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Biology revision - due 16/10/17 (Meiosis (DNA (genome - DNA (found on 46…
Biology revision - due 16/10/17
Meiosis
Gametes
egg cells
Sperm cells
fertilisation
fusion of 2 gametes
Zygote
fertilised egg
forms a ball of cells using mitosis
DNA
instructions for an organism are found here as code
genome - DNA
most cells contain a complete copy of the genome
found on 46 long molecules of DNA
each molecule is inside a chromosome
genes
sections of a DNA molecule that contain a code for making a protein
proteins
polymers
a chain of different amino acids linked together
there are 23 different chromosomes in humans
most nuclei contain 2 of each type
a human body cell contains 2 sets of 23 chromosomes, making a total of 46
diploid cell
cell with 46 chromosomes (23 pairs)
produces haploid cells
haploid cell
a cell with 23 chromosomes
each chromosome replicates
2 copies remain attached
the 2 sets pair up and then separate into 2 new cells
2 copies of the a chromosome split into 2 more new cells
(4 non-identical daughter cells, half amount of DNA)
2 daughter cells
(cell divides in 2, chromatids get ripped apart)
(copies of chromosome made, 2 chromatids)
DNA replicates
4 daughter cells
not genetically identical
gametes
divides twice
all 23 pairs match up to their number partner
crossing over (share genes)
random assortment
DNA
a molecule of DNA
contains 2 strands
each of which forms a shape called a double helix
2 strands are joined together by pairs of substances called bases
forms double helix
4 bases
Adenine (A)
always joined with Thymine(T)
(A) = (T)
complimentary base pairs
Thymine (T)
Always joined with Adenine (A)
(T) = (A)
complimentary base pairs
Cytosine (C)
always joined with Guanine (G)
(C) = (G)
complimentary base pairs
Guanine (G)
always joined with Cytosine (C)
(G) = (C)
complimentary base pairs
each base is attached to a sugar and each sugar is attached to a phosphate group
this grouping is called a nucleotide
The sugars and phosphate groups form the backbone of DNA strands
Hydrogen bonding
The base pairs are joined by the weak forces of attraction called hydrogen bonds between them
Cytosine (C) and Guanine (G) form 3 hydrogen bonds between them
this is why Cytosine (C) only matches with Guanine (G)
Adenine (A) and Thymine (T) form 2 hydrogen bonds
this is why Adenine (A) only matches with Thymine (T)
double helix
2 strands of DNA joined together by base pairs
Nucleotide
a molecule containing sugar, phosphate and base groups
Hydrogen bonds
weak forces of attraction between base pairs
Chromosome
contains DNA, there are 46 of them in a normal cell
long molecules that contains an organisms genome
Alleles