Non-Mendelian Genetics Flashcards
Non Mendelian genetics
Occurs because multiple alleles occur on one chromosomes
Linkage
Linked genes that do not segregate independently
Animal studied in linkage
Fruit flies
Morgan’s accomplishment
The mapped the distance between genes and order
How was gene distance measured?
By the likelihood of the genes assorting independently from one another.
Two steps of Morgan’s study
- Mixed two heterozygous flies and measured their results
2. Mixed an F1 fly with a homozygous recessive fly
Drosophila notation
Consists of normal or wild type genotypes
Mutant
A change from the wild type. Named based on phenotypes
Dominant
Start letter(s) of the phenotype. The first letter is capitalized
Recessive
Start letter(s) of the phenotype. The first letter is lowercase
Wild type allele
Add a + subscript
Morgan experiment start
Red eyes and normal wing length was mixed with recessive purple eyes and vestigial wings
F1 generation of Morgan’s experiment
Were all dihybrid Rr+RrVg+Vg
Step two of Morgan’s experiment
Wild tupes from F1 were mated with pure bread homozygous recessive
If purple and vestigial were on separate genes
Mendel’s principles of independent assortment would predict and be true of 1:1:1:1
Reality of Morgan’s results
There were more dominant and recessive organisms for both traits that there was a combination of one dominant and one recessive trait.
Why did Morgan’s results occur
The 2 genes are lined and further hypothesized that the behavior of linked genes is because of genetic recombination
Frequency of recombination
A function of the distance between linked genes
Pr+PrVg+Vg parents make
Pr+Vg+, PrVg be segregation
Pr+Vg, PrVg+- Occur because of crossing over
Parental offspring
Same genotype, not the same phenotype
10.7
This many offspring from parents had recombined chromosomes
Sturtevant
Morgan’s student used his work to map out the first chromosome
Linkage map
Shows the relative location of chromosomes
AB/Ac+BC gene distance
Almost similar but not because genes can cross over multiple times
Double cross over
Two cross overs occurring at the same time
The first linkage map was
A drosophila X chromosome
Centimorgan (Map unit)
The unit used to measure linkage maps. Equal to a recombinant offspring frequency of 1%.
Relative values not absolute
Current gene arranging
DNA sequencing which is more precise for physical gene location
Independent assortment occurs when
Genes are far apart enough, crossing over is almost guaranteed. Occurs at greater that 50 mu
In meiosis production
2 recombinant and 2 non recombinant offspring
Total test cross progeny
The number of genes that assorted independently/number of chromosomes
How to measure genes that are greater than 5o mu
Use a middle gene and add the 2 values together
Sex linked genes
Genes located on the sex chromosomes
XX
Homozygous and a produces a girl
XY
A short section of homologous with x chromosomes. Boys
XO
Just one X chromosome, no pair
zz
Male
ZW
Female
Sex determining region on the Y. SRY
The gene that causes a man to develop early in embryonic stages. Activates after 6-8 weeks
What does the SRY do
It stimulates protein production to regulate gene expression
All embryos
Tend toward females, except when the SRY is present
Sex linkages
Don’t follow Mandalin principles
How were sex linkages discovered
F2 flies had different eye color ratio for each gender
Sex linked genes
Located on the X chromosome and not on the Y chromosome
Reciprocal cross
White eyed female and males. In the F2 generation both males and females were 1:1 ratio, different than the other way around
Pedigree chart
A chart summarizing family geno and phenotype. Shows individual’s sex and the trait in question
Open circle and open Square
Unaffected female/male
Closed circle and square
Affected female and male
Males are more likely to
Have the genes active more often because they only need 1 chromosome
Sex linked traits examples
- Red green color blindness
2. Hemophilia
Hemophilia
Excessive bleeding due to a lack of protein for blood clotting
