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inheritance - Coggle Diagram
inheritance
terms and explainations
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genotype
-combination of alleles that an organism possesses for a particular gene
-homozygous dominant(TT)
-homozygous recessive(tt)
-heterozygous(Tt)
allele
-two copies of the same gene may have different forms
-alleles are different forms of the same gene
-occupy same relative position on a pair of homologous chromosomes
-can be dominant or recessive
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homologous chromosome
-pair of homologous chromosomes that carry the same gene sequence
--two copies of each gene in a pair of homologous chromosomes
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genetic variation
meiosis
-gametes produced during meiosis are genetically dissimilar due to different combinations of chromosomes
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mutation
-change in structure of a gene/number of chromosomes
-genes are not copied correctly before undergoing meiosis
-chromosomes fail to separate properly causing daughter cells with abnormal number of chromosomes
-can be inherited
-not entirely negative
chromosome mutation
-during gamete formation, mutation causes a gamete to form 2 copies of chromosome 21
-when its fused with a normal gamete, the zygote will have 3 copies of chromosome 21
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variation
continuous
-no clear, distinct differences
-skin colour
-mass
-weight
-many genes determine the final trait
-affected by environmental factors
discontinuous
-clear, distinct differences
-controlled by single gene
-blood group
-ability to roll tongue
-not influenced by environment
natural selection
-organisms with desirable traits are selected to survive and pass on their genes to their offspring
-a variety of offspring with desirable traits become more adapted, competetive and more resistant to diseases are more likely to survive and reproduce
-over many generations, nature selects the varieties with the favourable genes and characteristics best fitted to the environment to survive
-results in evolution which is the gradual change in the inheritable characteristics of a population over time
-individuals which possess the most advantageous traits are more likely to survive and pass on their traits
ratio of phenotypes
-observed ratio may be different from expected ratio
=>depends on chance and probabilities and fertilisation is random
=>sample size is too small
sex inheritance
-each human body cell has 23 pairs of chromosomes in the nucleus and can be called autosomes
-autosomes are chromosomes that do not have genes to determine sex
-in humans, there are 22 pairs of autosomes and 1 pair of sex chromosomes
-female: XX
-male:XY
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