Chromosomes

Ever wonder how a cow gets its muscles or a dog gets it’s fur color? The answer is in the chromosomes

WHAT ARE CHROMOSOMES?
  • When we zoom into the cells of any living thing we find molecules pieces called CHROMOSOMES.
  • Chromosomes are made of genetic material (DNA) wrapped around proteins.
  • CHROMOSOMES are the way that our bodies store and pass down heritable traits.
HOW MANY CHROMOSOMES DO HUMANS HAVE?
  • Every species has a unique number of chromosomes that come in pairs.
  • KARYOTYPES are made by pairing up chromosomes and organizing them from longest to shortest.
    • Peas have 7 pairs of chromosomes (14 total).
    • Humans have 23 pairs of chromosomes (46 total).
    • Cows have 30 pairs of chromosomes (60 total)
  • If you’re curious, here’s a crazy list of organisms by chromosome count.
Peas Chromosomes
Cow Chromosomes
Chromosomes are very disorganized when found in the cell, but scientists pair them up and organize them by length to form the Karyotype on the left. Chromosomes are fairly colorless, so dye was added to make it easier to see them.
WHAT’S THE DEAL WITH X AND Y?
  • In most species, there is a pair of chromosomes that determines whether an individual is a male or female.
    • XX is female
    • XY is male
  • There are instances of single X, single Y, XXX and XXY, but those are for the Genetic Disorder lesson.
We can tell by the 23rd pair whether someone is male or female.
WHERE DO CHROMOSOMES COME FROM?
  • We inherit one of each chromosome pair from each parent.
  • So in the case of humans, we inherit one copy of chromosome 1, 2, 3… 22 from parent 1 and one copy of chromosome 1, 2, 3… 22 from parent 2.
  • Females only have XX on the 23rd pair, so they always pass an X down to their offspring.
  • If the male gives an X, the child is female. If the male gives a Y, the child is a male.
HOW ARE CHROMOSOMES DELIVERED TO OFFSPRING?
  • Humans deliver chromosomes through specialized cells.
  • Males create sperm cells which contain one of each chromosome pair for a total of 23.
  • Females create egg cells which also contain one of each chromosome pair for a total of 23.
  • When they join, each pair joins up to create a ZYGOTE with 23 pair of chromosomes (46 total).

How is information stored on chromosomes?

What’s next?

I’m lost😱

Unclear on some vocabulary, click the buttons below for some foundation:

TRAITS
HERITABLE VS ACQUIRED TRAITS
PATTERNS OF INHERITANCE

I need practice🤔

I think I get it, but would like some more practice!

Let’s move on👍

How is heritable information stored on these chromosomes?

GENES & PROTEINS