That's doubtful. DNA was discovered well before 1973, and the double-helix structure was modeled in the 1950s. While we did not know nearly as much about DNA, and while the Supreme Court may not have known much about it in 1973, the general idea of genes and chromosomes and Mendelian inheritace was well-known at the time (and all of your points remain accurate if you replace "DNA" with "chromosomes."
It's not that pro-abortion folks don't understand that a fetus is a human life, it's that they just don't care.
——It’s not that pro-abortion folks don’t understand that a fetus is a human life, it’s that they just don’t care.——
When they want it dead, it’s a fetus. When they want to keep it, it’s a baby.
I’ve never in my 50 years heard anyone ask a pregnant woman, “how’s your fetus?”
However, my liberal BIL once referred to my wife’s “fetus,” and it gave us chills.