It is an experimental cross wherein the heterozygous dominant genotype is crossed with a homozygous recessive genotype. 

Cis Conformation vs Trans Conformation

When the genes are on different homologous chromosomes and they are not linked, but instead, are independently assorting, we can say that there is no linkage.

When genes are located on the same chromosome, they are said to be _________.

When the Parentals and Recombinants are evenly 50%,, the genes are on _____________ homologous chromosomes; they are not linked but are independently assorting.

It is the linear arrangement of non-allelic genes on the same chromosome. Genes do not assort independently. The loci of the genes are very close.  Genes can only be separated by crossing over.

During linkage in which genes do not undergo independent assortment, genes can only be separated by what event?

Number of Chromosomes vs Number of Genes

If there is no recombinancec, all we get are parentals from a test cross.

If the number of genes exceed the number of chromosomes, there will be __________.

The genes are very close to each other, and are thus, transmitted together. Genes are closely linked, so expected to be inherited together. All parental types are produced (100:0), no recombinant types are produced.

In writing linkage genotypes, we use two lines two represent the ___________ ____________.

Can crossing over separate completely linked genes? Clue: The genes are so close to each other in terms of their loci when there is complete linkage. 

You can get recombinant types in a complete linkage.

The genes are far apart from each other and thus, can be separated by crossing-over. Here, recombinant types are obtained through crossing over. Genes are in the same chromosome but ARE NOT CLOSE, so they can be separated via crossing-over. You will get recombinant types but parental types are > 50% and recombinant types are <50%. 

In incomplete linkage, the loci of the genes are far from each other but are on the same chromosome.

During incomplete linkage, what has a higher probability?

Wild type genotypes are represented by this sign

Crossing over has to happen between non-sister chromatids.

It is the physical association of genes on a chromosome. It is the haploid number. The number of this is equal to the "n" or the haploid number. Genes located together on the same chromosome.

It is the creation of new association of genes or chromosomes of parts of which.

Linkage was discovered in ___________ by Thomas Hunt Morgan. He discovered linkage as he stsudied X-linked traits in ___________ and confirmed the Chromosome Theory that genes are found in the chromosome.

What did Thomas Hunt Morgan confirm after studying X-linked traits in Drosophila which lead to his discovery of linkage?

They are the student of Thomas Hunt Morgan in 1915 who were responsible for discovering the phenomenon of crossing over. They used linkage as a tool for Chromosome mapping, and they came up with the unit of cM or centiMorgan as an acknowledgement for their teacher, Morgan.

Also, they studied X-linked MUTANTS.

In X-linked mutants, it is used as a measurement of distance. It answers the question, "How frequent is recombination?"

1 map unit or 1cM (centiMorgan) is the distance that gives how many percentage of recombination?

1 centiMorgan is equal to 

It is the linear arrangement (pagkakasunod-sunod) of non-allelic genes on the chromosome. The distance between genes in this is based on the % recombination. This tool establishes the correct gene sequence and their distances relative to each other in the chromosome. 

STEPS IN GENE MAPPING

Corresponding Formulas when Linkage Mapping: Computing for the Distance between Genes, Finding the Strength of Linkage, and Computing for the interference. 

Implications of the Value of i (can range from 0 to 1)

How do you compute for cc?

When computing for cc and using the SCOI and SCOII, use the decimal form in the calculation, not the value multiplied by 100.

In the REVERSE PROBLEM/BACKWARDS PROBLEM, what are the corresponding formulas for the #DCO, #SCOI, #SCOII, and #Parentals? Given the linkage map, the cc or i, and the total progeny.

In linkage mapping in haploids, the 1st Division Segregation has __ _________ _____.

In linkage mapping in haploids, the 2nd Division Segregation is ____ ________ ____.

How is percent recombination computed? (To get # Recombinants, add the recombinants)

It is the phenomenon where the sex chromosome carry other genes aside from the genes for sex determination.

It has two types of inheritance: X-linked recessive genes and X-linked Dominant genes.

This type of X-linked inheritance is where two recessive genes cause the manifestation of the disease. Examples of this inheritance are color blindness, hemophilia (blood genetic disease), absence of central incisors, congenital deafness, and congenital cataract.

This type of X-linked inheritance is where the dominant gene (heterozygous or homozygous dominant) causes the manifestation of the disease. An example of this inheritance are browning of teeth or defective enamel.

In X-linked recessive genes, the carrier genotype that is X^H X^h is still normal when the phenotype is assumed because being a carrier is just a genotype that does not physically show.

It is the type of sex linkage wherein the genes of inheritanec are on the Y chromosome. This type shows holandric transmission or "father-to-son transmission".

It means "father-to-son" transmission.

Trait examples of this inheritance are webbing of toes (2nd and 3rd toes are attached) and hypertrichosis of the ear (hairy ear).

Genetic Sex Determination has three types, what are those?

GENETIC SEX DETERMINATION

Neurospora and Chlamydomonas

GENETIC SEX DETERMINATION

Hymenopterans wherein it has 9 alleles. Heterozygous: female, Homozygous: male

GENETIC SEX DETERMINATION

Mollusks (Crepidula and Patella)

-sexuality shows continuous variation; hermaphrodites are the most frequent

An example of this is in marine worms wherein it is free-swimming at larval stage (female)

The larva attached to the female adult becomes male due to the masculinizing hormones secreted by females. 

Another example of this is with Coral reef fish (Labroides dimidiatus)

-here, one male in several females

-When male dies, the most dominant female will take over

-If successful, there will be sex reversal in two weeks. 

What are the three types of sex determination?

In 1900, McClung discovered the association of sex characteristics with a particular chromosome.

For XX-XY system

-females of humans, cats, and mice

-with Barr body at interphase

-discovered by Murray Barr

-number of Barr body (no. of X-1)

-inactive X

which is for dosage compensation

-Mary Lyon, 1961, Lyonization or X-inactivation

Mary Lyon in 1961 created X-inactivation or ________________. Here, one X chromosome is inactivated.

WHAT ARE THE TYPES OF LINKAGES?

X-LINKED RECESSIVE SEX LINKAGE RESULT:

X^H X^H

X-LINKED RECESSIVE SEX LINKAGE RESULT:

X^H X^h

X-LINKED RECESSIVE SEX LINKAGE RESULT:

X^h X^h

X-LINKED RECESSIVE SEX LINKAGE RESULT:

X^H Y

X-LINKED RECESSIVE SEX LINKAGE RESULT:

X^h Y

It is important to note that frequency are also counted as ratios. Furthermore, put a line under the gametes to correctly represent the gametes.

Also, DO NOT REPEAT A BRANCHING METHOD IF HOMOZYGOUS DOMINANT!!!

What is the number of Barr bodies in males showing normal phenotype?

This is the process of turning off one random X chromosome in each cell.

Why does lyonization occur?

% Cross over at Region II

In the forward gene mapping problem, to get the parentals, look at the genotypes which are the _____ frequent.

In the forward gene mapping problem, to get the double cross over events, look at the genotypes which are the _______ frequent.

Wild Type vs Mutants