17.2 Extending Mendel's Law Flashcards
Why was the fruit fly chosen to research?
Because it was economical to maintain and reproduces rapidly
What was the goal of Morgan?
To disprove Sutton’s suggestion that genes are located on chromosomes
Why did Morgan believe that the gene for eye color is located on the X chromosome?
Because when he crossed certain generations of fruit flies many females had a certain color and many males has a certain eyecolor
What is the chromosomal theory of inheritance?
The theory that genes are carried on chromosomes, and chromosomes segregate independently into gametes during meiosis
What did Sutton predict about Genes?
He predicted that when alleles of two different genes are on the same chromosome, they do not assort independently
What are Linked Genes?
Genes that are found on the same chromosome
What is Crossing Over of chromosomes?
A random event that occurs with equal probability at nearly any point on sister chromatids, except near the centromere
Where is crossover more likely to occur?
Between genes that are farther apart on a chromosomes
Why is crossover more likely to occur on genes further apart?
Because since the genes are further apart, there it is more likely that one gene will be switched with another chromatids while the other gene remains on the original chromatid. Instead of both genes that are switched
What does the Gene Chromosome theory state?
That genes exist at specific sites arranged in a linear manner along chromosomes
What is used to determine the relative position of genes on a chromosome?
The concept of crossing over
What is chromosome mapping?
The concept of using crossing over to determine the relative positions of genes on a chromosome
What is one map unit?
The distance between points on a chromosome where a crossover in 1 percent of all meiotic events
What is the map distance?
The distance between genes on a single chromosome
What are Recombinant types?
Offspring that have a different combination of alleles than the chromosomes of the parents
What are Parental Types?
Describes offspring that have chromosomes that are identical to those of their parents
How is the distance between linked genes related to it likeness to crossover?
The greater distance between linked genes, the more likely they are to crossover during meiosis
What is the percentage of recombinant types in the F1 generation proportional to?
The distance between the genes
What is the recombination frequency?
The percentage of time that a crossover has occurred as P gametes were formed
What is the formula for Recombination frequency?
(number of recombinant types)/(total number of offspring) x 100
What does a 1% recombination recombination frequency mean?
1 map unit
What are sex-linked traits?
Traits that are controlled by genes on either the X or Y chromosome
Why is it that women are able to possess two X chromosomes with no deficits?
On of the X chromosomes is inactive
What is a Barr Body?
structure formed when the inactive X chromosome is condensed tightly
What is a visible effect of the inactivation of chromosomes
In Calico cats, it is patched orange and black. the patches of orange and yellow dhow collections of cells in which the X chromosome that is carrying the black allele is deactivated and the patches of black show collections of cells where the X chromosome carrying the orange allele is deactivated
What is the max number of genotypes that can be produced by one gene with two alleles? And describe them
Three. Two of the genotypes are homozygous and for one of the two alleles and the third one is heterozygous
What does it mean to have multiple alleles?
A gene with more than two alleles.
How do most genes have two alleles?
There is one form on each homologus pair
What are the genes to describe blood type?
I(A) I(B) and i
What is I(A) allele responsible for?
The A antigen on red blood cells
What is the I(B) allele responsible for?
The presence of the B antigen on RBCs
What is the i allele responsible for?
No antigen on the red blood cells
Which blood Allele is recessive?
i
Which blood Alleles are dominant?
I(A) an I(B) they are co-dominant
What are continuous traits?
Trits for which the phenotypes vary gradually from one extreme to another
What an example of a continuous trait in humans?
Height
What are continuous traits usually controlled by?
More than one gene
What are Polygenic traits?
Traits that are controlled by many genes
What is a polygene?
A group of genes that all contribute to the same trait
