cell bio ch. 5 flashcards

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central dogma

DNA → RNA → protein
replication → transcription → translation

structure of nucleotides

repeating phosphate-sugar backbone
linked by phosphodiester bond = covalent (within strand)
hydrogen bond = in between separate strands

How are DNA strands oriented?

antiparallel, 5’ → 3’, complementary

how many hydrogen bonds does each base pair have?

A-T = 2
G-C = 3

differences in prokaryote and eukaryote chromosomes

bacteria = single, circular DNA w/ no nucleus
eukaryotes = double-stranded, longer but more organized, packaged into chromosomes, has nucleus

human chromosomes

23 pairs = 46 chromosomes
22 autosome pairs
1 pair of sex chromosomes

dark DNA

noncoding, intergenic DNA in btwn genes

4 phases of cell cycle contrasted

G1, S, G2, M
G1 + G2 are gap phases, cell grows + makes proteins
G1 = cells grow + prep for DNA replication
G2 = involves quality control to prepare for mitosis
S phase (interphase) = DNA replication
M (mitosis) = growth stops and cell divides into 2 identical daughter cells

differences in interphase + M phase chromosomes

interphase: long, thin tangled DNA, not mixed together, less compact = access for protein expression + replication
not easily visible in microscope,
M phase: dense + compact DNA, in standard chromosomal shape
easily visible

karyotype

display full set of chromosomes with respect to size, shape, #

genetic pattern across all humans

99.9% exactly the same, slightest change = genetic disorders

chromatin

DNA + histone protein complex, aids in folding and packing
also called nucleosome,
histone + non-histone proteins can form complex

nucleosome structure

DNA wrapped around protein core of 8 histone molecules
2 H2A
2 H2B
2 H3
2 H4
positively charged AA’s to bind to - charged DNA backbone

chromatin-remodeling complexes

use ATP to change position of DNA wrapped around nucleosomes
tightens or loosens
changes DNA accessibility to proteins
helps DNA open + close
repeated use of ATP helps complex loosen nucleosomal DNA by pushing it along histone core, exposing DNA to DNA-binding proteins

Heterochromatin + Euchromatin

heterochromatin = closed, most condensed form of interphase chromatin, can’t express genes b/c near centromeres + telomeres
Euchromatin = open, rest of interphase chromatin, located where we express genes

Epigenetics inheritance

how behaviors and environment can change our DNA
can also be inherited
famines, holocaust, etc

S phase + mitosis contrasted

genetic material: S phase doubles, mitosis stays the same
# of chromosomes: S phase stays the same, mitosis doubles

DNA dyes

toxic b/c they bind to DNA + change its shape → function
giemsa stain: binds to A-T rich regions + make zebra patterns, helps line DNA up to know that every person has 99.99% same banding pattern

Hoechst stain: fluorescent dye
Ethidium bromide: carcinogens

FISH

helps make karyotypes, binds to specific sequence with complementary DNA/RNA probes that have fluorescent dyes

5th histone

H1, linker histone that helps chromatin structure stay together

chromatin structure is changeable, why important

close proximity of nucleosomes dec. gene expression, bc proteins can’t easily reach the gene, gene expression inc. w distance

histone tail modifications

can cause histone tails to “open” or “close” chromatin structures
open: acetyl
close: methyl
helps control how we express our genes