story of us - part 2 Flashcards
how do cells divide
via mitosis
what must cells do before they divide and what is that process called
make an exact copy of each DNA molecule in the nucleus
process is called replication
what does each cell formed in replication receive
the same amount and type of DNA
DNA replication:
1) DNA helicase (enzyme) unravels the double helix - separating hydrogen bonds holding polynucleotide strands of DNA together
2) each strand acts as a template for the formation of a new strand of DNA
3) free DNA nucleotides in the nucleus align with complementary bases on both strands, according to the base-pairing rule
4) DNA polymerase (enzyme) forms the sugar phosphate backbone (fills gaps between bases to form backbone)
5) two identical DNA molecules are formed - each contains a new strand from the parent DNA and a new complementary strand
in protein synthesis what is the strand of DNA molecules that codes for the manufacture of proteins in a cell called
the template strand
in protein synthesis what is the strand of DNA molecules that doesn’t code for the manufacture of proteins in a cell called
the non-template strand
functions of proteins:
- hormones
- enzymes - controls processes in cells
- haemoglobin
- collagen - structures in skin, keratin in har, myosin in muscles, structural proteins
what are proteins made of
chains of amino acids
what codes for one amino acid
a sequence of three bases in the template strand of the DNA
how is the DNA code a triplet code
three bases are needed to code for one amino acid
DNA code is universal - what does this mean?
the same in all organisms
how many different types of amino acids are there
20
how is DNA degenerate
- more than one code
- 64 different amino acids could be coded for, but only need 20
how is DNA read
as non-overlapping code
why can DNA not leave the nucleus
it may get damaged
where does protein synthesis take place
in ribosomes
what does protein synthesis taking place in ribosomes mean for proteins to be made
for proteins to be made, the genetic code must be copied, then transferred out of the nucleus into the cytoplasm
what transfers out of the nucleus instead of DNA
RNA
differences between DNA and RNA
- RNA is single-stranded, DNA is double-stranded
- in RNA the sugar is ribose, not deoxyribose
- RNA has uracil instead of thymine
similarities between DNA and RNA
- both have A/C/G nitrogenous bases
- both polynucleotides (made up of nucleotides)
- both have phosphate
what 3 types of RNA take part in protein synthesis
- messenger (mRNA)
- transfer (tRNA)
- ribosomal (rRNA)
mRNA:
forms a copy of the DNA code
-> formed in nucleus by copying DNA code
tRNA:
carries amino acids to the ribosomes to make the protein
rRNA:
where protein synthesis occurs