Genetics

Genetics
DNA
Structure
Double Helix
Discovered by James Watson
and Francis Crick 1953
Nucleotide = Phosphate, base
and sugar
Base
Cytosine (C)
Thymine (T)
Adenine (A)
Guanine (G)
Replication
Enzymes (protein) break up the DNA
cell and helps form identical DNA
cells
Cell Division
Mitosis Somatic (body) cells
Stages:
Interphase: where DNA gets
photocopied (starts of as mother
cell)
Prophase: Centrioles produce spindle fibers
(like spaghetti), sister chromatids (2 sets),
nuclear membrane dissolves
Metaphase: Chromatids line up on metaphase plate
(middle), spindle fibers connect to centromere,
centrioles go to opposite poles (like north and south
pole)
Anaphase: Spindle fibers pull
chromatids apart and move to the
ends of cells
Telophase: Nucleus forms (ends as
daughter cells), chromosomes
decondense
Cytokinesis: Division of cytoplasm
Gamete Production: Meiosis
(Reproductive cells)
Meiosis I
Interphase I: Chromosomes duplicate
Prophase I: Homologous chromosomes pair and
exchange segments/switch and crossover (Synapsis
pairing of homologs to form tetrads/4 pairs of
chromosomes)
Metaphase: Tetrads line up in
the middle
Pairs of homologous chromosomes
split up (becomes sister chromatids
again)
Telophase & Cytokinesis: Two haploid (half
of the original information) cells form;
chromosomes still double
Meiosis II
Prophase II: Spindle fibers form again
Metaphase II: Sister chromatids
(23) line up in the middle
Anaphase: Sister chromatids
separate = 23 chromosomes
Telophase II: Haploid daughter
cells forming
Sister chromatids finally separate; four
haploid daughter cells result, containing
single chromosomes
Haploid (n): 1 set of
chromosomes in gametes
Diploid (2n): 2 sets of
chromosomes. One from each
parent
Genes
Code for specific trait
Chromosomes
DNA coiled around proteins
Human: 46
23 pairs
First 22 pairs are called autosomes
23rd pair called sexgender
Human Genome Project
Complete copy of the entire
set of human gene instructions
2003
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