in all living cells

• contains ribose (extra hydroxl group) (AUCG)

mRNA

messenger RNA

• carries genetic instructions from DNA

• complementary in sequence to the template strand of a gene that specifies a protein product

tRNA

a type of RNA that connects mRNA to amino acids during protein synthesis

rRNA

RNA that, with proteins, comprises ribosomes

Watson & Crick

20th century scientists who discovered the 3d double helix structure of DNA

• double helix

• antiparallel strands

• sugar-phosphate backbone

double helix

twisted ladder or spiral staircase

5-carbon sugar

deoxyribose, found in a DNA nucleotide

sugar-phosphate backbone

• the “rails” of a DNA double helix

• consisting of alternating deoxyribose & phosphate groups

• oriented opposite one another

nitrogenous bases

a nitrogen containing base that is part of a nucleotide

adenine

one of the two purine nitrogenous bases in DNA & RNA

cytosine

one of the two pyrimidine bases in DNA & RNA

guanine

one of the two purine nitrogenous bases in DNA & RNA

thymine

one of the two pyrimidine bases in DNA

purine

a DNA base with a two-ring structure

• adenine and guanine

pyrimidine

a DNA base with a single-ring structure

• cytosine, thymine, & guanine

base pair

a unit of two nucleotides bound together by hydrogen bonds (forms rungs of DNA/RNA ladder)

• DNA: (A)(T) and (C)(G)

• RNA: (A)(U) and (C)(G)

antiparallel

the head-to-tail position of the entwined chains of the DNA double helix

5’ & 3’ ends

two distinct terminal ends of DNA or RNA

5’ → the end that has a free, unattached phosphate group bonded to the 5th carbon atom

3’ → the end that has a free hydroxyl group attached to the 3rd carbon atom

phosphodiester bonds

strong chemical link that connects sugar & phosphate groups of adjacent nucleotides to form the structural backbone of DNA & RNA

• links 5’ carbon and 3’ carbon

hydrogen bonds

ribose

a 5-carbon sugar in RNA

deoxyribose

a 5-carbon sugar in DNA

chromosome

a structure in a cell’s nucleus that carries genes, a continuous molecule of DNA/proteins wrapped around it

chromatin

DNA and its associated histone proteins

nucleosome

a unit of chromatin structure

nucleotide

• the building block of a nucleic acid

consisting of:

• phosphate group

• a nitrogenous base

• 5-carbon sugar

histone

a type of protein around which DNA entwines

nucleus

a large, membrane-bounded region of a eukaryotic cell that houses DNA

nuclease

enzyme that breaks the bonds using nucleic acids (like DNA & RNA)