8521140
Description
Mind Map by freya hinks, updated more than 1 year ago
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Created by freya hinks
about 7 years ago
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the factors which determine an organisms phenotype
- sex-linkage
- when the certain allele is located on a sex chromosome
- females have two X
chromosomes and males
have one X and one Y
chromosome
- the Y chromosome is smaller so fewer genes are carried on
it, so most genes are carried on the X chromosome
- if a gene is carried on a Y
chromosome then a female will
not inherit the gene, therefore
it will not be expressed in her
phenotype
- the Y chromosome is smaller so fewer genes are carried on
it, so most genes are carried on the X chromosome
- males only have one X chromosome so they often only have one allele for
sex-linkage, so they often express the characteristic in thei phenotype even if
it is recessive so males are more likely than females to show recessive
phentoypes for genes that are sex-linked e.g. colour blindness
- when the certain allele is located on a sex chromosome
- dominant, recessive and codominant alleles
- dominant alleles
- an allele whose characteristic
appears in the phenotype even
when there is only one copy
- an allele whose characteristic
appears in the phenotype even
when there is only one copy
- recessive alleles
- an allele whose characteristic only appears in the
phenotype if tow copies are present
- an allele whose characteristic only appears in the
phenotype if tow copies are present
- codominant alleles
- alleles that are both expressed in the phenotype
- alleles that are both expressed in the phenotype
- dominant alleles
- epistasis
- many different genes can control the same characteristics - they
interact to form the phenotype
- if genes are epistatic they can mask or be masked.
- if genes are epistatic they can mask or be masked.
- many different genes can control the same characteristics - they
interact to form the phenotype
- mutations
- mutagenic agents
- increase the rate of mutation
- mutations occur randomly
- Ultraviolet
radiation, ionising
radiation,
chemicals and
viruses
- some chemicals called base analogs can
substitute for a base during replication,
changing the base sequence in the new DNA
- some chemicals can
delete or alter bases,
changing the
structure
- some types of rediation can change the
structure of DNA, which causes problems
during DNA replication
- increase the rate of mutation
- substitution - base/s
swapped for another
- deletion - base/s removed
- addition - base/s added
- duplication - base/s repeated
- inversion - a sequence of bases reversed
- translocation - a sequence of bases moved from
one location to another on the genome
- mutagenic agents
- monohybrid or dyhibrid genes
- monohybrid inheritance
- the inheritance of a
characteristic controlled
by a single gene
- the inheritance of a
characteristic controlled
by a single gene
- dihybrid inheritance
- the genes that determine the two characteristics are located on different pairs of
homologous chromosomes. Each of these genes can have two or more alleles.
- the genes that determine the two characteristics are located on different pairs of
homologous chromosomes. Each of these genes can have two or more alleles.
- monohybrid inheritance
- autosomal linkage
- genes on the same autosome are linked
- they're on the same autosome so will
stay together during independant
segregation of chromosomes in meiosis 1
- the alleles will be passed on
the the offspring together
- the alleles will be passed on
the the offspring together
- crossing over
occurs in meiosis
1, and the closer
the genes are, the
less likely
crossing over will
split them up
- they're on the same autosome so will
stay together during independant
segregation of chromosomes in meiosis 1
- genes on the same autosome are linked
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