05.07.2020 – Thursday –
Notes to go along with our video lesson. Please remember to look up and define and CAPITALIZED terms. (And, any terms with which you are unfamiliar.)
- Current Events: Link to CNN 10 - https://www.cnn.com/cnn10
- Two notes on Space travel: Especially, the use of Russian space launches to get Americans to the ISS (International Space Station.) Since the US Space Shuttle stopped flying in 2011 the US has relied on other countries to get to space while NASA is trying a joint venture with “Space X.” When I was a kid I remember Apollo astronauts landing on the moon.!
I. Genetics and chromosomes – Every living thing inherits TRAITS.
A., In the 1800’s a monk named Gregor Mendel studied the inheritance of pea plants. Like the example with squirrels or “Fuzzy Wuzzits” in our video lesson, Mendel “mixed” tall and short plants, but did NOT get medium-height plants. Just like the squirrels, when a white and black squirrel reproduce together they do not end up with grey squirrel offspring. Instead, there are often – two possibilities.
1. A TRAIT might be DOMINANT.
2. A TRAIT might be RECESSIVE.
II. In the case of pea plants, for a plant to be short, it must inherit two recessive ALLELES. One from each parent. If the pea plant just inherits a single recessive allele, the plant will be TALL. There is no “in-between.”
III. Genetics of humans: (The subject of tomorrow’s video lesson.) -
A. Humans have 46 PAIRS OF CHROMOSOMES in most of our cells. That’s capitalized because it’s very important.
1. Notice, we said, “most” cells. There are some cells called GAMETES.
a) Female GAMETE is called an EGG.
b) Male GAMETE is called a SPERM.
B. Each GAMETE is called HAPLOID. This is just a term that means it has 23 chromosomes, not 46. It has half as many as most of the cells in our bodies.
C. As you might have guessed, once an egg and a sperm cell meet (GAMETES) a new cell with 46 chromosomes (DIPLOID) is formed. This is called a ZYGOTE.
IV. Here’s the really important point … that new ZYGOTE is not identical to either the mother or the father. That fertilized OVUM, or cell with 46 chromosomes, is a genetic mix of the parents!
V. For two parents there are about 8.3 million (8,300,000) possible combinations of unique genetic offspring that are possible! That’s why two siblings are very similar, but never exactly alike! (We’ll talk about twins tomorrow as well.)