CCR Biology DSL
• List 5 of your genetic traits you want to pass
on to your children. Why those specific traits?
CCR Biology Agenda
• DSL
• Chromosome and Meiosis PowerPoint
• Meiosis Review Worksheet – Due Monday
CCR Biology Objectives
• I can compare mitosis and meiosis
• I can model the phases of meiosis
Chromosomes and
Meiosis
Genetics
LT1
Unit 5: Genetics
LT 1: Chromosomes and Meiosis
If stretched and laid end to end, the DNA in
just one of your cells would be about 3
meters (10 feet) long.
How does it fit inside the nucleus of a
microscopic cell?
Condensing our DNA
• A chromosome is:
– thread of DNA and proteins
– in nucleus of eukaryotic cells
– consists of genes and
regulatory information.
Chromosome Structure
Pg. 139
DNA condenses tightly during the early stages of mitosis
Stage 1: DNA
double helix
Stage 2: DNA
and histones
Stage 3: Chromatin
Stage 4:
Supercoiled DNA
Stage 5:
Condensed,
duplicated
chromosome
Region of chromosome
that holds sister
chromatids together
Two identical
chromatids that
make up 1
chromosome
Exploring your cells and chromosomes
• You have many specialized cells in your body
BUT they can be divided into 2 major groups:
1. Somatic (body) cells
2. Germ cells
Cell types
Somatic (body) cells:
• make up most of body
tissue and organs
• Ex: spleen, kidneys, and
eyeballs
• DNA in body cells is
NOT passed on to
offspring
• Divide by MITOSIS
Germ cells:
• cells in reproductive
organs, the ovaries or
testes
• Develop into gametes:
sex cells – eggs in the
female and sperm cells in
the male
• DNA in gametes IS
passed on to children
• Divide by MEIOSIS
Counting Chromosomes
• Each of your body cells contains a set of 46
chromosomes, which come in 23 pairs
– 23 from mom and 23 from dad
• These cells are genetically
identical to each other unless
mutations occurred
• Cells in your body differ because different genes are
expressed … NOT because they have different genes
“Homologous pairs”
• Each pair of chromosomes is referred to a
homologous pair
– Homologous chromosomes: 2 chromosomes – 1 from
mom and 1 from dad – that have the same length and
general appearance
• Autosomes: chromosome pairs 1 – 22
•
Contain genes not directly related to sex or organism
• Sex chromosomes: 23rd chromosome pair
•
•
Controls development of sexual characteristics
XX = Female
XY = Male
Mitosis Review
• Occurs in somatic cells
• Consists of 4 stages
• Produces 2 genetically identical daughter cells
PROPHASE
METAPHASE
ANAPHASE
TELOPHASE
AND
CYTOKINESIS
Meiosis
• Occurs in germ cells
• Consists of 8 stages
• Produces 4
daughter germ cells
with ½ the amount
of DNA