Note that all hex numbers and hashes here and in the protocol are little endian. So the ones I show will look backwards from a lot of sites which show them in big endian format.
The Merkle Root
This is a way to combine all the hashes of the transaction together into 1 hash. To do this we first need the hashes of all the transactions. There is only one transaction in the genesis block so let's find its hash. This is based off of this format.
#version 1, uint32_t
version = "01000000"
#1 input transaction, var_int
tx_in_count = "01"
#the default for generation transactions since there is no transaction to use as output
OutPoint_hash = "0000000000000000000000000000000000000000000000000000000000000000"
#also default for generation transactions, uint32_t
OutPoint_index = "ffffffff"
previous_output = OutPoint_hash + OutPoint_index
script_length = "4d"
#The coinbase. In a regular transaction this would be the scriptSig, but unused in generation transactions.
#Satoshi inserted the headline of The Times to prove that mining did not start before Jan 3, 2009.
#???????EThe Times 03/Jan/2009 Chancellor on brink of second bailout for banks
signature_script = "04ffff001d0104455468652054696d65732030332f4a616e2f32303039204368616e63656c6c6f72206f6e206272696e6b206f66207365636f6e64206261696c6f757420666f722062616e6b73"
#final sequence, means it can't be replaced and is immediately locked, uint32_t
sequence = "ffffffff"
tx_in = previous_output + script_length + signature_script + sequence
#1 transaction output, var_int
tx_out_count = "01"
#5000000000 satoshis == 50 bitcoin, uint64_t
value = "00f2052a01000000"
pk_script_length = "43"
#The scriptPubKey saying where the coins are going.
pk_script = "4104678afdb0fe5548271967f1a67130b7105cd6a828e03909a67962e0ea1f61deb649f6bc3f4cef38c4f35504e51ec112de5c384df7ba0b8d578a4c702b6bf11d5fac"
#We can decode this.
#41 push the next 65 bytes onto the stack
#04678afdb0fe5548271967f1a67130b7105cd6a828e03909a67962e0ea1f61deb649f6bc3f4cef38c4f35504e51ec112de5c384df7ba0b8d578a4c702b6bf11d5f the 65 bytes that get pushed onto the stack
#This is a pay-to-pubkey output, which is the default for generation transactions.
tx_out = value + pk_script_length + pk_script
#immediately locked, uint32_t
lock_time = "00000000"
transaction = version + tx_in_count + tx_in + tx_out_count + tx_out + lock_time
transaction_bin = transaction.decode("hex")
transaction_hash_bin = hashlib.sha256(hashlib.sha256(transaction_bin).digest()).digest()
transaction_hash = transaction_hash_bin.encode("hex")
So now that we have the transaction hash for the 1 transaction, we need to find the Merkle root. It turns out that the Merkle root of a single hash is... that single hash. So that is the Merkle root.
29ab5f49, uint32_t. This is 1231006505 in decimal and is a unix timestamp meaning January 3, 2009 at 6:15:05pm UTC.
ffff001d == 486604799, uint32_t. This is a way to represent the difficulty. It's a sort of floating-point-ish type number. This is difficulty 1 and requires hashes to be below or equal to the target of 0000000000000000000000000000000000000000000000000000FFFF00000000.
1dac2b7c == 2083236893, uint32_t
I covered most of this in the merkle root section.
If you want someone else's explanation of each byte of the genesis block, look here.