what is the genome?

a set of genetic information found in a nucleated eukaryotic somatic cell

what does DNA consist of?

nucleotides arranged into genes and chromosomes

DNA is

the structural blueprint for all genetic instructions

purines (heterocyclic compounds) are-

adenine (A) and guanine (G)

pyrimidines are-

cytosine (C) and thymidine (T)

the backbone of DNA is made of-

a phosphate group bound to pentose by a phosphodiester bond (phosphate-deoxyribose backbone)

the genetic code in the DNA is composed of how many bases

four

The phosphodiester bond and one of the four bases bind by a ____________________ to form nucleotides

a strong covalent bond

nucleotides bind to other nucleotides on the other DNA strand by ____________________

weak hydrogen bond

pentose molecules of the DNA backbone are asymmetrically joined to phosphate groups by

phosphodiester bonds

_________________ between complementary __________________ interact to stabilize and form the double helix structure.

hydrogen bonds;nucleotides

a DNA molecule is composed of

two antiparallel DNA strands held together by hydrogen bonds between the paired bases

A and T form ____ hydrgen bonds

2

G and C form ____ hydrogen bonds

3

bases can only pair if the two polynucleotide chains that contain them are __________________________

antiparallel to each other

a single strand of DNA consists of

nucleotides joined together by sugar-phosphate linkages

the asymmetry of the sugar-phosphate units give the backbone strand a definite-

directionality/polarity

DNA exists as a-

double helix with about ten nucleotide pairs per helical turn

the sugar in DNA is

deoxyribose

phosphodiester bonds are bonds that-

form between the 3'-OH groups of the deoxyribose sugar on one nucleotide with the 5' phosphate groups on the adjacent nucleotide

the 5' phosphate group of one nucleotide is bound to

the 3' hydroxyl group of the next nucleotide

the _____ end of one strand is base-paired with the ____ end of the other strand.

5' ; 3'

why do the bases in DNA have hydrogen bonds?

the hydrogen bonds between the bases can be made and broken easily, allowing DNA to undergo accurate replication and repair

what is a nucleoside?

made up of a five-carbon sugar (pentose) bonded to a nitrogenous base and are formed by covalently linking the base to C-1' of the sugar

what is a nucleotide?

they are formed when one or more phosphate groups are attached to C-5' of a nucleoside.

what is the Watson-Crick model?

the double-helix structure of DNA

what is Chargaff's rule?

amount of A = the amount of T, the amount of G = to the amount of C.

Total purines = to Total pyrimidines overall

what is denaturation?

separating/ breaking down DNA into two single strands

what is reannealing?

when two complementary strands are put back together

define chromatin

consists of DNA bound to histone and non-histone proteins

what are histones?

small basic proteins, a heterogeneous group of closely related arginine- and lysine-rich basic proteins, make up 1/4 of amino acid residues

histones-

bind tightly to the negatively charged sugar-phosphate backbone of DNA

functionally, histones-

provide for the compaction of chromatin

a chromosome is about-

1/3 DNA and 2/3 protein by mass

structure of a nucleosome:

8 histone protiens (2 of each: H2A, H2B, H3, and H4) w/ double stranded DNA wound around it

function of a nucelosome?

packaging DNA, regulate gene expression/activity

define nuclease:

an enzyme that breaks down DNA

what is formed during the progressive compaction of chromatin

higher order structures

each core histone has-

a structured domain and an unstructured amino-terminal "tail" of 35 to 40 amino acid residues

enzyme modification by _________________, __________________, or ______________ modifies the histones net elcteric charge and shape

acetylation, methylation, phosphorylation

(changes are physiologically reversible and help prepare chromatin for DNA replication and transcription)

heterochromatin is

densely packed or compacted regions of chromatin, and genetically inactive

(transcription is inhibited here because the DNA is packaged so tightly that it is inaccessible to the proteins responsible for RNA transcription)

euchromatin is-

less densely compact chromatin regions in a transcriptionally active nucleus. commonly undergoing, preparing for, or just having completed transcription.

euchromatin represents

uncoiled chromatin structures that allow RNA polymerases' and regulatory proteins' access to DNA

Telomeres:

hexametric DNA repeats (TTAGGG) found at the ends of chromosomes to protect the chromosome from degradation

Centromeres:

allow mitotic spindles to attach to the chromosome during cell activation

in order for DNA in chromosomes to replicate-

a certain nucleotide sequence acts as a DNA replication origin

(each chromosome contains many origins of replication)

kinetochore is

a protein complex that attaches the centromere to the spindle

a gene is

the complete sequence region necessary for generating a functional product

Translation

RNA ---> protein

Transcription

DNA ----->RNA