autosomal linkage

Question 1

what are autosomes?

Answer 1

chromosomes which are not concerned with sex determination
(all other pairs of chromosomes)

Question 2

how are autosomes different to sex chromosomes?

Answer 2

• entirely homologous
• each chromosome in the pair codes for the same genes so there are always 2 copies of the gene

Question 3

what are linked genes?

Answer 3

genes located on the same chromosome

Question 4

what is autosomal linkage?

Answer 4

if two or more genes are located on the same autosome

Question 5

chromosomes and chromatids are …. so gametes with …. ……. ……. form with ….. ……. of each allele combination

Answer 5

independently assorted
each possible combination
equal proportions

Question 6

what happens to linked genes in meiosis?

Answer 6

• crossing over can result in formation of recombinant chromatids from innermost chromatids
• allele combinations on outermost chromatids do not change

Question 7

why is the proportion of recombinant chromatids smaller than non recombinant?

Answer 7

because crossing over is random

Question 8

when chromatids are separated in ……… the allele combinations on the ….. sister chromatids will be passed onto many ……..

some gametes will inherit a …… chromatid

this results in smaller numbers of …… …… than ……

Answer 8

anaphase 2
gametes unchanged

recombinant

recombinant gametes
non recombinant

Question 9

genes that are found on separate ….. are ……

unlinked genes undergo …… assortment during meiosis. this results in …… proportions of recombinant and …….. gametes.

genes that are found on the ….. autosome are said to be autosomally …..
the alleles of linked genes stay together during independent assortment unless …….. ……. occurs
crossing over is ……

this means that if genes are linked there are likely to be higher proportions of gametes with the ….. allele combinations as the parent cell and fewer ….

the closer together the two genes are on the chromosome the …. crossing over is likely to occur. this is called …. linkage.

Answer 9

chromosomes
unlinked

independent
equal
non recombinant

same
linked
crossing over
random

same
recombinants

less
tight

Question 10

the effect of autosomal linkage on offspring phenotypic ratios depends on:

Answer 10

• genotypes of 2 parents
• arrangement of alleles on parent chromosomes
• distance between linked genes