pores are haploid and thus begin the life cycle again. Sordaria fimicola is often used to observe crossing wild type strain has black ascospores and the mutant type has tan ascospores. When a combination of o through meiosis, the location of the ascospores will directly show if crossing over has occurred. The hows a fruiting body with ascoscpores developing within an ascus. d) Meiosis Mitosis Filaments ation of non-crossover asci Meiosis II Mitosis *Ascospores (haploid) ver has not occurred (parental type), asci will be arranged as follows, with 4+4 black and tan: I U U U U Black spore (haploid) www.w30 of WWWXXX0
pores are haploid and thus begin the life cycle again. Sordaria fimicola is often used to observe crossing wild type strain has black ascospores and the mutant type has tan ascospores. When a combination of o through meiosis, the location of the ascospores will directly show if crossing over has occurred. The hows a fruiting body with ascoscpores developing within an ascus. d) Meiosis Mitosis Filaments ation of non-crossover asci Meiosis II Mitosis *Ascospores (haploid) ver has not occurred (parental type), asci will be arranged as follows, with 4+4 black and tan: I U U U U Black spore (haploid) www.w30 of WWWXXX0
Human Anatomy & Physiology (11th Edition)
11th Edition
ISBN:9780134580999
Author:Elaine N. Marieb, Katja N. Hoehn
Publisher:Elaine N. Marieb, Katja N. Hoehn
Chapter1: The Human Body: An Orientation
Section: Chapter Questions
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Question
Transcribed Image Text:1. Meiosis practice with ascospores
The life cycle of the fungus Sordaria fimicola begins in the haploid state.
After two different types of strains combine, they develop a diploid nucleus. As the life cycle continues, the diploid
nucleus undergoes meiosis (2 cell divisions, remember?) followed by mitosis (a trick the fungi do to make more mileage
out of the mating). This produces eight haploid ascospores which are stored in a sac called an ascus. The spores line up
in a way that shows these cell divisions. After the spores have matured, the sac will burst, allowing the ascospores to be
released. These spores are haploid and thus begin the life cycle again. Sordaria fimicola is often used to observe crossing
over because the wild type strain has black ascospores and the mutant type has tan ascospores. When a combination of
the two strains go through meiosis, the location of the ascospores will directly show if crossing over has occurred. The
below pictures shows a fruiting body with ascoscpores developing within an ascus.
Fertilization-
Fruiting
bodies
Asci
Tan spore
(haploid)
Zygote
(diploid)
m
Meiosis I
Meiosis. Mitosis
Filaments
When crossing over has not occurred (parental type), asci will be arranged as follows, with 4+4 black and tan:
Formation of non-crossover asci
m
'Ascospores
(haploid)
Meiosis II Mitosis
Black spore
(haploid)
of
![When crossing over has occurred, the asci will look like this: (2,2,2,2), (2,4,2) etc
ONI
m
Meiosis I
2.
m
Meiosis II
Mitosis
C
0000
OR
C
The above just shows single crossovers- what might happen if there are two? Typically, we look at recombination
between two genes. In this particular case, we are looking at recombination between the centromere (most visible in
the recombinant tan chromosome after meiosis I) and the gene locus for tan/black. In other words, black and tan are
two alleles that map to the same place. We can figure out how many map units this place is by calculating the % of
recombinants and dividing by 2 (because even within each ascus that shows recombination, half the spores are parental
and half are recombinant [on average]). Check out this video if you are confused: https://www.youtube.com/watch?
v=gXUxH1aFRp0
DR
1. Using the image below, mark the asci as recombinant or not, count the number of recombinant asci and divide by
the total number of asci.
OR
2. Multiply by 100 to get a percent.
3. Divide this number by 2 to get the number of map units between the centromere and the gene locus.
****](/v2/_next/image?url=https%3A%2F%2Fcontent.bartleby.com%2Fqna-images%2Fquestion%2F342015f0-19e8-40cd-98ef-dc8b52ff501d%2F4fd3a1e3-1d9a-49f5-b59b-e8d18cb32482%2Fhbb1c1_processed.png&w=3840&q=75)
Transcribed Image Text:When crossing over has occurred, the asci will look like this: (2,2,2,2), (2,4,2) etc
ONI
m
Meiosis I
2.
m
Meiosis II
Mitosis
C
0000
OR
C
The above just shows single crossovers- what might happen if there are two? Typically, we look at recombination
between two genes. In this particular case, we are looking at recombination between the centromere (most visible in
the recombinant tan chromosome after meiosis I) and the gene locus for tan/black. In other words, black and tan are
two alleles that map to the same place. We can figure out how many map units this place is by calculating the % of
recombinants and dividing by 2 (because even within each ascus that shows recombination, half the spores are parental
and half are recombinant [on average]). Check out this video if you are confused: https://www.youtube.com/watch?
v=gXUxH1aFRp0
DR
1. Using the image below, mark the asci as recombinant or not, count the number of recombinant asci and divide by
the total number of asci.
OR
2. Multiply by 100 to get a percent.
3. Divide this number by 2 to get the number of map units between the centromere and the gene locus.
****
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