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How crossing over and linkage effect the independent assortment?
Wiki User
∙ 9y ago
Crossing over results in recombination, which effectively cancels out linkage if it takes place between the linked genes. The closer together the two genes are, the less likely this is to occur. One percent recombination equals one MapUnit or one centiMorgan (cf. Nobel laureate Thomas Hunt Morgan) in the mapping of chromosomes. However, the virtual "distance" of genes thus gained is not necessarily directly proportional to their physical distance, as recombinant hotspots are more likely to participate in crossing over than other sites along the chromosome.
Wiki User
∙ 15y ago
Wiki User
∙ 12y agoLinkage
• Tendency of genes of same chromosome
to remain together .
• Such genes are called - linked genes.
Punjab EDUSAT Society{PES}
• Such genes are called - linked genes.
• Linked genes present only parental types
in progeny.
• Linkage refers to packaging genes onto
chromosomes
• Chromosomes (and therefore linkage) are for
organizing genes for their safe coordinated
transmission from cell to cell, parent to
Punjab EDUSAT Society{PES}
offspring
• Simply put, what's easier to handle:
30000 quarters (i.e., genes) OR
23 bags of quarters (i.e., chromosomes)?Some Definitions
• Complete linkage - Genes that are linked but
never crossover
Incomplete linkage - Genes that are linked
and can crossover
Punjab EDUSAT Society{PES}
• Parentals - Offspring that are like the parents
Recombinants - Offspring with arrangements
different from the parentsUnlinked genes
• Parents AABB X aabb
• Gametes AB, AB ab, ab
A A B B
a a
b b
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• Gametes AB, AB ab, ab
• F1progeny AaBb
• T.cross AaBb X aabb
• Progeny AaBb , Aabb , aaBb , aabb (1:1:1:1)Linked Genes
__ __ __ __
Parents AB / AB ab / ab
Gametes
F1
Progeny
__ __ __ __
X
__ __
AB / ab
AB AB ab
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__ __ __ __
Test Cross AB / ab ab / ab
Gametes
Test Cross
Progeny AB Test Ratio 1:1
ab AB / ab
X
ab
AB / ab
AB ab abFACTORS AFFECTING
LINKAGE
1. Age
Punjab EDUSAT Society{PES}
2. Temperature
3. X-RaysSignificance of Linkage
• Keeps parental / racial specific traits together.
• Valuable traits of new variety maintained.
• Disallows desirable mixing of traits.
Punjab EDUSAT Society{PES}
• No. of linkage groups = No. of chromosome
pairs.
This shows genes are located on chromosomes.• Linked genes are not inherited
together every time.
• Chromosomes exchange homologous genes
during meiosis.
Punjab EDUSAT Society{PES}Crossing- Over
Punjab EDUSAT Society{PES}Steps of Crossing- over
• Synapsis of homologous
chromosomes - Zygotene
• Tetrad formation- Pachytene
Punjab EDUSAT Society{PES}
• Tetrad formation- Pachytene
• Crossing over- Pachytene
• DisjunctionPunjab EDUSAT Society{PES}Punjab EDUSAT Society{PES}FACTORS AFFECTING
CROSS OVER
1. Temrperature
2. X-Rays
Punjab EDUSAT Society{PES}
3. Chemicals
4. Age
5. Interference
6. SexSignificance of Crossing-over
• Produces new combinations of traits.
• Forms raw material for evolution.
Punjab EDUSAT Society{PES}
• Establishes concept of linear arrangement
of genes.
• Helps to determine loci of genes in the
chromosomes.
Wiki User
∙ 11y agoCrossing over switches or exchanges parts of chromosomes
. This means that genes that were stuck together in the same chromosome
can end up with some different genes. So crossing over changes or "recombines" (makes a new combination) the linked genes
Wiki User
∙ 9y agoAccording to the Law of Independent Assortment every gene present on the chromosome has freedom to move independently in the gametes but cross overs and linkages restrict their independent movement. The linked genes mostly move together, similarly the cross overs also have segments of chromosomes having more than one gene aligning with the chromatids of homologous chromosomes.
Wiki User
∙ 11y agoIt involves a physical exchange of segments from homologous chromosomes.
Wiki User
∙ 10y agoI need help on this too!
Wiki User
∙ 11y agoit doesnt
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Which correctly describes the effect crossing over during meiosis?
It causes the cell to split into four haploid cells.
What serves as a standard of comparison to evaluate the effect of the independent variable on the dependent variable?
ControlThe answer will depend on the nature of the effect. IFseveral requirements are met (the effect is linear, the "errors" are independent and have the same variance across the set of values that the independent variable can take (homoscedasticity) then, and only then, a linear regression is a standard. All to often people use regression when the data do not warrant its use.
What is the independent variable in this experiment what effect does table salt have on the temperature of boiling water?
the temp of water (what they changed)
Definition of independent sample.?
two samples are independent if they are drawn from two different populations, and/ or the samples have no effect on each other. eg: We want to estimate the difference between the mean salaries of all male and all female executives. We draw one sample from the population of male executives and another from the population of female executives. These two samples are independent because they come from different populations and the samples have no effect on each other
What effect does crossing over have on variation in a specie?
In crossing over the chomosomal segments of the homologous chromosomes get interchanged. Thus the genetic configuration of recessive and dominant genes gets altered and new gene combinations are formed which ultimately leads to the variation in the offsprings.
Mendel's finding that the inheritance of one trait had no effect on the inheritance of another became known as the law of?
Law of Independent Assortment
When does independent assortment occur in mitosis?
Independent assortment does not happen in mitosis, it happens in meiosis. In metaphase I of meiosis, synapsed homologous chromosomes align independently of one another along the metaphase plate. That is to say, one aligning in a certain fashion has no effect on another aligning in a certain fashion. In mitosis, chromosomes are exact copies of the parental cell's and independent assortment is a method of achieving genetic variation, which does not happen in mitosis.
Does the inheritance of one trait effect the inheritance of another trait?
Inheritance all traits is independent, according to the Law of inheritance, unless there is linkage in the genes.
What is a backward linkage?
A backward linkage is an effect in which increased production by a downstream manufacturer provides positive pecuniary externalities to an upstream manufacturer.
Which did Mendel determined in his experiments on pea plants?
he determined three basic laws of genetic inheritance 1 law of dominance:each trait has two forms and one is shown in phenotype 2 law of segragation: each person have two alleles for a trait and the alleles do not blend rather they segragate during gamet production 3 independent assortment: each trait behaves independently meaning that which allele is segregated to which daughter cell does not effect the other alleles of different traits unless there is linkage between genes but mendel didnt know that genes coud be linked so his conclusion was made assuming that every trait's(inherited via genes)behavior was independent
Does crossing over affect one or many genes?
Crossing over can effect on more then one gene i.e. at least two as in crossing over the genes of homologus chromatin get interchanged so it effect at least two genes and can effect or change more then two genes depend upon the linking and crossing over capability
What effect does crossing over in propahse 1 have on the cells?
Crossing over creates a genetic recombination of the DNA.
Is cause the independent variable?
Not necessarily. The independent variable may have no effect at all.
How does George Washington crossing Delaware effect the war?
890 your mum
What is the independent variable in the stroop effect?
it is the people and the time
How does crossing over and independent assortment insure genetic variability?
It doesn't always. When crossing over occurs sections of nucleotide bases are switched. Lets take for example you have an original DNA of TTCTCCGATAGT and crossing over occurs to change this into TTCATGGATTCT. When this is now read by the mRNA only ATG will become a different protein meanwhile AGT on the original will be made into the same protein. This is because you have to look at the codon table to see which codons become which protein. Different codons may produce the same proteins so crossing over does not always ensure genetic variation but is gives genetic variation a more likely probability of happening. As for independent assortment, this doesn't lead to genetic variation. Really independent assortment will just lead to different phenotypes being expressed.
Which is a pair of independent events?
Two events are independent if the outcome of one has no effect on the probability of the outcomes for the other.
