genetics chapter 8- DNA: the chemical nature of the gene

chargaff's rule

A=T and C=G

what are the purines?

Adenine and Guanine

What are pyrimidines?

cytosine, thymine, uracil

what are nucleotides made of?

sugar, phosphate group, nitrogen base

deoxyadenosine

Adenine + deoxyribose (dAMP)

Deoxyguanosine

Guanine + Deoxyribose (dGMP)

deoxythymidine

thymine + deoxyribose (dTMP)

deoxycytidine

cytosine + deoxyribose (dCMP)

How are ribose and deoxyribose different?

deoxyribose has one less oxygen

how many bonds do C-G pairs have?

three hydrogen bonds

how many bonds to T-A pairs have?

two hydrogen bonds

how do nucleotides link?

a 5'-phosphate group links to the 3'-OH group of an adjoining nucleotide via a phosphodiester bond

Are DNA strands parallel or antiparallel?

antiparallel (5'-3' and 3'-5')

how many bases are in a turn of the DNA helix?

approximately 10

which end of a nucleotide is 5'?

phosphate

b-DNA

Right-handed helix structure of DNA that exists when water is abundant and is the most common DNA structure in cells

a-DNA

right-handed helix structure of DNA when there is less water present

z-DNA

left handed helix structure of DNA formed in high-salt conditions

according ot Chargaff's rules, if a genome is 30% adenine, then waht percentage of the genome should be guanine?

20%

all organisms use DNA as their genetic material

false

DNA consists of repeating units of nucleotides. Which is NOT a component of a nucleotide?

a ribose sugar

which is ture of the secondary structure of DNA?

bases on complementary strands are held together by hydrogen bonds

which form of DNA has a left-handed helix and its sugar-phosphate backbone zigzags back and forth?

Z-DNA

what secondary structures are formed when signle-stranded DNA or RNA is inverted and complementary?

hairpin

what is the difference between DNA and chromosomes?

chromosomes are DNA condensed plus other stuff

how many feet of DNA are located in the nucleus of a human cell?

6 feet

what shape is prokaryotic DNA?

circular

how is DNA condensed?

supercoiling by either overrotating and getting tighter or underrotating and unravelling 2 turns

is underrotating or overrotating more common in bacteria and why?

underrotating because it is easier

positive supercoiling

double helix is overrotated and twists on itself

negative supercoiling

double helix is underrotated and twists on itself and unwinds a bit

how many chromosomes do humans have?

23 pairs, 46 total

eukaryotic chromosome characteristics

- tightly packed DNA
- only found during cell division
- DNA is not being used for macromolecule synthesis

chromatin characteristics

- unwound DNA
- found throughout interphase
- DNA is being used for macromolecule synthesis

what is the only time condensed chromosomes are found?

during cell divison

eu-

true

euchromatin

normal, less condensed chromatin where most transcription takes place

heterochromatin

Highly condensed chromatin that is transcriptionally inactive and is found in centromeres and telomeres

telomere

repetitive DNA at the end of a eukaryotic chromosome

histone protiens

what DNA is wrapped around

what are the 5 types of histone proteins?

H1, H2A, H2B, H3, H4

what are scaffold proteins?

structural protiens that provide the platform for DNA to condense

nucleosome

repeating subunit of chromatin fibers, consisting of DNA coiled around histones

what ara the core histones?

H2A, H2B, H3, and H4

what is the centromeric sequence?

the seequence of nucleotide bases that is repeated at the centromeric region which is the binding site for the kinetochore

what are telomeric sequences?

they are the stabalizing strands at the end of the chromosome. one strand is longer and loops back to form a "knot" by pairing with a section of DNA to increase stablility

which statement is true regarding negative supercoiled DNA?

that negative supercoiled DNA is underrotated allowing for easier strand separation during replication and transcription

which is not true fo most bacterial DNA?

it is linear

if a piece of chromatin contained 200 copies of the histone H4 then how many nucleosomes would be present?

100

how many copies of each core histone are found in a histone octamer?

2 of each kind