Chapter 16 Autosomal Linkage
1. How autosomal linkage affects inheritance patterns
2. An example of autosomal linkage in fruit flies
3. How crossing over can affect linked genes
What is autosomal linkage?
Autosomes are chromosomes that do not determine the sex of an organism. When
genes are located on the same autosome, they are described as linked genes. Linked
genes tend to be inherited together in offspring, rather than assorting independently.
This means that:
There is a non-random association of alleles at different loci.
The phenotypic ratios observed in dihybrid crosses are different from those
expected from independent assortment.
Parental allele combinations are preserved across generations.
How crossing over affects autosomal linkage
During meiosis, crossing over can exchange genetic material between homologous
chromosomes at regions called chiasmata. Offspring that have different combinations
of alleles from their parents due to crossing over are called recombinant offspring.
The effects of crossing over on autosomal linkage:
Crossing over potentially separates linked genes.
However, when genes are linked, fewer recombinant offspring tend to be
produced.
This indicates less genetic variation being introduced from crossing over when
genes are linked.
The probability of linked genes being separated during crossing over is inversely
proportional to how close they are on a chromosome i.e., the closer the genes,
the more likely they will be inherited together.
, An example of autosomal linkage in fruit flies
In fruit flies, body colour and wing length are determined by genes that are linked on
the same autosome.
An example of autosomal linkage in fruit flies
In fruit flies, body colour and wing length are determined by genes that are linked on the same
autosome.
The alleles for these genes are:
B - Brown body colour (dominant)
b - Black body colour (recessive)
V - Long wings (dominant)
v - Short wings (recessive)
For instance, if a brown, long-winged fly (BbVv) is crossed with a black, short-winged fly (bbvv):
Autosomal linkage results in mainly parental phenotypes among offspring (BbVv and bbvv).
This is because the linked alleles for body colour and wing length are usually inherited together.
This produces very few recombinants with new genetic combinations.
1. How autosomal linkage affects inheritance patterns
2. An example of autosomal linkage in fruit flies
3. How crossing over can affect linked genes
What is autosomal linkage?
Autosomes are chromosomes that do not determine the sex of an organism. When
genes are located on the same autosome, they are described as linked genes. Linked
genes tend to be inherited together in offspring, rather than assorting independently.
This means that:
There is a non-random association of alleles at different loci.
The phenotypic ratios observed in dihybrid crosses are different from those
expected from independent assortment.
Parental allele combinations are preserved across generations.
How crossing over affects autosomal linkage
During meiosis, crossing over can exchange genetic material between homologous
chromosomes at regions called chiasmata. Offspring that have different combinations
of alleles from their parents due to crossing over are called recombinant offspring.
The effects of crossing over on autosomal linkage:
Crossing over potentially separates linked genes.
However, when genes are linked, fewer recombinant offspring tend to be
produced.
This indicates less genetic variation being introduced from crossing over when
genes are linked.
The probability of linked genes being separated during crossing over is inversely
proportional to how close they are on a chromosome i.e., the closer the genes,
the more likely they will be inherited together.
, An example of autosomal linkage in fruit flies
In fruit flies, body colour and wing length are determined by genes that are linked on
the same autosome.
An example of autosomal linkage in fruit flies
In fruit flies, body colour and wing length are determined by genes that are linked on the same
autosome.
The alleles for these genes are:
B - Brown body colour (dominant)
b - Black body colour (recessive)
V - Long wings (dominant)
v - Short wings (recessive)
For instance, if a brown, long-winged fly (BbVv) is crossed with a black, short-winged fly (bbvv):
Autosomal linkage results in mainly parental phenotypes among offspring (BbVv and bbvv).
This is because the linked alleles for body colour and wing length are usually inherited together.
This produces very few recombinants with new genetic combinations.
