genetic terms
DESCRIPTION
GENETIC TERMS. Key definitions. GENE A part of a chromosome which controls a specific feature of an individual. Key definitions. ALLELE Different forms of a gene, e.g. the gene for eye colour may include and blue allele and a brown allele. Key definitions. DOMINANT - PowerPoint PPT PresentationTRANSCRIPT
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GENETIC TERMS
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Key definitions
GENE
A part of a chromosome which controls a specific feature of an individual.
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Key definitions
ALLELE
Different forms of a gene, e.g. the gene for eye colour may include and blue allele and a brown allele.
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Key definitions
DOMINANT
An allele which is expressed (switched on) while another allele is switched off. Usually identified as a capital letter, e.g. R.
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Key definitions
RECESSIVE
An allele which is not expressed (switched off) while another allele is switched on. Usually identified as a lower case letter, e.g. r.
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Key definitions
HOMOZYGOUS
An individual who has inherited two identical alleles, e.g. RR or rr
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Key definitions
HETEROZYGOUS
An individual who has inherited two different alleles, e.g. Rr or Rr
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Key definitions
GENOTYPE
A description of the genes an individual carries, e.g. your genotype may be RR, rr, or Rr
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Key definitions
PHENOTYPE
A description of the feature an individual shows, e.g. your phenotype may be tongue roller or non-tongue roller.
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The inheritance of eye colour
A person with the genes BB will have brown eyes.
A person with the genes bb will have blue eyes.
A person with the genes Bb will have brown eyes.
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The inheritance of eye colour
In a person with the genes Bb only the effect of gene B shows.
The effect of gene B dominates the effect of gene b.
Gene B is dominant to gene b.
Gene b is recessive to gene B.
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B is the gene for brown eyes b is the gene for blue eyes
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B is the gene for brown eyes b is the gene for blue eyes
ParentsBB bbBody cell in father
with a pair of genes for brown eyes
Body cell in mother with a pair of genes for blue eyes
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B is the gene for brown eyes b is the gene for blue eyes
ParentsBB bbBody cell in father
with a pair of genes for brown eyes
Body cell in mother with a pair of genes for blue eyes
Gametes
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B is the gene for brown eyes b is the gene for blue eyes
ParentsBB bbbody cell in father
with a pair of genes for brown eyes
body cell in mother with a pair of genes for blue eyes
Gametes
B Beach sperm has a gene for brown eyes
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B is the gene for brown eyes b is the gene for blue eyes
ParentsBB bbbody cell in father
with a pair of genes for brown eyes
body cell in mother with a pair of genes for blue eyes
Gametes
B Beach sperm has a gene for brown eyes
b b each ovum has a gene for blue eyes
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B is the gene for brown eyes b is the gene for blue eyes
ParentsBB bbbody cell in father
with a pair of genes for brown eyes
body cell in mother with a pair of genes for blue eyes
Gametes
B Beach sperm has a gene for brown eyes
b b each ovum has a gene for blue eyes
At fertilizationThere are 4 possible ways of joining a sperm to an ovum
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B is the gene for brown eyes b is the gene for blue eyes
ParentsBB bbbody cell in father
with a pair of genes for brown eyes
body cell in mother with a pair of genes for blue eyes
Gametes
B Beach sperm has a gene for brown eyes
b b each ovum has a gene for blue eyes
At fertilizationThere are 4 possible ways of joining a sperm to an ovum
BB
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B is the gene for brown eyes b is the gene for blue eyes
ParentsBB bbbody cell in father
with a pair of genes for brown eyes
body cell in mother with a pair of genes for blue eyes
Gametes
B Beach sperm has a gene for brown eyes
b b each ovum has a gene for blue eyes
At fertilizationThere are 4 possible ways of joining a sperm to an ovum
BB
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B is the gene for brown eyes b is the gene for blue eyes
ParentsBB bbbody cell in father
with a pair of genes for brown eyes
body cell in mother with a pair of genes for blue eyes
Gametes
B Beach sperm has a gene for brown eyes
b b each ovum has a gene for blue eyes
At fertilizationThere are 4 possible ways of joining a sperm to an ovum
BB
b b
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B is the gene for brown eyes b is the gene for blue eyes
ParentsBB bbbody cell in father
with a pair of genes for brown eyes
body cell in mother with a pair of genes for blue eyes
Gametes
B Beach sperm has a gene for brown eyes
b b each ovum has a gene for blue eyes
At fertilizationThere are 4 possible ways of joining a sperm to an ovum
Bb BbBb Bb
BB
b b
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B is the gene for brown eyes b is the gene for blue eyes
ParentsBB bbbody cell in father
with a pair of genes for brown eyes
body cell in mother with a pair of genes for blue eyes
Gametes
B Beach sperm has a gene for brown eyes
b b each ovum has a gene for blue eyes
At fertilizationThere are 4 possible ways of joining a sperm to an ovum
Bb BbBb Bb
BB
b b
All the children of this F1 generation have genotype Bb and phenotype brown eyes
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Parentsfather with brown eyes
mother with brown eyes
Gametes
At fertilization
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ParentsBb Bbfather with brown
eyesmother with brown eyes
Gametes
At fertilization
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ParentsBb Bbfather with brown
eyesmother with brown eyes
Gametes
B b B b
At fertilization
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ParentsBb Bbfather with brown
eyesmother with brown eyes
Gametes
B b B b
At fertilization
Bb
B b
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ParentsBb Bbfather with brown
eyesmother with brown eyes
Gametes
B b B b
At fertilization
BB BbBb bb
Bb
B b
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ParentsBb Bbfather with brown
eyesmother with brown eyes
Gametes
B b B b
At fertilization
BB BbBb bb
Bb
B b
A child who inherits the genes BB will have brown eyesA child who inherits the genes Bb will have brown eyesA child who inherits the genes bb will have blue eyes
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ParentsBb Bbfather with brown
eyesmother with brown eyes
Gametes
B b B b
At fertilization
BB BbBb bb
Bb
B b
A child who inherits the genes BB will have brown eyesA child who inherits the genes Bb will have brown eyesA child who inherits the genes bb will have blue eyesIn the F2 generation the ratio of brown eyed children to blue eyes will be 3 to 1
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The work of Gregor Mendel
Just over 100 years ago a monk called Gregor Mendel tried to discover how characteristics are inherited.
For one of his experiments Mendel used pea plants which are either tall or dwarf (short)
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The work of Gregor Mendel
Flowers on tall plants were pollinated with pollen from tall plants.
Flowers on dwarf plants were pollinated with pollen from dwarf plants.
The seeds were collected. The seeds were planted. If all the new plants looked
the same as the parent plants they were pure breeding (true breeding)
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The work of Gregor Mendel Using these pure breeding
plants he pollinated flowers on a tall plant with pollen from a dwarf plant.
The plants grown from these seeds were called the F1 generation.
All the F1 were tall, tallness was the dominant gene.
The F1 were called hybrids because they inherited different characteristics from each parent.
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The work of Gregor Mendel
Mendel then pollinates one hybrid flower from the F1 with the pollen from another hybrid F1 flower.
The seeds were grown into the F2 generation.
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The work of Gregor Mendel
Three quarters of the flowers in the F2 generation were tall.
One quarter of the F2 were dwarf.
The dwarfness reappeared in the F2 generation.
Dwarfness was the recessive characterisitic.
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The work of Gregor Mendel