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Title: DNA, genes and chromosomes
Description: Includes meiosis and mitosis and DNA molecules.
Description: Includes meiosis and mitosis and DNA molecules.
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DNA, genes and chromosomes
Nucleotides
Deoxyribose
Phosphate group
Organic base – guanine, adenine, thymine, cytosine
Polynucleotide strand
Two nucleotides join together by phosphate groups via condensation; they form a sugar-phosphate
backbone
...
Guanine Ξ Cytosine (three hydrogen bonds)
These make the
DNA molecule
stable
...
The two polynucleotides form a double helix formation
...
A sequence of three bases (base triplet) carries the genetic code for each amino acid
...
The code
for a single polypeptide is called a gene
...
DNA feature
Length
Shape
Number of different molecules
per cell
Non-coding DNA
Meiosis
Prokaryotic cells
Short – few genes
Circular
One
Eukaryotic cells
Long – many genes
Linear
More than one
Absent
Present
Diploid
Diploid
Diploid
Chromosomes
replicate
Haploid
1s t meiotic
division
2nd meiotic
division
Independent assortment of homologous chromosomes
In the first meiotic division – not all maternal/paternal chromosomes have to go in the same
direction
...
If they break at
the same place, the broken segments can join the other member of the pair
...
Title: DNA, genes and chromosomes
Description: Includes meiosis and mitosis and DNA molecules.
Description: Includes meiosis and mitosis and DNA molecules.