unit 5 - dna Flashcards
(41 cards)
three parts of nucleotide
phosphate, sugar, base
what part of nucleotide has nitrogen
base
what kind of sugar is in nucleotide
deoxyribose
four bases in nucleotides of dna
adenine, thymine, guanine, cytosine
base pairing rules
a-t, g-c
what makes up rungs of dna ladder
bases
what makes up backbone of dna ladder
phosphate and sugar
steps of dna replication
strands of dna separate, hydrogen bonds between nucleotides break, free nucleotides are attracted to exposed bases on loose strands, hyrdrogen bonds form between nucleotides
which enzyme unwinds and breaks h bonds in dna
helicase
which enzyme copies the original dna strand (using base pairing rules) to replicate
polymorase
why is dna replication called semi conservative replication
one original strand remains in the new double helix (half the old double helix is conserved)
how does semi conservative replication help prevent mutations
uses the original strand as a template
loose dna inside a nucleus
chromatin
what part of the cell cycle is dna replicated
end of S (synthesis)
what part of the cell cycle is dna condenses into chromosomes
beginning of m (mitosis)
what structure holds sister chromatids together for cell division
centromere
how many base pairs are in an average human cell
3 billion (6 billion individual bases)
genes
sequence of DNA that encodes for a specific protein
how many amino acids
20
alleles
different form of a gene
two kinds of mutations
point mutations and frameshift mutations
what is point mutation
a single nucleotide mutation
three kinds of point mutations
nonsense (codes for a stop), missense (changes one amino acid), silent (doesn’t change amino acids)
two kinds of frameshift mutations
insertion (addition of nucleotide(s)), deletion (removal of nucleotide(s)); both alter amino acid sequence
