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CHROMOSOMES 8-1
CHROMOSOMES8-1
DNAFound in NUCLEUS
Carries the genetic code
http://web.jjay.cuny.edu/~acarpi/NSC/12-dna.htm
http://encarta.msn.com/media_461516495/Nucleus_of_a_Cell.html
NUCLEIC ACIDS are built from subunits called
____________________
Image by: Riedell
Changing the _____________and _______________produces different subunits
sugar
nitrogen base
5 NITROGEN BASES
_____________= A
_____________ = G
_____________ = C
______________ = T (only in DNA)
______________= U (only in RNA)
ADENINEGUANINECYTOSINETHYMINEURACIL
DNA molecule forms a HELIXor “twisted ladder”
A on one strand always bonds with T opposite it
G on one strand always bonds with C opposite it
Image from: http://evolution.berkeley.edu/evosite/evo101/images/dna_bases.gif
SPREAD OUT INNON-DIVIDING CELLS
SCRUNCHED UPIN DIVIDINGCELLS
DNA CAN BE:
PROTEINS that wrap up DNA
are called __________________
http://biology.kenyon.edu/courses/biol114/Chap01/chrom_struct.html
PROTEINS
Proteins- Combine with DNA to make chromosomes
Image from: http://employees.csbsju.edu/hjakubowski/classes/ch331/dna/chromosome.gif
Proteins that control the activity of genes are called ________________
http://www.blc.arizona.edu/courses/181summer/14.html
Cells turn genes on or off as needed (part of differentiation)
Example: Genes for making digestive enzymes are turned off in brain cells
Genes for making neurotransmitters are turned on
NON-HISTONES are the “on-off” switches for genes
CELL DIVISION GENES
Some cells divide frequently(some human skin cells divide once/hour)
Some cells divide occasionally (liver cells divide about once/year)
Some cells don’t divide once they form (nerve cells)
Cancer cells have lost control of their cell division genes
Cancer cells• Don’t stop dividing• Like a “car with no brakes”• Can spread to new places
(METASTASIS)
• ______________ are substances that can damage DNA
Ex: Radiation, cigarette smoke, chemicals in environment
DNA in PROKARYOTES
• BACTERIAL DNA is CIRCULAR
• HAVE ONE CHROMOSOME
• ATTACHED TO CELL MEMBRANE
http://www.origin-life.gr.jp/3202/3202121/fig6.jpg
DNA in EUKARYOTES(Plants & Animals)
• DNA is ROD-SHAPED CHROMOSOMES
• MANY PAIRS
• FOUND IN NUCLEUS
http://cellbio.utmb.edu/cellbio/chrom2.jpg
Chromosome structure• ___________________
2 identical arms
• __________________
constricted area holds chromatids together
•__________________ PAIR
2 of each chromosome(one from mom; one from dad)
HOMOLOGOUS CHROMOSOMES
http://arnica.csustan.edu/biol3020/cell_division/cell_division.htm
• SAME SIZE
• SAME SHAPE
• CARRY GENES for the SAME TRAITS
(Don’t have to have the SAME CHOICES)
CHROMOSOME NUMBERS• Each species has a
characteristic number of chromosomes
• HUMANS have 46 chromosomes (23 pairs)
You can’t judge a critter by its chromosomes
This critter has54 chromosomes
Corn has 10 pair of chromosomes
Snails have 18 pairs of
chromosomes
A mouse has 40 chromosomes
CHROMOSOME NUMBER DOESN’T CORRESPOND TO SIZE OF ORGANISM
Big animals DON’T have more chromosomes than small animals!
http://www.ocean.udel.edu/extreme2004/genomics/images/chromosomes.gif
• Chromosomes that determine the sex of an organism = _________________________
• All other chromosomes = _________________
Humans have two sex chromosomes
And _____ autosomes
A _____________is a picture of an organism’s chromosomes
A KARYOTYPE can tell the sex of an organism
In humans XY is a male
In humans XX is a female
Guess who?
XY
Karyotypes can also show some genetic problems
http://members.tripod.com/~yenial/chromosome.html
Eric has Down’s Syndrome
1 in 750 births
Has extra #21 chromosome
Mental retardation
DIPLOID & HAPLOID Some cells have 2 copies of each
chromosome = _______________
(one from mom; one from dad)
• All BODY cells are diploid
Image from: http://www.ncu.edu.tw/~ls/graph/faculty_pictures/whole_time/SLC/SLC_lab-1.jpg
DIPLOID & HAPLOID
Some cells have only one copy of each chromosome = ____________________
All sperm and egg cells are haploid
EGG + SPERM
If egg and sperm had same number of chromosomes as other body cells …. baby would have too many chromosomes!
http://www.angelbabygifts.com/
CELL DIVISION8-2
Mitosis and Meiosis
CELL DIVISION in PROKARYOTES
Bacteria
reproduce
using__________________
•DNA is copied•Cell wall forms•Cell splits into two new cells
http://www.tnau.ac.in/notesbscag/agm/UGMicro/AGM151_201/theory_files/image156.jpg
CELL DIVISION IN
EUKARYOTES
__________ OR __________
MITOSIS• Makes ____ cells
identical to parent cell
• Makes _____ cells
• Makes _______ cells
• Used to _____________& ____________________________________
MEIOSIS• Makes ____ cells with
different DNA
• Makes _____ cells
• Makes ____________
• Used ______________
CELL CYCLE
G0
CELL CYCLEINTERPHASE – non dividing phase
G1- Grow bigger Cell is “doing its job”
DNA is spread out as chromatin
S - Synthesis (copy DNA)
G2- Grow bigger, make organelles & molecules needed for cell division
CELL CYCLEMITOSIS – Cell division
Prophase
Metaphase
Anaphase
Telophase
Cytokinesis
G0 – cell stops dividing (Ex: nerve cell)
INTERPHASE (G1 - S - G2)
In between divisionsCells are in this phase most of the timeCan see nucleus DNA spread out as chromatin
Can’t see chromosomes DNA gets copied
Cell gets ready to divide
PROPHASE1st dividing phase
Spindle fibers form & attach chromosomes
Nuclear membrane & nucleolus disappear
DNA scrunches into chromosomes
Centrosomes containing centrioles appear & move to poles
METAPHASE
Chromosomes line up in ___________
ANAPHASE
Centrioles pull chromosomes ________
TELOPHASE (reverse prophase steps)See ______ nucleiNuclear membrane & nucleolus return
Chromosomes spread out as chromatinCentrioles disappear
Spindle fibers disappear
CYTOKINESISCytoplasm splits into 2 cells
ANIMAL CELLS pinch cytoplasm in two with a ______________________
CYTOKINESISCytoplasm splits into 2 cells
PLANT CELLS can’t pinch because they have a ______________
Separate cytoplasm by growing a _________________ down the middle.
CELL CYCLE
G0
